Homogeneous Charge Compression

Ignition (HCCI) Engine

By

Akshay Kumar Thakur & Saibal Sundar Panda

Mechanical Department

National Institute of Technology, Jamshedpur

Contents1. About HCCI

2. The Need For HCCI

3. Pollution Norms

4. Experiments

5. Results

6. Main Challenges

7. Conclusions

What is HCCI ?HCCI is a low temperature chemically controlled

combustion process. HCCI can be considered as a hybrid between diesel and

Otto combustion process.In the HCCI , there is neither a Diffusion Flame ( as in the

diesel engine) nor is there a flame front travelling through the premixed charge ( as in case of a spark plug petrol engine).

Various Combustion Processes

Working Principle of HCCIHomogenous charge is drawn in to the cylinder during

suction and compress to high enough temperature to achieve spontaneous ignition of the charge.

Observing the images taken by camera( 20 pictures per CAD) following points are noteworthy

1. Combustion starts in almost whole volume of C.C two degree before TDC (CAD- 02).

2. After Combustion initiation the temperature rapidly increases and whole fuel burns simultaneously (CAD0 to CAD +03).

Images of the HCCI process on 20 FP CAD camera

Control of CombustionVariable Compression Ratio helps to adjust

the compression ratio of the engine is while it is in operation. This is done to increase fuel efficiency while under varying loads.

Exhaust Gas Recirculation(EGR) increases ignition delay , lowers ignition temperature and results in dilution of charge

It is a proven way to reduce the NOx emission , wherein 30 to 35 % reduction in Nox is achieved by 20% EGR.

Need for HCCITo bring down exhaust emissions.To achieve the EURO 5 norms.To attain higher thermal efficiency.To reduce the consumption of fuels.It has the potential for being less costly than the

conventional SI and CIDI engines, as they are likely to use low pressure fuel injection technology.

The emission control systems would be less cheaper as HCCI engines are less dependent on precious scarce materials.

Emission Legislation

Experimental Results

Challenges Ahead Effective control system for ignition timing.To achieve practically Variable Compression Ratio.Combustion Rate control for high load operation.Emission control at high load operations.Fuel Delivery System for various kinds of fuels to

practically achieve fuel flexibility.

ConclusionsHCCI engines are more efficient than SI and CI engines.Lower emission of PM and NOx to meet future norms

(Euro 5 Norms ).It has fuel flexibility.The mentioned challenges must be overcome in order to

make the HCCI a practically usable technology.