FUEL-SUPPLY SYSTEM FOR A COMPRESSION IGNITION ENGINE

TECHNICAL FIELD

The present invention relates to a fuel-supply system for a compression ignition engine and includes an engine incorporating such a system, a method of using fuel for such an engine and a vehicle having such an engine or system incorporated therein.

Reference will be made to use of the present invention with respect to a fuel- supply system utilising ethanol as a supplementary fuel. However the invention is not necessarily limited to use with ethanol, and that other fuels, and in particular other alcohols, could be used as the supplementary fuel in place of ethanol.

BACKGROUND ART

It is known to incorporate ethanol with diesel fuel and then use such a liquid fuel mixture in place of conventional diesel for compression ignition engines.

Unfortunately, ethanol is prone to have a quantity of water in it which in current systems of using diesel fuel can be damaged by corrosion for instance on the surface of injector pins from such water content.

This either means keeping the quantity of ethanol as a proportion of the total fuel very small or finding ways to keep water content low. An advantage of ethanol is that it is considered by many to be a sustainable energy for transport purposes so it would be of substantial benefit if the proportion of ethanol to diesel fuel could be raised. However it seems up till now to be most difficult to achieve without potential for damage to an engine of the type described.

My proposal is to introduce an alternate liquid fuel into the air intake of the compression ignition engine. This avoids a problem of damage from water in injectors. My proposal is to effect an evaporation of the liquid alternate fuel prior to introduction into a main inlet manifold air stream.

My discovery is that this can be achieved effectively and economically and that the result is of significant benefit without the disadvantage of being sensitive to water content.

The proposal will describe a supplementary fuel being ethanol with a small water content but the method on experiments conducted so far has shown itself to be able to use any of a much larger varieties of liquid fuel and especially any alcohol based or inclusive liquid and it is able to use and in some cases improves the performance of the engine by containing a significant quantity of water.

Ethanol has slower flame rate than diesel properties under typical compression ignition engine operating conditions, as the temperature and pressure characteristics of a compression ignition engine cause a longer ignition delay when using ethanol.

When supplementing diesel fuel supply to a compression ignition engine with ethanol using a fumigation technique, a portion of the fuel is supplied by introducing the ethanol through the engines air intake. Diesel fuel can and normally will be delivered by a high-pressure direct injection system.

If is an object of the present invention to provide an arrangement for supply of liquid fuel into a compression ignition engine that facilitates supply of at least some of the fuel through an air intake of the engine.

If is an object of the present invention to provide an arrangement for supply of liquid fuel into a compression ignition engine that facilitates supply of at least

some of the fuel through an air intake of the engine and which facilitates for a quantity of water to be within the said further liquid fuel.

It is a further object of the present invention to provide a fumigation system for a compression ignition engine that facilitates for the engine to use as a supplementary fuel a lower proof alcohol.

Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed.

DISCLOSURE OF THE INVENTION

What I propose in one form of this invention is to effect an evaporation of a supplementary liquid fuel by using a supply of air that has been heated to a substantial temperature which I then mix with the liquid supplementary fuel with the fuel in an evaporated form being introduced into an air intake of the engine.

In one form of this invention there is proposed an arrangement for supply of fuel into a compression ignition engine where a liquid as a supplementary fuel is to be introduced into a cylinder of the compression ignition engine, the arrangement including a supply of air at a pressure above atmospheric, a passageway directing the air from said supply of air through a heat exchange means associated in a heat exchange relationship with an exhaust outlet of the engine, then through a mixer, and thereafter through a conduit to the air inlet of the engine, and means to direct liquid fuel addition to be vaporised within the mixer of the heated air.

In preference the mixer includes a vortex creator with the heated air being urged through the vortex creator and having the liquid fuel to be evaporated introduced into a vortex so created.

This has the advantage that this assists in causing evaporation of the liquid fuel.

Preferably, the supply of air at a pressure above atmospheric is provided by air downstream from a turbo charger of the compression ignition engine and there being a smaller quantity of air from such a location which is tapped off to be supplied through the heat exchange association to the mixer and then to a lower pressure location in the air inlet of the engine downstream from an intercooler of the air supply.

Preferably, the heat exchange is by using a coil which is positioned within an exhaust outlet of the compression ignition engine.

Preferably, air to be heated and used is bled off from downstream of the compressor side of the turbocharger and before any intercooler.

Preferably, the supplementary fuel is injected into a vortex creator through a solenoid-controlled valve which is adapted to be opened and closed with a ratio of periods that is controlled in response to a pressure and temperature of the inlet manifold.

The invention can also apply to a compression ignition engine with any of these features.

Also the invention can apply to a vehicle whether this is a land sea or air based vehicle having at least one engine with any of these features.

In a further form, the invention may be said to reside in a method of providing a supplementary fuel to a compression ignition engine, comprising the steps of effecting a heating of a supply of air to be a sufficient temperature and volume to effect a subsequent evaporation of a liquid fuel supplement, then causing the air to be directed into a mixer, directing a controlled quantity at a controlled rate of a supply of fuel supplement as a liquid into an upstream portion of the mixer, with a downstream end of the mixer being directed into an air inlet of the compression ignition engine and such that the liquid fuel is fully evaporated upon such direction..

Preferably, the supplementary fuel is injected into the mixer by a solenoid- controlled valve being opened and closed with a ratio that is controlled in response to a pressure and temperature detected from a selected location within the inlet manifold of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of this invention and the principle that it involves it will now be described with respect to the preferred embodiment which shall be described herein with the assistance of drawings wherein;

Figure 1 is a schematic illustration of a compression ignition engine and its fuel supply systems, and Figure two is a detail perspective of a vortex arranged to effect a mixing of liquid fuel into a heated supply of air, and

Figure 2 is a perspective view of the vortex creator.

A turbocharged diesel engine 1has an inlet manifold 2 and an exhaust manifold 4. As per standard practice, exhaust gases are expelled from the cylinder combustion chambers via exhaust manifold 4 and they are then passed through a turbine 6 of a turbocharger 8, which in turn drives a turbochargers compressor

10 by virtue of the fact that the turbine and the compressor ride on a common shaft.

Inlet air is drawn through air filter 12 and passed to the compressor 10 side of the turbocharger 8 via a pipe, where it is compressed to a pressure above atmospheric which air is also at an elevated temperature by reason simply of its compression. This compressed and somewhat heated air is then passed through the intercooler 14 to reduce its temperature where the drop in its temperature increases density and mass flow rate of air passing in through the inlet manifold 2 of the engine 1 to the cylinders.

A much smaller proportion of the air available of the compressed air is bled off from the compressor 10 side of the turbocharger 8 and passed through a pipe 16 to a heat exchanger coil 18 positioned in the exhaust pipe within the , where it is heated. The arrangement is such that the velocity of air and the volume will result in a substantial rise in temperature of the air. This actual temperature will vary with each engine and the load placed on the engine but is chosen so far to be within the range of from 300 degrees centigrade to 500 degrees centigrade (a high temperature) upon exit from the heat exchanger. This heat exchanger is a coil with a small profile and as such can be placed in the axial center of an exhaust outlet of conventional type without causing an undue increase in backpressure. The length of the coil is chosen also with the heat exchange capacity in mind.

This heated and compressed air is then passed through a pipe 20 to a vortex generator 22 where it is swirled into a vortex. This mechanism which has been previously described is a useful mixer and has the advantage of causing a high velocity of fluid with appropriate turbulence which assists significantly the mixing and evaporation of the liquids.

There is a liquid injection nozzle for the supplementary fuel (ethanol with water in this case) positioned in the wall of the vortex generator 22 toward its upstream end. A fuel pump 23 pumps the ethanol from a fuel tank 25 to the injection nozzle. A pulse width modulating (PWM) solenoid actuated valve 24 then controls introduction of ethanol and water into the vortex of air, mixing the air and ethanol.

Diesel fuel is fed to the engine as per standard practice, wherein a pump 30 pumps fuel from a fuel tank 32, and then on to an injector rail 34 and the fuel injectors, which inject the fuel into the combustion chamber.

In use, the engine in trials conducted so far, is started and run at light loads on diesel fuel only. As engine load, and therefore inlet manifold pressure increases, a pressure sensor reads inlet manifold pressure (IMP) (and also inlet manifold temperature) and sends a signal to a programmable controller or micro-controller 36 that controls the solenoid-controlled valve 24 in response to this IMP.

Pulse width will vary then from 10% effective on at 3OkPa inlet manifold pressure to 100% effective on at 7OkPa IMP, which typically corresponds with an engine load of approximately 50%.

Ethanol substitution of up to 50% ethanol by useful energy supply and 50% diesel is chosen to occur at 50% engine load. Between 50% and 100% engine load the volumetric flow rate of ethanol provided is chosen to remain constant, but the relative substitution rate is chosen to diminish to 25% ethanol effective energy contribution and 75% diesel effective energy contribution at full engine load.

The embodiment illustrates only one example but illustrates a general principle that is a subject of this description.

Alternatives that are also noted are the available use of many different fuels which are primarily liquid but which can be evaporated as described.

While the provision of a tap from downstream of the turbocharger allows for a supply of air to be available at a higher relative pressure to the pressure at the inlet manifold, none the less the air can be separately obtained and pressurised for supply through a heat exchange mechanism prior to mixing with the liquid supplementary fuel.

A factor in the extent of volume and temperature of the heated air and extent of supplementary fuel is that by effecting evaporation, this will cause the air to be substantially saturated. However, by then introducing this small volume of substantially saturated (depending upon the load settings) air into a much larger volume of air even though this is at a lower temperature this is then, in trials conducted so far, able to be done without substantial condensation within the main air inlet. This is however a constraint in relation to the proportion of supplementary fuel that can be introduced in the air inlet in this way. The amount of air and in turn the quantity of supplementary fuel introduced into that air can be chosen based on the extent to which such mixture may then enter into the main air stream without undue condensation occurring. A small momentary condensing that would re evaporate as the introduced vapour mixes generally with the main stream air is considered at the moment in practise to be satisfactory. These factors are necessarily different for each engine type and size and would in practise be determined by trial for each set up so as to enable a maximum of fuel to be able to be introduced without undue condensation on reinsertion. The system explained also then has the advantage that a very significant proportion of supplementary fuel and especially including water as well will be able to be effectively and compatibly used with a diesel fuel based compression ignition engine.

There is some further advantage of introducing a mixer for instance diversion vanes within the downstream location of the air inlet passageway to the engine so as to assist in mixing the introduced air with fuel vapour before it enters the inlet manifold. This also assists then in ensuring a reasonable uniformity in supply to multiple cylinders of the engine.