Internal combustion engines

Details Internal combustion engines Internal combustion engines

1997-07-30

1998-11-03

Nelli, Raymond A.

Internal-combustion engines

Precombustion and main combustion chambers in series

Having combustible mixture forming means

F02M 1900

Patent

active

058294074

DESCRIPTION:

BRIEF SUMMARY
This invention relates to the combustion process of an internal combustion engine and particularly to the enhancement of that process to reduce the level of exhaust emissions, improve the fuel consumption and/or improve combustion stability and/or otherwise enhance the combustion process. More particularly, the invention relates to internal combustion engines wherein fuel is directly injected into the cylinders of the engine.
All major industrial countries currently have regulations relating to the level of exhaust emissions from motor vehicles, particularly passenger type vehicles. The controlling authorities are generally progressively reducing the permitted level of emissions that such vehicles may emit thereby increasing the demand for greater control of the combustion process of internal combustion engines. The regulations regarding the control of exhaust emissions generally provide for a test procedure wherein engine operation at low to medium load is typically a significant factor and unfortunately these areas of operation of the engine generally present a substantial difficulty in control of the combustion process.
It has been recognised that in the low to medium load range of operation of an engine, the distribution of fuel within the air charge in the engine combustion chamber is preferably of a stratified nature in order to provide improved fuel consumption. The creation of such a stratified fuel distribution is particularly difficult to achieve where the fuel is introduced into the air charge prior to the air charge entering the combustion chamber. This is particularly so as the fuel must be delivered into the air charge at a specific time related to the engine cycle which will ensure that all of the fuel reaches the combustion chamber before the inlet port associated therewith is closed. Thus there is a substantial time interval for the fuel to disperse in the air charge, both in the air intake system and in the combustion chamber, before and after closing of the inlet port; and prior to ignition of the air/fuel mixture.
Some degree of success has been achieved in establishing a stratified fuel distribution by the use of a fuel injector to deliver the fuel into the air charge at a location only a relatively short distance upstream from the inlet port. This permits relatively late injection of the fuel and restricts the time available for dispersion of the fuel within the air charge prior to ignition. Further improvement has been obtained by the injection of pressurised fuel directly into the combustion chamber. However, this introduces the further problem that the fuel must be injected at a near sonic velocity to achieve the necessary degree of atomisation of the fuel. Moreover, the necessary high velocity also results in a significant dispersion of the fuel within the combustion chamber.
It has also been proposed to introduce an ignition enhancing substance with a lean air fuel mixture to assist in the promotion and reproducibility of initial ignition of the lean air/fuel mixture. Hydrogen is typically a preferred enhancing substance to be used in this procedure, but, due to its high rate of dispersion, (approximately 10 times faster than oxygen), relatively large quantities of hydrogen are usually required, particularly where the fuel and hydrogen are introduced into the air charge prior to the delivery thereof to the combustion chamber. Also, as it is desirable for practical reasons to produce the hydrogen within the vehicle rather than merely to supply a reservoir of pre-produced hydrogen, the resulting large consumption of hydrogen necessitates a substantial "on-board" hydrogen generating capacity which consumes energy, occupies space in, and adds weight to, the vehicle.
It is also known that the introduction of other selected substances into the fuel/air charge or mixture in the combustion chamber of an engine can be beneficial to the management of the combustion process. Furthermore, it is also known that the effectiveness of some of these substances is related to the location of the su

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