Internal-combustion engines – Charge forming device – Fuel injection system
Patent
1993-07-09
1995-01-10
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Fuel injection system
123301, 123 27GE, F02M 5100
Patent
active
053797400
DESCRIPTION:
BRIEF SUMMARY
This invention relates to fuel injection internal combustion engines and the operation of such an engine on two different fuels.
The invention will be generally discussed in relation to the operation of a petrol vehicle with liquefied petroleum gas as a second fuel but the invention is not restricted to these two fuels.
It is particularly desirable on the grounds of economics to have only one set of fuel injectors for the two fuels and this presents the problem that there must be some way of separating the two fuels and also to provide the ability to change injection timing to ensure that the correct amount of fuel enters the engine with the alternative fuels. If one investigates petrol and LPG it can be noted that on a gravimetric basis propane which is the predominant component in LPG contains 6% more energy than petrol whereas on a volumetric basis petrol contains 35% more energy than propane. For these reasons it is necessary to operate the two fuels in the dual fuel engine arrangement at different pressures and even so different injection timings are necessary. In such a system for instance petrol may be supplied to the engine at 250 kilopascals whereas LPG may be supplied to the engine in a pressure range of from 500-2000 kilopascals.
Another problem with fuel injection systems which this invention may solve is the problem of heating of the injectors with consequent vapourisation in the injector before injection.
The engine control computer in a petrol driven vehicle is arranged to provide the required amount of fuel to efficiently combine with the amount of air and in particular oxygen allowed into the engine by the throttle setting. The optimum amount of fuel varies with air and engine temperatures, running conditions demanded such as engine speed, acceleration, steady running for economy and the like. The typical computer system has inputs sensing engine speed, throttle position, air temperature, engine temperature, manifold or inlet air pressure, air-conditioning condition and whether at idle or over-run etc. All such inputs along with a feedback input from an oxygen sensor sensing the actual combustion conditions as detected in the exhaust system combine to allow the computer to optimise the quantity of fuel admitted to the engine.
For a petrol engine the petrol admission to each cylinder is controlled by an electric valve, an injection valve, which admits petrol under pressure to the inlet manifold of the engine for as long as the valve is opened. The actual time of opening may be adjusted to allow for opening or closing delays so that a selected amount of petrol is injected.
The existing vehicle computer therefore takes into account all of these variables to command the injectors to open for a time such as to allow the calculated amount of fuel for optimum combustion to reach the engine.
It is the object of this invention to provide a control system by which an optimum amount of a second fuel in a dual fuel internal combustion engine can be injected. In general the second fuel discussed in this invention will be LPG but a similar logic may be used for an alternative second fuel such as methanol.
This present invention provides an arrangement whereby such an engine can be controlled and supplies a control arrangement for such an engine.
In one form therefore the invention is said to reside in a dual fuel injection arrangement for an internal combustion engine comprising a single fuel rail supplying either a first or a second fuel to at least one injector for injecting fuel into an inlet manifold of the engine, a first control unit acting upon engine parameters and demand parameters for the first fuel to determine injector timing for the first fuel and a second control unit to convert injection timing for the first fuel into injector timing for the second fuel dependent upon the supply characteristics of the second fuel.
In an alternative form the invention may be said to reside in a method of providing an injection pulse time for a second fuel for an internal combustion engine connected for dua
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Kavarnos Manos
Moore Christopher P.
Biocom Pty, Ltd.
Nelli Raymond A.
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