Field of Invention

The present invention relates to internal combustion engines, in particular to such engines adapted to utilise heat generated by the combustion process and conventionally wasted to generate steam for augmenting the power output of the engine.

Background

The waste heat produced during the power stroke of a conventional internal combustion engine is generally dissipated in two ways:-

(i) the hot exhaust gases are rapidly released into the atmosphere via an exhaust pipe;

(ii) heat is removed from engine components by, typically, a water cooling system, and dissipated to the atmosphere through a radiator.

The thermal efficiency of such engines is low with consequent high fuel running costs and high levels of emissions. Moreover the cooling system referred to in (ii) above significantly adds complexity to the engine leading to greater capital and ownership costs.

Many attempts have been made to use this waste heat to convert water into steam, and to subsequently use the steam to augment the power output of the engine.

U.S. Patent Number 1,424,798 to Black discloses a hybrid two-cycle engine, which produces steam by mixing pre-heated water with a portion of the combustion gases, which is isolated into a secondary chamber shorty after conventional combustion. Steam is separately generated in the secondary chamber during the conventional power stroke of the engine, and then introduced into the combustion chamber to produce a steam-driven power cycle. The engine therefore operates on alternate steam/conventional combustion power cycles. The isolation of a portion of gases during each conventional power cycle to produce steam results in a corresponding power loss, significantly offsetting the benefits of the steam-driven power cycle.

Also, only a small portion of the combustion gases is utilised for the production of steam, and the bulk of the hot combustion gases are not used for the generation of steam, thus resulting in considerable heat wastage and severely limiting the potential additional power that may be produced by this engine. Furthermore, this engine comprises a construction which is expensive and complex and does not lend itself to retro fitability, particularly on engines operating on a four-stroke cycle.

U.S. Patent Number 4,433,548 to Hallstrom discloses an internal combustion engine having a steam generation chamber. At the end of the exhaust stroke, the combustion gases are exhausted from the combustion chamber to the atmosphere via the steam generation chamber, which comprises a quantity of heat conductive material. The heat stored in the steam generation chamber during the exhaust stroke of the engine, particularly the heat conductive material, is used for converting water that is injected into the steam generation chamber into steam. The steam is subsequently introduced into the combustion chamber to produce a power stroke. The steam generation chamber requires costly and complex modifications to the engine.

Furthermore, the temperature of the exhaust gases is not diminished significantly in heating up the heat conductive material, so that a cooling system is still needed, and, full use of the waste heat present in the combustion gases is not made, thus severely limiting the potential steam power output of the engine.

U.S. Patent Number 5,191,766 to Vines discloses an internal combustion engine modified to introduce water into the exhaust port of each cylinder concurrently with the end of the exhaust stroke, and the exhaust gases are thus used to produce steam outside the combustion chamber. Steam generated according to this reference is directed to a steam powered take off device, for example a steam turbine operatively connected to the crankshaft of the engine or to the wheels of an associated vehicle, to produce additional power. Thus complex and costly modifications are required for this engine. Water is converted to steam directly by the exhaust gases, which being at a considerably lower temperature than at the beginning of the power stroke, significantly limits the steam power that may be generated by this device.

U.S. Patent Numbers 3,959,974, 4,301,655 and 4,417,447 to Thomas disclose internal combustion engines wherein water is cyclically introduced into a portion of the cylinder or piston for providing steam. In U.S. Patent Number 3,959,974, water is injected through the cylinder head into the combustion space above a ringless high temperature piston. In U.S. Patent Number 4,301,655, water is injected into a cavity formed in a cylinder head having recess means for increasing surface area for maximising the absorption of heat of combustion. In U.S. Patent Number 4,417,447, water is introduced into a bulbous cavity formed in the specially thickened upper portion of a ringless piston. In each reference, the engines are operated on alternate

steam/combustion cycles, wherein water introduced into the cylinder is vaporised on direct contact with the corresponding portion of the cylinder or piston which was previously heated to a high temperature dunng the preceding combustion power stroke, rather than directly by the combustion gases. The engines need to be run at a high temperature, and therefore require ringless high-temperature pistons, as well as comprising other costly and complex modifications to the engines. Furthermore, the temperature of the combustion gases is not diminished significantly in heating up the corresponding portion of the cylinder or piston, so that a cooling system may still be needed, and, full use of the waste heat present in the combustion gases is not made, thus severely limiting the potential steam power output of the engine.

An aim of the present invention is to provide an integrated internal combustion/steam engine which overcomes the above-mentioned limitations, in particular to substantially maximise the utilisation of waste heat in the combustion gases.

Another aim of the present invention is to provide a method for augmenting the power output of an internal combustion engine by utilising as much as possible of the of the heat of the combustion gases during the combustion stroke for producing additional power for the engine.

Another aim of the present invention is to provide such an integrated engine having significantly lower fuel consumption than a conventional engine of similar power output.

Another aim of the present invention is to provide such an integrated engine of lower overall weight and size than a conventional engine of similar power output.

Another aim of the present invention is to provide such an integrated engine having significantly lower cooling requirements than a conventional engine of similar power output. It is a further aim to remove the need for a cooling system entirely.

Another aim of the present invention is to provide such an integrated engine having significantly smaller exhaust pipe and silencer requirements than a conventional engine of similar power output. It is a further aim to remove the need, in some cases, for a catalytic converter in the silencer.

Another aim of the present invention is to provide such an integrated engine having significantly higher power output at substantially the same fuel consumption than a conventional engine of similar size and specifications.

Another aim of the present invention is to retroactively provide a conventional internal combustion engine with water injection means to augment the engine power output and/or to reduce fuel consumption.

These aims are achieved by a revolutionary approach to the design of such an integrated engine, wherein a conventional internal combustion configuration is retained and modified to include at least one water injector in each cylinder capable of supplying a predetermined volume of water into the combustion chamber just after ignition and combustion of the fuel/air mixture therein. The heat of the combustion gases converts water into steam, which augments the pressure in the combustion chamber at the beginning of the power stroke, thus increasing the power output of the engine as compared to a conventional

engine of similar specifications. Additionally, the temperature of the gases in the combustion chamber is reduced, resulting in a comparatively cooler exhaust.

Another aim of the present invention is to provide an integrated internal combustion/steam engine having any suitable combination of the advantages as set out in the above aims, wherein the combustion is either spark- initiated or which employs compression-ignition such as in diesel engines.

Another aim of the present invention is to provide such an engine which is readily retrofittable with respect to conventional engines in a host of settings including their employment as motor vehicle, marine, and aircraft engines, as well as powerplants for the generation of electricity.

Summary of Invention

An integrated internal combustion/steam engine comprising: at least one cylinder having at least one combustion chamber and a reciprocating internal piston operatively connected to a crankshaft; means for introducing air and combustible fuel separately or premixed into said combustion chamber to provide a power stroke for said piston; ignition means for igniting said air/fuel mixture; means for exhausting fluid contents of cylinder after power stroke; and characterised in further comprising: means for introducing a predetermined volume of water into said cylinder during the power stroke at a predetermined period after ignition and combustion of said air with said fuel, wherein at least a portion of said volume of water is directly vaporised by the heat of said combustion gases into a pressurised volume of steam.

Description of the Figures

Figure 1 illustrates in cross-sectional view some of the major components of a typical internal combustion spark-ignition engine of the prior art.

Figure 2 illustrates in partial cross-sectional view some of the major components of a preferred embodiment of the present invention.

Figure 3 illustrates in cross-sectional view some of the major components of a typical internal combustion compression-ignition engine of the prior art.

Figure 4 illustrates in partial cross-sectional view some of the major components of another embodiment of the present invention.

Description

The present invention relates to an integrated internal combustion/steam engine comprising:-

- at least one cylinder having at least one combustion chamber and a reciprocating internal piston operatively connected to a crankshaft;

- means for introducing air and combustible fuel separately or premixed into said combustion chamber to provide a power stroke for said piston;

- ignition means for igniting said air/fuel mixture;

- means for exhausting fluid contents of cylinder after power stroke;

and characterised in further comprising:-

- means for introducing a predetermined volume of water into said cylinder during the power stroke_ at a predetermined period after ignition and combustion of said air with said fuel, wherein at least a portion of said volume of water is directly vaporised by the heat of said combustion gases into a pressurised volume of steam.

Referring to Figure 1, conventional internal combustion spark-ignition engines comprise at least one cylinder (10) having an internal reciprocating piston (16) operatively connected to a crankshaft (20), and an upper combustion chamber (22).

Said cylinder (10) further comprises means for introducing air and fuel separately, comprising: an air inlet pipe (61) in open communication with an inlet port, having an inlet valve (12), and an air supply, typically the atmosphere; and a fuel inlet pipe (not shown) in communication with an inlet port (not shown) in the combustion chamber (22) and a fuel supply (not shown). Alternatively, said cylinder comprises means for introducing air and fuel which has been previously premixed, for example, in a carburetor, said means comprising an inlet pipe (61) in open communication with said carburetor and an inlet port in the combustion chamber having an inlet valve (12). Said cylinder (10) further comprises means for exhausting the fluid contents of the cylinder after the power stroke, comprising an outlet pipe (30) in open communication with an outlet port in the combustion chamber (22) having an outlet valve (14).

The said cylinder (10) further comprises ignitor means (18) such as a spark plug.

Most conventional internal combustion spark-ignition engines operate on a four-stroke cycle, though some engines work on a two-stroke cycle. On a typical four-stroke Otto cycle, the first - inlet - stroke consists of a downwards motion of the piston (16), the inlet valve (12) being synchronised to open and draw in an appropriate air/fuel mixture from a carburetor or, with a fuel injection system, only air, wherein the cylinder (10) further comprises a fuel injection port (not shown) for introducing a predetermined amount of fuel at synchronised times. In the second stroke, also known as the compression stroke, the piston ( 16) moves upwards compressing the air/fuel into the combustion chamber (22). Typically, shortly before the piston reaches top dead centre, the air/fuel mixture is ignited by the ignitor means (18). Rapid combustion occurs, accompanied by the production of combustion gases having high temperature and pressure. In the third stroke, the power stroke, the high pressure combustion gases force the piston (16) downwards, providing a rotary power output via the crankshaft (20). In the fourth - exhaust - stroke, the outlet valve (14) is synchronised to open, so that the combustion gases may flow out of the cylinder (10) as the piston (16) moves upwards to top dead centre again to commence another cycle.

The timing and duration of the spark as well as the proportions of the air/fiiel mixture are important parameters which vary with engine speed and load, and which have to be controlled carefully. Though mechanical systems have been used in the past for control, electronic microprocessors operatively connected to suitable fuel injection systems provide greater and more reliable control, and are known in the art.

The present invention also relates to an integrated internal combustion/steam engine comprising:-

- at least one cylinder having at least one combustion chamber and a reciprocating internal piston operatively connected to a crankshaft;

- means for introducing air into said combustion chamber, wherein said air is compressed to provide an air temperature greater than a predetermined minimum temperature preceding a power stroke;

- means for introducing fuel into said combustion chamber to provide a power stroke, said fuel igniting on contact with said air at said air temperature;

- means for exhausting fluid contents of cylinder after power stroke;

and characterised in further comprising:-

- means for introducing a predetermined volume of water into said cylinder during the power stroke at a predetermined period after ignition and combustion of said fuel with said air, wherein at least a portion of said volume of water is directly vaporised by the heat of combustion gases into a pressurised volume of steam.

Such conventional internal combustion engines thus employ compression ignition, and are also known as Diesel engines. Typically, the operation of a Diesel engine is similar to the spark-ignition engine hereinbefore described, mutatis mutandis, having similar four-stroke cycle of a reciprocating piston (see Figure 3). The major difference is the absence of an ignitor means (18), as well as ancillary electrical and/or electronic equipment, and, air alone is introduced into the combustion chamber during the induction stroke. At top dead centre during the compression stroke, after the air is heated by the

compression, fuel is introduced into the combustion chamber via fuel port

(28) and subsequently ignites on contact with the hot compressed air. The injection of fuel typically continues for a substantial portion of the power stroke. Since the air has to be heated to a relatively high temperature by compression, Diesel engines tend to have a high compression ratio and a high working temperature.

The following description, though directed at internal combustion engines operating on the Otto cycle, is also applicable to other internal combustion engines including Diesel engines, mutatis mutandis.

According to the present invention, and with reference to Figure 2, a preferred embodiment of the engine (1) comprises at least one said cylinder (10), having an inlet pipe (61) comprising an inlet valve (12), and an outlet pipe (30) comprising an outlet valve (14), a combustion chamber (22) and ignitor means (18), and an internal reciprocating piston (16) operatively connected to a crankshaft (20), substantially as hereinbefore described. Said engine (1) further comprises water introduction means comprising at least one water introduction inlet port (50) in open communication with a pressure delivery means (60), via a high pressure connecting pipe (65) comprising a one-way valve (62). Said pressure delivery means (60) enables water to be pressurised to a pressure greater than that of the combustion gases. A control system (90) controls said pressure delivery means (60) to deliver a predetermined volume (V) of water to the inlet (50) and into the combustion chamber (22), at a predetermined period (T) after ignition and combustion of said air with said fuel, according to the mode of engine operation and its corresponding control parameters. The said engine (1) further comprises a water tank (70) in communication with the said inlet (50). A suitable filter

(78) and the said pressure delivery means (60) are disposed between the tank

(70) and the inlet (50). A low pressure pjpe (75) delivers water to the said pressure delivery means (60) from the tank (70) via the filter (78).

Advantageously, the volume (V) of water that is injected into the combustion chamber may be preheated, e.g. by a heating element or preferably by heat transfer from the engine block by any suitable means, e.g. a heat exchanger or condenser (80) by re-routing (broken line (A) in Figure 2) the said high pressure pipe (65) through same, are hereinafter described. Said pressure delivery means (60) may comprise, for example, a suitable water pump, many varieties of which are well known in the art.

In the preferred embodiment, the engine (1) further optionally comprises a condenser (80) in open communication with the outlet pipe (30) and the tank (70). With reference to Figure 2, as the combustion gases together with steam are passed through the condenser (80), the steam condenses into water and is separated from the combustion gases and re-routed back to the tank (70), thereby minimising consumption of the water in tank (70). The combustion gases are exhausted to the atmosphere via an exhaust duct (35), in open communication with said condenser (80), and typically a silencer (not shown). The condenser (80) may be coupled to the high pressure pipe (65) so that as the steam is condensed, the released heat of condensation is utilised for preheating water in said high pressure pipe (65) prior to injection into the combustion chamber (22).

In the present invention, a predetermined volume (V) of water is injected under pressure into the combustion chamber (22) shortly after ignition and combustion of the gases, i.e., shortly after the beginning of the power stroke. Preferably, said volume (V) is chosen as the maximum volume of water that

may be fully evaporated according to conditions in the combustion chamber, i.e., the temperature and pressure therein after ignition and combustion, and will thus vary according to the load and speed of the engine. Typically, said volume (V) may only comprise a few drops of water. The volume (V) of water is directly converted to steam - typically explosively - by the heat of the combustion gases, thereby increasing the pressure in the combustion chamber and simultaneously reducing the temperature of the combustion gases and of the engine. In a preferred embodiment, the volume (V) of water that is introduced into the combustion chamber is carefully metered, preferably controlled by a control system (90) hereinafter described. Further, the volume (V) is preferably not allowed to exceed an upper limit that would reduce the temperature of the gases and steam to below the critical point of steam, i.e., approximately 374.4°C, for at least a major portion of the power stroke. The vaporisation of said volume of water (V) into steam instantaneously increases the mean pressure of the combustion gases/steam mixture relative to the mean pressure of the combustion gases prior to said vaporisation. The power generated during the power stroke is thus significantly increased. Furthermore, the running temperature of the engine is also reduced, thereby requiring a lower capacity cooling system in relation to a conventional internal combustion engine of comparable power output.

Preferably, the necessity for an engine cooling system is altogether negated by ensuring that sufficient water is added at each power stroke so that the temperature of the engine body is reduced to well below 99°C during the exhaust stroke. This may be particularly suitable for applications in which engine acceleration is experienced for only a very small percentage of the engine running time. It is then preferable to maintain the engine thermally insulated from the external environment, so that, contrary to conventional

practice, rather than attempt to rid the engine of unwanted waste heat, it is desired to conserve as much heat as possible in order to utilise the same for the production of steam, and thus further increase the efficiency of the engine of the present invention.

The precise synchronisation of the introduction of water into the combustion chamber (22), i.e., timing of introduction of water after ignition or period (T), time window (t) during which water is introduced, volume (V) of water that is introduced and pressure of the water are determined and controlled by the said control system (90). Typically, water is introduced just after ignition and combustion of the air/fuel mixture which is determinable according to engine specifications such as the type of ignitor and fuel, and is usually expressed as a number of degrees of revolution of the crankshaft (20) after top dead centre of the piston during the power stroke.

As the rotational speed (RPM) of the said engine (1) is increased, there is a possibility that the time window (t) available for introducing water during the power stroke reduces, and at times may not permit sufficient water to be introduced to provide adequate power augmentation. Optionally, then, the running of the engine may be modified to include the introduction of a predetermined auxiliary volume, (V2), of water during the inlet stroke or even the compression stroke. The said control system (90) may thus be programmed to enable said volume (V2) of water to be introduced via said water introduction means during the inlet or compression stroke, when required. Of course, the magnitude of (V2) has to be carefully controlled, since, if too much water is introduced prior to the combustion stroke, the efficient combustion of the fuel/air mixture may be hampered or altogether prevented; alternatively, if (N2) is too low, and not sufficient water may be

introduced at the combustion stroke, due to, e.g., high RPM of the engine, then not enough steam may be produced .to sufficiently augment the power output of the engine.

In the preferred embodiment of the present invention, the water introduction means may be integrated into the engine design to provide, for example, a smaller engine having the same power output as a larger conventional internal combustion engine. Alternatively, the said water injection means are suitably retrofitted onto a suitable conventional internal combustion engine, thereby increasing its power output.

Said water introduction means may also be incorporated into the design of the fuel injection means, for example by having twin corresponding feeder pipes with a common entry port to the combustion chamber, each feeder pipe being controlled separated according to the control system (90).

In a different embodiment of the invention, a conventional engine having a power output of, say P kW, may be replaceable with an integrated engine according to the present invention which would have a comparatively lower power output if run conventionally, i.e., without water being introduced. Thus, for example, a vehicle having a conventional engine rated at P kW may be replaced with a significantly smaller engine according to the present invention capable of generating less power when operated in a conventional manner. When adapted to be operated according to the present invention, the additional power provided by utilising the excess heat to produce steam enables the engine to produce approximately P kW, comparable to the larger original conventional engine. In this embodiment, the costs and complexity associated with the modifications to the engine according to the present invention may be substantially offset against the gains in achieving a smaller

and potentially less expensive engine. Furthermore this embodiment comprises a cooling system of substantially lower duty than a corresponding conventional internal combustion engine of substantially similar size or power output. Further still, a smaller exhaust duct and silencer is required, since there is a smaller quantity of combustion gases in the exhaust, and, if this quantity is small enough falling below the prescribed legal minimum levels for which installation of a catalytic converter is mandatory, the need for the same is also negated, resulting in a cheaper exhaust, duct.

Alternatively, in another embodiment, the cooling system is not retained.

In the preferred embodiment of the present invention, said engine ( 1 ) further comprises a control means, comprising a control system (90) preferably including an electronic microprocessor. When the said engine (1) incorporates fuel injection means, the said control system (90) optionally also controls the amount of fuel injected into said combustion chamber (22) and timing thereof. Said control system (90) determines the magnitude of the said volume (V) of water, as well as the said predetermined period (T) for introducing same during the power stroke and the time window (t). Preferably, said control system (90) determines the magnitude of the volume (V) of water, said predetermined period (T) and time window (t) according to a pre-programmed algorithm. In the preferred embodiment of the present invention, the said cylinder (10) further comprises a suitable heat sensor means (40), for example, a high temperature thermocouple, which may be located proximal to or within the combustion chamber, or, preferably, within the said outlet pipe (30) proximal to said outlet valve (14). Said heat sensor means (40) is operatively connected to the said control system (90). At the end of a power stroke, the said heat sensor means (40) measures the corresponding temperature at its location. Alternatively, a gas sensor means

(not shown) may be used in place of or in addition to said heat sensor means

(40) to monitor the concentration of a predetermined component of the exhaust products, such as the level of hydrocarbons (CH), carbon monoxide

(CO), carbon dioxide (C0 ₂ ), residual oxygen (0 ₂ ) or oxidising free radicals.

This temperature measurement or exhaust product concentration may then be used by the control means (90) for determining the magnitude of the said volume (V) (and optionally (V2) as well) of water that is required to be introduced into the said combustion chamber (22) during the succeeding power stroke, according to the preprogrammed algorithm of the control system (90). Methods for constructing a suitable control system and for formulating an appropriate algorithm as described are known in the art. Said algorithm may require appropriate calibration of engine control parameters such as the said working temperature and exhaust product concentrations under different engine loads and conditions, and methods for conducting such calibrations are also known in the art.

In a similar manner to conventional internal combustion engines, the engine ( 1 ) may optionally further comprise suitable means for supercharging the air prior to introducing the same into the said combustion chamber (22), or for turbocharging the engine. Means for supercharging air and turbocharging engines are well known in the art and are easily adaptable to said engine (1).

The aforegoing description also applies to other embodiments of the present invention relating to different forms of internal combustion engines, mutatis mutandis. In particular, and with reference to Figure 4, a different embodiment of the present invention relating to compression ignition engines such as Diesel engines comprises an engine (2), which while lacking the ignitor means (18) comprises all the other features of the preferred

embodiment as hereinbefore described, mutatis mutandis. Thus, said engine

(2) further comprises a fuel system (not shown) for delivering fuel via fuel port (28) into the combustion chamber (22) when required.

The present invention also relates to a method for augmenting the power output of an internal combustion engine comprising the steps of providing an internal combustion/steam spark-ignition engine comprising as hereinbefore described, and further providing said engine with means for introducing a predetermined volume of water into said cylinder during the power stroke at a predetermined period after ignition and combustion of said fuel with said air, wherein at least a portion of said volume of water is directly vaporised by the heat of combustion gases into a pressurised volume of steam.

The present invention also relates to a method for augmenting the power output of an internal combustion engine comprising the steps of providing an internal combustion/steam compression-ignition engine comprising as hereinbefore described, and further providing said engine with means for introducing a predetermined volume of water into said cylinder during the power stroke at a predetermined period after ignition and combustion of said fuel with said air, wherein at least a portion of said volume of water is directly vaporised by the heat of combustion gases into a pressurised volume of steam.

Though only a few embodiments have been described in the foregoing description, the present invention is not limited thereto, and is only defined by the scope of the claims.