AU597871B2

AU597871B2 - Improved fuel combusting system

Info

Publication number: AU597871B2
Application number: AU35430/84A
Authority: AU
Inventors: William Reginald Bulmer Martin; Eric Edward Milkins; Harry Charles Watson
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-11-14
Filing date: 1983-11-14
Publication date: 1990-06-14
Anticipated expiration: 2004-11-14
Also published as: AU3543084A

Description

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9 9 COPIPLETE SP;EC IF ICAT ION3 FOR. AN I lENT I O ENT ITLED: I MFR'J',,-EC FUEL COMBI$T IN MAAILOf Cl The -folIlow irv- taemn is -kJill d:escrip ~t ion 0f th is 1 n'...erriIon. in: 1 'uli the bes=± rie±hrx o-P. p:er-Pormrv- i ~j-I knioon -to role Dated this ay o01 To: (Signature) THE COMMISSIONER OF PATENTS (Sign This form must be accompanied by either a provisional specification (Form 9 and true copy) or by a complete specification (Form 10 and true copy). This invention relates to improvements in fuel combusting systems for spark ignition and other internal combustion engines, and more particularly to an improved fuel combusting system for hydrogen fuel engines.

The proposal to use hydrogen as the fuel for an internal combustion engine is not new. Ricardo back in 1923 did considerable testing of hydrogen as a fuel in engines of that time, but as with all experimenters since, he found that back-firing and pre-ignition were serious problems that could not be overcome. Current work around the world on hydrogen as an internal combustion engine fuel, whilst claiming to have found ways of preventing back-firing, have not removed this problem to an acceptable extent.

In the course of research lasting over some fifteen years by the Applicants the problems of back-firing and pre-ignition have been closely studied and it is believed that the principal multiple causes have been identified as: Hot residual gas in the cylinders which raise the temperature of directly admitted hydrogen plus air mixture beyond ignition temperature, before the inlet valve has completely closed, thus releasing all the energy of the burning and rapidly expanding gases into the induction pipe instead of into the exhaust system.

Carbonaceous deposits that form from engine oil moving up into the combustion space. These deposits raise the film surface temperature well above the metal surface temperatures and are probably catalytic and constitute a source of uncontrolled combustion additional to that which comes into play under different circumstances as stated in (1)

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4 above and below.

in/32/July89 Metal surfaces and various parts of the cylinder cavity, in particular the valves, which have higher than average working temperatures which form "hot spots" and therefore constitute another undesirable ignition source.

It have also been noted that the nature of these surfaces and their catalytic effect may also be very important, for example, surfaces coated with copper, which is highly conductive, to even out surface temoeratures were a very bad source of backfiring ignition.

0 It is an object of the present invention to provide a means whereby these o0a o problems may be reduced sufficiently to enable acceptable combustion of *hydrogen in an engine.

aoo 4 o .0 0 It is a more specific object of the present invention to provide a combination of means by which hydrogen fuel may be combusted in an engine whilst reducing the problems of pre-ignition and back-firing to a rminimum.

I 00 o The invention, in its broadest sense, includes a system for combusting hydrogen gas in an internal combustion engine wherein ignition during the charge induction process is reduced or eliminated, characterised in that compact liquid water is introduced into the combustion chamber when the S" piston is at or near its top dead centre position and prior to the induction of the hydrogen the quantity of water being such that the heat capacity thereof and its capacity to transfer heat reduces the temperature of any "hot spot" to a temperature below that at which hydrogen ignition occurs in the conditions pertaining.

V AL4 In experiments leading to the present invention, it was discovered that the -3- )j^ul eigrtin/32/March90 improvement in back-firing claimed to be achieved by others by the aspiration of an atomised water spray into the combustion chambers of the engine produced no observable beneficial effect. Theo.etical consideration to the likely effect of atomised water on the reduction of hot spots in the combustion chamber indicated that the water spray would rapidly cool the entering gas but have little or no effect on the transference of heat from the walls of the combustion chambers. However, it was determined that heat transfer from the walls of the order of two magnitudes greater would be achieved if water in liquid form were to contact the walls of the combustion chamber prior to the introduction of the hydrogen gas. Thus, if a "slug" of water is able to be rolled around in the combustion chamber, a significant effect can be achieved.

In a preferred form of the invention, water is injected, preferably through a low velocity jet, in the required quantity into the inlet manifold of the engine so as to build up behind the inlet valve prior to the opening of that valve.

The injection of water is preferably controlled so that the water is injected only when required by the engine, as mentioned above, during periods of sustained high level load conditions and/or during rapid energy demand, when hot spots are likely to develop in the combustion chamber.

It is already known that individual cylinders are likely to be hotter than others and will therefore require the injection of larger volumes of coolant at the required times. The injection jets ar,; therefore calibrated to this end for each particular engine type.

The system may also include means for causing cooling of the residual gas Sartin/32/; uly rtin/32/July89 in the combustion chamber prior to or with the admission of the hydrogen gas to the combustion chamber. This may be achieved either by delaying the admission of the hydrogen gas into the induction air until sufficient air has entered the combustion chamber to cool the residual hot gas below the ignition temperature or by the aspiration of an atomised water or other coolant spray into the combustion chamber either prior to or with the hydrogen gas.

In a preferred form of the invention, a delay valve is used to delay the admission of hydrogen gas into the induction air until after the inlet valve to the combustion chamber is open.

It will be seen that the system of the invention in its broadest sense tends to overcome problem which has been the most intractable and also permits problem to be overcome by ensuring cooling of the residual gasee either with the cooling of the combustion chamber itself or independently.

Problem may be overcome or reduced by carefully selecting the lubricating oil used in the engine and, at the same time, the deposits will tend to be quenched as hot spots with the introduction of liquid water into the combustion chamber.

Problem it has been found can be reduced by the use of a non-catalytic material on the surfaces and, particularly, non-catalytic aluminium with its single chemical valency as this was found to be a good and cheap suppressor.

Al Where aluminium cylinder heads and pistons are used, it may not be 0 necessary to coat the major surfaces of the combustion chamber although Martin/ 32/Ju y89* it may still be necessary to coat the exposed surface of the valves.

As mentioned above, the problem of the carbonaceous deposits, as described in above, may be avoided or reduced by the careful selection of the lubricating oil to have a high breakdown temperature. It has not at this stage been determined whether the coating of the surfaces of the combustion chamber and the careful selection of lubricating oil will be necessary in combination with the present invention to achieve an acceptable combustion of hydrogen gas.

The control of the introduction of coolant to the combustion chamber may be by means of the detection of predetermined changes in the hydrogen manifold pressure and/or by the detection of predetermined increases in the temperature of the exhaust gas. By controlling the introduction of the coolant to the required conditions described above, the amount of water required to overcome the problem of uncontrolled ignition may be less than the amount which can be conveniently condensed from the exhaust gases of the fuel and recycled within the vehicle system so that no demand to fill auxiliary water tanks will be made on the driver.

An experimental fuel combusting system is shown schematically in Figure 1 of the accompanying drawings. In this arrangement, the fuel combusting system has been applied to a standard two litre, four cylinder Ford Pinto internal combustion engine. The hydrogen supply tank is connected via a pressure regulator to a variable area choked nozzle which performs the "throttle" function of the engine. The hydrogen line terminates at a delayed introduction valve, to be described in greater detail below, while induction air is introduced into the engine by means of a resonance J manifold into which coolant water is injected through 1.5 mm water entry -6- Martin/32/.Ju y89

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i be incorporated to account for short transients in the hydrogen gas pressure signal so that the water pump is operated only when a condition exists which may be reasonably expected to result in undesirable increases in the temperature of the surfaces of the combustion chamber. Thus, the control mean, responds not only to the rate of demand of hydrogen gas but also to the average demand of hydrogen gas and causes the pump to deliver greater quantities of water for higher hydrogen pressures and for higher engine speeds indicating higher fuel demand. The control parameters may be determined for each engine to ensure that the required amount of water is delivered to each inlet manifold to overcome the uncontrolled ignition of the hydrogen gas whilst not allowing excessive quantities of water to enter the combustion chamber to result in crank case lubricant emulsification Referring now to Figure 2 of the drawings, the delayed introduction valve may be seen to include a modified inlet valve guide defining a chamber into which the hydrogen gas is introduced and also defining a cylindrical valve surface and a valve seat. The hydrogen gas valve is secured to the stem of the air inlet valve and comprises a sliding seal made from "teflon" which contacts the cylindrical surface of the modified valve guide and an O-ring seal which contacts the valve seat on the valve guide when the air inlet valve is fully closed. In use, the air inlet valve is opened and the O-ring seal is displaced from its seat but the slide seal remains within the valve guide substantially preventing the flow of hydrogen gas into the induction chamber. As the inlet valve further opens, the slide seal is removed from the valve guide and hydrogen gas is allowed to flow int&, the induction chamber for mixture with the induction air. Thus, the introduction of k hydrogen gas is delayed and a quantity of cool air is introduced into the p combustion chamber to sufficiently cool the hot residual gas in the -8- Mart in/32/ u y 89 combustion chamber prior to the introduction of the hydrogen gas.

Extensive tests have shown that this delay valve quite satisfactorily overcomes the problem referred to above.

-9- Martin/32/July89 ILik II -r P1~

Claims

1. A system for combusting hydrogen gas in an internal combustion engine wherein ignition during the charge induction process is reduced or eliminated, characterised in that compact liquid water is introduced into the combustion chamber when the piston is at or near its top dead centre position and prior to the induction of the hydrogen the quantity of water being such that the heat capacity thereof and its capacity to transfer heat reduces the temperature of any "hot spot" to a temperature below that at which hydrogen ignition occurs P S in the conditions pertaining. 1

2. A system as claimed in claim 1 wherein the quantities of water required to quench 'hot spots' sourced pre-ignition or backfiring can be varied depending on the conditions on each particular cylinder.

3. A system as claimed in claim 2 wherein the quantity of water necessary to suppress pre-ignition and backfiring is determined from the exhaust gas temperature of individual cylinders when the exhaust gas temperature is measured immediately behind the exhaust valve of 0 0 S"

4. A system as claimed in claim 3 wherein the varying quantity of water necessary to suppress pre-ignition or backfiring in individual cylinders can be separately controlled.

A system as claimed in claim 2 wherein the control of the water ar in/32/March90 j I supply may be controlled f'om pre-determined measurement of hydrogen delivery flow rat ana engine speed.

6. A system as claimed in any one of claims 2 to 5 wherein the control of the individual cylinder water supply identified can be effected through the use of adjustable throttles in the pressurized delivery lines to each cylinder.

7. A system as claimed in any one of claims I to 6 wheein at least part of the quantity of water required for pre-ignition or backfiring o 0e 9 r suppression is obtained from the condensation of the exhaust carried ,water as a supply for the water delivery pump. 6 00 0 0

8. A system as claimed in claim 7 wherein water is not introduced during 0 warm up and wherein the amount of water in the exhaust gas is always greater than that needed to quench 'hot spots' so that the total a*0 0 required water is obtained from the exhaust gas. a

9. A system as claimed in any preceding claim wherein the surfaces in the combustion chamber are of or are coated with a ron-catalytic metal. 0

10. A system as claimed in claim 9 wherein the metal is aluminium.

11. A system as claimed in any one of claims 1 to 8 wherein 'hot spots' on the surfaces of the valve faces are reduced by application of a material of higher thermal diffusivity than the base metal in a thin art in/32 layer or film.

12. A system as claimed in claim 11 wherein the material applied is alu minium.

13. A system as claimed in any preceding claim in which the temperature of the residual gas from the previous combustion process in the combustion chamber of a reciprocating internal combustion engine is reduced by mixing it with the entering oxidant gas, the temperature of the oxidant-residual gas mixture being reduced below the ignition temperature of hydrogen under the conditions pertaining, before S. hydrogen is admitted into the combustion chamber.

14. A system for combusting hydrogen gas substantially as hereinbefore described with reference to the accompanying drawings. I DATED this 13th day of November, 1984 THE UNIVERSITY OF MELBOURNE I By its Patent Attoreys A. TATLOCK ASSOCIATES ,2" 0EBNS -12- Mart in/32