ANNAMALAI UNIVERSITY DEPARTMENT OF MECHANICAL ENGINEERING … · 2017-09-08 · 2 ANNAMALAI...

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ANNAMALAI UNIVERSITY

DEPARTMENT OF MECHANICAL ENGINEERING

FACULTY OF ENGINEERING AND TECHNOLOGY

III SEM B.E ELECTRICAL AND ELECTRONICS ENGINEERING

LABORATORY INSTRUCTION MANUAL CUM OBSERVATION

NOTEBOOK

NAME : ___________________________

ROLL No : ____________________________

SUBJECT : ____________________________

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ANNAMALAI UNIVERSITY DEPARTMENT OF MECHANICAL ENGINEERING

III SEM. BE EEE 2016-2017 MECHANICAL ENGINEERING LABORATORY

LIST OF EXPERIMENTS PAGE NO

1. Study and valve timing on Anil 10 HP Engine. 10

2. Study and port timing on Petter 3 HP Engine. 16

3. A) Study of Loco & Cochran boilers. 19

B) Study of Greenbat turbine and condenser 23

4. Performance test on Experimental central air conditioning plant. 31

5. Performance test on Refrigeration Trainer. 43

6. Study &Volumetric Efficiency test on Kaeser air compressor test rig. 53

7. Study and valve timing on Field marshal 8HP Engine. 61

8. Load test on Kirloskar AV I Engine (Double arm type). 64

9. Load test on PSG 5 HP Engine. 75

10. Load test on Batliboi Engine. 82

REFERENCES :

1. EXTRAPOLATION METHOD 73

2. GENERAL SHAPE CHARACTERISTIC CURVE 74

VENUE:

1. I C Engines Laboratory annex [For experiments 1 and 2]

2. Steam Laboratory [ For experiment 3]

3. R&A/C Laboratory [ For experiments 4 and 5]

4. I C Engines laboratory Main[For experiments 6 to 10]

GIVEN : Calorific value of Diesel : 42,000 kJ/kg. Specific Gravity of Diesel : 0.835 Density of water : 1000 kg/m3

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Instructions to the students

1. Be regular and be punctual to classes

2. Come in proper uniform stipulated

3. Ensure safety to your body organs and laboratory equipment

– SAFETY FIRST DUTY NEXT

4. Read in advance the contents of the instruction manual pertaining to the

experiment due and come prepared. Understand the related basic principles.

5. Maintain separate observation and record note books for each laboratory

portion of the course wherever justified.

6. Though you work in a batch to conduct experiment, equip yourself to do

independently. This will benefit you at the time of tests and university

examinations.

7. Independently do the calculations and sketching. If there is difficulty, consult your

batch mate, classmate, teacher(s) and Laboratory in-charge.

Do not attempt to simply copy down from others. You may fulfill the formalities

but you stand to loose learning and understanding

8. Obtain the signature of teacher (s) in the laboratory observation note book and

record note book then and there during class hours (with in a week subsequent to

experimentation).This will relieve the teacher (s) from giving reminder.

9. Help to maintain neatness in the laboratory.

10. Students are advised to retain the bonafide record notebook till they successfully

complete the laboratory course.

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CONTENTS

Sl No Date Name of the Experiment Staff Signature

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CONTENTS

Sl No Date Name of the Experiment Staff Signature

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STUDY AND VALVE TIMING ON FOUR STROKE IC ENGINES

Aim:-

To determine the valve timings/settings of a four stroke IC engine and to draw the valve timing diagram.

Valve timing Diagram:- Valve timing diagram is the graphical form of representing the timings (instants) in terms of the corresponding crank positions at which the inlet and exhaust valves open and close. The crank positions and the sequences are described with reference to the nearest dead center.

Purpose:- At the time of every overhauling and repairing, the engine parts are dismantled and reassembled. After such reassembling, the valve timings are to be verified with the manufacturers recommendations, i.e, the original settings, and adjusted using the valve tappet if required. The valve timings are also to be periodically verified with original settings because of the wear and tear of the elements of the valve mechanism.

Procedure:-

Identification of valves:- The engine cylinder head cover is removed to facilitate the observation of valves, valve mechanisms and their workings in case of multi cylinder engine. Incase of single cylinder engine the rocker arm box cover is removed. The engine crank shaft is manually turned in the correct direction (clockwise from the cranking end) and the functioning of valves is noted. Both inlet and exhaust valves will be in simultaneous operation at a particular period. This period represents the overlapping between two cycles (the suction process of later cycle overlapping with the exhaust process of the current cycle.) The valve which closes during this period is the exhaust valve while that opens is the inlet valve.

Rotating member for markings:- A circular member (flywheel /pulley/brake drum) mounted on the crankshaft is used for making the markings related to the various events (IVO,IVC,EVO & EVC) with reference to the nearest dead center IDC/ODC for horizontal engine or TDC/BDC for vertical engine. The circumference of the circular member used will be useful in determining the various crank angles. A pointer or an indicator fixed on the engine frame serves as the reference against which all the markings are made on the rim of the circular member.

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Dead Centers:- When the engine runs, the piston reciprocates between two extremities of the stroke. These extreme positions are called as dead centers, the velocity of reciprocation being zero at these instants. The crank positions corresponding to the dead center positions of the piston are termed TDC/ BDC or IDC /ODC positions. The crank is turned manually and the marking is made on the rim of the circular member when the piston is at a definite position (piston bottom coincides with the bottom of the cylinder) during its downward journey. On further rotation of the crank, the piston moves down, reaches the BDC position and reverses its direction to move up. During the upward journey the piston will reach the same definite position at which a marking was done earlier on the rim of the circular member. Now another marking is done on the rim of the circular member. Mid point of the two markings (on the shorter arc length) is the BDC marking on the rim. TDC marking is made diametrically opposite to the BDC marking. At the commencement of valve just moving away from its seat due to the actuation by cam through push rod, the valve is said to have opened. When the valve has completed the movement against its seat by spring action, it is said to have closed. When the crank is turned, the instant at which a piece of paper inserted in-between the valve stem and tappet/rocker arm is just gripped is the valve opening. IVO and EVO markings are made on the circular member corresponding to the openings of the inlet and exhaust valves. Similarly the instant at which the paper just looses the grip in between the valve stem and tappet/rocker arm is the valve closing. IVC and EVC markings are made on the circular member.

The distances of the IVO,IVC,EVO & EVC markings on the circular member, from the nearest dead center are measured.[Fuel injection timing can also be noted by noting down the starting and ending of fuel injection through nozzle( i.e., fuel injector)] The observed diagram is drawn using the dimension details of markings on the circular member and the direction of rotation of the flywheel. The circle, drawn of any convenient radius, represents the circular member (flywheel/pulley/brake drum). Inferring from the observed diagram, the events, their sequences and timings in relation to the nearest dead center are tabulated as shown. The arc lengths are expressed as crank angles in the last column of the table. The valve timing diagram is drawn using the details (event, sequence and crank angle) in the table.

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Observation tabulation:- Circumference of flywheel =

............cm. Sl. No.

Events

Sequence of Operation

Distance from the nearest dead center ‘x’ in cms

Crank angle ‘θ’ in degrees

1 2 3 4

IVO

IVC

EVO

EVC

Crank angle, 𝜃𝜃 = 𝑋𝑋 ×360

𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶𝐶 𝑜𝑜𝐶𝐶 𝑡𝑡ℎ𝐶𝐶𝐶𝐶𝑒𝑒𝑒𝑒𝑒𝑒ℎ𝐶𝐶𝐶𝐶𝑒𝑒/ 𝑏𝑏𝐶𝐶𝑏𝑏𝑏𝑏𝐶𝐶 𝑑𝑑𝐶𝐶𝐶𝐶𝐶𝐶/𝑝𝑝𝐶𝐶𝑒𝑒𝑒𝑒𝐶𝐶𝑒𝑒

Model OBSERVED DIAGRAM

X1

X2 X3

X4

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Procedure for drawing V.T.D. Draw a vertical line to represent the line of stroke. Mark a point 1 on it. Draw a semi-circle of any convenient radius taking point 1 as center to its RHS of the vertical line from ‘a’ to ‘b’. Then mark another point 2 little above the point 1 on the vertical line (say 5 to 10 mm). Then draw another semi-circle from ‘b’ to ‘c’ taking 2 as center on the LHS of the vertical line. Similarly draw semi-circles from ‘c’ to ‘d’ on the RHS taking 1 as center and from ‘d’ to ‘e’ on the LHS taking 2 as center. Then extend the arcs to the desired length from ‘a’ as well as from ‘e’. Then locate all the events on the circular arcs as per the tabulation . Join these points with the center of the circle (Take point 1 as center) by radial lines. This radial line represents the crank positions corresponding to the events.

Result: The angle through which the inlet valve remains open : The angle through which the Exhaust valve remains open : The angle of overlap :

----------------------------------------------------------------------------------------------Note: In the place of θ1, θ2, θ3 & θ4 , the actual values of the crank angles in degrees are to be substituted

c

b

a

2 1

d

e

θ4

θ3 θ2

θ1

Model VALVE TIMING DIAGRAM

S – Suction C – Compression P – Power E – Exhaust

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Expt.No : Date:

STUDY AND VALVE TIMING ON ANIL 10 HP ENGINE

Aim:-

To study and determine the valve timings/settings on Anil 10 HP engine and to draw the valve timing diagram.

Requirements:-

Measuring tape A circular member attached to crank shaft A reference point

Specifications:- Type :

Fuel used :

Power :

Speed :

Bore :

Stroke :

Type of Cooling :

Valve mechanism :

OBSERVED DIAGRAM

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Observation tabulation:- Circumference of flywheel = cm.

Sl. No.

Events


Distance from the nearest dead centre ‘x’ in cms


1 2 3 4

IVO

IVC

EVO

EVC

SPECIMEN CALCULATIONS:

θ1 = 𝑋𝑋1𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑

Circumference of the flywheel / pulley / brake drum =

θ2 = 𝑋𝑋2 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ3 = 𝑋𝑋3 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ4 = 𝑋𝑋4 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


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VALVE TIMING DIAGRAM

RESULT: The experiment was conducted and the Valve Timing Diagram for Anil 10 HP

engine was drawn. From the valve timing diagram the following values are obtained

Crank angle for which the Inlet Valve remains open( θ1+180+ θ2) =

Crank angle for which the Exhaust valve remains open(θ3+180+ θ4) =

Angle of over lap (θ1+ θ4) =

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General Instruction and procedure for

STUDY AND PORT TIMING ON TWO STROKE IC ENGINES

Aim : To determine the port timings of Two stroke IC engines and to draw the port

timing diagram.

Ports:

The ports in a two stroke engine are small openings in the cylinder walls

diametrically opposite to each other. The piston reciprocating inside the cylinder uncovers

(opens) and covers (closes) the ports, thus performing the function of valves in 4 - stroke

engines. The exhaust port lies slightly above the inlet (transfer) port. Hence during the

ascending of the piston in a vertical engine, the closing of exhaust port precedes the

closing of transfer port. Similarly in the descending of the piston, the exhaust port is

uncovered first and then the inlet (transfer) port. The above said facts help in identifying

the inlet and exhaust ports.

Procedure: Dead centers: On removal of the cylinder head, the piston top can be visualised. Rotation of the flywheel makes the piston reciprocate. Make a mark on the flywheel against the fixed pointer corresponding to a specific position of the piston in its upward stroke. On further rotation of the flywheel piston reaches the TDC position (maximum height) and reverses its direction of motion down wards. The position at which a mark was made earlier during upward stroke will be reached again during the downward stroke. Now make a mark on the flywheel. The mid point of the markings is the TDC point on the flywheel. As the direct location of TDC point requires visual judgment and is difficult, the procedure mentioned is suggested. The BDC point is marked in the flywheel diametrically opposite to TDC point. A port is said to open when the piston just starts uncovering it. It is said to close only when piston has totally covered it After marking the dead center positions on the flywheel, markings are made corresponding to the opening and closing of the inlet and exhaust ports.

Observed diagram:

A circle of any convenient radius is drawn to represent the flywheel. The markings made on the flywheel are also shown in the circle and the distance of them from the nearest dead center are marked. When the sense of rotation of the flywheel is added, the observed diagram becomes complete.

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The details of the observed diagram ie. the crank positions (angle and sequence) in relation to the nearest dead center, corresponding to the opening and closing of the inlet and exhaust valves are tabulated. The respective crank angles are calculated from the arc lengths in observed diagram.

Observation tabulation:-

Circumference of flywheel = ............cm. Sl. No.

Events




1 2 3 4

IPO

IPC

EPO

EPC

Crank angle, θ = 𝐗𝐗 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑

Circumference of the flywheel / pulley / brake drum

Model OBSERVED DIAGRAM

IPO IPC

EPO EPC

X1 X2 X3 X4

TDC

BDC

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Port Timing Diagram:

The port timing diagram is drawn using the inferences from the table. The crank

angles, the sequences in relation to the nearest dead center position of the crank and

the required direction of travel of the observer along the circular diagram are furnished

in the port timing diagram.

Result: The angle through which the inlet port remains open : The angle through which the Exhaust port remains open :

_______________________________________________________________ Note: In the place of θ1, θ2, θ3 & θ4 , the actual values of the crank angles in degrees are to be substitute.

Model PORT TIMING DIAGRAM

θ1 θ2 θ3 θ4

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Expt. No : Date:

STUDY AND PORT TIMING ON PETTER 3 HP ENGINE Aim :

To study and determine the port timings of Petter 3 HP engine and to draw the port

timing diagram.

Requirements:- Measuring tape A circular member attached to crank shaft A reference point


Fuel used :

Power :

Speed :

Bore :

Stroke :

Type of Cooling :

OBSERVED DIAGRAM

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Observation tabulation:- Circumference of flywheel = cm.

Sl. No.

Events




1 2 3 4

IPO

IPC

EPO

EPC

SPECIMEN CALCULATIONS

θ1 = 𝑋𝑋1𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑Circumference of the flywheel / pulley / brake drum

=

θ2 = 𝑋𝑋2 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ3 = 𝑋𝑋3 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ4 = 𝑋𝑋4 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


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PORT TIMING DIAGRAM

RESULT:

The experiment was conducted and the Port Timing Diagram for the Petter 3 HP

engine was drawn

Crank angle for which the Inlet port remains open ( θ1 + θ2) =

Crank angle for which the Exhaust port remains open

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Expt.No : Date:

A. STUDY OF LOCO &COCHRAN BOILERS

Aim: To study the loco type and Cochran boilers

i) LOCO BOILER

SPECIFICATIONS: Type : Horizontal, Fire tube Working pressure : 8.2 bar Evaporating capacity : 800 kg/hr Area of heating surface : 31.9 m2 Grate area : 0.88 m2 Diameter of boiler shell : 1.14 m Length of the boiler : 4.12 m Number of tubes : 56 Diameter of the tube : 63.5 mm Diameter of chimney : 457 mm Height of the chimney : 8.2 m Description:

This boiler is stationary, horizontal, fire tube, loco type boiler. This has a plain

grating surface and is provided with gusset stays to prevent the bulging of end plates. The water is fed initially to the boiler by means of a pump and when the boiler is in operation an injector operated by steam is used to suck the water into the boiler. Water is drawn by the suction effect produced by the steam jet provided near the water pipe. Mud if any in the water is collected at the bottom. Four hand holes are provided for removing the mud. Grate is composed of number of iron bars with a gap of about 10 mm between them.

The draught is a natural one. Since the hot air is lighter than the atmospheric air,

the hot flue gases rise to the atmosphere. The draught can be controlled by adjusting a butterfly valve provided at the chimney bottom. The water level is indicated by a pair of water level indicators positioned in the front side. The water level should not fall below the marks made on the indicator. A pressure gauge and a Rams bottom safety valve are mounted on the top of the boiler. A manhole is provided to inspect and clean the interior surface of the boiler. A blow- off cock is provided at the bottom for cleaning purposes. There is a fire door to feed the coal to the furnace. A damper is provided below the grate to control natural draught. The boiler is provided with a fusible plug to protect the boiler from overheating

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due to fall in water level. It is fitted over the crown of the furnace and is exposed to the flames. The boiler has an anti-priming pipe to separate water particles from the out coming steam. Steam always contains some amount of water particles. The water having much higher specific gravity than the steam tends to fall back as steam ascends. The higher the steam rises in the steam space, lesser is the water particles suspended in it.

LO

CO

TY

PE B

OIL

ER

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ii) COCHRAN BOILER Specifications:

Type : Vertical, Fire tube, Oil fired Working pressure : 6.9 bar Evaporating capacity : 436 kg/hr Area of heating surface : 9.28 m2

Grate area : 0.905 m2 Diameter of boiler shell : 1.37 m Number of tubes : 65 Diameter of tube (outer) : 63.5 mm Thickness of tube : 4 mm

Length of tube : 0.895 m Height of boiler : 3.28 m Stay tube diameter (outer) : 63.5 mm Construction: There are various designs of vertical multi tubular boiler, of which COCHRAN is one. Usually the crown of this boiler is made hemispherical in shape, which for a given amount of material in weight, gives the maximum space for steam. The hot gases from the fire box pass through the short flue pipe into the combustion chamber lined with fire bricks. The gases then flow through a set of fire tubes into the chimney. A spring loaded safety valve is provided at the top, the blow-off cock at the bottom and the pressure gauge with siphon and the water level indicator at the side. The boiler is provided with a manhole and a hand hole. The boiler effects economy in operation. The large steam and water spaces prevent priming. The heating surface is also invariably large as compared to other types of smoke tube boilers.

Fusible Plug: It is a simple device to prevent overheating due to low water level. It is fitted on the top of the crown box. When the water level falls below the plug, the core melts and drops down, allowing the steam to enter the furnace and put down the fire.

Burner:

Liquid fuel possesses a superior heating value. The main principle is to atomize the oil through some means and spraying the atomized liquid in to the burners. The major requirements for this are oil fuel, installation of an arrangement for lightening it

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up, to preheat the oil, if necessary, both suction and discharge filters, and air distributors. The burners generally used may be of three types. (i) Pressure type (ii) Steam atomizing (iii) Air pressure type.

Pressure Type The oil is drawn from the oil tank and is supplied through a horizontal or vertical

fuel pump. The oil may be pre-heated to rise its temperature up to the flash point and the burner receives it from the discharge of an oil filter. The oil is atomized by the tangential slots of burner and is thrown on the furnace.

Steam Type In an atomized steam type fuel burner, the steam and oil enter the burner

through different passage shown in figure. The high velocity steam imparts a whirling motion to atomized fuel and the mixture is carried by the air draught.

Air Pressure Type The principle is the same as that of a steam type system. The only difference is

supply of oil mixture with air, to the burners by blower. It is to be noted that oil should be of low viscosity when it comes to the burner.

Oil Burner Oil Burner atomization

COCHRAN BOILER

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B. STUDY OF GREENBAT TURBINE AND CONDENSOR

(I) GREENBAT TURBINE

Aim: To study the Greenbat turbine with geared turbo generator set.

Specifications:

Turbine:

Power : 7.46 kW (10 H.P)

Generator speed (or reduced turbine speed) : 2400 rpm

Steam pressure : 3.5 kg/cm2 (3.4 bar)

No. of nozzles : 5

Generator:

Power : 6.5 kW.

Voltage : 220 Volts.

Current : 29.5 Amps.

Loading Arrangement : Electrical resistance type.

Description:

This is a single stage simple impulse turbine having the rotating element actuated by the impact of steam passing through the blades at a relatively high velocity. The whole of expansion of the steam from admission pressure to the back pressure take place in the nozzles. The heat drop is converted into the Kinetic energy. The whole of the kinetic energy of the steam is absorbed in the single row of moving blades.

Vt = ½ V cos θ Where,

Vt Velocity of blade.

V Absolute velocity of steam from nozzle.

θ Nozzle angle

The rotor of this turbine runs at 24,000 rpm. It is made of forged, heat treated, nickel chrome steel having one row of stainless steel blades made with a bulb shank fitted in slots drilled in the rim of the wheel. The turbine wheel is mounted on a flexible shaft supported between self aligning bearings. The shaft is made of heat treated Nickel chrome. Molybdenum steel upon which pinion is cut. A gear meshing with this pinion gives the reduced speed of 2400 rpm. to the output shaft to which it is attached.

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At the bearing, glands are provided on the rotor to prevent leakage of steam. When the steam next to a gland is exhaust steam on its way to the condenser, there is no tendency for steam to escape past the gland into the atmosphere, but there will be a leakage of air inwards, as is the case here. To prevent this air leaking in, the gland is supplied with steam pressure above the atmosphere which expands through the labyrinth packing to the condenser.

This turbine is a condensing turbine. Condensing turbine means condenser is attached to the exhaust of the turbine. The condensing turbine increases its power output compared with the non condensing type.

Governing Mechanism:

The object of governing is to maintain the speed of a turbine sensibly constant irrespective of load. The turbine is fitted with 5 nozzles to achieve part load efficiency. Any nozzle is designed for a particular maximum discharge. Under part load conditions the turbine work either

1. With the same isentropic total enthalpy drop of steam whose quantity is

reduced or

2. With a lesser isentropic total enthalpy drop of same quantity of steam,

The turbine is fitted with a constant speed governor. The governor shaft is coaxial with the out put shaft. The flying outwards or inwards of two spring loaded weights due to speed change of the turbine by a system of levers actuate a double beat throttle valve which controls the admission pressure according to the requirement. The reduction in the load on the turbine manifests itself as increase in speed of the turbine shaft, which causes the governor weight to fly outwards and this motion is communicated to the throttle valve which reduces the passage of steam i.e., the inlet pressure is decreased by throttling.

Lubrication and Cooling:

The question of lubrication is very important to the satisfactory operation of all machines. All shafts are lubricated by oil supplied by a gear type pump driven by a counter shaft from the reduction gear. The oil which has lubricated and cooled all the bearings and reduction gear will be hot. Therefore it is passed through a oil collect where it is cooled by circulating water. The oil pump supplies oil to the bearings and gearing at a pressure of 0.352 bar.

Loading Devices:

The output shaft of the turbine is coupled to the armature of a DC generator. The generator is loaded by a rheostat. There is provision to measure the current and voltage and hence the output of the generator.

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(II)STEAM CONDENSER (SURFACE)

SPECIFICATIONS:

Outer diameter of the condenser tube [Do] = 0.0158 m Length of condenser tube [Lo] = 0.826 m Number of tube [Zo] = 82

OBJECT OF CONDENSING EXHAUST STEAM:

In any heat engine the amount of work done per unit weight of working fluid depends on the range of temperature of that fluid in the engine. Efficiency is greater when the range is greater. In other words if the extent of the expansion of the fluid cannot be used over again and hence it has to be discharged to the atmosphere and the atmospheric pressure fixes the lower limit of expansion. When steam is the working fluid, it may be returned to the boiler in the form of liquid and used over again. This can be done most conveniently and most economically by pumping water rather than steam into the boiler. ELEMENTS OF CONDENSING PLANT:

For the purpose of maintaining vacuum during condensation and removal of the exhaust steam the principal requirements are 1. A condenser in which steam is condensed. 2. Supply of cooling water. 3. A pump to circulate the cooling water. 4. A pump called the air pump for removing the condensed steam and air. 5. A tank for collecting the condensed steam discharged by the air pump. DESCRIPTION OF THE CONDENSER:

The surface condenser consists of: 1. A horizontal shell of circular cross section. 2. Flat tube plates bolted on to ends of the shell to support the tubes. 3. Water boxes open to the tubes and surrounding them the water box at one end has a horizontal partition about half way up. The other box has only one compartment. 4. A large number of tubes extending between the tube plates and providing communication between the water boxes. 5. A large opening in the top of the shell to admit steam to the condenser. 6. A small opening at the bottom of the shell to lead the condensate.

Cooling water is pumped into the water compartment at front end which it passes through the lower nest of tubes to the water compartment at the other end. It then returns through the upper nest of tubes to the upper water compartment which then leads through the outlet at top. The steam enters the shell by the opening at the

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top of the shell and passing over the tube it is condensed and leaves through the opening at the bottom.

Thermometer pockets are provided to facilitate the measurement of temperatures of the cooling water at inlet and outlet and the incoming steam and condensate. A flow meter is fixed in the cooling water line so that the cooling water flow rate may be determined.

The air pump which creates vacuum as well as removes the condensate from the condenser is driven by electric motor through a V-belt drive. The motor is mounted on trunnions so that its output which is also the input to the air pump may be determined.

AIR PUMP

The main function of an air pump is to maintain a vacuum in the condenser as nearly as possible, corresponding to exhaust steam temperature. This is done by removing uncondensable air from the condenser. Another common, but not the essential function of the pump, is to remove both air and condensate from the condenser.

The air pump, which extracts both the condensate and air, is called a wet air pump. But a pump which extracts only moist air is known as dry air pump. The air pumps may be of reciprocating type or rotary type.

EDWARD'S AIR PUMP:

It is a wet air pump of the reciprocating type. The Edward’s air pump consists of delivery head valves as shown in figure. These valves are placed in the cover which is the top of the barrel lever. The reciprocating piston of the pump is flat on its upper surface and conical at the bottom as shown. The pump lever has a ring of ports around its lower end for the whole circumference this communicates with condenser.

When piston is at the top of the barrel, the condensate and air from the condenser are collected in the conical portion. In lower part of the barrel, through the ports on the downward stroke of the piston, the vacuum is produced above it since the head valves are closed and sealed by water. The piston uncovers the ports. When it moves downwards, the mixture of condensate, vapour and air rushes into the space above the piston. This mixture is compressed, when the piston goes to the top and raises the pressure slightly above the atmospheric pressure. The head valves are now open, which allow the mixture to pass on the weir to the hot well, which is at atmospheric pressure. A relief valve is placed in the base of the cylinder to release the pressure.

RESULT:

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TWO – PASS CROSS FLOW SURFACE CONDENSOR

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EDWARD’S AIR PUMP

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Expt No : Date : EXPERIMENTAL CENTRAL AIR CONDITIONING PLANT

Aim:

1. To study the various parts and their purposes in the plant. 2. To conduct the Performance Test on the Air-conditioning system

Description: This plant consists of three circuits. 1. Cooling water circuit. 2. Refrigerent circuit. 3. Air circuit. Cooling Water Circuit:

The water from the bottom tank of the cooling tower is pumped to the condenser by means of condenser pump. It removes the heat from the refrigerant and gets heated and then goes to the top of the cooling tower and the water is sprayed from the top with help of sprayers. The heated water gets cooled and collected at the bottom tank. The cycle is repeated. Refrigerant Circuit:

The R-22 vapour is compressed in the compressor and then sent to the condenser where it gets cooled and the liquid R-22 goes to the cooling coil through a thermo static expansion valve (Th. N). The liquid R 22 removes the heat from the air to be conditioned and the R-22 vapour to the compressor for the next cycle of operation. Air circuit:

The air from the A/C room and from the atmosphere is sucked and passes through a pre heater and then through an Air Filter by the vacuum created by the blower . There is a damper to regulate the air flow drawn into the blower. On its way, the conditioned air is humidified with the help of a humidifying sprayer . The humidifying sprayer sprays water which is pumped by means of humidifying pump . The pump draws water from the sump. The water is collected at the bottom in a tray after spraying and the collected water is sent to the sump.

The conditioned air is circulated through duct by blower and passes through a reheater , enters the room to be conditioned. The duct through which the conditioned air flows is lagged by thermocole to prevent heat transfer from the surroundings.

32

The various controls employed in the plant: Dual pressure control, High & Low pressure cut out:

Low pressure cut out stops the compressor when the pressure falls below 0.3445 bar and there by allowing non-condensable gas to enter the system and also prevents oil from carried away to the coil. The high pressure control is set to 20 bar and stops the compressor when the head pressure reaches 20 bar . Humidistat:

Humidistat is set for 55% RH and this controls the humidity. This controls puts the humidity pump or heater in the room with reference to the meeting on the humidistat. Thermostat :

This controls the room temp. in the A.C. room around 25 0C When the temp falls below this point this de-energise on the solenoid coil and the supply of refrigerant to the coil is out. The compressor pumps down and this low pressure cut out trips the compressor. Heating thermostat:

The heating thermostat switches the pre-heater on during winter when the room temp is below 25 0C This setting can be altered as per our requirements. Compressor details: 1. Specification: Number of Cylinders : 2 Displacement / Revolution : 245.5 cm3 Oil Capacity : 2 litres Service Valve : Brass Weld-in Line Suction Valve : 1 1/8 " Discharge Valve : 7 / 8 " Number of Belts : 2 Belt Section : B – Section Maximum Motor HP : 7.5 Lubrication System : Splash Type Fly Wheel Diameter : 210 mm Total Height : 382 mm

Total Length (With flywheel) : 350 mm Total Width : 335 mm Total Weight (Without flywheel): 49.5 Kg

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Total Weight (With flywheel): 53.0 Kg 2. Capacity 3.5 Tonnes for SST( Suction Saturation Temperature) 4.4 ºC, Condensing Temperature at 48.8 ºC and Motor RPM 1200. Refrigerant used: R-22 Monochlorodifluoromethane ( CHClF2)

Suction temp. Capacity

4.4 º C 10.5 kJ/sec

Condenser Details: 1. Specifications: Type : Shell & Tube Water Cooled Condenser Diameter of Condenser: : 15 cm Length of Condenser : 90 cm Number of tubes : 24 2. Standard Ratings: 1) Water quantity of 45 litres/min. 2) Water entering temp. 28 ºC 3) Water leaving temp. 33 ºC 4) Condensing temp. 48.8 ºC

34

EXPERIMENTAL AIR CONDITIONING PLANT OPERATING INSTRUCTIONS Precautions:

1. Check whether the cooling tower basin is with water.

2. Check up whether there is water in the sump of the humidification pump. The temperature of humidification water should be around 30ºC

3. Check up whether refrigerant service valves in the compressor are open (This will be the normal condition)

4. Open the liquid outlet valve of the condenser fully (This will be normal case)

5. Check up for electrical supply in three phases.

6. Check the belt tension in the motor - compressor and motor - blower

7. Check the settings in the automatic controls.[Relative humidity in humidistat and dry bulb temperature in cooling thermostat]

FOR SUMMER OPERATION Starting:

Follow this order given below Switch on the Power supply. Switch on the condenser cooling water pumpset and check for the water flow

through all the nozzles in the cooling tower. Start the blower-motor [Note that there are-two main switches] Switch on the solenoid valve switch and High and Low pressure compressor cut-out

switch. Switch on the humidification pumpset and reheater and leave it for automatic

selective operation. Switch on Immersion heater if sump water is very low i.e. below 25º C. Switch on the preheater for operation only during winter season for winter air

conditioning.

Stoping: Switch off the reheater, humidification pump and immersion heater. Switch off the Solenoid valve. Wait for five minutes and switch off the condenser pump Switch off the blower Switch off the Power supply.

35

FOR WINTER OPERATION

Starting: 1. Pump down the system and close the liquid valve, suction and discharge service

valves. 2. Start the blower. 3. Start on the humidification pump. 4. Switch on the preheater and reheater and allow it for automatic operation.

Stopping:

1. Switch off the heater switches and humidification pump 2. Switch off the blower. 3. Switch off the Power supply.

PUMPING DOWN THE SYSTEM

If the plant is to be kept for long time pumping down is to to be done.

o Close the liquid valve completely. o Run the plant till low pressure cut-out stops the compressor. o Close the discharge service valve first and then suction service valve in the

compressor.

Re-setting:

1) Open the compressor discharge service valve completely 2) Open the liquid line valve completely 3) Suction valve to be opened half-turn. 4) Start the plant following the systematic starting procedure. 5) Gradually the suction valve is to be opened completely.

DEFINITION:

Air-conditioning is the simultaneous control of temperature, Relative Humitity, Purity and motion of air.

TEMPERATURE OF AIR:

In air conditioning, the control of temperature means the maintenance of any desired temperature within an enclosed space even though the temperature of the outside air is above or below the desired room temperature. This is accomplished either by the addition or removal of heat from the enclosed space as and when demanded. It may be noted that a human being feels comfortable when the air is at 21°C with 56% relative humidity.

36

HUMIDITY OF AIR:

The control of humidity of air means the increasing or decreasing of moisture contents of air during summer or winter respectively in order to produce comfortable and healthy conditions. The control of humidity is not only necessary for human comfort but it also increases the efficiency of workers. In general, for summer air conditioning, the relative humidity should no be less than 60% whereas for winter air conditioning it should not be more than 40%. PURITY OF AIR:

It is an important factor for the comfort of a human body. It has been noticed that people do not feel comfortable when breathing contaminated air, even if it is within acceptable temperature and humidity ranges. It is thus obvious that proper filtration, cleaning and purification of air is essential to keep it free from dust and other impurities. MOTION OF AIR:

The motiion or circulatiion of air is another important factor which should be controlled, in order to keep constant temperature throughout the conditioned space. It is, therefore, necessary that there should be equi-distribution of air throughout the space to be air conditioned. Classification of Air Conditioning systems The air conditioning systems may be broadly classified as follows:

1. According to the purpose:

(a) Comfort air conditioning system, and (b) Industrial air conditioning system

2. According to season of the year

(a) Winter air conditioning system, (b) Summer air conditioning system, and (c) Year-round air conditioning system.

3. According to the arrangement of equipment

(a) Unitary air conditioning system, (b) Split air conditioning systme (c) Central air conditioning system

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a) UNITARY AIR CONDITIONING SYSTEM Unitary systems are tailor-made, self-contained air conditioning and refrigeration units for HVAC [Heating,Ventilating and Air conditioning] purpose. They can be classified as

(i) Room Air Conditioner (or Window Air Conditioner) (ii) Package Air conditioning system

(i) Room Air Conditioner: Room air conditioners are available in capacities of 0.5 to 3 tons . These units are

fitted with flush window sills, projecting out of the room supported on brackets. The cost of such air conditioners for large premises is 150% to 200% of central type of air conditioning equipment for equal effect, but room air conditioners, have advantage of better flexibility in meeting the partial loads and maintenance. These require very few structural modifications or provisions and no ducting is required. One ton of air-conditioner is able to look after 18.5 m2 of area, with ceiling height of 3 m.

Room air conditioner consists of a hermetically sealed compressor driven by suction cooled motor and direct expansion evaporator over which hot air from outside is allowed to flow by suction created by centrifugal blower. The evaporator is in form of copper tubing with corrugated aluminium fins. Condenser is a forced convection air cooled, chassis mounted type.. They are provided with easy slide or rotary type control for positive exhaust and fresh air adjustment.

Room air conditioners do not have any humidity control but fairly maintain it around 65% R.H.

(ii) Packaged airconditioning system (Indoor application):

It is defined as a self-contained unit primarily for floor mounting purposed, designed to provide free delivery of conditioned air to and enclosed space. It includes a prime source of refrigeration for cooling and dehumidification and means for circulation and cleaning of air, with or without external air distribution ducting. It may also include means for heating, humidifying or ventilating air. The condenser may be water cooled or air cooled.

These are custom-made, total air conditioning units for medium size areas like offices, show rooms, restaurants, hotels, beauty-parlours, hospital wings, electronic data procesing (Computer) rooms and multi-storeyed houses. They can be with in-built condensers-air or water cooled type or may have remote air cooled condenser also.

These units utilize semi-sealed compressors upto 7.5 tons and open type beyond it. Both condensers and evaporators are open coil type with 3 rows and copper tubes with aluminium fins.

38

They don't have any precise humidity control normally but can Split Air-Conditioning System: The Air conditioning System is split into two sections, called the Indoor Unit and the Outdoor Unit. The units are connected by a small diameter copper piping, which can be concealed within the wall, below the floor or above the false ceiling. THE OUTDOOR UNIT

The Outdoor Unit housing the compressor, which is heart of the Air-conditioning System can be kept upto 30 feet away from the cooling area. This can be kept in your balcony, bathroom, garden, terrace or anywhere else to suit your convenience. Since the compressor and the condenser are kept outside, the noise level in the cooling area is reduced appreciably. THE INDOOR UNIT

The Indoor Unit is a sleek model, comprising of the cooling coil and a fan, whose only function is to regulate the uniform cool air distribution inside the air-conditioned area. It has a washable filter which can be taken out and cleaned easily. ADVANTAGES OF THE SPLIT SYSTEM

1) No window or wall opening required. 2) Makes no noise, while giving you comfort and convenience. 3) As convenient as central air-conditioning and as flecible as room air conditioners

CAPACITY:

The split Air conditioning systems are available in three cooling capacities of 1, 1.5 and 2 Tons of Refrigeration. CENTRAL STATION AIR-CONDITIONING SYSTEM:

In a central station air-conditioning system, all the components of the system are grouped together in one central room and conditioned air is distributed from the central room to the required places through extensive duct work. The central air- conditioning system is generally used for the load above 25 tons of refrigeration and 2500 m3/min. of conditioned air. The unitary system can be more economically used for low capacity (below 25 tons) units. The central plants require the following components and all the components are assembled on the site.

1) Cooling and Dehumidifying coils. 2) Heating coils. 3) Blower with motor. 4) Spray for cooling, dehumidifying or washing. 5) Air-cleaning equipments 6) Control Device

The central system serves different rooms through extensive duct work with individual

control. The system may use one of the following methods to supply the conditioned air.

39

(a) Air is conditioned in the central conditioned room and is supplied to the required rooms with controlled air discharge in each room.

(b) The water is chilled in the central conditioned room and is supplied to the required rooms with individual flow control.

(c) Individual evaporators in each room with thermostatic flow control or direct expansion system.

Advantages: The capital cost and running cost are less per unit of refrigeration. It can be located away from the air-conditioned places which is useful and less costly. Noise and vibration troubles are less to the people leaving in air-conditioned places

as the air conditioning plant is far away from the air conditioned places. Better accessibility for maintenance.

The Central Air Conditioning System works on vapour compression cycle. The p-h

and T-s diagram of a vapour compression cycle is given below. T-s Diagram: p- h Diagram: 2 T E 3 2a M P (T) 4 1 ENTROPY ENTHALPY

Process 1 to 2 ----------- Compression Process 2 to 3 ----------- Condensation Process 3 to 4 ----------- Expansion Process 4 to 1 ----------- Evaporation

1 1

2 3

4

PRESSU

RE

40

EXPERIMENTAL AIR CONDITIONING PLANT.

Observations: 1. Dry Bulb and Wet Bulb temperatures before the cooling coil - S1 2. Dry Bulb and Wet Bulb temperatures after the cooling coil- S2 3. Area of outlet grill in Airconditioned room - A1= [0.91 x 0.15 m2 ] 4. Velocity of air using anemometer at A1 = V1 = m/sec 5. Quantity of water circulated through the condensor – Q= lit/min 6. Temperature of cooling water at inlet and outlet of condenser t1 º C and t2 º C respectively. 7. Dry Bulb & Wet Bulb temperature of air entering the Air-Conditioned room - S3 8. Dry Bulb & Wet Bulb temperatture of air in Air-conditioned room - S4 9. Ambient air Dry Bulb & Wet Bulb temperatures - S5 10.Time for 10 revolutions of Compressor Energy Meter reading - Meter constant -

41

CALCULATIONS: From Psychrometric chart, 1. Enthalpy of air before cooling coil corr. to S1 - A kJ/kg Enthalpy of air after cooling coil corr. to S2 - B KJ/kg Mass of Air flow through coil - (Ma) = Volume of Air (Va) in kg/sec

------------------------------------------ Sp. Volume (va)

Volume of air(Va) = Average Velocity of air at outlet grill × Area of grill ----m3/sec Sp. volume from Psychrometric chart corr. to S3 --- m3/kg Capacity of the plant (C) = Ma [ A - B ] ------------------------ Tons of refrigeration. 3.5 2. Net Refrigerating effect = Ma [ A - B ] KJ/sec

3. Input to the compressor = kW

ttConsMeter m −−−−×

× ηtan

360010

Assume( η m) Motor efficiency = 0.9. t = time taken for 10 revolutions in seconds. 4.Actual C.O.P. of Refrigerating Plant = Net Refrigerating effect in kW (or) kJ / sec --------------------------------- Act. work of compression in kW 5.Actual heat removed by condenser = Q x Cpw x [ t2 - t1] kJ/min = Refrigerating effect plus actual work of compressor minus losses from the compressor

42

43

Expt No : Date :

REFRIGERATION TRAINER (With Fault Simulator)

Aim: To study the various parts of vapour compression cycle refrigeration trainer and conduct a performance analysis on the same. Description: Vapour compression cycle is widely used refrigeration cycle. The main object of the trainer is to demonstrate refrigeration system with basic components and necessary controls. The practical working is demonstrated in the system and considerable amount of the theoretical analysis and performance can be studied. The trainer consists of components of a refrigeration system viz., Hermetically sealed compressor, evaporator, condenser, capillary tube. The condenser is air- cooled type for which a condenser fan and motor has been provided Evaporator is shell and coil type which is housed in a thermally insulated calorimeter. Calorimeter is provided with an electric heater, which can be used for heating the water initially to a desired temperature. In addition to capillary tube a thermostatic expansion valve is also provided. We have to select either a capillary tube or thermostatic expansion valve at a time using a toggle. A temperature indicator with Six point selector switch has been provided to get the various temperatures of R–134a viz., before & after compressor & after expansion and water temperature. Special gauges have been provided for indicating R–134a pressures at above-mentioned points except for flow meter water. An energy meter has been provided that indicates the energy consumption of compressor. An additional energy meter has been provided to indicate the energy consumption of water heater. The students are advised to find out the saturation temperatures of R–134a after knowing the pressures at various points and based on the saturation temperatures study the working of refrigeration considering the cycle based on

a) Reversed Carnot cycle b) Simple vapor compression cycle

The interested students can also study the saturation temperature against the

actual temperatures obtained during the experimentation and thus study the actual cycle

of refrigeration system

44

Specifications

1. COMPRESSOR: Hermetically sealed compressor 2. Air cooled condenser 3. Expansion valve

a) Capillary tube b) Thermostatic Expansion valve

4. Evaporator 5. Rotameter : For liquid refrigerant flow rate 6. Refrigerant : R–134a 7. Energy meters for power measurement of compressor & the fans and heater 8. Pressure gauges – 4 Nos. (Two for H.P & Two for L.P) 9. Temperature Indicator 10. Solenoid valves 11. H.P/L.P cut out 12. Ammeter 13. Voltmeter 14. Thermostat

FUNCTION AND SELECTION OF SYSTEM COMPONENTS

The construction and working of the different refrigeration components are explained below 1. Compressor

Compressor is the most important component of the system. The Compressor raises the pressure of the incoming vapor from the evaporator to a higher pressure, according to the requirement. Different types of Compressors are

a) Reciprocating Compressor b) Rotary Compressor c) Screw Compressor d) Centrifugal Compressor

The selection of the type of compressor depends upon the usage. Usually domestic refrigerators are installed with reciprocating compressors. 2. Condensers The function of a condenser is to remove heat from the superheated high-pressure refrigerant vapor and to condense the vapor into a sub-cooled high-pressure refrigerant liquid. This is accomplished by passing a cooling medium which picks-up heat from the refrigerant flowing through the condenser. The cooling medium is generally either air or water.

45

Applications Condenser type Condensing temp Domestic refrigerator

(Low temp) Static cooled Highest

Commercial / Window A/c Fan cooled Medium

Large systems ≥ 5 ton Water cooled Least

However, the actual condensing temperature depends on

1. Heat transfer area 2. Heat transfer coefficient 3. Quantity of cooling medium flowing through it. 4. Temperature of the cooling medium

3. Evaporators The function of Evaporator is to remove heat from water and to maintain it at any desired temperature. Various types of construction of the Evaporator used in Refrigeration systems include.

a. Finned Tube Evaporator Coil, blowing air on it b. Bare Tube soldered/ clamped to the tank c. Bare Tube dipped in the liquid to be cooled d. Tube in tube type e. Shell and coil type

The choice of particular construction depends on the type of appliance. However, in every case the heat capacity depends on three factors viz. Temperature difference between the load and the refrigerant, heat transfer co-efficient and area of heat transfer. A Vapor Compression Refrigeration system is usually so operated that the temperature of refrigerant leaving the Evaporator is almost equal to the refrigerant entering to compressor. In other words almost the entire tube area is utilized for evaporation of the refrigerant. 4. Expansion Devices An expansion device is a link between condenser and evaporator. As the high-pressure sub cooled refrigerant liquid from the condenser passes through the expansion device its pressure and temperature are reduced and the refrigerant mostly will be in liquid stage. The desired operating pressures of the system determine the pressure drop across the expansion device. Once this is fixed, the size of expansion device has to be so adjusted that it will allow the required refrigerant mass flow (determined by compressor capacity) at the required pressure drop.

46

Expansion devices are of many types and are selected as per the requirement.

Condition Types of Expansion valve

Constant evaporator pressure Automatic

High variable in cooling load Thermostatic Hermetic compressors almost invariably are used with capillary tubes though a few of them might also be used with Thermostatic Expansion Valves

A. Capillary Tube: Capillary Tube is the simplest and cheapest form of expansion device. It does not include any moving part hence no maintenance is required. Capillary tube is supposed to be a single point operation device in the sense that the best control is achieved only at a given set of operating parameters For the selection of capillary many theoretical methods have been developed but these methods are highly complicated and require computations. So, even today the capillary selection is still an art and is left to the human judgment and repeated trials. One can select the bore of the capillary tube and can conduct the trials by cut & try methods and arrive at the suitable capillary length. Experience shows that a large bore and large length Capillary gives a more stable operation under varying ambient temperatures. It should be preferred rather than a small bore, small length Capillary

i) More restriction (lower bore and /or higher length) makes liquid to back-up in the condenser increasing the discharge pressure and decreasing the backpressure. If one is charging the system by observing backpressure. It will be overcharged further increasing head pressure. This will also increase pressure equalization time and restarting trouble can be expected. ii) Less restriction than desired (larger bore and/or lower length) will increase the backpressure and decrease the discharge pressure, which is in desirable .Under varying loads the Capillary tube does not function satisfactorily. For example, at lower loads than designed value Capillary tube may overfeed the evaporator causing liquid to return to compressor. Under higher loads than designed the Capillary tube starves the evaporator, causing excessive return gas superheat. Hence for large variation in cooling loads, it is not suitable.

B. Thermostatic Expansion valve:

Thermostatic Expansion valve controls the mass flow rate of Refrigerant by sensing evaporator outlet temperature. Thus the valve is sensitive to the cooling load. If the load is more, the degrees of superheat increases. To maintain the degree superheat to preset level more liquid is fed to the evaporator. When the load is low, valve closes and less liquid quantity is fed.

Selection of thermostatic Expansion valves is done on the basis of refrigerant used & capacity

47

5. H.P. / L.P Cut Out: A high pressure cut out often-called pressure-limiting device is a safety device, which stops the compressor before head pressure goes to excessively high values. The cut out is connected to high-pressure side of the system. It opens the circuit on rising pressure and closes on dropping pressure. Some H.P cut outs have inter locks which when the circuit once opens, must be manually reset to close the circuit. The L.P cutout does the same function as the H.P cutout. It is connected to the low side of the system and opens the circuit when the low side pressure decreases the pressure value. 6. Thermostat: In any refrigerant plant, a particular temperature is required to be maintained to perform a particular job. A common method of controlling the temperature is starting and stopping of the compressor, but the use of simple temperature control is known as “Thermostat”. The refrigerant or a volatile fluid is in the control bulb. Vapor evaporated from this fluid exerts its vapour pressure in the flexible metallic bellows. Bellows movement is opposed by a spring. An increase in temperature of the liquid in the bulb increases the pressure in the bellows and causes the movement against the spring. The movement trips a toggle switch, which closes an electric contact to complete an electric circuit. A drop in temperature will open the contact

7. Liquid line drier filter: Liquid line drier filter is provided to absorb and retain residual moisture in the system. It also filters and retains foreign particles such as copper burr, dirt, dust etc. this protects the expansion device from getting blocked due to ice(moisture) or other particles. It also protects the compressor from damage due to metal burr of dust/dirt etc. 8. Suction line accumulator: It prevents liquid refrigerant to entering the compressor under low load conditions. T-S Diagram: P-H Diagram: 2 T P 3 2a 2 E 3 2a R M E P S (T) (P ) 4 1 4 1 ENTROPY ENTHALPY(H)

48

A vapour compression cycle with dry saturated vapor before compression and super heated vapour after compression is shown on T-s and p-H diagram in fig. 1. Compression Process: The vapour refrigerant at low pressure P1 and temperature T is compressed isentropic ally to pressure of P2 and temperature T2. the vertical line 1-2 in T-s diagram and the line 1-2 on pH diagram represents the compression process 2. Condensation Process: The high pressure and temperature vapour refrigerant from the compressor is passed through a condenser. When it is completely condenses at constant pressure P2 and temperature T2. In this cycle the cooling of superheated vapour will take place in two stages. Firstly it will be condensed to dry saturated stage at constant pressure (shown by 2-2 A) and secondly it will be condensed at constant temperature (as shown by 2a-3)

3. Expansion Process: The liquid refrigerant at pressure P3 =P2 and temp T3 = T2a is expanded by throttling process through the expansion valve to a low pressure P4=P1 and Temperature T4 =T1 as shown by the curve on T-s diagram and by the vertical line 3-4 on p-H diagram 4.Evaporation Process: The liquid vapour mixture of the refrigerant at pressure P4 =P1 and temperature T4 =T1 is evaporated and changed into vapour refrigerant at constant pressure and temperature as shown by the horizontal line 4-1 on T-s and p-H diagrams. During evaporation the liquid vapour refrigerant absorbs its latent heat of vaporization from the medium (air, water or brine), which is to be cooled. The heat, which is absorbed by the refrigerant, is called the Refrigerating Effect. The process of vaporization continues up to point 1, which is the starting point and thus the cycle, is completed. Precaution: (Very Important) See whether all valves in the running circuit are opened (normally this is in open position) Procedure: 1 Switch ON the mains. 2 Switch ON the fan motors and then compressor motor 3 Allow the plant to run to reach steady state conditions. Take reading for every 10

minutes to know the steady state. 4. Observe the readings in compressor motor energy meter. Refrigerant flow

meter, Pressure Gauges & Thermometers and record it in a tabular form.

5. Switch OFF the plant after experiment is over by switching OFF the compressor motor first. Allow the fan motors to run for 10 minutes and then switch OFF.

6. Draw a flow diagram of the plant indicating the names of different parts

49

Observation Table: Mass of water = 40 Kg ( OR AS MEASURED )

Compressor Energy Meter Constant = 600 Rev/Kw-hr

Time

Temperature in °C Pressures in PSIG Refrigerant

Flow Rate in lit/hr

Time for 10 revolutions of compressor Energy Meter

“t” in sec T1 T2 T3 T4 T5 P1 P2 P3 P4

CALCULATION:

1 Find refrigerating effect 2 Find Theoretical & Experimental C.O.P

Specimen Calculation: Pressure Gauge Readings: P1=Pressure of the refrigerant before Compression P2=Pressure of the refrigerant after Compression & before Condenser P3=Pressure of the refrigerant before the expansion P4=Pressure of the refrigerant after expansion

Temperature Indicator Reading: T1= Temperature of refrigerant before compression T2= Temperature of refrigerant after compression T3= Temperature of refrigerant before Evaporation T4= Temperature of refrigerant after Evaporation I. To find C.O.P [ Carnot ]

LH

Lcarnot TT

TPOC−

=...

50

Where TL = Lower temperature to be maintained in the evaporator in absolute units (K) TH = Higher temperature to be maintained in the condenser in absolute units (K) To find TL: Take the average of P1 & P4 (in bar abs.) and find the corresponding saturation temperature from P-h chart for R–134a Note: To convert Pressure in PSIG to Bar multiply by 0.07 and add 1.013 to get bar (abs) To find TH: Take the average of P2 & P3 (in bar abs) and find the corresponding saturation temperature from P-h chart for R–134a II. To find C.O.P (Theoretical) Enthalpy is to be found out from the P-h diagram

12

41...hhhh

POC ltheoretica −

−=

Where h1 = Enthalpy Corresponding to Pressure P1 and refrigerant entering temperature at T1 ˚ C

h2 = Enthalpy Corresponding to Pressure P2 and refrigerant leaving temperature at T2 ˚ C

h4 = h3 = Enthalpy Corresponding to Pressure P3 and refrigerant temperature after condensing at T3 ˚ C III. To find C.O.P (Actual)

)(

Re... )( CompressortoInputWorkdone

Timeeffectgfrigeratin

POC Actual =

tTCpmtime

effectgfrigeratinww ∆

∆=Re

Where mw = mass of water in kg Cpw = Specific heat of water = 4.186 kJ/ kg K

51

∆ T = temperature drop in the water in K ∆ t = time duration for temp. drop in seconds. Work Done = Energy consumed by the compressor motor to be found out from the Energy meter

kWXt

×

×=

360010

Where X = Energy meter constant = 600 rev/kW-hr t = Time taken in sec for 10 revolutions of Compressor energy meter reading Therefore

doneWork

tTCpm

POC wwActual

∆∆

=)(...

IV To find relative C.O.P Relative C.O.P = Actual C.O.P / Theoretical C.O.P

Result Tabulation: The results obtained are furnished in the table below.

Carnot Theoretical Actual Relative

C.O.P.

52

53

Expt. No : Date :

STUDY &VOLUMETRIC EFFICIENCY TEST ON KAESER AIR COMPRESSOR Study on Kaeser Air compressor

Introduction:- Air Compressors are used to raise the pressure of air with the minimum expenditure of energy. An air-compressor sucks the air from the atmosphere, compresses it and delivers the same under high pressure to a storage tank. Since the compression of air requires some work to be done on it, some form of prime mover must drive a compressor. The compressed air is used for many purposes such as for operating pneumatic drills, rivets, road drills, paint spraying, air motors and in starting and supercharging of I.C. Engines etc. It is also utilized in the operation of lifts, rams, pumps and a variety of other devices. In heavy vehicle automobile, compressed air is also used for power brakes.

Air Compressors are classified into: a) Reciprocating air compressors b) Rotary air compressors. Classification of Reciprocating Air Compressor:

(i) Single acting compressor, (ii) Double acting compressor, (iii) Single stage compressor, (iv) Multi stage compressor

Single acting reciprocating compressor: In single acting compressor the air is compressed in the cylinder on one side of the piston only. Double acting compressor: In double acting compressor the air is compressed on both sides of the piston. Single stage compressor: In single stage compressor, the air is compressed in a single cylinder. Multi stage compressor: In multistage compressor, the air is compressed in two or more cylinders. Multi stage compression is done to achieve high pressure ratio. In a compressor when compression ratio exceeds 5, generally multistage compression is adopted. The following arrangements are generally in practice for reciprocating compressors. No. of stages Delivery press

One up to 5 bars Two 5 to 35 bar Three 35 to 85 bar

Four above 85 bars According to pressure range the compressors are also classified as: Fans : Pressure ratio is 1 to 1.1

Blowers : Pressure ratio is 1.1 to 4.0

54

Compressors : Pressure ratio is above 4 In this experiment the compressor given for study is Kaeser air compressor, which is a

single acting, two stage, air cooled reciprocating air compressor. The specifications of the compressor is given under volumetric efficiency test.

Some Important parts and its functions Low pressure cylinder: Air is compressed from atmospheric pressure to intermediate pressure in L.P. Cylinder. High Pressure Cylinder: Air is compressed from intermediate pressure to delivery pressure in H.P Cylinder. Inter Cooler: Air is cooled in between the two compression stages at constant pressure. After Cooler: Air is cooled after the compression is over to accommodate more air in the receiver tank. Air Filter: It filters dust particles from the air. Otherwise the dust particles will adhere the inner surface of the cylinder and thereby increases the friction between the cylinder and piston. Due to this more power loss, wear and tear will be taking place. Orifice Meter: It is used to measure the actual flow of air for compression by measuring pressure difference across the orifice using manometer. Air Stabilising Tank: During suction stroke, the air from atmosphere is sent into the LP cylinder. During compression, air is sent to HP cylinder through inter cooler. The flow of air in the pipe line from atmosphere to the LP cylinder is not uniform (i.e. intermittent) due to the suction of the air taking place in the alternative strokes. To measure the flow rate of air, the flow must be uniform across the orifice. Otherwise the manometer reading will fluctuate. Hence an air stabilising tank is introduced between orifice meter and LP cylinder. This stabilises the flow of air between the air filter and stabilising tank. While connecting the pipe line and the stabilisingtank,see, that these are connected in diametrically opposite. However, air stabilising tank, is fitted only in the experimental air compressors to measure the flow rate of air. Safety Valves: It releases the air when the pressure of air exceeds the desired limit. Pressure Cut off Switch: It is a device used todisconnectthe electrical circuit, when the pressure of air in the receiver tank reaches the desired pressure. This disconnects the circuit of no volt coil in the Star-Delta Starter; thereby it switches off the motor. Prime mover and Dynamometer:The prime mover used for the compressor is a trunnion type electrical motor. This motor itself is acting as dynamometer to measure the input power of the compressor.

55

The schematic diagram of Kaeser air compressor is shown below

56

Work done on P-V diagram of compressor:

Fig.2 P-V diagram for Single stage air compressor. The P-V diagram of a single stage reciprocating air compressor with zero clearance is shown in Fig.2 The air is sucked in from the atmosphere during the suction stroke AB at pressure Pa(i.e. at atmospheric pressure). At the end of suction stroke the air is compressed polytropically during the part of its return stroke (process BC). During compression stroke the pressure and temperature of air increases and volume decreases. This happens until the pressure Pd (delivery pressure) in the cylinder is sufficient to force open the delivery valve at C after which no more compression takes place. The delivery occurs during the remainder of the return stroke CD. The work done on the air per stage is area ABCDA. In the case of air compressors, the inlet and outlet valves are operated by pressure difference only. Not by any external means.

Fig.3 P-V diagram for two stage air compressor with inter cooling.

The air is sucked in LP cylinder during the suction stroke at intake pressure Pa and Temperature Ta. After compression in the first stage from B to E it is delivered to the intercooler, at a constant pressure Pi. The air is cooled in an intercooler, at a constant pressure Pi before passing it to second stage. The process of inter cooling is represented by the line EF. The air from the intercooler is then directed to the second stage ofcompression FG to the delivery pressure Pd. Then the air delivered to the receiver tank at constant pressure Pd. This process is represented by GD in the P-V diagram. The shaded area CEFGC shows the amount of work saved due to two stage compression with intercooling per cycle.

D C

57

Volumetric efficiency test Aim: To determine the volumetric efficiency of the low pressure cylinder of Kaeser Air Compressor at NTP condition. Specifications:

Type :

Speed :

Type of cooling :

Bore

L.P. cylinder :

H.P. cylinder :

Stroke :

Maximum pressure :

Motor output :

Free air delivered :

Precautions:

1. Before starting the experiment, the air which is already compressed if any in the reservoir is released out so that initial gauge pressure in compressor reservoir is zero.

2. The initial load on the motor while starting should be avoided by opening the valves provided at the top of the L.P. and H.P. cylinders.

3. The pin is inserted on the torque arm hole to prevent jerk while starting.

Procedure:

1. The motor is started using the automatic star-delta starter by pressing the green color button.

2. The valves provided at the top of the LP and HP cylinders, water drain cock and the air outlet valves are closed after speed of the motor has increased to the rated speed. The increase in pressure of air in the receiver tank is indicated by the pressure gauge.

3. The pressure of air is maintained constant to the desired value [say 2 kgf /cm2] by adjusting the opening of the compressed air outlet valve. [by trial and error method]

4. The following observations are to be made by keeping reservoir pressure constant. [ 2 kgf /cm2]

a) Speed (N) ; b) Manometer reading (hw) (Pressure difference across orifice)

58

5. The same observations are to be made for the other reservoir pressures [4, 6, 8, 10, 12 kgf /cm2.]

6. Then the motor is switched off by pressing the red color button of the starter after opening the valves provided at the top of LP and HP cylinders. Observations: Room Temperature [Ta] :--------- oC Orifice dia. [do] :---------- mm.

Sl. No Receiver pressure (P3) Speed

N Rpm

Manometer reading(hw) in mm kgf/cm2 (gauge)

Bar (abs.)

L (left arm)

R (right arm)

L+R

Note:1 kgf /cm2 (gauge) = (1 x 0.981) + 1.013 bar[Absolute] Specimen calculations: (For gauge pressure =--------- kg/cm2)

1. Density of air (ρa)�𝑏𝑏𝑘𝑘𝐶𝐶3� = 𝑃𝑃𝑏𝑏

𝑅𝑅𝑏𝑏𝑇𝑇𝑏𝑏 = 1.013 x 105

287 ×(273+ ) =

Where Pa = Atmospheric pressure, 1.013 x 105N/m2

Ra = Universal Gas constant, 287 J/kgK

Ta = Room Temperature in Kelvin

2. Pressure head in terms of air (ha), m ρa ha = ρw hw

ℎ𝑏𝑏 = ℎ𝑒𝑒𝜌𝜌𝑒𝑒𝜌𝜌𝑏𝑏

= × 1000 =

where ρw = density of water = 1000 kg/m3

hw = head of water in m

59

3. Velocity of air through orifice, (Va), m/sec. = �2𝑘𝑘ℎ𝑏𝑏

4. Area of orifice, (m2) = (Ao) =𝜋𝜋𝑑𝑑02

4where do = dia of orifice= 18 mm = 0.018 m

5. Volume flow rate of air at inlet condition (Qa), (m3/sec) = Cd x Ao x Va

Where Cd = Coefficient of discharge of orifice = 0.6

6. Vol.of air compressed at NTP (Normal Temp. and Press.),( m3/sec.) Qa at NTP = 𝑄𝑄𝑏𝑏

273𝑇𝑇𝑏𝑏

7. Theoretical Volume of air, m3 /sec Qth = 𝜋𝜋𝐷𝐷2𝐿𝐿𝐿𝐿

4 × 60

where L = Stroke length of LP cylinder in m N = Speed in rpm D = Diameter of LP Cylinder in m 8. Volumetric efficiency of the L.P. Cylinder, % = 𝑄𝑄𝑏𝑏𝑏𝑏𝑡𝑡𝐿𝐿𝑇𝑇𝑃𝑃

𝑄𝑄𝑡𝑡ℎx100

60

Result Tabulation: Sl..No. Receiver Pressure

P3, (bar) (abs.) Qa at NTP

m3/s Qth

m3/s Vol.η %

1 2 3 4 5 6

Result:

The experiment was conducted and the volumetric efficiency of the LP Cylinder of Kaeser Air Compressor at NTP condition

was determined at various receiver pressures.

Graph A graph between receiver pressure(P3) and Volumetric efficiency(ηvol) is to be drawn .

61

Expt.No : Date:

STUDY AND VALVE TIMING ON FIELDMARSHAL 8HP ENGINE

Note : Basic procedure for valve timing on page No 6 Aim:-

To study and determine the valve timings/settings on Field marshal 8HP engine and to draw the valve timing diagram.

Requirements:-

Measuring tape A circular member attached to crank shaft A reference point


Fuel used :

Power :

Speed :

Bore :

Stroke :

Type of Cooling :

Valve mechanism :

OBSERVED DIAGRAM

62

Observation tabulation:-

Circumference of flywheel = cm.

Sl. No.

Events




1 2 3 4

IVO

IVC

EVO

EVC

SPECIMEN CALCULATIONS:

θ1 = 𝑋𝑋1𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ2 = 𝑋𝑋2 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ3 = 𝑋𝑋3 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


θ4 = 𝑋𝑋4 𝐱𝐱 𝟑𝟑𝟑𝟑𝟑𝟑


63

VALVE TIMING DIAGRAM

RESULT: The experiment was conducted and the Valve Timing Diagram for Field marshal 8HP

engine was drawn. From the valve timing diagram the following values are obtained

Crank angle for which the Inlet Valve remains open( θ1+180+ θ2) =

Crank angle for which the Exhaust valve remains open(θ3+180+ θ4) =

Angle of over lap (θ1+ θ4) =

64

Expt.No: Date:

LOAD TEST ON KIRLOSKAR AV-I(Double arm) ENGINE Aim: To conduct a load test on Kirloskar AV-I engine by running the engine at different loads at 1500 rpm and to find the economic load. Also determine the load characteristics of the engine and generator. Instruments required:

Swing field [DC] generator/motor type dynamometer, AC-DC converter with starting device [panel board], Bank of electrical resistances to apply load, Tachogenerator with speed indicator to measure the speed of the engine, Stop-watch to note the time for a definite volume of fuel consumption.

Specifications: Type :

No. of strokes per cycle :

Type of cooling :

Fuel used :

Speed :

Power :

Bore :

Stroke :

Preliminary calculations:

While conducting load test the speed is retained constant and the load is varied (viz, no load, light load, medium load & full load). Normally six equi-distributed loads are chosen in the range from no load to full load. Preliminary calculations are made to determine the net tension (T1-T2) or a tangential force (W) needed at the dynamometer to effect the desired power output (Load).

In this test setup the engine is coupled to a swing field DC shunt-wound generator/motor type dynamometer. There are provisions to measure both the electrical output of the generator and the mechanical output of the engine. When the electrical resistances are included in the output circuit, the generator and hence the engine gets loaded. The generator swings about the trunnion and force required to keep the torque arm horizontal is the measure of engine output.

65

The net tension (T1-T2) corresponding to the rated power output is calculated using the expression for brake power. Then the values of net tension for other part load outputs (0%,20%,40%,60%,80%) are calculated and tabulated in the observation table. We know that Brake power (BP) = Torque x Angular Velocity

BP =(T1 –T2) Re ×2π N 60

Where, BP = Brake Power in kilowatts

(T1 - T2) = Load or net tensions in Newton

N = Speed of the engine in rpm

Re = Torque arm length

{Torque arm length = Half of the distance between the center lines of the spring balances. This has to be

measured from the dynamometer spring balances}

Hence Re=

The equation to find BP is: BP in kW = 2 πRe N(T1−T2)

60 x 1000

Hence (T1- T2) = B.P x 60 x 1000

2 π Re Nin Newton's

The value for ‘B.P’ and ‘N’ are to be taken from the specifications of the engine. The value obtained for (T1- T2) from the above equation is the full load of the engine in

Newton.

(T1- T2) = ---------------------------------------------- = in N (T1- T2) = N

(T1- T2)= (𝑇𝑇1− 𝑇𝑇2)𝐶𝐶𝐶𝐶 𝐿𝐿

9.81 in kgf

66

Precautions:- a) Ensure that the electrical main switches (one in the panel board intended for running the DC machine as a motor to find friction power and the other in the resistance load bank intended for loading the DC machine as generator during load test) are in OFF position.

b) Electrical starter has to be in OFF position. c) Speed regulator knob shall be set for minimum position.

Procedure: 1. After evaluating the loads to be applied on the engine, check the fuel level in fuel tank, flow of cooling water to the engine, level of lubricant in the sump as indicated by the dipstick and no-load on the engine as indicated by the loading device etc. The DC machine coupled to the engine is run as a generator and the applied load is varied by altering the load resistances.

2. After observing all the precautions, the engine has to be started. Starting Procedure:-

i. The decompression lever located at the rocker box is turned to the vertical upward position. [Decompression On]

ii. The starting handle is inserted on the cam shaft iii. The cam shaft is manually rotated faster in clockwise direction. iv. After the engine shaft has gained sufficient momentum, the decompression lever is

brought to the horizontal position [Decompression Off]. Then the engine gets started. 3.Allow the engine to run for 5 to 10 minutes to attain steady condition at its rated speed of 1500 rpm. 4. Now, load the engine approximately to 20 % of full-load by switching on the load mains and suitable electrical resistances. 5. The speed of the engine is to be maintained at 1500 rpm. The generator output voltage is also to be maintained at 220 V by adjusting the field rheostat. 6. The actual spring balance readings are noted after the generator torque arm to its horizontal position by adjusting the hand wheels located above the spring balance 7. Note the time for 10 cc of fuel consumption twice at this load and average the values.

Engine

Generator

Load

67

8. Ammeter reading is also to be noted for the same load. 9. In the same way, maintain the speed at rated value and note the time for 10cc of fuel consumption at 40 %, 60 %, 80 % of full load, full load and at no load. 10. After taking all the readings, the engine is switched off at no load by pulling the control rod of the fuel injection pump. Observations:-

Speed to be maintained: ________rpm

Sl. No.

%of load

Cal. Load (T1-T2)

App. load (T1-T2)

Voltmeter reading

in 𝑉𝑉𝑜𝑜𝑒𝑒𝑡𝑡𝑉𝑉

Ammeter reading

in 𝐴𝐴𝐶𝐶𝑝𝑝𝑉𝑉

Time taken for 10 cc of fuel consumption

in sec. 𝐿𝐿 𝑏𝑏𝑘𝑘𝐶𝐶 𝑏𝑏𝑘𝑘𝐶𝐶 𝐿𝐿

𝑡𝑡R1 𝑡𝑡R2 𝑡𝑡𝑏𝑏𝑎𝑎𝐶𝐶

Note: At the beginning of the experiment, the conditions of viscous friction will be more than that at steady running. Hence observation at no load if made at the beginning will result in arriving of incorrect higher fuel consumption value. In order to overcome this error observations at no load are to be made at the end of the experiment

Specimen calculations: (For ……………% of load) 1. Fuel Consumption [FC], kg/hr

= Vol. flow rate, cc/s x density of fuel, kg/cc x 3600 s/hr.

=� 10tave

� x Sp. gravity of diesel x density of water in kg/cc x 3600

FC = � 10

�x 0.835 x 1000 x 10−6 x 3600 = _____________kg/hr

68

2. Brake Power [BP], (kW) = 2 πRe N(T1−T2)

60 x 1000

𝑆𝑆𝐶𝐶𝑏𝑏𝑉𝑉𝐶𝐶𝑡𝑡𝐶𝐶𝐶𝐶𝑡𝑡𝐶𝐶 (𝑇𝑇1 − 𝑇𝑇2) 𝑉𝑉𝑏𝑏𝑒𝑒𝑎𝑎𝐶𝐶 𝐶𝐶𝐶𝐶 "N𝐶𝐶𝑒𝑒𝑡𝑡𝑜𝑜𝐶𝐶"

BP = 2 π x x 1500 ( )

60 x 1000=

3. Specific Fuel Consumption [SFC], (kg/kW-hr) = FC

BP

SFC = --------------- = …………. kg/kW-hr

4. Frictional Power [Fr. P], kW

To be obtained from the graph of BP Vs FC by extrapolation method. Frictional power is assumed to be constant at all loads.

Fr.P =

5. Indicated Power [IP], (kW) = BP+ Fr.P

IP =

69

6. Mechanical Efficiency = Brake powerIndicated power

x 100

ηMech =

7. Fuel Power [Fu.p] (or) Heat Input, (kW) = FC ,�kg

hr �xC .V,(kJkg )

3600 [C.V of Diesel 42,000(kJ

kg)]

Fu P =

8. Brake Thermal Efficiency = BPfuel power

x100

ηBth =

9. Indicated Thermal Efficiency = IPFuel power

x100

ηIth =

70

10.Brake Mean Effective Pressure [BMEP],(bar) = BPx 103 x60

105 x L x A x N ′ x n

= BP x 60

100 L A N ′ n in bar

BMEP =

11. Indicated Mean Effective Pressure [IMEP] (bar) = IPx 60100LA N ′ n

IMEP =

N’ = Number of power strokes per minute.

For 4 stroke engine N' =𝐍𝐍𝟐𝟐; For 2 stroke engine N' = N; n = Number of cylinders

A = Area of bore(m2)= 𝜋𝜋𝑑𝑑2

4(d = Dia of bore in m)= …………….m2; L = Length of stroke,m

71

12. Torque, Nm = (T1 - T2) x Re

Torque =

13. Generator power output, (kW) = Vx I1000

=

1000 kW

14. Generator efficiency, (%) = Generator power outputBrakePower of the engine

x100

ηgen = Draw the following Graphs:

1. BP Vs SFC, B.Th. efficiency,

2. BP Vs I.Th.efficiency,

Mech. efficiency, IMEP, BMEP , Torque and Generator Efficiency.

72

RESULT TABULATION

Result: The Load test on KIRLOSKAR AV I Engine was conducted at different load condition, the economic load of engine was found at ___________rpm is ________kW - and the corresponding performance characteristic curve were also drawn.

l. No.

𝐾𝐾𝑒𝑒

B.P

𝑏𝑏𝑘𝑘/ℎ𝐶𝐶

F.C

𝑏𝑏𝑘𝑘/𝑏𝑏𝑒𝑒. ℎ𝐶𝐶

SFC

𝑏𝑏𝑒𝑒

Fu.P

𝑏𝑏𝑒𝑒

I.P

%

I.Th.η

%

B.Th.η

%

Mech.η

𝑏𝑏𝑏𝑏𝐶𝐶

BMEP

𝑏𝑏𝑏𝑏𝐶𝐶

IMEP

𝐿𝐿𝐶𝐶

Torque

%

Generator Efficiency

73

Extrapolation (or) Willan’s line method: Extrapolation (or) Willan’s line method:

This is a method of determining the friction power and hence the indicated power of C.I engine. It is based on the fact that at part loads the combustion is completed within the engine cylinder. Hence at a given speed the rate of fuel consumption bears a linear relationship with power output/torque.

A plot therefore of rate of fuel consumption versus power output/torque at a particular speed will be a straight line in the light load region. This straight line is Willan’s line. The amount of negative power output/torque obtained by extrapolation of the plot at zero rate of fuel consumption represents the frictional power (power required to over come friction) of the engine at the specified speed.

The rapid increase in the slope of Willan’s line at high load denotes a reduction in combustion efficiency as more and more fuel is pumped in to the given volume of air.

Since petrol engine is throttled to maintain a high fuel/air ratio with load, combustion is not complete with in the cylinder. In this case a plot of power output versus rate fuel consumption does not yield a straight line. Hence extrapolation is difficult and not suitable for use with petrol engines.

Note: Finding friction power in this method directly depends on the flow rate of fuel consumed. It has to be noted that any fuel leak in the fuel line will result in incorrect frictional power.

BP in kW

BP Vs. FC (Extrapolation Method)

0 0.2 0.4 0.6 0.8

1 1.2 1.4 1.6 1.8

2

-1.5 -1 0 0.5 1 1.5 2 2.5 3 3.5 4 -0.5 Friction Power

74

The general shape of characteristics curve are shown – For reference

ECONOMIC LOAD CURVE

75

Expt.No : Date:

LOAD TEST ON PSG 5 HP ENGINE Aim: To conduct a load test on PSG 5 HP engine by running the engine at different loads at 610 rpm and to find the economic load. Also to determine the load characteristics of the engine. Instruments required:

Friction brake to indicate the load, Digital tachometer to measure the speed of the engine, Stop-watch to note the time for a definite volume of fuel consumption.

Specifications:

Type :


Type of cooling :

Fuel used :

Speed :

Power :

Bore :

Stroke :

Procedure: 1. After evaluating the full-load of the engine in 𝑏𝑏𝑘𝑘Rf with the help of specifications given, check the fuel level in fuel tank, flow of cooling water to the engine, level of lubricant in the sump as indicated by the dipstick, and no-load on the engine as indicated by the loading device etc., before starting the engine. 2. Start the engine by cranking and allow it to run for 5 to 10 minutes to attain steady condition at its speed of 610 rpm. Allow the cooling water for the brake drum in order to cool it while applying loads. 3. Now, load the engine to 20 % of full-load. Then check for its speed and note down the actual load on the engine. 4. Note the time for 10 cc of fuel consumption twice at this load and average the values. 5. In the same way, maintain the speed at its rated value and note the time for 10cc of fuel consumption at 40 %, 60 %, 80 % of full load, full load and at no load. After taking no load reading the engine is stopped by engaging the fuel cut off lever.

76

Preliminary calculations: The loading device attached to this Engine is Mechanical Brake drum type.

We know that ,

Brake power (BP) = Torque x Angular Velocity

BP =(T1 –T2) Re ×2π N 60

Where, BP = Brake Power in kilowatts

(T1 - T2) = Load or net tensions in Newton

N = Speed of the engine in rpm

Re = Effective radius of brake drum in meters = (R +t2 )

(Where ‘R’ is the radius of the brake drum , obtained from its circumference and ‘t’ is the thickness of the belt = 8 mm = 0.008 m) Circumference of the brake drum, 2πR = (To be obtained from Engine brake drum)

R =

Hence Re =

The equation to find BP is: BP in kW = 2 πRe N(T1−T2)

60 x 1000

Hence (T1- T2) = B.P x 60 x 1000

2 π Re N in Newton's

The value for ‘B.P’ and ‘N’ are to be taken from the specifications of the engine. The value obtained for (T1- T2) from the above equation is the full load of the engine in

Newton.

(T1- T2) = N

(T1- T2) = (𝑇𝑇1− 𝑇𝑇2)𝐶𝐶𝐶𝐶 𝐿𝐿9.81

in kgf

77

Observations:-

Speed to be maintained :__________ rpm

Sl. No

%of load

Calculated load (T1-T2)

Applied load (T1-T2)

Time taken for 10cc of fuel consumption in sec

N kgf kgf N t1 t2 tave

Note: At the beginning of the experiment, the conditions of viscous friction will be more from that at steady running. Hence observation at no load if made at the beginning will result in arriving of incorrect higher fuel consumption value. In order to overcome this error observations at no load are to be made at the end of the experiments.

Specimen Calculations: (For ……………% of load) 1. Fuel Consumption [FC], kg/hr


=� 10tave


FC = � 10

�x 0.835 x 1000 x 10−6 x 3600 = ________________ kg/hr

2. Brake Power [BP], (kW) = 2 πRe N(T1−T2)

60 x 1000

𝑆𝑆𝐶𝐶𝑏𝑏𝑉𝑉𝐶𝐶𝑡𝑡𝐶𝐶𝐶𝐶𝑡𝑡𝐶𝐶 (𝑇𝑇1 − 𝑇𝑇2) 𝑉𝑉𝑏𝑏𝑒𝑒𝑎𝑎𝐶𝐶 𝐶𝐶𝐶𝐶 "N"

𝐿𝐿 = 𝑆𝑆𝑝𝑝𝐶𝐶𝐶𝐶𝑑𝑑 𝑜𝑜𝐶𝐶 𝑡𝑡ℎ𝐶𝐶 𝐶𝐶𝐶𝐶𝑘𝑘𝐶𝐶𝐶𝐶𝐶𝐶.

BP = 2 π x x N ( )

60 x 1000 =

78

3. Specific Fuel Consumption [SFC], (kg/kW-hr) = FCBP

SFC = --------------- = …………. kg/kW-hr



Fr.P =


IP =


x 100

ηMech =


hr �xC .V,(kJkg )


kg)]

Fu P =

79


x100

ηBth =


x100

ηIth =


105 x L x A x N ′ x n

= BP x 60


BMEP =





80


IMEP =


Torque =

Draw the following Graphs:



Mech. efficiency, IMEP, BMEP and Torque .

81

RESULT TABULATION

Sl No Appl.load BP F C S F C Fu.P I P 𝜂𝜂𝐵𝐵 𝑡𝑡ℎ 𝜂𝜂𝐼𝐼 𝑡𝑡ℎ 𝜂𝜂𝐶𝐶𝐶𝐶𝐶𝐶 ℎ BMEP IMEP Torque

𝐿𝐿 𝑏𝑏𝑘𝑘 𝐾𝐾𝑘𝑘/ℎ𝐶𝐶 𝐾𝐾𝑘𝑘/𝑏𝑏𝑘𝑘 − ℎ𝐶𝐶 𝑏𝑏𝑘𝑘 𝑏𝑏𝑘𝑘 % % % 𝑏𝑏𝑏𝑏𝐶𝐶 𝑏𝑏𝑏𝑏𝐶𝐶 𝐿𝐿𝐶𝐶

1

2

3

4

5

6

Result : The Load test on PSG 5HP Engine was conducted at different load condition, the economic load of engine was found at ___________rpm is ________kW and the corresponding performance characteristic curve were also drawn.

82

Expt.No : Date:

LOAD TEST ON BATLIBOI ENGINE

Aim: To conduct a load test on BATLIBOI engine by running the engine at different loads at 1500 rpm and to find the economic load. Also determine the load characteristics of the engine. Instruments required:

Tachometer to measure the speed of the engine Stop-watch to note the time for a definite volume of fuel consumption.

Specifications: Type :


Type of cooling :

Fuel used :

Speed :

Power :

Bore :

Stroke :

Procedure: 1. After evaluating the full-load of the engine in kgf with the help of specifications given, check the fuel level in fuel tank, level of lubricant in the sump as indicated by the dipstick, and no-load on the engine as indicated by the loading device etc, before starting the engine. 2. Start the engine by cranking and allow it to run for 5 to 10 minutes to attain steady condition at its rated speed of 1500 rpm. 3. Now, load the engine to 20 % of full-load. Then check and adjust for its rated speed and note down the actual load on the engine. 4. Note the time for 10 cc of fuel consumption twice at this load and average the values.

83

5. In the same way, maintain the speed at rated value and note the time for 10cc of fuel consumption at 40 %, 60 %, 80 % of full load,full load and at no load. After taking no load reading at last the engine is stopped by engaging the fuel cut off lever. Note: At the beginning of the experiment, the conditions of viscous friction will be more from that at steady running. Hence observation at no load if made at the beginning will result in arriving of incorrect higher fuel consumption value. In order to overcome this error observations at no load are to be made at the end of the experiments. Preliminary calculations: Full-load can be estimated by using the following equation.

BPrated = 𝑘𝑘𝑋𝑋𝐿𝐿𝐶𝐶

Where, BPrated - Brake power in kW Wmax - Maximum load applied on the hydraulic dynamometer in Newton N - Speed in rpm. C - dynamometer constant [29323.3] Wmax = 𝐵𝐵𝑃𝑃×𝐶𝐶

𝐿𝐿

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Observations:- Speed to be maintained ___________rpm

Sl. No

%of load

Calculated load (T1-T2)

Applied load (T1-T2)

Time taken for 10cc of fuel consumption in sec

N kgf kgf N t1 t2 tave

1

2

3

4

5

6

Note: At the beginning of the experiment, the conditions of viscous friction will be more than that at steady running. Hence observation at no load if made at the beginning will result in arriving of incorrect higher fuel consumption value. In order to overcome this error observations at no load are to be made at the end of the experiment Specimen calculations: (For ……………% of load) 1. Fuel Consumption [FC], kg/hr


=� 10tave


FC = � 10

�x 0.835 x 1000 x 10−6 x 3600 = _____________kg/hr

85

2.Brake Power (BP) = 𝑘𝑘𝑋𝑋𝐿𝐿𝐶𝐶

3. Specific Fuel Consumption [SFC], (kg/kW-hr) = FC

BP

SFC = --------------- = …………. kg/kW-hr



Fr.P =


IP =


x 100

ηMech =

86


hr �xC .V,(kJkg )


kg)]

Fu P =


x100

ηBth =


x100

ηIth =


105 x L x A x N ′ x n

= BP x 60


BMEP =





87


IMEP =


Torque = Draw the following Graphs:



Mech. efficiency, IMEP, BMEP , Torque

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RESULT TABULATION

Sl No Appl.load BP F C S F C Fu.P I P 𝜂𝜂𝐵𝐵 𝑡𝑡ℎ 𝜂𝜂𝐼𝐼 𝑡𝑡ℎ 𝜂𝜂𝐶𝐶𝐶𝐶𝐶𝐶 ℎ BMEP IMEP Torque

𝐿𝐿 𝑏𝑏𝑘𝑘 𝐾𝐾𝑘𝑘/ℎ𝐶𝐶 𝐾𝐾𝑘𝑘/𝑏𝑏𝑘𝑘 − ℎ𝐶𝐶 𝑏𝑏𝑘𝑘 𝑏𝑏𝑘𝑘 % % % 𝑏𝑏𝑏𝑏𝐶𝐶 𝑏𝑏𝑏𝑏𝐶𝐶 𝐿𝐿𝐶𝐶

1

2

3

4

5

6

Result : The Load test on BATLIBOI Engine was conducted at different load condition, the economic load of engine was found at ___________rpm is ________kW and the corresponding performance characteristic curve were also drawn.

89

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ANNAMALAI UNIVERSITY DEPARTMENT OF MECHANICAL ENGINEERING … · 2017-09-08 · 2 ANNAMALAI...

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