Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2002-06-25
2004-08-03
Tran, Binh Q. (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
C060S274000, C060S278000, C060S279000, C060S288000, C060S289000, C060S293000, C048S127300, C048S127700, C048S198700, C048S198800, C048S211000
Reexamination Certificate
active
06769244
ABSTRACT:
DESCRIPTION OF THE INVENTION
This invention relates to a method of operating a combustion apparatus and more particularly but not exclusively an internal combustion engine e.g. for a vehicle. Such an engine typically includes at least one combustion chamber with an inlet port for primary combustion air, means to introduce into the combustion chamber primary fuel for combustion with the primary air, an outlet port for combustion products, and an exhaust system for exhausting the combustion products to atmosphere. The primary fuel may be petrol, diesel, liquid petroleum gas, for example, or any other suitable fuel or mixture of such fuels.
The development of internal combustion engines has tended to focus on maximising the power output of the engine, achieving economy of fuel use, and the reduction of harmful emissions.
Particularly in the case of achieving reduction of harmful emissions, development has tended to concentrate on improving combustion within the engine for example by developing fuel injection systems which provide for improved fuel/air mixing in combustion chambers of the engine, and then cleaning combustion products, for example by passing the combustion products through catalytic converters for example.
The provision of catalytic converters is problematic because such devices only tend to operate to their maximum performance once very hot, such that during short journeys for example in which engines may not attain an optimum operating temperature, such catalytic converters provide substantially no beneficial effect. Moreover, such converters are expensive and require frequent replacement, as they are easily contaminated.
In previous patent application EP-A-0744006 there is proposed an apparatus for improving combustion, by introducing into the combustion chamber of the engine, a vaporised secondary hydrocarbon based high calorific value fuel, obtained by heating a mineral oil. Thus the efficiency with which the primary fuel is burned in the engine is enhanced, and this has the effect of reducing the production of harmful exhaust emissions.
In previous patent application EP-A-041831 there is described an exhaust aspirator which is adapted to permit the introduction of relatively clean air into an exhaust manifold of the engine to promote more effective exhaust gas discharge and to cause aspirated air to be drawn into a combustion chamber of the engine through an exhaust port thereof, rather than exhaust gases, during cyclic pressure changes which occur in normal engine operation.
According to a first aspect of the invention we provide a method of operating a combustion apparatus which includes at least one combustion chamber with an inlet port for primary combustion air, means to introduce into the combustion chamber primary fuel for combustion with the primary air, an exhaust port for combustion products, and an exhaust system for exhausting the combustion products to atmosphere, the method including introducing into the exhaust system secondary air, mechanically acting upon the secondary air and products of combustion in the exhaust system in the presence of a catalyst, to produce a reformed fuel, introducing the reformed fuel into the combustion chamber for combustion with primary fuel and primary air.
Preferably, the reformed fuel is introduced into the combustion chamber via the exhaust port, e.g. soon after production, but it is envisaged that the reformed fuel may be collected and stored, for later use, and may be fed with the primary fuel into the combustion chamber.
It has been found that by utilising the method of the invention, a substantial improvement in combustion efficiency can be achieved, resulting in much cleaner exhaust emissions and a significant improvement in power output. Also whereas with previous proposals for improved e.g. engine designs, it has been necessary to compromise between fuel efficiency and power output, utilising the present invention, such compromise is unnecessary.
Where the invention is applied to an engine, the method may include introducing the secondary air into the exhaust system via an exhaust aspirator e.g. similar to that disclosed in EP-A-0041831, which draws air into the exhaust system during low pressure or partial vacuum conditions occurring during the cycle of pressure changes which occur in the exhaust system during normal operation of the engine. However whereas in EP-A-0041831, the primary function of the aspirator is to damp down vacuum waves occurring in the exhaust system to improve the efficiency of exhaust gas discharge, in the method of the invention the exhaust aspirator is tuned to draw air into the exhaust system and mechanically to act upon the secondary air and products of combustion by means of pressure pulses, in a manner to optimise reformed fuel production.
Typically, an aspirator means suitable for the purpose of the method of the invention, includes a valve with a spring biased valve member, the force of the spring acting to urge the valve member into engagement with a valve seat to close the valve, and the force of the spring being overcome when sufficiently low pressure is developed in the exhaust system, to allow the secondary air to be drawn in through the valve. Tuning of such an aspirator means for the performance of the invention may involve adjusting the spring pressure so that the valve responds to a desired low pressure or partial vacuum at an appropriate time during the engine cycle, and in a manner to produce strong pressure pulses in the exhaust system adequate mechanically to act upon the combustion products and secondary air present in the exhaust system to produce reformed fuel.
It will be appreciated that in the case of an engine having a single combustion chamber, the spring may be adjusted to open the valve and allow the secondary air to be drawn into the exhaust system at commencement of the piston's induction stroke, when a low pressure is developed in the exhaust system as a result of the (single) piston moving in the combustion chamber to induce air therein through an air inlet port, prior to the exhaust port being completely closed by an exhaust outlet valve or the piston. In a multi-combustion chamber engine, where each piston will be in a different stroke position, the valve may respond to low pressure developed in the exhaust system when one or all of the pistons are at other stroke positions.
It will be appreciated that reference in this specification to primary air being induced into the or each combustion chambers includes air being introduced into the combustion chamber or chambers by e.g. turbo or other primary air introduction means.
The aspirator may be tuned to produce from the secondary air and combustion products, which typically include un-burnt hydrocarbons, nitrous oxide gases (commonly known as “NOx”), carbon dioxide, carbon monoxide and water (usually in the form of steam), reformed fuel including one or both of methanol and hydrogen gas, both of which may satisfactorily provide a supplementary fuel. By operating an engine in accordance with the invention, the amount of un-burnt hydrocarbons, NOx and carbon monoxide in the exhaust gases eventually emitted from the exhaust system to atmosphere has been found to be greatly reduced, and the amount of carbon dioxide produced is significantly reduced
Preferably, the catalyst is provided by materials from which the aspirator is at least partly made, such as for example copper, but if desired Cerium may be provided in the vicinity of the aspirator which is particularly good at enhancing secondary fuel production.
Where the apparatus is an engine, the reformed fuel may be introduced into the or each combustion chamber of the engine as a result of a partial vacuum being established at the exhaust port at the end of an exhaust stroke of a piston thereof as the piston commences its next induction stroke, before the exhaust port is completely closed by an exhaust outlet valve or the piston.
Thus the reformed fuel will combust in the combustion chamber simultaneously with the primary air and primary fuel in
Headley Ronald
Jones Patrick
MacMillan Sobanski & Todd LLC
Ribbit Limited
Tran Binh Q.
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