Lab Manulal

8/13/2019 Lab Manulal

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EXPERIMENT NO : 5

CONSTANT AIR SPEED BLOWER TEST

RIG


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AIM:

To conduct test on the given blower and to determine the overall efficiency

using Forward ,Backward and Radial vanes provided.

DESCRIPTION:

The given constant air speed blower is a single stage centrifugal type. Air is

sucked from the atmosphere in the suction side and the slightly compressed air

pases through the spiral case before it comes out through the outlet.

The given blower is provided with the three interchangeable impellers namely

forward ,backward and radial vanes. The vanes are pressed out of sheet metal

and riveted to the shrouds. This volute contour helps in reducing the eddy

current loses along the path. The casing is designed such that it can be

seperated to facilitate easy interchanging of impellers.

The blower is directly coupled to a swinging field induction motor of 5 HP,

2880 rpm. The outlet of the blower is connected to a pipe line of 3 meters

length. A Venturimeter ,a flow control valve and pressure tappings are provided

along the pipe. Pitot tubes for measuring thetotal head are also provided on the

suction and delivery of the blower.

A Panel mounted on the sturdy iron stands, with switch starter for the blower

motor, A 3- phase energy meter to measure the input energy for the blower,

and manometers tomeasure the flow, static and the total head.


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EXPERIMENTAL PROCEDURE:

1. Fill mercury in the Manometer provided for Venturimeter , thelevels mustbe equal, if not remove air blocks.

2. Fill water in the manometer provided for Prandle Pitot tubes, provided onthe suction and delivery side.

3. Close the cock connected to the inner pipie of the pitot tube and leavethis column of the manometer open to the atmosphere.

4. Open the cock connecting the static pressure end of the pitot tube.5. Close the delivery control valve and start the unit .6. Note the time taken for 10 revolution of energy meter reading .

7. Note the spring balance reading connected to the torque arm of theswinging field motor.

8. Note the speed of the motor.9. Note the manometer readings.10.Repeat the experiment for different openings of the delivery valve and

for different impeller vanes.


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CALCULATIONS :

To find the blower discharge Qt =K m3

/sec.

Where K = a1*a2 /

where g = 9.81m/sec2

h = h1- h2(S1/S2 - 1)m of air column where S1and S2are the densities ofmanometric fluid and air respectively.

h1-h2are manometric readings in m of mercury column.

a1= Area of venturimeter inlet , diameter of inlet =100mm

a2= Area of venturimeter throat, diameter at throat = 60mm

To find the total head H=Hd+Hsof the blower,

Hd & Hs = h1- h2(S1/S2 - 1)m of air column where S1 and S2are densities ofmanometric fluid and air respectively.

h1- h2 are manometric readings in m of water column .

Blower Output P0= a*Q*9.81*H Watts

Where a is the density of air.

The input to the Blower Pi =3600/E *10/t Watts, Where E=energy meter

constant and t is the time taken (seconds) for 10 revolutions of energy meterdisc.

Hence the blower efficiency= P0/Pi*100 %


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In the case of the blower provided with swinging field motor the input power

may also be calculated as follows.

Input Power Pi =2NT/60 watts.

Where T is the torque = Torque arm length * spring balance reading in Kg * g

N=speed of the motor.

CONSTANT AIR SPEED BLOWER TEST RIG

Calculation:

To find the blower discharge Qt =K m3

/sec.

The values of Qt =0.091879 to 0.294155

Where K = a1*a2 /

where g = 9.81m/sec2

The value of K= 0.013417

S. No

Venturi head Delivery head Suction head Time for 2 rev

energy meter

Spring

balance Blowe

efficienh1m h2m h1m h2m h1m h2m Sec Kg %

1.2.


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EXPERIMENT NO : 6

RECIPROCATING AIR COMPRESSOR

TEST RIG


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INTRODUCTION:

The reciprocating compressor consists of a cylinder , piston ,inlet and exit

valves.

During the downward motion of the piston, the pressure inside the cylinder

drops below the atmospheric pressure and the inlet valve is opened due to the

pressure difference. The air is taken into the cylinder until the piston reaches

the bottom dead centre.

As the piston starts moving in the upwards, the inlet valve is closed and thepressure of the delivery side which is connected to the receiver (tank) . Then the

delivery valve opens and the air is delivered till the TDC is reached. At the end of

the delivery stroke a small volume of high pressure air is left in the clearance

volume starts expanding as the piston starts moving downwards and the

pressure of the air falls until it is just below the atmospheric pressure and the

air is taken into the cylinder. Thus the cycle is repeated. The suction

compression and the delivery of air takes place within two strokes on the

piston or one revolution of the crank.


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SPECIFICATIONS :

COMPRESSOR :

Low pressure cylinder High pressure cylinderBORE 79mm 63mmSTROKE 80mm 80mm

Orifice diameter = 12mm

Torque Arm Length = 300mm(Distance between motor shaft and spring balance)

Motor : 5 H.P. ,1440rpm. Three phase induction motor.

DESCRIPTION :

In a two stage compressor air is first sent into the low- pressure cylinder. After

compressing it to some desired intermediate it is inter cooled in the cooler and

then supplied to the high- pressure cylinder. The air is finally compressed to trhe

delivery pressure and discharged to the reciever in th H.P. cylinder.

An AC motor drives the two-stage compressor. The tank is mounted on a base.

The outlet of the air compressor is connected to reservoir. The pressure of the

air compressed in indicated by a pressure guage. Adjusting a valve can regulate

the airflow at the outlet of the tank. Safety valve is also provided for safety. An

air tank measures the suction with an orifice plate through a water manometer .

An energy meter records the input to the motor. Since the motor is swinging

field type the torque arm of the motor is connected to a spring balance. By


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measuring the spring balance reading the input power for the motor can be

calculated.

PROCEDURE :

The outlet valve in th receiver tank is closed. The manometer is checked for

equal water level in the limbs. The compressor is then started and the pressure

is allowed to build up inside the reciever tank. The outlet valve is opened slowly

and adjusted so that pressure is maintained constant at some valve.

Note the Pressure guage reading. Note the Speed of the motor and compressor. Note the manometer reading. Note the time taken for 15 revolutions of the energy meter disc. Note the spring balance reading. Note the compressor air inlet and outlet temperature.

GRAPHS :

Plot Graphs for, Guage Pressure vs Vol.

vs iso.

vs overall vs Input Power.


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TWO STAGE AIR COMPRESSOR TEST RIG

WITH SWINGING FIELD MOTOR

Table 2

Energy meter Constant :

Torque arm length :

Orifice diameter :

Compressor stroke :

Bore :

.No. PressureKg/cm2

Manometerh1

Manometerh2

Time for

5 rev.ofenergy

meter

Spring

balancereading

Speed

of themotor

Speed of the

compressor

Temp(T1)

T

Kg/cm2 cm cm sec Kg rpm rpm

oC

1.2.3.4.

No. Actualdischarg

e

(Va)

Theoritical

discharge(Vt)

Volumetric

Efficiency( )

Power

input Outputpower Overalleff.(0)

Iso.Work

done(Iwd)

Polytropic

work done(Pwd)

Isot

Effi

(

m3/sec m3/sec % Kw Kw % J/Kg J/Kg %

.

.

.

.


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ACTUAL DISCHARGE OF THE AIR

Va = Cd*a*a

a =/4 d2 (d=orifice dia) , ha=w/a *(h1-h2)

[w =1000Kg/m3, a = 1.16Kg/m3]Va =

THEORITICAL DISCHARGE OF AIR

Vt = LAN/60

L = stroke length =

A = Piston area = /4 (bore dia)2

=

N = Speed of the RPM

Vt=

Volumetric Efficiency = Va / Vt=

Shaft Power = 2**N*T/(60*1000)Kw =

Input Power using Energy Meter = 3600/ 180*(5/time taken)=

Output Power = a *Va *P0 *9.81 =

Overall Efficiency = Output Power/ Input Power =


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Polytrophic Work Done

Pwd = (nR/n-1)(T0-Ti)

Compression Index (n) =1/(1-Ln (T0-Ti)/ Ln(P0-Pi))

Ti= Inlet temperature of air in deg.C , To= Outlet temperature of air in deg.C

P0= Outlet Pressure in absolute unit Kg/cm2,

Pi = Inlet Pressure in absolute unit Kg/cm2

Pwd =

Isothermal work done

Iwd = R*Ti*Ln(P0-Pi))

Isothermal efficiency =( Iwd/ Pwd)*100

Isothermal efficiency =


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EXPERIMENT NO : 7

WIND TUNNEL


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AIM:

To conduct the test on a wind tunnel and to find out the pressure distribution ,

velocity distribution and different forces acting on a airfoil model.

DESCRIPTION :

A wind tunnel is an equipment used to examine the stream lines and forces that

are induced as the fluid past a fully submerged body. The wind tunnel consisting

of a square test section with transparent sidewalls, size 300*300 *1000mm long.

The bottom and sides of the test section with the window opening to enable fix

models.

A bell mouthed entry with honey comb network and screens with smooth

settling length provided before the test section. Air flow generated by a suitably

designed axial flow fan, with an A.C. motor of 5H.P. ,2800 rpm and a variable

speed drive for speed control. The approximate volume flow rate 10,000 cmh

with static pressure 50 mm of W.C. under free running condition. Sturdy angular

stand are provided for vibration free running .

A Prandtl Pitot tube is provided to measure the velocity of airflow. The aerofoil

is two- dimensional body, which is streamlined so that the separation occurs

only at the extreme range of the body. The aerofoil model conforms to NACA

0018 Axial chord 16cm and span 29cm with 12 piezometric tapping for pressure

distribution studies. The separation point is near the trailing edge and width of

the resulting wake is small so as to provide low drag.

The drag coefficient is small at low angles because of appearances of wake

behind the body and the separation of flow from the upper surface. The aerofoil

is made of seasoned teakwood to provide long lasting usage.

A suitable stand is provided with precision 2 component force transmitter to

mount the aerofoil model. A digital force indicator to measure lift force of 5-kgf

and drag force of 5-kgf is provided. The indicator is calibrated to read in grams.

A multi tube manometer is provided to measure the pressure distribution.


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PROCEDURE :

1. Mount the aerofoil model on the stand provided and keep the model inthe Wind Tunnel through the opening at the bottom. The tail edge facing

the fan. Care should be taken to ensure that the rod connecting the model

to the balance does not touch the wind tunnel wall. This should be

checked even when the wind tunnel is in operation.

2. Calibrate the strain guage balance to indicate an initial value of lift force 0and drag force 0.

3. Connect the pressure tapping to the multi tube manometer as per thetable give and note the angle of incidence of air on the model. The

incidence angle is changed by loosening the bolts and manually

positioning the aerofoil at the required incidence angle. Give pitot tube

connections.

4. Connect constant 440 V AC power supply to drive unit using suitablerating wire. Connect the A.C. motor with the drive.

5. If the direction of rotation of the fan to be changed, interchange the wirein the drive unit.

6. Ensure that the speed is in minimum position and turn on the mainswitch.

7. Operate the push button switch slowly to obtain the required test sectionvelocity

8. Note the reading on differential pressure water connected to the pitottube.

9. Note the readings on the multi tube manometer P1 to P12 and P13corresponds to the atmospheric pressure.

10.Note the angle of inclination of the manometer.11.For different angle of incidence of airfoil model and for different air flow

rate, the experiment may be repeated.


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CALCULATIONS :

Specifications:

Aerofoil = Chord length=160mm

Span =290mm

Cylinder = Diameter = 90mm

Span = 250mm

Sphere=Diameter =100mm

To determine the velocity of a pitot tube (v) =a

Where ha =w/a *(h1-h2)mtrs

Coefficient of lift (CL) = Actual lift Kg / Theoritical lift force Kg

Actual lift force measured on the digital indicater.

Theoritical lift force = a * a * V2

/2g

a = Planform area for air foil (0.16 * 0.29 sq.mtrs)

Density


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