Homogeneous charge Compression Ignition (HCCI) EngineA New Trend in Automobile field

ByPallav V. BarhateRoll No. :- 71PVG’s COET

Demerits of existing I.C.Engine

Spark Ignition Engine-

1. Losses during gas exchanges

2. Poor Thermodynamic efficiency

3. Low combustion efficiency

Compression Ignition engine

1. Emission of NOx,Soot particles and PM

Carbon monoxide(CO)

Diesel Engines Contribute to

Multiple Air Pollutants

Ozone( NOx)

Particles (PM)

(NOx, SOx, ) Toxics- Diesel particles

Greenhouse Gases

- CO2, methane

To meet demand

Reduction in exhaust emission ( CO2 & NOx) To achieve EURO5 norms by 2010 Higher Thermal efficiency Energy Economy

soHOMOGENOUS CHARGE

COMPRESSION IGNITION ENGINE IS

THE EFFECTIVE WAY TO MEET

THESE REQUIREMENTS

Why HCCI Engine ?

High efficiency and ultra low emission w.r.t conventional Diesel engine.

To achieve near zero NOx and soot emission to achieve latest Euro Norms ( E5)

To reduce fuel consumption, greenhouse gas emission.

(Law of Diesel HCCI – In Germany, every one percent increase of diesel HCCI car saves 90 million liters of fuel per year. This corresponds to emission saving of some 210000 metric tones of Co2 )

Source- BOSCH news letter-GmbH- April 2008

What Is HCCI?

HCCI is a combustion process. HCCI is not an engine concept. HCCI must be incorporated in an engine concept.

HCCI is a low temperature chemically controlled (flameless) combustion process.

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

However combustion process is different. So there is neither Diffusion flame (as in a diesel engine) nor a flame front traveling through a premixed charge ( as in SI engine).

WORKING PRINCIPLE OF HCCI

Homogenous charge(mixture of air & fuel) should be mixed before combustion and compress to high enough temperature to achieve spontaneous ignition of the charge.

Thus HCCI is similar to SI in the sense that both processes use premixed charge and that of CI as both rely on autoignition for combustion initiation.

HCCI WORKING

Fuel injected through fuel injectors. Air induction through intake plenum. Air & Fuel mixed in combustion chamber. As piston moves back up(compression stroke) sufficient heat has

accumulated. This heat (no spark) spontaneously combust A/F mixture which forces

piston down for power stroke. This process is lean , low temp. ,flame-less energy released. Entire mix. burned simultaneously produces equivalent power using

much less fuel & low emissions. At exhaust stroke , exhaust valves closes early ,trapping some latent

combustion heat & preserved. Now small amount of fuel injected in chamber for pre-charging before

next stroke.

ADVANTAGES

15% increase in fuel efficiency over SI engines.

Can be operated at high compression ratios(>15).

Can be operate on gasoline , diesel fuel and most alternative fuel.

Omission of throttle losses improves efficiency.

No shock wave propagation ,so no knocking.

Cleaner combustion and lower emission.

DISADVANTAGES

High in-cylinder peak pressure.

Engine wear due to high heat release and pressure rise.

Auto-ignition is difficult to control.

Small power range, constrained at low loads,high loads.

Carbon Monoxide(CO) & Hydrocarbons(HC) emissions are higher.

CHALLENGES OF HCCI

Control over HCCI is major problem.

High peak pressure & high heat release rate.

Engine has to be stronger so heavier.

Low power ranges.

High Carbon Monoxide(CO) & Hydrocarbon(HC) emissions

CONTROL APPROACHES

Variable compression ratio (VCR)

Variable exhaust gas percentage

Variable valve actuation

Variable fuel ignition quality

Direct injection PCCI or PPCI combustion

Variable induction temp

Controlling exhaust gas emissions

Strategies to lower rate of combustion &to reduce high peak pesssure

Different ways to increase the power

PROTOTYPES

The future of HCCI looks promising specially with partial HCCI mode.

Major companies such as GM, Mercedes-Benz, Honda, and Volkswagen have invested in HCCI research.

CONCLUSION

HCCI 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.

HCCI engines will be cheaper than the presently used engines because of simplicity.

But

Control on Ignition timing is essential.

Thank you