Internal-combustion engines – Combined devices – Generating plants
Reexamination Certificate
2000-04-06
2001-11-06
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Combined devices
Generating plants
Reexamination Certificate
active
06311649
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an internal combustion gasoline engine having a fuel fractioning system supplied with a blend of volatile liquid fuel from a fuel storage tank.
DESCRIPTION OF THE PRIOR ART
U.S. Pat. No. 5,373,825 discloses a fuel vapour extraction system intended for an engine burning a heavy oil that comprises a volatising chamber separate from the fuel tank for volatising the lighter fraction of the oil. Within the volatising chamber, the oil is heated by a heating element and the lighter fraction of the oil is driven out by the applied heat and entrained by ambient air drawn through the volatising chamber which transports the vapour to the intake system of the engine. The remaining liquid fraction that is not vaporised is mostly returned to the fuel tank, though a small proportion may be cooled and delivered to the engine as part of the metered fuel to be burnt in the engine.
A serious problem of the above vapour extraction system is that no attempt has been made to ensure that the vapour and liquid fuel fractions be burnt in the engine in the same proportion as that in which they are present in the original composition of the fuel. As a result, after prolonged use, the liquid fuel remaining in the fuel tank is depleted of its vapour fraction. In fact, it was proposed that the old fuel in the tank should be discarded from time to time and fresh fuel added to replenish the supply of fuel vapour. This suggestion is not acceptable in a motor vehicle.
GB-A-2,209,796 shows an engine having a fuel tank and a distillation unit for producing from fuel drawn from the fuel tank two fuel flow streams of different volatility. The engine also has a management system for separately metering fuel to the engine from the two streams and adjusts the rates of the flow streams so that the flow streams are consumed in the engine continuously.
It has been proposed by the present Applicant in British Patent Application No. 9716156.6 to provide a fuel vapour extraction system for a gasoline engine capable of continuously separating the fuel into a lighter vapour fraction and a heavier liquid fraction. In the latter proposal, the operating pressure in the volatising chamber is variable such that the vapour production rate always matches the vapour demand flow rate from the engine. The remaining liquid fraction that has been depleted of vapour is also metered to the engine and burnt, so that both the vapour and liquid fuel fractions are consumed together in the same proportion as the original composition of the fuel in the fuel tank. No fuel is returned to the fuel tank and there is no uncontrolled accumulation of any one of the fractions even after prolonged use. Such a system has advantage in that it is self-regulating based on achieving equilibrium between the rate of vapour production in the volatising chamber and the rate of vapour demand from the engine, the system being demand-driven, i.e., the engine sets the demand of the vapour fuel flow and the volatising chamber responds by adjusting its supply of fuel vapour to match the demand. A disadvantage however is the slow response time of the system and, under extreme conditions, the demand from the engine may exceed the supply capacity of the volatising chamber.
SUMMARY OF THE INVENTION
With a view of mitigating at least some of the above disadvantages, there is provided in the present invention an automotive internal combustion gasoline engine comprising a fuel storage tank, means for drawing liquid fuel from the storage tank, and a distillation unit for producing from the fuel drawn from the storage tank at least two fuel flow streams of different volatility, wherein the engine further comprises an engine management system for separately metering fuel to the engine from the different flow streams, the management system being responsive to the rates at which the different flow streams are produced by the distillation unit and serving to adjust the relative usage rates of the flow streams in dependence upon the rates at which they are produced by the distillation unit in such a manner that, at least during steady state operating conditions, the flow streams are all consumed in the engine continuously in substantially the same proportion as they are produced by the distillation unit, wherein the distillation unit comprises a continuous flow boiler for heating a flow of gasoline fuel and evaporating a flow of the low and medium boiling point vapour fuel fractions to leave behind a flow of the high boiling point liquid fuel fraction, a compressor for compressing to a high pressure the flow of the low and medium boiling point vapour fuel fractions, a condenser for receiving the compressed flow of fuel vapour from the compressor and condensing a flow of the medium boiling point liquid fuel fraction to leave behind a flow of the low boiling point vapour fuel fraction, and a high pressure fuel storage reservoir for accumulating at the bottom of the reservoir the flow of the medium boiling point liquid fuel fraction and in the ullage space of the reservoir the flow of the low boiling point vapour fuel fraction, and the engine management system comprises sensing means for measuring the accumulated quantity of the low boiling point vapour fuel fraction in the ullage space of the reservoir, sensing means for measuring the accumulated quantity of the medium boiling point liquid fuel fraction at the bottom of the reservoir, and regulating means for adjusting the relative usage rates in the engine of the low, medium and high boiling point fuel fraction flow streams drawn separately from the respective sections of the distillation unit in such a manner as to keep substantially constant the equilibrium quantities of the respective accumulated vapour and liquid fuels stored in the reservoir.
Unlike the vapour extraction system described in copending British Patent Application No. 9716156.6, the present invention is supply-driven, i.e., the distillation unit sets the supply of different proportions of the fuel fraction flow streams and the engine management system responds by adjusting the relative usage rates of these fuel streams metered separately to the engine to match the supply proportions. As a result, the invention can cope with variations in the composition of the original gasoline fuel and variations in the operating temperatures in various sections of the distillation unit by adjusting the relative usage rates of the separate fuel streams and metering each stream adaptively so as to maintain equilibrium condition for all the streams within the distillation unit.
It should be clear that the actual amounts of the vapour and liquid fuel fractions stored under equilibrium in the reservoir are not significant in the invention as long as they are kept constant by ensuring that the out-flows balance the in-flows within the reservoir. Moreover it is advantageous to provide relatively large amounts of the vapour and liquid fractions stored in the reservoir to act a buffers for coping with temporary changes in demand from the engine. For example, during transient operation of the engine, the buffer storage may permit the equilibrium to be temporarily shifted in either direction to cope with the dynamic fuel response changes thereby maintaining smooth operation. During cold start and warm up operations, the stored fuels may be used to meet all the engine fuel requirement while the engine and the distillation unit are still cold, and may be replenished gradually after the engine and the distillation unit have reached their normal operating temperatures.
In a preferred embodiment of the invention, the fractioning of the gasoline fuel may be determined according to the so-called E100 and E40 points along the fuel distillation curve, E100 being the percentage by volume of fuel vaporised up to 100° C. and E40 being the percentage by volume of fuel vaporised up to 40° C. By selecting the boiler temperature at 100° C. which can be conveniently provided using hot coolant thermostatically controlled from the engine, and by selecti
Ali Hyder
Argenbright Tony M.
Ford Global Technologies Inc.
Hanze Carlos L.
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