Internal-combustion engines – Charge forming device – Combined liquid and gaseous fuel
Patent
1993-07-09
1995-01-03
Nelli, Raymond A.
Internal-combustion engines
Charge forming device
Combined liquid and gaseous fuel
123514, 123478, F02M 2102, F02M 3704, F02M 5100
Patent
active
053776453
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method of fuel injection and more particularly to the injection of low boiling point liquid fuels into an engine in liquid form.
As an example of a low boiling point liquid fuel Liquid Petroleum Gas is a good fuel for motor vehicles as it has a high calorific value per unit volume at high pressures and is particularly good in the liquid form as it does not require very high pressure tanks to store it. The liquid does has a relatively high vapour pressure and particularly at very high engine operating temperatures there is a danger that the LPG can vaporize and exhibit poor injection characteristics. It is desirable therefore to inject LPG into a motor vehicle engine at a pressure which ensures the LPG is in liquid form at the highest ambient temperatures but this may require a very large pump to maintain a high constant pressure because of the low vapour pressure of the LPG in cold weather. Such a large pump can be relatively heavy and have a very high power draw so that in fact it may be necessary to actually drive the LPG pump directly from the engine rather than as an electric pump.
It is the object of this invention to provide a method of injecting low boiling point liquid fuels which does not require such an energetic pump.
In one form therefore the invention is said to reside in a method of operating a low boiling point liquid fuel injection system for an internal combustion engine wherein the fuel is stored in a tank and has a vapour pressure in the tank dependant upon ambient temperature, the method comprising pumping the fuel to an operating pressure a fixed differential above the vapour pressure and monitoring the absolute pressure of the fuel and varying fuel injection timing for the fuel dependant upon the absolute pressure determined.
The absolute pressure of the fuel may be determined directly by the use of a pressure transducer or alternatively it may be determined by indirect methods such as to monitor the temperature and the density of the fuel and this will enable a determination of the absolute pressure.
In a preferred form of the invention the low boiling point liquid fuel may be Liquid Petroleum Gas (LPG) and the invention will be discussed in relation to this fuel. Petrol may also be used with the method of the invention in a closed fuel system which will prevent the release of hydrocarbons into the atmosphere.
It will be seen that by this invention there is provided an arrangement by which only a relatively small pump is required to raise the pressure of the low boiling fuel such as LPG a fixed amount above that vapour pressure thereby ensuring that the LPG will stay liquid at operational temperatures and flow rates.
In one particular example LPG may have a vapour pressure of from 300 to 1500 kilopascals dependant on ambient temperature and the differential pressure may be 200 to 300 kilopascals. This means that the absolute pressure of the LPG can range from as low as 500 kilopascals up to as high as 1800 kilopascals and hence the LPG injection timing can be varied to ensure that the correct amount of LPG is injected dependent upon that absolute pressure.
The advantage of this arrangement is that a fixed size and power output pump is needed and in fact a relatively low pressure and high flow rate pump is needed to at all times ensure that the LPG entering the injectors is in liquid form.
It is to be noted that the arrangement according to this invention could be used with a dual fuel engine so that an engine may run on a first fuel such as petrol and then be changed over to run on a second fuel such as LPG. Petrol with a relatively low vapour pressure can be operated at a fixed pressure which will always ensure that the petrol will not vaporize but as discussed above this invention proposes operating the LPG system at a fixed differential above the vapour pressure at a given time to ensure liquidity of the LPG.
For the present invention there may be used an electric fuel pump of a constant speed roller cell, gear (positive displacement) or turbine type. S
REFERENCES:
patent: 4430978 (1984-02-01), Lewis et al.
patent: 4505249 (1985-03-01), Young
patent: 4508064 (1985-04-01), Watanabe
patent: 4606322 (1986-08-01), Reid et al.
patent: 4617904 (1986-10-01), Pagdin
patent: 4632083 (1986-12-01), Reggiani
patent: 4742801 (1988-05-01), Kelgard
patent: 4774909 (1988-10-01), Dolderer
patent: 4846126 (1989-07-01), Stannard
patent: 4865001 (1989-09-01), Jensen
patent: 5067467 (1991-11-01), Hill et al.
patent: 5291869 (1994-03-01), Bennett
patent: 5315973 (1994-05-01), Hill et al.
Tadahiro Yamamoto, "Engine Fuel Feeder", Patent Abstracts of Japan, M-870, p. 14, JP,A,1-151760, Jun. 14, 1989 (Nissan Motor Co., Ltd.).
Biocom Pty. Ltd.
Morris Thomas
Nelli Raymond A.
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