EFFICIENCY ENHANCEMENT OF IC ENGINE BY USING EXHAUST …€¦ · In other research paper (V.Pram...

EFFICIENCY ENHANCEMENT OF IC ENGINE BY USING EXHAUST GASES

TO PREHEAT INCOMING AIR TO ENGINE BY MOUNTING HEAT

EXCHANGER

Zeeshan Bashir, Sajid Waqar, Ahmed Wisal, M Arifeen

BSC Mechanical Engineering

University of Engineering and Technology Peshawar, Pakistan

Email: [email protected]

Supervisor: Dr. M Alam Zaib Khan, Assistant Professor UET Peshawar, PHD in IC engines from Loughborough University

ABSTRACT

Exhaust gas that results from combustion in an engine are wasted without being utilized .Energy provided to

engine is transformed into useful work in a very little margin and wasted energy is more compared to that

which produces useful work thus resulting in lower fuel economy. Thermal efficiency of IC engines usually

ranges from 15% to 35% percent which is quite inefficient. The exhaust gases that flows out of the engine have

the potential to be reused for increasing engine efficiency. This research paper is focused on recovering and

reusing exhaust gases for preheating of inlet air to engine to improve thermal efficiency. Further, this method

also helps in reducing global warming by reducing exhaust gas temperature to atmosphere after exchanging

heat with inlet air .For recovering exhaust gases, a heat exchanger has been fabricated and mounted on exhaust

manifold of an engine. Thermocouples, eddy current dynamometer, strain gauges and data acquisition unit

have been used for experimental setup.

Key words: Exhaust gas, Thermal efficiency, Thermocouples, Dynamometer.

INTRODUCTION

The purpose of this research project is to increase inlet air temperature by mounting a heat exchanger on

exhaust manifold. Air humidity has a significant impact on combustion and fuel consumption. Increased air

humidity doesn’t aid combustion thus more fuel is needed to achieve complete combustion in an IC engine.

Preheating inlet air to engine reduces moisture content thus reducing humidity .It results in ease of combustion

ensuring less fuel consumption and prevents pitting of engine components. This preheating can be done by

utilizing exhaust gases with high temperature to raise temperature of inlet air .Exhaust gases after exchanging

heat loose temperature which results in reducing global warming. The increased temperature of inlet air

ensures complete combustion and increased engine thermal efficiency.

Previous methods used for exhaust gas recovery were different from the method we used. In one research

paper (A. Rameshbabu1, K. Arunkumar , Increase Engine Efficiency by Using Inlet Air Preheating Method

through Exhaust Gas Temperature with Convective Mode of Heat Transfer) exhaust gases were extracted after

muffler and then directed towards heat exchanger .As a result of long path, exhaust gases temperature was

reduced and thus resulting in less preheating. Air was preheated only to about 10°C and which resulted in less

efficiency enhancement.

International Journal of Scientific & Engineering Research Volume 10, Issue 9, September-2019 ISSN 2229-5518

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In other research paper (V.Pram Kumar, V.Moovandhan, AIR PREHEATER IN TWO WHEELER) only part of exhaust

gases were extracted and fed to heat exchanger .As a result, less mass flow rate was available for preheating

of air, resulting in less preheating .Preheating was done to about 18 °C and efficiency was enhanced to about

1 %. In this research method, full exhaust gases have been bled for preheating and heat exchanger has been

mounted close to exhaust manifold .Benefit of this approach includes high exhaust temperature of around

220°C resulting in high preheating of inlet air. Preheating of inlet air was about 40°C which was very much

compared to previous methods we discussed resulting in efficiency enhancement to about 3.5 %.

METHODOLOGY

Exhaust gas recovery method has been used for increasing thermal efficiency of IC engine. Heat exchanger has

been designed and simulated on ANSYS software and then fabricated and mounted on exhaust manifold of an

IC engine .Exhaust gases passed through shell side and fresh inlet air to engine through tube side of heat

exchanger .Air after passing through tubes and exchanging heat with exhaust gases from shell side, resulted in

increased temperature .This preheated air when entered the engine consumed less amount of fuel which

resulted in increased thermal efficiency of engine and less fuel consumption.

Engine model used in this project was 152 CC petrol engine .It was a 4 stroke carbureted engine.

ANSYS software has been used as a design tool for a heat exchanger analysis and fabrication.

Advantages of EGR

Fuel consumption is reduced

Engine thermal efficiency is improved

Exhaust gas temperature to atmosphere is reduced there by reducing global warming

Complete combustion is ensured by reducing moisture content in air prior to combustion

Disadvantages of EGR Additional component (air preheater) installed alongside engine

Fouling in air preheater thereby causing maintenance issues

Installation issues near engine

Cost of having additional component

Compression performance of engine deteriorates by preheating but not significant due to controlled

amount of preheating ensured through ANSYS

DESIGN OF HEAT EXCHANGER

Shell and tube heat exchanger with one shell and 3 tube passes has been used. ANSYS CFD module has been used for

simulating the results of heat exchanger.

Geometry Module

Pro E software has been used for designing 3D model of heat exchanger. CAD model was transferred to ANSYS

CFD module .First setup module was opened and some changes were made in model so that it can be effective

as per requirements of CFD.


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Figure 1: 3D CAD model in PRO E

FILL command was used to make shell filled for mesh generation .If shell is not filled there will be no solution

in hollow side of shell and no heat exchange will be shown in hollow side .Similarly, fill command was used on

tube too. Then Boolean command was used to join the tubes together and named tube to be FLUID DOMAIN

and shell to be SHELL DOMAIN .Naming makes it easy to define inlet and outlet sections in SETUP module.

Mesh

In mesh module unstructured mesh was used.

Figure 2: Mesh module

High smoothing and center soft span angle was used for mesh .There were approximately 18000 nodes from

mesh that were generated. Different sections were named as hot inlet, hot outlet, cold inlet and cold outlet for

making it easy to assign right fluid properties in SETUP domain.


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Figure 3: Mesh generated on model

Setup Module Solver type was made pressure based and transient response was used. Gravity effects were included in Z

direction. In MODEL, energy equation was considered and K epsilon, realizable and scalable wall function was

used.

Fluid was used for both air and exhaust gases. Since specific heat of exhaust gases and air are not that different

and INCROPERA book of heat transfer also used that assumption in most of heat transfer numerical where

exhaust gases were used, so this assumption is valid.

In cell zoned condition, fluid zone and shell zone was defined to be fluid, which was air. In boundary condition

inlet conditions were given which were measured practically. Cold inlet condition was given with velocity of

6.5m/s and temperature of 30°C. Anemometer was used to measure velocity of air at inlet of an engine and

temperature on the exhaust by thermocouples. Similarly hot inlet conditions were given by giving hot inlet

velocity of 8.6m/s and hot outlet temperature of 220°C .These readings were taken before mounting heat

exchanger.

In solution method, Pressure was made second order and Momentum to be second order upwind.

In solution control, following relaxation factors were given

Pressure =0.3

Momentum 0.7

Turbulent kinetic energy 0.8

Hybrid initialization was used in solution initialization.

In run calculation, time step size was selected to be 1, number of time steps to be 7 and max iterations/time

step to be 20.

In run calculation about 120 iterations were made and there was no divergence detected.


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Figure 4 Run Calculations

Results Results were checked in Result command of CFD. Volume rendering was done to visualize field variables

through entire domain.

Figure 5 & 5a: Volume Rendering

Streamline Command Stream line command uses Runge Kutta method. Number of particles in stream line command used were

200.


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Figure 6: Streamlines with contour plane shown

Contour Command In this project, 150 no. of contours were used. Contours were selected on plane which was created at centre

of geometry as shown in the above figure .Temperature was selected as contour variable in order to see

temperature effects and heat exchange which has occurred at different sections. At cold outlet, temperature

came out to be 75°C and at hot outlet, temperature came out to be 130°C.

From these readings it was concluded that the designed heat exchanger can raise temperature of cold air

from 30°C to 75°C .This is how CFD showed temperature readings at different section of heat exchanger.

FABRICATION OF HEAT EXCHANGER

Heat exchanger was fabricated from local vendor. These dimensions and material are the same as the one

used in CFD analysis of heat exchanger. Dimensions of a heat exchanger are as follow

Length of tube 600 mm

Diameter of tube 35mm

Diameter of shell 220mm

Length of heat exchanger

200 mm

Tube & Shell material Mild steel Mild steel


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First long pipe of mild steel was cut according to required length .Then pipe was bend into U shape at

required dimensions and three passes were made at specified length .Material of pipe was chosen to be mild

steel .Then shell was fabricated. End of a steel sheet was welded to form a cylinder and circular plates were

inserted on each side of heat exchanger .Bent pipe was inserted in shell and required holes were made in

plates so that pipe could pass out from a heat exchanger .Then end of the pipe was welded with plates .At

end of the pipe, threaded holes were made in order to fix thermocouples at required sections.

Thermocouples were inserted at threaded holes and connected to a controller.

EXPERIMENTAL SETUP FOR ENGINE PERFORMANCE

All the necessary components that were used for calculation of engine performance are discussed below .4-

stroke air cooled engine was used.

Cooling type Air cooled engine

Displacement 153 CC

Bore 62 mm

Stroke 48.8 mm

Maximum power 14 @7500 RPM

Maximum torque 11 @7200 RPM

Compression ratio 11:1

Energy Carburator

Figure 8 Fabricated heat exchanger


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Figure 6 & 6 a: Dynamometer connection setup

Load cell S Type load was used in this project

Dynamometer Eddy current dynamometer was used to calculate torque at different RPM by giving different loading

condition from a control unit.

Dynamometer connection setup The input shaft of the dynamometer was coupled with the output shaft of the engine through a universal

joint.

Control unit The purpose of control unit is to give different loading condition at different RPM.

In this experiment, load was applied by turning the knob of dynamite. The knob is used for increasing or

decreasing the amount of current transfer to the dynamometer coils and correspondingly applying magnetic

field and load.

Figure 7: Control unit


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Data Acquisition Unit Data acquisition (DAQ) is the device used for measuring strain applied on strain gauge .This strain value was

used to measure force which was then used to measure torque exerted by an engine.

Tachometer Tachometer was used to measure RPM of engine at different loading condition .Tachometer used in this

project has a range up to 7000 RPM.

Connection of the control unit It is directly connected to the power supply and dynamometer. AC voltage is supplied to the control unit and

through circular knob, the load on engine can be varied

Experimental Setup Procedure

Engine was mounted on a table first.

Dynamometer shaft and engine shaft was coupled through a universal joint.

Connected the battery with two terminals of the engine.

Connected the control unit with the dynamite and AC (220v) supply.

Joined load cell with dynamite to measure load of an engine and also joined with data acquisition unit

to take readings.

Connected wires of tachometer with engine properly to measure the RPM of engine.

Connected wires of AFR with voltmeter to find out AFR of an engine.

Ensuring fuel will be properly supplied to an engine and there will be a calibrated scale mark on the fuel

tank, so that to measure mass flow rate of an engine.

Figure 8: Data acquisition unit


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Figure 9 : Schematic sketch of experimental setup and mounting of heat exchanger with IC engine

Figure 10: Experimental setup Figure 11: Heat exchanger mounted on exhaust manifold

Performance of Engine without Heat Exchanger First, efficiency of IC engine was measured without heat exchanger. Loading condition was given through black

box dynamite at different values for torque and fuel consumption measurement .Torque was measured when

dynamite exerted load on engine shaft which resulted in stretching of S shaped load cell attached to

dynamometer .Wiring of load cell was connected to data acquisition unit which measured the torque exerted

at given RPM and loading condition. Mass flow rate was measured at given condition by measuring time taken

by fuel to drop from one graduated scale to another .Beaker was graduated in milli liters .After measuring

torque ,mass flow rate and loading condition, these values were put in efficiency formula for calculating engine

thermal efficiency without air preheater.

Performance of Engine with Heat Exchanger For this, a heat exchanger was mounted on exhaust outlet of an engine. Exhaust pipe of an engine was bolted

with hot inlet of a heat exchanger .Thermocouples were connected at hot gas inlet, hot gas outlet, cold air inlet

and cold air outlet section of a heat exchanger .In this arrangement, air inlet path was from tube side of a heat


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exchanger which allowed it to get preheated from exhaust gases on shell side .Readings were taken with air

preheater. Same procedure was applied by giving loading condition at specific RPM. Steps followed were

Connected the shell and tube type heat exchanger at the exhaust manifold of an engine which

preheated the inlet air.

Connected the thermocouples at the inlet and outlet of a heat exchanger and noted out

temperatures.

Took readings by checking the fuel consumption versus time and at the same time took readings of

AFR.

Repeated this procedure for various values of RPM and noted different readings.

From these readings calculations were made for measuring thermal efficiency.

By comparing the values of efficiencies with and without a heat exchanger, it was concluded that the

efficiency has been increased by mounting heat exchanger.

RESULTS AND DISCUSSIONS

Following results were obtained as shown in the table below .Air inlet temperature was 30°C before mounting

a heat exchanger .After mounting a heat exchanger, thermocouple showed temperature rise of inlet air to 66°C

which was very much comparable with the results shown by ANSYS CFD.

RPM

Torque (N.m)

Fuel Consumption Before heat exchanger

Fuel consumption After heat exchanger

POWER OUTPUT (In watts)

Efficiency Before Heat Exchanger %

Efficiency after Heat Exchanger %

Time taken to Drop 5ml before hx ( In seconds)

Time taken to Drop 5ml after hx ( In seconds)

3000 7.50 20881.8 15232.59 2355 11.3% 15.35% 8.17 11.20

3300 7.69 21219.52 16110.59 2658.1 12.52% 16.30% 8.04 10.59

3700 8.21 22243 167753.1 3179.83 14.29% 18.9% 7.67 10.17

4000 8.510 22838 17958.42 3573.2 15.6% 19.81% 7.47 9.5

4400 8.911 25387 19431.09 4099.9 16.14% 20.99% 6.72 8.78

4700 9.132 27123 20431.7 4495.2 16.5% 21.8% 6.29 8.35

5000 9.414 28529 23370.6 4928.5 17.3% 21.0% 5.98 7.30

5200 9.56 31019 25015.3 5205.7 16.78% 20.8% 5.50 6.82

5500 9.71 318887 25693.5 5590.1 17.5% 21.6% 5.35 6.64

5800 9.93 34052.8 27037.2 6092.7 17.711% 22.0% 5.01 6.31

6000 10.16 35468.81 27831.1 6385.7 18.01% 22.9% 4.81 6.13

Note: hx denotes heat exchanger

Efficiency =output/input

Output = Torque * RPM

Input=mass flow rate *calorific value


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Calorific value=45.8 MJ/Kg

Above calculations are for 12 % loading conditions

Calculations for 8%, 17.5% and 25% loading conditions were also taken and their results were almost similar

Following are the results of torque and RPM calculated at different loading conditions.

Figure 11: 12.2 % loading condition Figure 12: 8 % loading condition

Figure 13: 17.5 % loading condition Figure 14: 25 % loading condition

STAT DESIGN EXPERT DATA

Following graphs are made in STAT DESIGN EXPERT software and they show a relationship between torque,

loading conditions and RPM.


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GRAPH OF LOAD, RPM AND TORQUE shown in above figures


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CONCLUSION AND FUTURE WORK

From the results, it is obvious that thermal efficiency of an IC engine has been increased to around 3.5 %

.Efficiency has been enhanced significantly because full exhaust gases have been bled from an IC engine

compared to the previous method where only part of the exhaust gases were used for preheating. Secondly

heat exchanger used in this project was bigger in dimension and was mounted directly to exhaust manifold

thus providing minimum heat loss of exhaust gases to atmosphere. In order to make this project practical for

use in vehicles, heat exchanger with smaller dimension has to be used so that it can be easily mounted and

adjusted on any vehicle for which we want to improve thermal efficiency.

Reducing heat exchanger dimensions will result in less preheating and as a result less efficiency will be

enhanced but still it will be around 1 to 1.5 % which is still good enough to reduce fuel consumption. Mounting

heat exchanger closer to exhaust manifold can increase efficiency significantly ever with heat exchanger having

smaller dimension.

In future work this heat exchanger should be designed in more compact way so that it can be mounted on

exhaust outlet of Motor cycle .Air preheater can be installed by removing silencer and mounting air preheater.

Also air preheater can be mounted on any motor car .This will need some adjustment in bonnet after which it

can be installed for better fuel mileage.


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REFERENCES

[1] B. b. A. M. a. T. Eastop, Applied Thermodynamics for Engineering Technologists.

[2] B. b. F. P. .incropera, Fundamentals of Heat and Mass Transfer.

[3] T. b. M. A. B. a. Y. A. Cengel, Thermodynamics an engineering approach.

[4] V. V.Pram Kumar1, "Air preheating in two wheelers," International Journal of Innovative Research in Science,, vol.

Vol. 4, no. Special Issue 13, p. 08, december 2015.

[5] K. A .Rameshbabu, "Increase Engine Efficiency by Using Inlet Air Preheating Method through Exhaust Gas

Temperature with Convective Mode of Heat Transfer," International Journal of Scientific Engineering and

Research (IJSER), vol. 4, no. 4, p. 5, april 2016.

[6] P. B. 1. A.-A. U. A. E. Al-Ain Technical School, "Using exhaust gas recirculation in internal combustion engine : a

review G.H Abd -Alla," EnergyConversion and Management 43 (2002) 1027–1042, no. accepted 25 April 2001, p.

16, Received 17 January2001.

[7]

[8]

J. HOLMAN, HEAT TRANSFER, Published by McGraw-Hill, 2001.

Effect of exhaust gas reciculation on performance of petrol engine by Tairu Onawale, Research & Reviews: Journal

of Engineering and Technology

[9] Exhaust Gas Recirculation in CI Engines by Edwin Jose ,International Journal for Research in Applied Science &

Engineering Technology (IJRASET)

[10] Experimental Study of Diesel Engine Using Exhaust Gas Recirculation by Savan D. Patel ,International Journal of

Science and Research (IJSR)


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