CAREER POINT UNIVERSITYKOTA

Assignment- 3Subject- I.C. ENGINE [MEL-345]

COMPARATIVE STUDY OF C. I. ENGINE

SUBMITTED TO:-Mr. Amrdeep sir

(Mechanical Dept.)SUBMITTED BY:-

KRISHNA MURARIUID-K10619 (3 rd year )

B.TECH MECH.

Table of content Introduction CI Engines Formation of CO in Emissions Control Historical outline of HCCI combustion The advantages of HCCI engines Working principle of the HCCI engine

technology Current application of HCCI y Experimental studies Conclusion reference

Introduction During the 1940s air pollution as a problem was

first recognized in the Los Angeles basin. Two causes of this were the large population

density and the local weather conditions. Smoke and other pollutants combined with fog to

form smog. In 1966 HC and CO emission limits were

introduced. By making more fuel efficient engines and with

the use of exhaust after treatment, emissions per vehicle of HC, CO, and NOx were reduced by about 95% during the 1970s and 1980s.

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Anatomy of Catalytic Converter for CI Engines•All catalytic converters are built in a honeycomb or pellet geometry to expose the exhaust gases to a large surface made of one or more noble metals: platinum, palladium and rhodium.•Rhodium used to remove N and platinum used to remove HC and CO.

CI Engines Formation of CO in The mean air-fuel mixture present in the combustion chamber

per cycle is far leaner in the diesel engine than in the SI engine. Due to a lack of homogeneity of the mixture built up by

stratification, however, extremely “rich” local zones are exist. This produces high CO concentrations that are reduced to a

greater or lesser extent by post-oxidation. When the excess-air ratio increases, dropping temperatures

cause the post-oxidation rate to be reduced. The reactions “freeze up”. However, the final CO concentrations of diesel engines

therefore are far lower than in SI engines. The basic principles of CO formation, however, are the same as

in SI engine.

Emissions Control Three basic methods used to control engine

emissions: 1)Engineering of combustion process -

advances in fuel injectors, oxygen sensors, and on-board computers.

2) Optimizing the choice of operating parameters -two Nox control measures that have been used in automobile engines are spark retard and EGR.

3) After treatment devices in the exhaust system -catalytic converter.

Historical outline of HCCI combustion HCCI combustion was discovered as an alternative

way for two stroke engines. A first study on such type of combustion process was made by in 1979 [1]. This completely new type of combustion adopted to the piston engines has been called Active-Thermo Atmosphere Combustion as a promising alternative for existing spark and diesel engines. The drawbacks of two stroke engines are a high residuals emissions at low and partially loads, and the tendency to run on (knock effect) when the engine is stopped.

The advantages of HCCI engines

Apart from that the up to date spark ignition engines fitted with a three way catalyst can be regarded as a very clean engines, problem appears during part load conditions. Low efficiency at partial load results from pumping losses. It follows from specific SI engine load control. SI engine is controlled by changing air flow rate. The air flow through venturi throat is throttled by reducing the flow area. Suffering the consequence of throttling, pumping losses increase during the gas exchange and considerable amount of work produced by the engine must be used for scavenging.

Working principle of the HCCI engine

The HCCI concept, which is proposed as an ultimate method of lean burn, is completely different from other conventional combustion concepts like spark or compression ignition. In the HCCI engine homogeneous mixture is created and it depends on solution in the intake system or inside the cylinder. Homogeneous charge or air is drawn into the cylinder during suction stroke and compressed to high enough temperature and pressure.

Current application of HCCI y

At present two engines run in HCCI mode are commercially available in the world. First of them is delivered by Nissan fitted with new technology combustion called MK Combustion System, second is developed by Honda called AR Combustion System.

The ”MODULATED KINETICS” – MK – system, developed by Nissan [38] (see figure 2), incorporated in a regular CIDI engine using diesel fuel. At light load, the engine operates with high swirl ratio, high EGR quantity and retarded injection timing.

Experimental studies

This piece of work presents the results of the tests of engine, during which distribution of fuel

between the direct injection system and port injection system was changed.

For each test the constant injection and ignition timing and the stoichiometric composition of

the mixture was maintained. The direct injection timing was determined in preliminary tests

at 281° CA before TDC, which means direct injection of fuel during the intake stroke.

Experimental studies

The carried-out simulations of the engine working with fuel injection only into the intake

manifold and dual-injection of fuel gave the following conclusions:

• Obtaining with the dual-injection of fuel the same mixture composition, which occurred

with indirect injection, requires a slightly larger amount of fuel. This fact points to improve

of volumetric efficiency for the engine working with dual-injection in those simulation

conditions.

Conclusions

On the basis of the results of carried out considerations the following conclusions can be presented:

• The outcome of computational part of the work are convergent with the experimental research results. This confirms the proper design of the model and indicates the its further use.

References

[1] Kedzia, R., Okoński, A., „Układy paliwowe systemów wtryskowych silników z zapłonem

iskrowym”, Poradnik Serwisowy Nr 1/2002, Instalator Polski, Warsaw 2002, Poland

[2] Kochersberger, K., Hyde, K. W., Emsen, R., Parker, R. G., „An Evaluation of the 1910

Wright Vertical Four Aircraft Engine”, AIAA-2001-3387, American Institute of Aeronautics

and Astronautics, Reston 2001, United States of America [3] Mason, F. K., „Messerschmitt Bf-109B,C,D,E in

Luftwaffe & Foreign Service”, Aircam Aviation Series No. 39 (Vol.1), Osprey Publishing Limited,

ISBN 0-85045-152-3 Berkshire 1973, United Kingdom

THAN

KS