GB2541018A

GB2541018A - An energy recovery apparatus and an internal combustion engine

Info

Publication number: GB2541018A
Application number: GB1513928.0A
Authority: GB
Inventors: Joseph George
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-08-06
Filing date: 2015-08-06
Publication date: 2017-02-08
Also published as: GB201513928D0; WO2017021737A1

Abstract

Disclosed is an energy recovery apparatus 100 for an internal combustion engine 102 having an exhaust outlet 110. The energy recovery apparatus 100 comprises: a fluid supply means 114 arranged to supply a fluid and a piston-less rotary expander mechanism 118. The piston-less rotary expander mechanism 118 is arranged to receive exhaust gases from the exhaust outlet 110 and fluid from the fluid supply means 114. The piston-less rotary expander mechanism 118 is powered by the fluid and the exhaust gases. An internal combustion engine comprising the energy recovery apparatus 100 is also disclosed. The fluid may be heated by a heat source and the fluid may comprise water. The piston-less rotary expander 118 may comprise a rotary Wankel engine. The piston-less rotary expander mechanism is used to recover otherwise lost energy from exhaust gases and may be used to rotate a drive shaft.

Description

An energy recovery apparatus and an internal combustion engine

The present invention relates to an energy recovery apparatus for an internal combustion engine and, further relates to an internal combustion engine. The present invention may in particular relate to an internal combustion engine for a vehicle, but may also be suitable for use with a fixed or stand-alone engine for a generator.

During operation of an internal combustion engine, it is known that significant amounts of energy can be lost as thermal energy rejected to a cooling system and both thermal and kinetic energy in the engine exhaust gasses. This lost energy is not converted to useful kinetic energy in the form of rotation of the engine drive shaft, and so reduces the overall efficiency of the engine.

Several systems to recover energy lost from internal combustion engines are known in the art. It is known, for example, to employ a six-stroke engine cycle in which water is injected directly into the cylinders of an internal combustion engine. The water is vaporised by heat from the exhaust gases remaining in the cylinder and the heated surfaces of the cylinder itself. When the water is vaporised, the piston is reciprocated through an additional cycle without the use of any further fuel ignition, thus recovering energy that would otherwise be lost. This system may be problematic because water injected into the cylinder may cause corrosion and damage to surfaces within the cylinder.

It is also known to use a turbocharger in which a turbine is driven by pressure in the exhaust output of the engine. This however recovers only kinetic energy from the exhaust. Alternative systems include the use of a Rankin cycle in which a fluid is vaporised by heat from the engine exhaust. The vaporised fluid is then used to drive an expander which produces a rotary output. The rotary output can then be coupled to the engine crankshaft or an electric generator. This however recovers only thermal energy from the exhaust.

In a first aspect, the present invention provides an energy recovery apparatus for an internal combustion engine, the internal combustion engine comprising an exhaust outlet, the apparatus comprising any one or more of the following features: a fluid supply means arranged to supply a fluid; and a piston-less rotary expander mechanism arranged to receive exhaust gases from the exhaust outlet and heated fluid from the fluid supply means, wherein the piston-less rotary expander mechanism is powered by the heated fluid and the exhaust gases.

The energy recovery apparatus of the present invention provides a piston-less rotatory expander mechanism that is powered by the energy recovered from exhaust gases from the engine by vaporising the fluid. By introducing fluid into the exhaust gases within the rotary expander, rather than within the combustion engine, damage or corrosion within the internal combustion engine is reduced.

Optionally, the fluid supplied by the fluid supply means may be heated by a heat source. This means that the fluid may be more efficiently vaporised and may mean that energy from the exhaust gases is more efficiently converted into movement of the expander mechanism.

Optionally, the heat source may comprise at least part of the internal combustion engine. This allows the energy recovery apparatus to recover energy from both the heated exhaust gases and heat generated by the internal combustion engine that would otherwise not be converted into useful kinetic energy. This may allow a greater proportion of energy to be recovered by the energy recovery apparatus of the present invention compared to those of the prior art.

Optionally, the apparatus may further comprise a heat exchanger arranged to heat the fluid by transfer of thermal energy from a cooling system of the internal combustion engine. This means that the fluid can be heated by an existing cooling system of the internal combustion engine. The energy recovery apparatus can therefore be fitted to existing internal combustion engine designs.

Optionally, the fluid supply means is arranged to transfer heat directly from the internal combustion engine to the fluid. This means that the fluid is heated directly by the internal combustion engine and the fluid supply means can therefore act to both cool the engine and power the rotary expander mechanism.

Optionally, movement of the piston-less rotary expander mechanism is powered by energy from the heated fluid and exhaust gases. The rotary expander mechanism is therefore arranged to convert energy from the heated fluid and exhaust gases to movement of the rotary expander, thereby recovering energy from the energy of the heated fluid and exhaust gases in the form of movement of the expander mechanism.

Optionally, the piston-less rotary expander mechanism comprises a housing and a rotary member movable within the housing, wherein movement of the rotary member is caused by expansion of the fluid, the exhaust gases or both. Expansion of the fluid and the exhaust gases pushes against the rotary member, thereby converting energy in the fluid and exhaust gases into kinetic energy of the rotary member.

Optionally, the housing and rotary member define a moving expansion chamber arranged to receive the exhaust gases and wherein the piston-less rotary expander mechanism further comprises a fluid injection means arranged to inject fluid from the fluid supply means into the expansion chamber. By injecting fluid into the expansion chamber the exhaust gases may vaporise the fluid, thus creating a rapid expansion of the fluid to drive the movement of the rotary member.

Optionally, the piston-less rotary expansion member may further comprise an inlet port in communication with the exhaust outlet, and wherein the rotary member may be movable to draw exhaust gases into the expansion chamber via the inlet port. This draws exhaust gases into the expansion chamber by movement of the rotary member and therefore avoids the need to use valves or the like to inject exhaust gasses. This is advantageous because such valves may become blocked by waste deposits from the fluid when vaporised. This means pure water is not required for the fluid.

Optionally, the rotary member may be movable to compress exhaust gases within the expansion chamber and wherein the fluid injection means is arranged to inject the fluid into the expansion chamber during or after compression of the exhaust gases. By compression of the exhaust gases the temperature and pressure of the gases within the expansion chamber may be increased before being combined with the fluid.

Optionally, the fluid injection means may be arranged to inject the fluid into the expansion chamber at or near the point of maximum compression of the exhaust gases.

This means that the fluid is injected after the exhaust gases have been compressed and heated so as to more efficiently and effectively vaporise the fluid to drive the rotation of the rotary member.

Optionally, the piston-less rotary expander mechanism may further comprise an outlet port, and wherein the rotary member may be movable to vent the expansion chamber via the outlet port. This means that the rotary member cyclically vents the expansion chamber such that the exhaust gases and fluid vapour (or remaining un-vaporised fluid) are expelled from the housing.

Optionally, piston-less rotary expander mechanism further comprises a sealing means arranged to provide a seal between the rotary member and the inner surface of the housing, wherein the sealing means is further arranged to at least partly remove deposits from the inner surface of the housing.. This means that material deposited on surfaces of the housing may be removed during use of the expander mechanism such that corrosion and seizing is reduced.

Optionally, the rotary member may be coupled to a motor arranged to rotate the rotary member from rest. This provides a starter motor to rotate the rotary member when the apparatus is first started and before the rotary member is driven by expansion of the fluid. In some embodiments, the motor may also act as an electrical generator which is powered by the rotation of the rotary member. In yet other embodiments, a separate electric generator and motor may be provided.

Optionally, the fluid supply means may comprise a fluid reservoir arranged to replace fluid vented from the outlet during use of the energy recovery apparatus. This means that the fluid does not need to be recovered from the vented gases. This reduces the number of components of the heat recovery apparatus so that it is less complex and lightweight. The reservoir may be refilled with fluid by the user when required.

Optionally, the piston-less rotary expander mechanism further comprises a condenser arranged to condense at least some of the fluid vented from the outlet, and wherein the condenser may be arranged to return the condensed fluid to the fluid supply means to form a closed system. This means that the fluid may be reused by the piston-less rotary expander mechanism so that a fluid reservoir may be smaller or not required which may reduce the overall weight of the heat recovery apparatus.

Optionally, the fluid may comprise water. Water may be advantageous because it provides a large ratio of expansion when converted from liquid to a vapour. As water expands by a factor of about 1700 times when it turns to steam a large ratio of expansion is produced so that potential energy can be efficiently converted into movement of the expander mechanism. In some embodiments, the water may be water that is not distilled e.g. tap water. Non-distilled water can be used as the sealing means and rotary member may act to remove deposits left by impurities in the water when it is vaporised. In some embodiments, softened water may be required to reduce deposits created by evaporation of the water.

Optionally, the piston-less rotary expander comprises a Wankel engine. Optionally, the piston-less rotary expander may be valve-less. This is advantageous because valves may become blocked during operation and so a valve-less system may be less complex and more reliable.

Optionally, the piston-less rotary expander mechanism may be coupled to an electrical generator or a turbo-charger. This allows the energy recovered from the exhaust gases and engine coolant to be used to generate electricity or force air and fuel into the engine to improve the efficiency of the engine.

Optionally, the piston-less rotary expander mechanism may further comprise a NOx reduction means. This allows NOx reduction and energy recovery to be combined into a single unit. By providing the dual function of energy recovery and NOx reduction, a separate NOx reduction means may not be required, thus saving space and weight.

Optionally, the NOx reduction means may comprise a reducing agent supply means arranged to introduce a chemical reducing agent into the expansion chamber of the piston-less rotary expander mechanism. By introducing the chemical reducing agent into the expansion chamber at the point of maximum compression the increased temperature of the exhaust gases within the expansion chamber may be utilised to increase the efficiency of the NOx reducing reaction.

Optionally, the reducing agent supply means may be arranged to inject the chemical reducing agent during or after compression of the exhaust gases. This means that the reducing agent is combined with the exhaust gases when they have been compressed and so when they are at or near the highest temperature generated within the expansion chamber.

Optionally, the chemical reducing agent may comprise urea solution or ammonia solution. By adding the urea to the chamber of the rotary expander it undergoes thermal decomposition in the heat and pressure generated. This may increase the efficiency of the NOx reducing reaction.

Optionally, the reducing agent may further comprise an oxidising agent. The oxidising agent may preferably comprise ammonium nitrate or hydrogen peroxide. This may help to increase the rate of the NOx reduction process.

Optionally, the NOx reduction means may comprise a catalyst disposed on a surface of the rotary member, the housing or both. The catalyst may combine with the reducing agent to provide a selective catalytic reduction (SCR) process. This may improve the efficiency of the NOx reducing reaction.

In a second aspect, the present invention provides an internal combustion engine comprising: an exhaust outlet and the energy recovery apparatus of the first aspect.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 shows a schematic of an energy recovery apparatus according to an embodiment of the invention;

Figures 2a to 2d show a schematic of an expander mechanism of an embodiment of the invention; and

Figure 3 shows an expander mechanism according to another embodiment of the invention.

An energy recovery apparatus 100 according to the present invention is shown schematically in Figure 1 coupled to an example of an internal combustion engine 102. The figures show a schematic representation of the invention only. The internal combustion engine may be a petrol or diesel engine and may in particular be suitable for use in a vehicle. In other embodiments, the internal combustion engine may be used for a different purpose, and may be for example a fixed position or stand-alone engine used to power a generator or the like. The present invention may therefore be suitable for internal combustion engines of any scale and may be suitable for use with small scale engines used in a vehicle or larger scale fixed engines used to drive generators in which energy recovery may be even more significant. The example internal combustion engine 102 shown in Figure 1 is a reciprocating engine and may therefore comprise one or more cylinders 104 (only one of which is shown in the schematic of Figure 1) as is known in the art. In other embodiments, the internal combustion engine may be a turbine engine or the like, rather than a reciprocating engine as shown. The cylinder 104 of the example internal combustion engine shown in Figure 1 is arranged to receive a piston 106 which is coupled to a crank shaft (not shown in the figures) such that reciprocating movement of the piston 106 causes rotation of the crank shaft, thus providing a rotary output from the internal combustion engine 102. The internal combustion engine 102 further comprises one or more inlet valves 108 arranged to supply the cylinder 104 with air and fuel. The internal combustion engine 102 further comprises an exhaust outlet 110 arranged to allow waste gasses (i.e. exhaust gases) to be vented from the cylinder.

The internal combustion engine 102 may in some embodiments further comprise a cooling means arranged to cool the engine. The cooling means may comprise a coolant circuit 112 arranged to cool the cylinder 104 and piston 106. Such a coolant circuit 112 may comprise a coolant conduit arranged to carry a coolant, which in some embodiments may be oil for example. The internal combustion engine 102 may have additional features that are known in the art and so are not shown in Figure 1 and will not be described in detail in this application.

Referring again to Figure 1, the energy recovery apparatus 100 (herein referred to as The apparatus’) comprises a fluid supply means 114 arranged to supply fluid, and a piston-less rotary expander mechanism 118 (herein referred to as The expander mechanism’) arranged to receive exhaust gases from the exhaust outlet 110 and fluid from the fluid supply means 114.

The piston-less rotary expander mechanism of the present invention is a piston-less rotary engine which, rather than using reciprocating pistons, relies on a rotor to covert pressure into rotating motion. Such an expander mechanism may be less reliant on valves for its operation and so may be less complex and more reliable. In some embodiments, the piston-less rotary expander mechanism may be valve-less (i.e. may operate without the use of valves). This is advantageous because valves may become blocked during operation and so a valve-less system may be less complex and more reliable.

In some embodiments, the fluid supplied by the fluid supply means may be heated by a heat source. The fluid may be pre-heated to a temperature close to (or part way towards) its boiling point or flash evaporation point. By pre-heating the fluid, the fluid may be more efficiently converted into a vapour by the heat of the exhaust gasses. This means that the heat from the exhaust gases may be required only to vaporise the fluid, rather than heat it to its boiling or flash evaporation temperature. This allows the energy of the exhaust gases to be more efficiently converted into movement of the expander mechanism such that the energy more effectively converted into useful kinetic energy. In other embodiments, the fluid supplied by the fluid supply means may not be pre-heated (e.g. may be at or close to ambient temperature). In such an embodiment, the fluid may comprise alcohol (or other volatile substances) rather than water.

In the preferred embodiment, the heat source comprises at least part of the internal combustion engine 102. In this embodiment, the fluid is heated at least partly by heat generated by the internal combustion engine 102. In some embodiments, the heat source may comprise a part of the exhaust system of the internal combustion engine 102 such that the fluid is heated by the exhaust of the internal combustion engine. In other embodiments, the heat source may be independent of the internal combustion engine 102 and may for example comprise an electric heater or the like. In other embodiments, the heat source may be powered by solar energy (e.g. the fluid may be solar heated) or may comprise any other low-grade thermal source. This may be particularly advantageous in embodiments where the internal combustion engine is used as a standalone engine for a generator, where the weight of the heat source is less important.

The expander mechanism 118 is powered by the fluid (which may be pre- heated) and the exhaust gases such that energy from the fluid and exhaust gases is used to generate movement of the expander mechanism 118. The expander mechanism 118 is therefore arranged to convert energy from the fluid and exhaust gases to movement of the expander mechanism 118. The fluid is expanded by converting the potential energy (thermal energy) stored in the fluid and the compressed exhaust gasses into kinetic energy. This allows energy that would otherwise have been lost in the energy of the fluid and exhaust gases to be recovered in the form of movement of the expander mechanism.

The expander mechanism 118 is arranged to mix or combine the exhaust gases and fluid as will be described in more detail in the following sections. When mixed, the exhaust gases cause the fluid to vaporise and rapidly expand in volume. For example, in embodiments where the fluid is water, the fluid is vaporised to create steam. This expansion is utilised to power the expander mechanism 118 to provide a rotary output.

The expander mechanism 118 may therefore in some embodiments allow part of the energy to be recovered from the exhaust gases (which may contribute about 30% of energy lost by the internal combustion engine 102) and coolant (which may contribute about 30% of the energy loss) of the internal combustion engine 102. The rotary expander of the present invention may therefore recover both kinetic and thermal energy which would otherwise be lost from the internal combustion engine 102. In particular, the apparatus 100 of the present invention may allow thermal energy to be recovered from the heated exhaust gasses and the engine coolant. The apparatus 100 may further allow energy in the form of kinetic energy to the recovered from the pressurised exhaust gasses. By converting energy from the heated fluid and exhaust gases into movement of the expander mechanism 118, energy in a more useful form is produced that can be utilised for various purposes. For example, the expander mechanism may be used to power an electrical generator or a turbo-charger or the like.

The fluid may be directly or indirectly heated by waste heat energy generated by the internal combustion engine (or any other heat source). The fluid may be heated to close to 100 °C (or may be at a pressure greater than atmospheric pressure and heated to a temperature greater than 100°C) such that it remains a liquid until vaporised in the expander mechanism 118. In the embodiment shown in Figure 1, the apparatus further comprises a heat exchanger 116. The heat exchanger 116 is arranged to transfer heat from the coolant within the coolant circuit 112 of the internal combustion engine cooling means to the fluid within the fluid supply means 114. The fluid is therefore heated by transfer of thermal energy from the coolant circuit 112 which carries thermal energy generated by the internal combustion engine 102. In this embodiment, the fluid in the fluid supply means is heated indirectly by the internal combustion engine (e.g. via the coolant circuit 112 and heat exchanger 116). This therefore means that the apparatus of the present invention recovers heat from the existing cooling circuit of the engine and so can be used with existing engine designs.

In some embodiments, the heat transfer from the coolant to the fluid supply means 114 may cool the coolant to sufficiently maintain the internal combustion engine 102 at a suitable operating temperature. In other embodiments, the coolant circuit 112 may further comprise an additional cooling means such as a radiator to further cool the coolant to maintain the internal combustion engine 102 at a suitable operating temperature.

In an alternative embodiment (not shown in the figures), the fluid within the fluid supply means may be heated directly by the internal combustion engine without the use of the heat exchanger 116. In such an embodiment, the fluid supply means may be arranged to cool the internal combustion engine 102 in place of, or in addition to, the coolant circuit 112. In this embodiment, the cooling means is therefore arranged to transfer heat from the internal combustion engine directly to the fluid to cool the engine and heat the fluid.

The fluid supply means 114 comprises a fluid conduit arranged to provide a supply of fluid from the heat exchanger 116 or internal combustion engine 102 to the expander mechanism 118. In some embodiments, the fluid supply means may further comprise a pump (not shown in the figures) to pump the fluid through the fluid conduit. The fluid may in some embodiments comprise water, or a mixture of water and urea or ammonia solution or other ΝΟχ reducing solutions. The fluid may in some embodiments also include an oxidising agent such as ammonium nitrate or the like, that may help provide a fast SCR reaction. The water may in particular be un-distilled water (i.e. mains supply water, or tap water, and may be for example softened tap water) as will be described later.

In the described embodiment, the rotary expander mechanism 118 comprises a housing 120 and a rotary member 122 movable within the housing 120. The rotary member 122 is arranged to define one or more moving expansion chambers within the housing 120. The number of expansion chambers may depend on the shape of the rotary member 122. For example, in the described embodiment, the rotary member 122 has a generally triangular cross section with convex arcuate side portions as can be seen in the figures. In this embodiment, the rotary member 122 is thus arranged to form three moving expansion chambers within the housing 120. In other embodiments, the rotary member 122 may have a different cross section and so form one, two, four, five or any other number of moving expansion chambers. In the described embodiment, the housing 120 is generally trichoidal in cross section, where the trichoidal shape is determined by the shape of the rotary member. In other embodiments, the housing may be any suitable shape (e.g. oval) such that it may be adapted to the shape of the rotary member 122 to allow a seal to be created between the housing and the rotary member. For example, the shape of the housing may be chosen to provide a substantially constant separation between an apex of the rotary member and the inner wall of the housing.

The rotary member 122 may in some embodiments be attached to a drive shaft 124 disposed at the centre of the housing via an eccentric coupling. The rotary member 122 is arranged to rotate within the housing 120 such that three moving expansion chambers are defined between the housing 120 and the rotary member 122 as described later. The expander mechanism 118 of the described embodiment may be of the type known generally as a Wankel engine in the art.

In the described embodiment, the expander mechanism 118 comprises an exhaust inlet 126 arranged to supply exhaust gases from the exhaust outlet 110 of the internal combustion engine into the expansion chamber. In some embodiments, the exhaust inlet 126 comprises a port through which exhaust gases are drawn into the expansion chamber(s) of the expander mechanism 118 by rotation of the rotary member 122. This means that the exhaust inlet 126 means does not require any moving parts (e.g. valves) to control the flow of exhaust gasses. This is advantageous because such moving parts may become blocked by fluid that has not been fully vaporised (e g. the expander mechanism may not be as susceptible to hydro-locking) or by deposits created by the vaporisation of the fluid or from the exhaust gases. The exhaust outlet 110 of the internal combustion engine 102 and the inlet 126 of the expander mechanism 118 may be connected via a connecting conduit. In some embodiments, the expander mechanism 118 may be disposed adjacent the internal combustion engine such that the exhaust inlet 126 and outlet 110 are in close proximity (e.g. the length of the connecting conduit is minimised). This may increase the pressure and temperature of the exhaust gasses entering the expander mechanism and may increase the amount of energy that may be recovered by the apparatus 100. In embodiments where the internal combustion engine 102 comprises more than one cylinder, the connecting conduit may comprise a manifold arranged to connect an exhaust outlet of each of the cylinders to the expander mechanism 118. In yet other embodiments, the connecting conduit (or manifold) may further comprise a turbocharger (or other such recovery apparatus) powered by the pressure of the exhaust gasses. In some embodiments, a plurality of recovery apparatuses 100 according to the described invention may be provided so as to extract energy from the appropriate cycle of each chamber of the internal combustion engine.

The expander mechanism 118 further comprises a fluid inlet 128 arranged to supply fluid from the fluid supply means 114 into the expansion chamber 118 (or chambers). The fluid supply means 114 may in some embodiments comprise a valve or the like arranged to periodically move from a closed state to an open state to allow a predetermined volume of fluid to intermittently enter the housing 120 (and therefore into the moving expansion chamber(s)). In some embodiments, the fluid inlet 128 may comprise a pressure injector (such as a diesel engine pressure injector or the like) arranged to inject the fluid into the housing under pressure. The pressure may be greater than the pressure within the expansion chamber at the point of injection, such that the fluid is forced into the expansion chamber. The timing of the operation of the valve may be such that fluid is supplied to the expansion chamber (or chambers) during or after the exhaust gases have been compressed. In other embodiments, the fluid supply means may be arranged to supply fluid such that it enters the expansion chamber at any point during its movement within the housing 120. In yet other embodiments, the fluid inlet means may be arranged to provide a continuous injection of pressurised fluid into the housing 120

The expander mechanism 118 further comprises an outlet 130. The rotary member is arranged to cyclically vent the expansion chamber via the outlet 130 as it rotates within the housing 120 during an outlet phase. Exhaust gases and vaporised fluid within the moving expansion chamber are therefore at least partly expelled from the housing 120 via the outlet 130 once the expansion process is complete. The outlet 130 may be connected to an exhaust system of the vehicle such that the exhaust gasses and vaporised fluid are expelled from the vehicle to the atmosphere thus forming an open system. In such an embodiment, fluid lost during use of the apparatus is replaced by fluid from a fluid reservoir forming part of the fluid supply means. The reservoir may be refilled with fluid by the user when required. This reduces weight and complexity of the apparatus as no additional components are required to condense the fluid from the exhaust gases. In some embodiments, the vaporised fluid vented from the expander mechanism 118 may be at least partly recovered and may be returned to the fluid supply means 114 to form a closed circuit. In some embodiments, the vaporised fluid may be at least partly recovered by a condenser or the like. In some embodiments, heat rejected by the condenser may be used to heat the fluid before being supplied to the expander mechanism (i.e. the heat source may comprise the condenser).

In some embodiments, the expander mechanism 118 further comprises a sealing means (not shown in the figures) arranged to provide a seal between the rotary member 122 and the housing 120. In some embodiments, the sealing means may comprise a sealing member disposed at some or all of the points of contact between the rotary member and the housing. For example, a sealing member may be disposed at each apex and/or each face of the rotary member 122. In some embodiments, the sealing means may comprise a metal or alloy seal, and may in some embodiments be biased towards the housing to maintain a sufficient seal. In some embodiments the sealing means may also be arranged to at least partly remove deposits formed on an inner surface of the housing 120 or fluid that has not been vaporised. This allows waste materials such as impurities or fluid which may be deposited on the inner surface of the housing 120 to be removed during operation of the expander mechanism 118. This may be particularly advantageous in embodiments where the fluid provided by the fluid supply means 114 comprises un-distilled water (e.g. tap water or softened tap water). In such an embodiment, impurities contained within the water may become deposited on the inner surfaces of the housing 120 of the expander mechanism 118 and may cause corrosion or seizing of the expander mechanism 118 if not removed. The sealing means may therefore advantageously provide the dual function of providing a seal between the rotary member 122 and the housing 120, and to remove waste deposits from inside the housing 120.

The rotary expander mechanism 118 may cause back pressure within the exhaust outlet 110 of the internal combustion engine 102 with may affect the efficiency of the internal combustion engine 102. This back pressure may be greater during an initial start-up period of operation of the internal combustion engine 102 in which the heat recovery apparatus has not reached normal operating temperature (due to friction with the apparatus). In some embodiments, a bypass means (e.g. a bypass valve or the like provided between the exhaust outlet 110 and the inlet 126) may be provided to bypass the expander mechanism 118 such that exhaust gasses from the internal combustion engine 102 are not passed through the expander mechanism 118. Such a bypass means may also allow the heat recovery apparatus 100 to be bypassed at any other time that it is not required.

In some embodiments, during the start-up phase the rotation of the rotary member 122 may be driven by a motor (and additionally the fluid may not be supplied by the fluid supply means 114) so that the apparatus reaches operating temperature more quickly. This may allow the apparatus to more quickly reach its normal operating temperature at which expansion of the fluid can be used to power the rotation of the rotary member 122. Furthermore, by reaching normal operating temperature more quickly, a NOx reduction process (as described later) may be activated more quickly. The effect of back pressure on the efficiency of the internal combustion 102 may be greater in embodiments where the internal combustion engine 102 is a turbine engine as their efficiency may be affected by the rotation speed of turbine which may be more susceptible to the effects of back pressure within the exhaust outlet.

Operation of the expander mechanism 118 is shown schematically in the sequence of figures from Figure 2a to Figure 2d which show one example of a rotation of the rotary member 122. The rotary member is arranged to rotate within the housing such that each expansion chamber moves through an intake phase, a compression phase, an expansion phase and an outlet phase. An example of these phases is shown in Figures 2a to 2d for the first of the three expansion chambers (shaded in the figures) of the described embodiment.

The rotary member 122 is arranged to move between a first position and a second position as shown in Figure 2a to provide the intake phase. As the rotary member 112 moves from the first position to the second position the volume of the expansion chamber increases. During the intake phase the first expansion chamber is coupled to the inlet 126 such that exhaust gases are drawn in to the first expansion chamber by the movement of the rotary member 122 between the first and second position. In some embodiments, the pressure of the exhaust gasses may act to move the rotary member 122 between the first position and the second position (for example before expansion of the fluid within the expansion chamber is sufficient to provide rotation).

In some embodiments, the rotary expander mechanism 118 may comprise a motor arranged to rotate the rotary member 122 from rest. This may occur when the expander mechanism is first started (e.g. when the internal combustion engine is started). The electric motor may be arranged to rotate the rotary member before expansion of the exhaust gasses and fluid takes over to power the expander mechanism.

Following the intake phase, the rotary member 122 is arranged to move between a third position and a fourth position as shown in Figure 2b to provide the compression phase. In some embodiments the compression phase may immediately follow the intake phase (e g. the second and third position of the rotary member may be the same). During the compression phase, the expansion chamber is sealed against the inner wall of the housing 120 and the volume of the expansion chamber decreases as the rotary member 122 moves from the third position to the fourth position. During the compression phase the exhaust gases within the expansion chamber are compressed, thus increasing the temperature within the expansion chamber.

Following the compression phase, the rotary member 122 is arranged to move from a fifth position to a sixth position as shown in Figure 2e to provide the expansion phase. In some embodiments the expansion phase may immediately follow the compression phase (e.g. the fourth and fifth position of the rotary member may be the same). At or near the start of the expansion phase, the fluid injections means is arranged to inject a predetermined volume of fluid into the expansion chamber. The injection means may be arranged to inject the fluid at or near the point of maximum compression of exhaust gases within the expansion chamber. When the fluid enters the expansion chamber and contacts the heated exhaust gases the fluid is vaporised. The exhaust may be at a temperature of about 200 to 300°C or more and when mixed with the heated fluid may cause the fluid to flash evaporate (e.g. in embodiments where the fluid comprises water the fluid may flash to steam at temperatures of 180°C). The flash evaporation may allow more efficient recovery of energy compared to boiling. Vaporisation creates a rapid increase in volume of the fluid, thereby forcing the expansion chamber to expand by pushing against the surfaces of the rotary member 122 and the housing 120. This expansion powers the rotation of the rotary member 122 and allows energy to be recovered from the fluid and exhaust gases by converting it into rotation of the rotary member 122 (which is coupled to an output of the expander mechanism). The fluid injection means may in some embodiments be arranged to inject fluid when the expansion chamber has contracted to its smallest volume. This means that the exhaust gasses will have increased in temperature during the compression phase and may therefore more efficiently (e.g. more rapidly and more completely) vaporise the fluid. In some embodiments, flashing of the fluid to steam (where the fluid is water) may occur which may extract heat from the expansion chamber (thereby converting thermal energy within the expansion chamber to kinetic energy of the steam). Increasing the temperature of the exhaust gases during the compression phase may also have the effect of reducing particulates present in the exhaust gases (e.g. particulates such as soot remaining from incomplete combustion of fuel within the internal combustion engine).

In some embodiments, the arcuate side portions of the rotary member 122 may comprise one or more recessed portions 301a, 301b, 301c arranged to receive the vaporised fluid as shown in Figure 3. The recessed portion(s) 301a, 301b, 301c may in some embodiments be at or near a leading edge of each of the side portions of the rotary member 122 in the direction of rotation of the rotary member 122. The recessed portion(s) may act as a chamber to receive the fluid as it expands. In this embodiment, the compression and expansion of the exhaust gases may create a force suitable to cause rotation of the rotary member 122. In some embodiments, this may allow continuous supply or injection of the fluid into the housing. In some embodiments, at least part of the rotary member 122, at least part of the housing 120 or at least part of both may comprise or be lined with a corrosion resistant surface. The corrosion resistant surface may comprise a ceramic or metal alloy material. This may extend the life of the apparatus by reducing the corrosion that may be caused by condensation of the fluid within the housing. In some embodiments, the condensed fluid may be acidic and so may cause increased corrosion of the apparatus. In such an embodiment it may therefore be particularly advantageous to provide a corrosion resistant material.

In some embodiments, the recessed portion(s) 301a, 301b, 301c may comprise a generally sinusoidal surface (e.g. the rotary member may have one or more edges having a sinusoidal cross section). In some embodiments, each of the recessed portions 301a, 301b, 301c may be the same shape, or in other embodiments may be different shapes. The depth of the recessed portion(s) 301a, 301b, 301c may be adapted to the type of internal combustion engine with which the apparatus is used (e.g. petrol and diesel) as different engines may have different compression ratios (within the engine) so the kinetic energy of the exhaust gases may be different. The shape of the recessed portion(s) 301a, 301b, 301c may additionally or alternatively be adapted to reduce mixing of the gases near the inlet 126 and outlet 130.

The rotary member 122 is arranged to move between a seventh position and an eighth position as shown in Figure 2d to provide the outlet phase. In some embodiments the outlet phase may immediately follow the expansion phase (e.g. the sixth and seventh position of the rotary member may be the same). During the outlet phase the expansion chamber is coupled to the outlet 130 such that exhaust gases and fluid vapour within the expansion chamber may be expelled. As the rotary member 122 moves between the seventh position and the eighth position the expansion chamber reduces in volume to expel exhaust gases and fluid via the outlet 130. The outlet 130 and the inlet 126 are arranged such that sufficient distance is provided between them to reduce mixing of the intake and the exhaust gasses during the transition between the outlet and intake phase. For example, the inlet 126 and outlet 130 may be positioned such that the moving expansion chamber is not connected to the inlet 126 and outlet 130 at the same time.

Rotation of the rotary member 122 continues in this manner to repeat the sequence of phases described above. A corresponding sequence of phases is provided by the second and third expansion chambers of the described embodiment, thus producing three expansion phases for every complete rotation of the rotary member 122. The sequence shown in Figure 2a to 2d is only one such example of the operation of the expander mechanism and in some embodiments some of the phases may be omitted or modified. The sequence or phases may for example be adapted for different forms of expander mechanism.

Although the described embodiment comprises an expander mechanism of the Wankel engine type, in other embodiments, an alternative piston-less rotary expander mechanism may be used. Such alternative expander mechanisms may include any suitable rotary engine, rotary compressor, rotary expander, disc or blade expander, scroll expander or screw expander, or the like. In a preferred embodiment, the expander mechanism comprises a Wankel engine as described. This is advantageous over other piston-less rotary expander mechanisms because it may have less leakage and is therefore more efficient. It may also have fewer valves and is thus less complex and more reliable.

In some embodiments, the expander mechanism 118 may be coupled to an electrical generator or a turbo-charger. Rotation of the rotary member 122 may therefore be converted into electrical energy or be used to increase the efficiency of the internal combustion engine by forcing air and fuel into the cylinder(s) of the engine.

In some embodiments, the expander mechanism 118 may further comprise a NOx (i.e. nitrogen oxide) reduction means. The NOx reduction means is arranged to reduce the amount of NOx present in the exhaust gasses that are vented from the expander mechanism. By including a NOx reduction means within the expander mechanism 118, the expander mechanism 118 may serve the dual purpose of energy recovery and NOx reduction. The energy recovery apparatus of the present invention may not therefore require a separate NOx reduction system that may otherwise be included in the vehicle exhaust system. This may save space and may reduce the overall weight of the vehicle.

In the described embodiment, the NOx reduction means comprises a reducing agent supply means 132 arranged to introduce a chemical reducing agent into the expansion chamber of the expander mechanism 118. In some embodiments, the NOx reducing means further comprises a catalyst material disposed within the expansion chamber. In some embodiments, the catalyst material may be included in the rotary member 122. In some embodiments, a mesh or slot may be provided in the body of the rotor to allow access to the catalyst material. In some embodiments, the catalyst may be disposed within a recessed portion of the rotary member 122, and may in some embodiments be arranged at the leading edge of the rotary member 122. In other embodiments, the catalyst may be disposed substantially over the entire length of one or each of the arcuate side portions of the rotary member 122. By including the catalyst in the rotary member 122, an increase in temperature obtained during the compression phase of the expander mechanism 118 may allow early activation of the catalyst and may therefore mean a separate catalytic converter is not required, thus reducing the overall weight and complexity of the internal combustion engine.

In some embodiments, the NOx reduction means may be arranged to implement a Selective Catalytic Reduction (SCR) process. The reducing agent may be chosen from any one of, or a combination of any one or more of: anhydrous ammonia, aqueous ammonia, ammonia solution, and urea solution. The reducing agent may in some embodiments comprise urea or ammonia alone, or in other embodiments the reducing agent may further comprise an oxidising agent such as ammonium nitrate or hydrogen peroxide to enhance the SCR reaction. In some embodiments, the reducing agent and oxidising agent may be provided from dissolved carbamide peroxide. This is advantageous because the carbamide peroxide is a relatively stable solid which may be more safely handled. The carbamide peroxide solid may be dissolved in a suitable solvent (e g. water) to provide a source of urea and hydrogen peroxide solution. Additional urea may be added to the resulting solution to increase the concentration of urea if required. Urea and carbamide peroxide solids may be packaged separately and combined in required quantities so that the concentration of the solution can be varied according to any specific pollution control needs.

The catalyst material may comprise any suitable SCR catalyst material that is known in the art, including for example oxides of base metals (such as vanadium, molybdenum and tungsten, zeolites or other various precious metals). The catalyst may in some embodiments be an alloy of platinum or palladium. The catalyst material may in some embodiments comprise a carrier material (e.g. a ceramic material) arranged to support the active catalytic component.

In some embodiments, the reducing agent supply means may comprise a valve or the like arranged to supply a predetermined volume of the reducing agent. The reducing agent supply means 132 may therefore be arranged to introduce the reducing agent into the expansion chamber of the expander mechanism 118. The reducing agent supply means 132 may be arranged to introduce the reducing agent during or following the compression phase of the expansion mechanism 118 (e.g. when the rotary member has moved from the third to the fourth position). In other embodiments, the reducing agent may be injected during expansion of the exhaust gases and fluid. In yet other embodiments, the reducing agent may be injected at or near the point of maximum compression of the exhaust gases within the expansion chamber. This may be particularly advantageous because the increase in temperature of the exhaust gases during the compression phase may increase the efficiency of the reduction reaction and may lead to early activation of a catalyst used in the NOx reducing reaction. Early activation of the catalyst may result in less NOx being present in the expelled exhaust gases when the internal combustion engine 102 is first started. Injecting the reducing agent into the exhaust gases after being heated by compression may also be advantageous in embodiments where the reducing agent comprises urea, or a combination of urea and an oxidising agent such as ammonium nitrate, which may increase the rate of the SCR reaction. Urea, for example, must undergo chemical decomposition in order to release ammonia (which is the active substance in the reduction reaction) which may be aided by the increased temperature caused by compression of the exhaust gases by the rotary member 122. Furthermore, the increase in temperature of the reducing agent may mean that in some embodiments less catalyst, or no catalyst, is required to achieve the same NOx reduction efficiency. In other embodiments, the reducing agent (with or without the oxidising agent described above) may be mixed with the fluid and injected into the expansion chamber by the fluid injection means.

In yet other embodiments, the reducing agent may be introduced into the expansion chamber at a different point in the rotation of the rotary member 122 (e.g. during any one of the intake, compression, expansion and outlet phases). In yet other embodiments, the reducing agent supply means may be arranged to supply reducing agent such that it combines with the exhaust gasses before they enter the expander mechanism 118 (e.g. at the inlet 126 or within the connecting conduit) or after the exhaust gasses leave the expander mechanism 118 (e.g. at the outlet 130).

In other embodiments, the NOx reduction means may be arranged to provide a selective non-catalytic reduction (SNCR) process. In this embodiment, the catalyst material is not required, with the reducing reaction occurring with only the reducing agent supplied by the reducing agent supply means. This reduces the complexity of the NOx reduction means as the catalyst is not required.

Claims

1. An energy recovery apparatus for an internal combustion engine, the internal combustion engine comprising an exhaust outlet, the apparatus comprising: a fluid supply means arranged to supply a fluid; and a piston-less rotary expander mechanism arranged to receive exhaust gases from the exhaust outlet and fluid from the fluid supply means, wherein the piston-less rotary expander mechanism is powered by the fluid and the exhaust gases, wherein the fluid supplied by the fluid supply means is heated by a heat source comprising at least part of the internal combustion engine.

2. An energy recovery apparatus according to claim 1, further comprising a heat exchanger arranged to heat the fluid by transfer of thermal energy from a cooling system of the internal combustion engine.

3. An energy recovery apparatus according to claim 1, wherein the fluid supply means is arranged to transfer heat directly from the internal combustion engine to the fluid.

4. An energy recovery apparatus according to any preceding claim, wherein movement of the piston-less rotary expander mechanism is powered by energy from the fluid and exhaust gases.

5. An energy recovery apparatus according to any preceding claim, wherein the piston-less rotary expander mechanism comprises a housing and a rotary member movable within the housing, wherein movement of the rotary member is caused by expansion of the fluid, the exhaust gases or both.

6. An energy recovery according to claim 5, wherein the housing and rotary member define a moving expansion chamber arranged to receive the exhaust gases and wherein the piston-less rotary expander mechanism further comprises a fluid injection means arranged to inject fluid from the fluid supply means into the expansion chamber.

7. An energy recovery apparatus according to claim 6, wherein the piston-less rotary expansion mechanism further comprises an inlet port in communication with the exhaust outlet, and wherein the rotary member is movable to draw exhaust gases into the expansion chamber via the inlet port.

8. An energy recovery apparatus according to claim 6 or claim 7, wherein the rotary member is movable to compress exhaust gases within the expansion chamber and wherein the fluid injection means is arranged to inject the fluid into the expansion chamber during or after compression of the exhaust gases.

9. An energy recovery apparatus according to claim 8, wherein the fluid injection means is arranged to inject the fluid into the expansion chamber at or near the point of maximum compression of the exhaust gases.

10. The heat recovery apparatus according to any of claims 6 to 9, wherein the pistonless rotary expander mechanism further comprises an outlet port, and wherein the rotary member is movable to vent the expansion chamber via the outlet port.

11. The heat recovery apparatus according to any of claims 5 to 10, wherein pistonless rotary expander mechanism further comprises a sealing means arranged to provide a seal between the rotary member and an inner surface of the housing, wherein the sealing means is further arranged to at least partly remove deposits from the inner surface of the housing.

12. The heat recovery apparatus according to any of claims 5 to 11 wherein the rotary member is coupled to a motor arranged to rotate the rotary member from rest.

13. An energy recovery apparatus according to any preceding claim, wherein the fluid supply means comprises a fluid reservoir arranged to replace fluid vented from the outlet during use of the energy recovery apparatus.

14. An energy recovery apparatus according to any preceding claim, wherein the piston-less rotary expander mechanism further comprises a condenser arranged to at least partly condense fluid vented from the outlet, and wherein the condenser is arranged to return the condensed fluid to the fluid supply means to form a closed system.

15. The heat recovery apparatus according to any preceding claim, wherein the fluid comprises water.

16. The heat recovery apparatus according to any preceding claim, wherein the piston-less rotary expander is valve-less.

17. The heat recovery apparatus according to any preceding claim, wherein the piston-less rotary expander comprises a Wankel engine.

18. The heat recovery apparatus according to any preceding claim, wherein the piston-less rotary expander mechanism is coupled to an electrical generator or a turbo-charger.

19. The heat recovery apparatus according to any preceding claim, wherein the piston-less rotary expander mechanism further comprises a NOx reduction means.

20. The heat recovery apparatus according to claim 19, wherein the NOx reduction means comprises a reducing agent supply means arranged to inject a chemical reducing agent into an expansion chamber of the piston-less rotary expander mechanism.

21. The heat recovery apparatus according to claim 20 when dependent on claim 8, wherein the reducing agent supply means is arranged to inject the chemical reducing agent during or after compression of the exhaust gases.

22. The heat recovery apparatus according to claim 20 or claim 21, wherein the chemical reducing agent comprises urea solution or ammonia solution.

23. The heat recovery apparatus according to claim 22, wherein the chemical reducing agent further comprises an oxidising agent, wherein the oxidising agent preferably comprises ammonium nitrate or hydrogen peroxide.

24. The heat recovery apparatus according to any of claims 19 to 23, wherein the NOx reduction means comprises a catalyst disposed on a surface of the rotary member, the housing or both.

25. An internal combustion engine comprising an exhaust outlet; and the energy recovery apparatus of any preceding claim.

26. An energy recovery apparatus or an internal combustion engine substantially as described herein with reference to, or as shown in, any one or more of the accompanying drawings.