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1Sixth national conference on automotive infotronics, 17th & 18th December 2010 - CHENNAI, INDIA

Cooling System Optimization of an Enclosed Air-Cooled Engine

Cooling System Optimization of an enclosed

Air-Cooled Engine

SAEINDIA 1001001

Anirudh Reddy EDepartment of Mechanical Engineering, IIT Madras, India

Om Prakash Singh, Bhavesh Kumar Sharma, M. KannanResearch & Development, TVS Motor Company, Hosur, India

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Contents

1. Background & applications

2. Theoretical model and validation

3. CAD and CFD modeling

4. Results & discussions

5. Conclusion

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Background & applications

Engine system

Scooter engine Enclosed Air-Cooling system

Fan cooling system used where natural air cooling insufficient

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Background & applications

Fan cooling system used where natural air cooling insufficient

Auto Rickshaw Enclosed Air-Cooling system

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High engine oil temperature.

High engine oil consumption.

Excessive wear of bore, piston and piston rings.

Heavy carbon deposit on piston leading to knocking.

Piston seizures.

Oil seals at various shafts getting permanently set or worn out leading

to oil leakages.

Insufficient cooling can cause:

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Heavy carbon deposits on the

piston top

Heavy carbon deposits on thecylinder head combustion chamber

Effects of engine overheating

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White carbon deposits on thepiston top

White carbon deposits on thecylinder head combustion chamber

Effects of engine overheating

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Temperature measurementswith backward curved fan

High temperature at Spark plug ~ 1700C

High engine oil temperature ~ 1300C

High fin temperature cylinder block ~ 1800C

High air temperature at fan inlet ~ 460C

High inlet air temperature ~ 650C

Ineffectivecooling system

Inlet air temperature should ideally be at atmospheric temperature.

A theoretical model was developed to quantify the the fan flow rates needed to bringdown the engine temperature to a desired level.

Temperature measuring points

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A new theoretical model developed

Lumped Parameter model with transient inlet air temperature Engine geometry parameters considered

Fin temperature = f(Engine temperature)

where K1 and K2 are:

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Validation of the theoretical model

Experiment : Steady state temperature = 1770CTheory : Steady state temperature = 1790C

110.0

120.0

130.0

140.0

150.0

160.0

170.0

180.0

190.0

0 100 200 300 400 500 600 700

Time (s)

F

inTemp(degC)

Experiment

Theory

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Parameter sensitivity analysis to bring down fin temperature to 150C

Changing A, kair

andair

is difficult, volume flow rate of the fanwas targeted to reduce engine temperature.

A 2D CFD model of the fan developed for backward and forward curvedfan

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CAD and CFD model

2D model from CAD software Pro E

2D model exported to HyperMesh

2D to 3D CAD conversion and meshing

3D to 2D conversion Star CCM+

Macro for CAD model generation in ProE No GUI

Macro for 2D to 3D conversion in HyperMesh No GUI

Macro for CFD simulation in Star CCM+ No GUI

Automation

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Movie: 2D CAD & Mesh preparation

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Boundary & flow conditions

Boundary conditions:

Inlet: Stagnation inletOutlet:pressure outlet

Blades:wall

Flow conditions:

K-epsilon realizable model

Moving reference frame model

State state

Incompressible flow

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Results & discussionsError estimation

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Backward curved fan : Pressure at 100 rpm

2D 3D

Symmetry is maintained

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Forward curved fan: Pressure at 5000 rpm

2D 3D

Symmetry is lost in 2D at higher rpm, error may increase

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Backward curved (BC)

fan: 2D & 3D comparison

Forward curved (FC) fan:

2D & 3D comparison

Error increases with rpm, error is 2 ~ 3 times higher in FC fan

Forward curved fan gives higher mass flow rates

Different parameters like no. of blades, inlet and outlet angles optimized

Prototypes of FC fan made and tested on engine

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Results and experimental measurement

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Performance curve Comparison: FC & BC fans at 5000 rpm

0

500

1000

1500

2000

2500

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

VFR (m3/s)

StaticPressure(Pa)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Power(bhp)

System Curve

FC 5000

BC 5000

FC 5000 Power

BC 5000 Power

Performance curve comparison: FC & BC fans at 5000 RPM

FC fan shows higher mass flow rates, power consumption than BC fan

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Experimental measurement using the Forward Fan

Figure shows reduction in temperature of various components when compared to BC fan

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Effect of BC and FC fan

Oil temperature Spark plug seat temperature

Significant drop in temperature is observed with FC fan

Failures on engines eliminated

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Engine failures were seen due to overheating

A theoretical model using lumped parameter model developed

The model predicts transient engine fin temperature

Centrifugal fan design is optimized to increase the flow rates

CFD simulation of 2D & 3D forward and backward curved fan for a wide range of

rpms was carried out

It is observed that as rpm increases deviation in the flow field between 2D & 3D

simulations increases

Error in mass flow rates (MFR) increases as rpm increases between 2D & 3D

simulations

Forward curved fan shows 2 to 3 times more error in MFR compared to backward

curved fan

Failure due to inefficient cooling can be avoided by proper design changes.

Conclusion

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