Internal-combustion engines – Precombustion and main combustion chambers in series – Having combustible mixture forming means
Patent
1994-11-21
1996-09-17
Nelli, Raymond A.
Internal-combustion engines
Precombustion and main combustion chambers in series
Having combustible mixture forming means
F02M 1900
Patent
active
055558682
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a gas delivery system for an internal combustion engine and more particularly, but not exclusively, to a spark ignition engine which operates on gaseous fuel. In one arrangement this invention relates to a spark ignition engine converted from a diesel fuelled or compression ignition engine. In another arrangement this invention relates to a dual fuel engine operating as a compression ignition engine. In such an engine operating in the dual fuel mode, it is common for a gaseous fuel to be mixed with the air before induction of the air into the engine whilst reducing the amount of diesel injected. In this specification the term "compression ignition engine" is intended to refer not only to an engine operating on a constant pressure, that is a diesel cycle, but also to an engine operating on a compression ignition cycle.
BACKGROUND TO THE INVENTION
When operating an engine with a gaseous fuel it is a well known practice to introduce the gaseous fuel with the inlet air to the cylinder during the air inlet stroke, thus causing a relatively homogenous mixture of gas and air during the combustion stroke. It is advantageous to reduce the fuel/air ratio to a minimum value in the combustion of gas as a fuel, as this reduces the carbon monoxide and hydrocarbon content of the exhaust and enhances fuel efficiencies. If the ratio is reduced sufficiently beyond the stoichiometric value a substantial reduction in the nitrous oxide content of the exhaust gas may also be achieved. This is commonly called a lean burn regime. With current gas engines the limiting factor in the reduction of the ratio to achieve lean burn is that which occurs when the average ratio of fuel to air is lowered to a level where the density of the fuel is such as to prevent initiation of fuel ignition, and thus the engine misfires.
SUMMARY OF THE INVENTION
The present invention was developed with a view to providing a method of gas delivery and a gas delivery system for a gas fuelled internal combustion engine wherein the fuel/air ratio can be minimised without the onset of misfire of the engine.
According to the present invention there is provided a gas delivery system for a gas fuelled internal combustion engine, the system comprising: to a region adjacent a source of ignition, said region comprising a pre-combustion zone located in a separate pre-combustion chamber which is located in immediate proximity to said ignition source and which is in direct communication through an orifice with a combustion zone located in a cylinder of the engine, said gas fuel delivery means comprising first and second gas delivery lines for delivering a controlled amount of gaseous fuel to said pre-combustion zone and combustion zone respectively from a common gas injector, and further comprising gas control means for controlling the relative proportions of gaseous fuel delivered by said first and second delivery means respectively whereby, in use, combustion in said combustion zone can be achieved with minimum gaseous fuel by initiating ignition of gaseous fuel in said pre-combustion zone.
In this specification the pre-combustion zone is that zone within which it is desirous to initiate the combustion process, and the combustion zone is that region to which the resultant effects of gaseous fuel ignition in the pre-combustion zone are directed to achieve combustion of the remaining gaseous fuel.
Advantageously said gas control means comprises a gas flow valve for controlling the quantity of gaseous fuel delivered to said pre-combustion zone and/or combustion zone. More particularly, said gas flow valve may be a one way valve for controlling the quantity of gaseous fuel delivered via said first gas delivery line to said pre-combustion chamber.
Typically the relative proportions of gaseous fuel delivered by said first and second delivery means is fixed for a particular engine. The relative proportion of gaseous fuel delivered by said first delivery means may be in the range of 1 to 10 percent of the total quantity
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Nelli Raymond A.
Transcom Gas Technologies Pty. Ltd.
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