GB2547948A

GB2547948A - Method of operating an internal combustion engine, exhaust aspirator for an internal combustion engine, and an internal combustion engine

Info

Publication number: GB2547948A
Application number: GB1603784.8A
Authority: GB
Inventors: Patrick Jones David; john ryan Christopher
Original assignee: Clearairtech Ltd
Current assignee: Clearairtech Ltd
Priority date: 2016-03-04
Filing date: 2016-03-04
Publication date: 2017-09-06
Anticipated expiration: 2036-03-04
Also published as: GB2547948B; GB201603784D0; WO2017149304A1

Abstract

A method of operating an i.c. engine includes: combusting primary fuel and primary air in a combustion chamber 11; exhausting the combustion products to an exhaust system 24; introducing secondary air into the exhaust system 24; and mechanically acting on the secondary air and the combustion products in the exhaust system in the presence of a catalyst to produce an oxidising agent, eg molecular oxygen produced by a steam reforming reaction. The secondary air may be introduced using an aspirator 26 having a valve (35, fig.2) which opens and closes sharply so that the secondary air is introduced in strong pulses which produces pulse waves to act mechanically on the secondary air and the combustion products. The valve (35, fig.2) may comprise a disc (40) biassed against a seat (36) by a weak spring (41). The aspirator 26 may be connected to the exhaust manifold 23 by a tube 32 made of, or lined with, catalytic material, eg copper, cerium, platinum or rhodium. The aspirator 26 may be located at the location of maximum amplitude of the pressure waves, eg determined using an ultrasonic probe.

Description

Title: Method of operating an internal combustion engine, exhaust aspirator for an internal combustion engine, and an internal combustion engine

Field of the Invention

This invention relates to a method of operating an internal combustion engine, e.g. for a vehicle. In particular, although not exclusively, to a method including catalytic fuel reforming and/or catalytic emissions reduction, an exhaust aspirator for use in the method, and an internal combustion engine including the aspirator.

Such an engine typically includes at least one combustion chamber with an inlet port for primary air, means to introduce into the combustion chamber primary fuel for combustion with the primary air, an outlet port for combustion products, and an exhaust system for exhausting the combustion products to atmosphere. The primary fuel may be petrol, Diesel, liquid petroleum gas, for example, or any other suitable fuel or mixture of such fuels.

Background of the invention

Particularly in the case of achieving reduction of harmful emissions, development has tended to concentrate on improving combustion within the engine. Combustion may be improved, for example, by developing fuel injection systems which provide for improved fuel/air mixing in combustion chambers of the engine, and then cleaning combustion products, for example by passing the combustion products through catalytic converters.

The provision of catalytic converters is problematic because such devices only tend to operate to their maximum performance once very hot. During short journeys for example in which engines may not attain an optimum operating temperature, such catalytic converters provide substantially no beneficial effect. Moreover, such converters are expensive and require frequent replacement, as they are easily contaminated.

In previous patent application W002/35078 there is described an exhaust aspirator and a method of operating an internal combustion engine including introducing into the exhaust system secondary air, mechanically acting upon the secondary air and products of combustion in the exhaust system in the presence of a catalyst, to produce a reformed fuel, introducing the reformed fuel into the combustion chamber for combustion with primary fuel and primary air.

Summary of the invention

There is provided a method of operating an internal combustion engine, including: combusting primary fuel and primary air in a combustion chamber to produce combustion products; exhausting the combustion products to an exhaust system for exhausting the combustion products to atmosphere; and introducing into the exhaust system secondary air and mechanically acting upon the secondary air and the combustion products in the exhaust system in the presence of a catalyst to produce an oxidising agent.

The oxidising agent may be molecular oxygen (O2).

The molecular oxygen may be produced by a steam reforming reaction:

The secondary air may be introduced into the exhaust system via an exhaust aspirator which draws air into the exhaust system during low pressure or partial vacuum conditions occurring during the cycle of pressure changes which occur in the exhaust system during normal operation of the engine.

The catalyst may be provided by materials from which the aspirator is at least partly made.

The aspirator may be connected to the exhaust system by a connector.

The catalyst may be provided by materials from which the connector is at least partly made.

The exhaust system and the connector of the aspirator may include complementary tapered threads.

The aspirator may be tuned to draw air into the exhaust system and mechanically act upon the secondary air and products of combustion by means of pressure pulses in a manner to optimise production of the oxidising agent.

The aspirator may include a control valve assembly including: a valve seat member having an annular valve seat; a valve disc for engaging the valve seat, wherein the valve disc includes a non-metal material; and a resilient biasing element for biasing the valve disc towards the valve seat.

The valve disc may include a plastics material and/or a polymer material.

The internal combustion engine may have a plurality of combustion chambers each having an exhaust port, each exhaust port opening into an exhaust manifold, and wherein the aspirator is connected to the exhaust manifold.

Optionally, the aspirator does not protrude into the exhaust manifold.

The aspirator may be attached to the position where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.

The aspirator may be secured to the engine block so as to reduce vibration of the aspirator.

There is also provided a method of adapting an internal combustion engine for operation in accordance with any one of the preceding claims, the method including providing the internal combustion engine with an exhaust aspirator for introducing into the exhaust system secondary air, mechanically acting upon the secondary air and products of combustion in the exhaust system in the presence of a catalyst to produce an oxidising agent.

The method may include replacement of the engine’s piston rings and/or refurbishment of valves and/or valve seatings.

The engine which is to be adapted may include an engine management system.

The method may include derating and/or detuning the engine management system to provide less fuel and/or air in response to a power demand.

There is also provided an exhaust aspirator for admitting air to the exhaust system of an internal combustion engine including: an air admission tube; a connector at one end of the tube for connecting the tube to an exhaust system; and a control valve assembly at the other end of the tube for controlling the passage of air into the air admission tube, wherein the control valve assembly includes: a valve seat member having an annular valve seat; a valve disc for engaging the valve seat, wherein the valve disc includes a non-metal material; and a biasing element for biasing the valve disc towards the valve seat.

The valve disc may include a plastics material and/or a polymer material.

The connector may include a portion lined with a catalytic material.

There is also provided an exhaust aspirator for admitting air to the exhaust system of an internal combustion engine including: an air admission tube; a connector at one end of the tube for connecting the tube to an exhaust system; and a control valve assembly at the other end of the tube for controlling the passage of air into the air admission tube, wherein the connector includes a portion lined with a catalytic material.

The catalytic material may include a material selected from the group consisting of copper, cerium, platinum, rhodium, and combinations thereof.

There is also provided an internal combustion engine including an exhaust aspirator as disclosed herein.

The internal combustion engine may include: at least one combustion chamber for combusting primary fuel and primary air to produce combustion products; and an exhaust system including at least one exhaust manifold connected to the or each combustion chamber for receiving the combustion products, wherein the exhaust aspirator is connected to the exhaust system for introducing secondary air into the exhaust system.

The aspirator may be connected to the exhaust manifold.

Optionally, the aspirator does not protrude into the exhaust manifold.

There is also provided an internal combustion engine including an exhaust aspirator for admitting air to the exhaust manifold of an internal combustion engine, the aspirator including: an air admission tube; a connector at one end of the tube for connecting the tube to an exhaust manifold; and a control valve assembly at the other end of the tube for controlling the passage of air into the air admission tube, wherein the aspirator does not protrude into the exhaust manifold.

There is also provided a method of determining an optimum location for positioning an aspirator for admitting air to the exhaust manifold of an internal combustion engine, the method including: operating the internal combustion engine and scanning an ultrasonic probe across the exhaust manifold to determine a location where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.

There is also provided an internal combustion engine including: at least one combustion chamber for combusting primary fuel and primary air to produce combustion products; an exhaust manifold connected to the or each combustion chamber for receiving the combustion products; and an exhaust aspirator for introducing secondary air into the exhaust manifold, wherein the exhaust aspirator is attached to the position where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.

Individual features disclosed in relation to methods of the invention may be used in combination with the apparatus disclosed herein. Likewise, individual features of the apparatus of the invention may be used in combination with the methods disclosed herein.

Description of the drawings

Embodiments of the invention will now be described with reference to the accompanying drawings in which:

Figure 1 is a schematic illustration of an engine being operated in accordance with an embodiment of the invention;

Figure 2 is an illustrative partly exploded side sectional view of an exhaust aspirator of an embodiment of the invention; and

Figure 3 is an illustrative part sectional view of an exhaust manifold for use with embodiments of the invention.

Description of embodiments

Referring to figure 1, an engine 10 has at least one combustion chamber 11. In this example the engine 10 is of the reciprocating type, in which the combustion chamber 11 is a cylinder in which a piston 12 reciprocates. The invention is however applicable to other kinds of internal combustion engines such as for example rotary engines.

The or each combustion chamber 11 has an inlet port 15 through which, in this example, primary combustion air is introduced, either by simple induction due to piston 12 movement, or with turbo or supercharger assistance as is known, and an exhaust outlet port 16. Both the inlet and outlet ports 15,16 in this example are opened and closed by the operation of respective valves 17,18 which typically are controlled to open and close in accordance with the engine cycle, e.g. by operating rods driven from a camshaft.

In this example, the engine is a Diesel engine in which primary fuel for combustion is injected into the engine by an injector 19, and is ignited as a result of heat generated as air is compressed in the cylinder. In another example, ignition of the primary fuel may be achieved with spark assistance, and particularly in the case of a petrol spark ignition engine, primary fuel may be introduced into the combustion chamber 11 along with the primary air.

The primary air may be introduced into the combustion chamber from an inlet manifold 20. Of course, where the engine 10 has a plurality of combustion chambers 11, the inlet ports 15 for each combustion chamber 11 may be connected to an inlet manifold 20. Air is provided to the inlet manifold 20 from an air inlet 21, via air filters etc. as is well known in the art, and/or the air may be provided via a turbo device or otherwise.

The or each exhaust outlet port 16 is connected to an exhaust manifold 23 of an exhaust system 24. Again, in the case of a multi-combustion chamber 11 engine, the outlet ports 16 for each combustion chamber 11 may be connected to the exhaust manifold 23. Combustion gases pass, possibly via a catalytic converter 25, from the exhaust manifold, to atmosphere.

There is provided a means for introducing secondary air into the exhaust system 24, and in the present case, this is an aspirator device 26 which is described in more detail below with reference to figure 2. The aspirator 26 is adapted to mechanically act upon the exhaust gases and secondary air to provide a reformed fuel. The reformed fuel is then fed back into the combustion chamber 11 as is known, and is subsequently burnt in the combustion chamber 11 along with primary fuel.

It will be appreciated that immediately subsequent to the piston 12 performing an exhaust stroke in the combustion chamber 11, i.e. moving upwardly as seen in the drawings whilst the exhaust outlet port 16 is open, and the piston 12 moving downwardly again to enable at least primary air to be introduced into the combustion chamber 11 with the inlet port 15 open, there will be a short but finite period in which both the inlet 15 and outlet 16 ports will simultaneously be open. During that period a reduced pressure or partial vacuum will be established at the outlet port 16 and, as a consequence, gases from the exhaust system 24 will be drawn into the combustion chamber 11 along with the primary air from the inlet port 15. Thus, where the exhaust gases include reformed fuel, the reformed fuel will be introduced into the combustion chamber 11.

Moreover a very small amount of the reformed fuel may pass through the combustion chamber 11 to the inlet port 15 and, notwithstanding flow will be predominantly in an opposite direction, a very small amount of the reformed fuel may pass to the inlet manifold 20 for mixing with primary air. Thus the primary air subsequently introduced into the combustion chamber 11 may contain a very small proportion of reformed fuel.

The introduction of secondary air by the aspirator 26 catalyses redox reactions and thereby reduces pollutant concentrations in the exhaust gases of the engine 10.

Without wishing to be bound by theory, the reactions catalysed by the introduction of secondary air and the catalyst are as follows: a) Steam reforming whereby the 70% steam content in the exhaust gases is dissociated in to hydrogen and oxygen, as follows:

b) Methanol (a reformed fuel) production by the hydrogen produced above catalytically re-acting, under high pressure and temperature, with carbon monoxide:

CO 2H2 ^ CH3OH CO2 3H2 ^ CH3OH H2O c) Water gas reaction: GO -I- H2O CO2 -I- H2 d) Producer gas reaction:

C 7202 ^ CO

Reactions c and d take place, using hot exhaust gases, in an oxygen rich atmosphere, and are promoted by the mechanical action of the secondary air in the exhaust system, i.e. by the energy in the exhaust pulse waves and the mechanical action of the aspirator 26.

Reactions c and d are also utilised in the conventional catalytic converters. However, the excess oxygen required for the catalytic converter operation is added to the primary fuel/air inlet to the engine. Therefore, in the prior art the engine has to be operated in lean burn mode which is associated with increased ΝΟχ production. ΝΟχ (the oxides NO and NO2) are known to be harmful to the environment and reducing ΝΟχ production of engines is a known aim.

The redox chemistry of the engine 10 provides oxygen from the steam reforming process (see a above). Therefore, it is not necessary to operate the present engine 10 in a lean burn mode in order for sufficient oxygen to be available for oxidation reactions c and d - reaction a produces oxygen in situ. Because it is not necessary to operate the engine 10 in lean burn mode ΝΟχ production (i.e. pollution) can be reduced.

Further, because the ΝΟχ production is reduced, whereas in the prior art Exhaust Gas Recirculation (EGR) systems have been used to reduce ΝΟχ production, such systems (which may be expensive) are advantageously not required when the methods above are practiced.

Referring now to figure 2, an aspirator 26 suitable for allowing secondary air to be introduced into the exhaust system 24 is shown. The aspirator 26 is tuned to optimise catalytic redox reactions and thereby to reduce pollutant concentrations in the exhaust gases of an engine.

The aspirator 26 includes a tube 32 which may be provided at one end 33, e.g. the lower end indicated in figure 2, with a connector 50, to enable the aspirator 26 to be attached to the exhaust system 24, e.g. by the exhaust manifold 23.

The tube 32 is preferably made of a catalytic material, such as copper, which promotes catalytic redox reactions and thereby the reduction of pollutant concentrations. The copper used may be half hard copper, which can be bent into position whilst cold; other coppers may also be used. Alternatively, other catalytic materials may be used, for example, catalytic materials including any catalytic metal such as cerium (Ce), platinum (Pt) and/or rhodium (Rh). Particularly when the catalytic material is expensive, the tube 32 may be lined with a or the catalytic material rather than made of it to reduce the need for large amounts of expensive catalytic material. Additionally, catalytic materials may be present in the exhaust system 24 (e.g. in the exhaust manifold 23) and these may further promote redox reactions and the reduction of pollutant concentrations.

The connector 50 may have a condensing portion 52 which comprises heat exchange fins 54. The condensing portion 52 cools the exhaust gases as the gases pass from the exhaust manifold 23 to the tube 32 and as the gases (including the secondary air) pass from the tube 32 to the exhaust manifold 23. The use of a condensing portion 52 may help to reduce pollutant concentrations in the exhaust gases.

The connector 50 is in the form of a tube having screw-threaded end portions 58,59. Screw-threaded end portion 58 is to be received in an appropriately threaded hole formed in the exhaust system 24 (e.g. manifold 23) of the engine 10. The threaded hole in the exhaust system 24 may be formed by drilling and tapping. The screw threaded end portion 58 and the threaded hole in the exhaust system 24 have complementary tapered threads. Such complementary tapered threads can provide a suitable seal between the connector 50 and the exhaust system 24.

It has surprisingly been found that when screw-threaded end portion 58 and the threaded hole of the exhaust manifold 23 are sized such that the connector 50 does not protrude into the exhaust manifold 23 of the system 24, and therefore not into the exhaust gas stream, the aspirator 26 is particularly effective. Without wishing to be bound by theory, it is thought that this arrangement can reduce disadvantageous disruptions of the wave patterns in the exhaust flow and thereby increase the performance of the aspirator 26.

Air admission tube 32 has a flanged end 39 at end 33 which co-operates with a nut 60 to join tube 32 to connector 50.

As in the prior art, the connector 50 may be made of steel. It has been found advantageous for the connector 50 to comprise at least a portion 56 which is lined with a catalytic material. The portion 56 may be provided in the region of the condenser 52. The portion 56 which is lined with a catalytic material may be achieved either by provision of a discrete liner, e.g. a push fit liner as shown in Figure 2, or making a part of the connector 50 from a catalytic material, i.e. the provision of an integral liner. Whether or not the condensing portion 52 is present, another part of the connector 52 may comprise a portion 56 lined with a catalytic material.

However, in some embodiments, it has been found advantageous not to line a portion in the vicinity of the tapered thread 58 with a catalytic material. This is because the connector 50 may be of a more durable material than the liner, and this can ensure that there is sufficient material of the connector 50 in the region of the tapered thread 58.

The preferred catalytic material for the liner is copper. However, other oatalytic materials may be used, for example, any oatalytio metal suoh as oerium (Ce), platinum (Pt) and/or rhodium (Rh).

The inclusion of a portion 56 lined with a catalytic material in the connector 50 has been found to be effeotive in reducing pollutant oonoentrations in the exhaust emissions of the engine and inoreasing fuel eoonomy. It is not fully understood why inolusion of the oatalytic material in the connector is particularly effective in catalysing redox reactions whioh lead to the reduction in pollutant concentrations. However, without wishing to be bound by theory, it is thought that the mechanioal aotion of the air by the control valve assembly 35 in the region closest to the exhaust system 24 (e.g. exhaust manifold 23) is particularly effective. This is thought to be due to the nature of the interactions between the exhaust emissions and the secondary air introduced by the control valve assembly 35 in the region of the connector and that these interaotions promote the redox chemistry discussed above. Again, without wishing to be bound by theory, this is thought to be the case particularly where the connector 50 connects the aspirator 26 to the exhaust manifold 23 in the optimum location, as described in more detail below.

Additionally, it has been found that reformed fuel production may be increased by the inclusion of a portion 56 lined with a catalytic material in the connector 50. Again, it is not fully understood why this results in such effective catalysis of reformed fuel production. However, without wishing to be bound by theory, it is thought that the mechanical action of the air introduced by the control valve assembly in the region of the connector is particularly effective.

At an opposite end 34 of the tube 32, e.g. at the top as shown in figure 2, there is provided a valve 35. The valve is accommodated in a housing which is in the form of a mushroom shaped cap in this example. Outer cap 37 is proportioned to fit over inner cap 38 to define a housing. The two caps 37,38 are secured together during assembly. A gap for the entry of air into the valve 35 is provided between the two caps 37,38.

The valve 35 includes a valve seat 36. A valve member, which in this case is a disc 40, is urged by a resilient biasing element 41, e.g. a spring, into engagement with the valve seat 36, which is shaped to receive the disc 40, normally to close the valve and prevent air passing the valve 35 into the tube 32. The spring 41 is relatively weak, and in the event that a low pressure or partial vacuum is experienced within the tube 32, the force of the spring 41 will be overcome and the disc 40 will be removed from the valve seat 36 so that air may be drawn in through the valve 35, and hence to tube 32 and the exhaust system 24.

It has surprisingly been found that when the valve disc 40 is made from a material including non-metal material, e.g. a polymer or plastics material, the aspirator 26 is particularly effective in reducing pollutant concentrations in the exhaust emissions of the engine and in improving fuel economy.

The valve disc 40 may be at least 50wt%, 60wt%, 70wt%, 80wt%, 90wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt% non-metal materials. The valve disc 40 may be of non-metal materials.

The non-metal material may be or include a polymer or plastics material, e.g. a polyester. The polyester sold under the trademark Melinex® has been found to be particularly effective. In some examples, valve discs made from materials including a polyester, such as Melinex®, having a titanium content were found to be particularly effective. The valve disc 40 may be of a polyester, such as Melinex®, or of a polyester, such as Melinex®, including a titanium content.

In some embodiments, the non-metal material may be or include a ceramic material. For example, the non-metal material may be or include a ceramic composite. In embodiments, the non-metal material may be or include carbon, e.g. the non-metal material may be or include a carbon composite. In embodiments, the non-metal material may be or include graphene, e.g. the non-metal material may be or include a graphene composite.

The use of a non-metal material has been found to provide significant advantages over the use of a metal or alloy material. In particular, a valve disc 40 including a non-metal material can provide an improved speed of response over a valve disc including a metal or alloy material in the mid to high r.p.m. bands.

It is not fully understood why a non-metal valve disc 40 is particularly effective in the reduction in pollutant concentrations and increasing fuel economy. However, without wishing to be bound by theory, it is thought that the mechanical action of the secondary air by the control valve assembly 35 is particularly effective due to the way the valve disc 40 opens and closes in response to pressure changes within the air admission tube 32. In particular, it is thought that the spring 41 and valve disc 40 made from a material including a non-metal results in the secondary air being introduced as strong pulses, with the valve opening and closing sharply. The pulses thus produced mechanically act upon the combustion products and secondary air in the exhaust system 24 in the presence of the catalytic material, to promote the redox chemistry discussed above. In this way, the aspirator 26 may be tuned to increase pollution control by use of a valve disc 40 made from a material including non-metal material, e.g. a polymer or plastics material.

Other aspirator 26 constructions are no doubt possible. For example, the valve 35 construction may incorporate other than a disc shaped valve member 40 with the valve seat 36 being appropriately configured so that the aspirator 16 is tuned to optimise pollutant reduction. In figure 1 the tube 32 is shown to be bent, whereas in figure 2 the tube 32 is straight. The tube 32 may be bent as desired to fit within an engine compartment of a vehicle. It has been found advantageous to ensure that the tube 32 does not become too hot by ensuring that the tube is well ventilated. This may be a particular issue if the tube 32 is coiled. A stay 62 having an internal rubber grommet 64 is provided to receive through an aperture 66 a bolt (not shown). The stay is secured to the engine block so as to reduce vibration of air admission tube 32 and valve 35 during use. This can help to reduce metal fatigue in the tube 32 and thereby prolong the life of the tube 32 and consequently the aspirator 26.

The operation of the aspirator 26 has been described with reference to a single combustion chamber 11 engine 10 in which the low pressure or partial vacuum necessary to cause the valve 35 to open, to allow secondary air to be drawn into the exhaust system 24, occurs when the piston 12 is at or substantially at the top of its stroke with the inlet 15 and exhaust ports 16 open. It will be appreciated that in a multi-combustion chamber 11 engine 10, in which multiple pistons 12 will be at different positions in their cycles at any one time, in order to balance the engine 10, the valve 35 of the aspirator 26 may be arranged to open at a time which may not coincide with the piston 12 of any combustion chamber 11 being at the top of its stroke with the inlet 15 and exhaust ports 16 open. In a multi-combustion chamber 11 engine 10, the pressure in the exhaust system 24 will tend to change according to a complex pattern. Nevertheless, the valve 35 of the aspirator 26 may be arranged to open against the force of the spring 41 when a set low pressure or partial vacuum is experienced in the exhaust system 24. Thus the low pressure or partial vacuum required for the introduction of secondary air into the exhaust system 24 may not coincide with the low pressure or partial vacuum experienced locally of the exhaust outlet ports 16 of the combustion chambers 11. It has been found that in an engine having multiple pistons 12 the location at which the aspirator 26 is attached to the exhaust manifold 23 can have a significant effect on fuel consumption of the engine and also upon emissions reduction.

The aspirator 26 has also been described in an arrangement in which the aspirator 26 is attached to the exhaust manifold 23. However, it has been found that attaching the aspirator 26 to other parts of the exhaust system 24 may also be advantageous. For example, even where the exhaust system 24 includes a turbocharger, the aspirator may be attached on the downside of such a turbocharger, i.e. as part of the exhaust system but after the exhaust manifold 23 and turbocharger.

Referring now to figure 3, there is shown an exhaust manifold 23 of a four cylinder Diesel engine. The exhaust manifold 23 is connected to four combustion chambers 11 by four exhaust ports 16, as is known. The exhaust manifold has an opening 28 which is fed to a conventional exhaust system, which may or may not include a traditional catalytic converter 25, again as is known.

It has been found that by scanning 101 an ultrasonic probe across the exhaust manifold, a location 29 at which the pressure waves, which result from the operation of the engine 10 and the opening and closing of the exhaust valves 18 in the ports 16, are greatest can be determined. It has also been found that by attaching the aspirator 26 to this location 29 (where the pressure waves are greatest) on the exhaust manifold 23 increases the effect of reducing fuel consumption of the engine and also reducing pollutant concentrations within the emissions. Without wishing to be bound by theory, it is thought that this is because the amount of secondary air introduced by the valve 35 is increased, thereby increasing the mechanical action and thereby promoting the redox chemistry which results in a reduction in fuel consumption and pollutant concentrations.

In the particular example illustrated in figure 3, an inline or straight 4 having a single exhaust manifold 23, it has been found ultrasonically that a location 29 at which the pressure waves are greatest is towards the opposite end from the opening 28 of the exhaust manifold 23 to the exhaust system 24. Specifically, it has been found that an advantageous location 29 for attaching the aspirator 26 to the exhaust manifold 23 is approximately 4 cm from the end opposite to the opening 28.

If an engine 10 has multiple exhaust manifolds, as is common in some V engine designs and some straight engine designs, then a separate aspirator 26 is advantageously fitted to each exhaust manifold 23. Using the same ultrasonic technique explained above, an advantageous location (where the pressure waves are greatest) can be determined for each manifold 23.

It is therefore disclosed to design an engine 10 including an aspirator 26 by first constructing a test engine 10 and then ultrasonically determining a location 29 where the pressure waves are greatest within a or the exhaust manifold 23 and then attaching an aspirator 26 at this location. As explained above, such engines 10 have advantageous fuel economy and reduced pollution concentrations within their emissions.

Because of the reduced pollutant concentrations resulting from the methods and apparatus described above, the exhaust system of the engine may not need to include a catalytic convertor 25 or alternatively a smaller, less complex, catalytic converter 25 than would otherwise be necessary to achieve satisfactory emissions for the same or an equivalently sized engine may be used. Omission of or use of a smaller catalytic converter 25 results in an increase in fuel economy; in particular, all catalytic converters create a resistance to the flow of exhaust gases and this resistance increases fuel consumption. Therefore, by omitting a or use of a smaller catalytic converter 25 the fuel economy of the engine can be yet further increased.

Where the exhaust system 24 includes a catalytic converter 25, depending on whether this is a passive or active device, when adapting an engine for performance of the present method, additional steps may advantageously be performed. For example, where the catalytic converter 25 includes a sensor 80 which provides an input to an engine management system 81, indicative of the concentration of un-burnt hydrocarbons and carbon monoxide in the exhaust gases, the engine management system conventionally responds by setting the richness of the primary fuel/air mixture to a level where the catalytic converter 25 can operate most efficiently. Where the method is performed, and the level of un-burnt hydrocarbons and carbon monoxide in the exhaust gases are reduced by the method, the sensor 80 needs to be disabled and/or the engine management system 81 re-programmed to ensure that the richness of the primary fuel/air mixture is not unduly increased.

There is also provided a method of adapting an internal combustion engine for operation in accordance with the above method. This method includes providing the internal combustion engine 10 with an exhaust aspirator 26 as described above to produce an oxidising agent.

The fuel economy of an engine 10 including the aspirator 26 may be further increased by de-rating or detuning the engine 10 to compensate for the presence of the aspirator 26. For example, in an engine 10 having an engine management system 81, where the method is performed the engine management system 81 may be programmed to dispense less fuel/air mixture in response to a demand for power from a user. Because the engine 10 is more efficient than a conventional engine the same power is produced with a lesser amount of fuel air mixture. In this way, the fuel economy of the engine 10 can be further increased. In another example, in an engine 10 not having an engine management system but having, for example, a carburettor fuel system the carburettor may be adjusted to dispense less fuel/air mixture in response to a demand for power form a user. Again, in this way the fuel economy of the engine 10 can be further increased.

An engine 10 that is worn, particularly in an engine 10 which is not well maintained and/or looked after, wear can affect the piston rings and/or cylinder head valves and seatings, as is known per se. Additionally, there is usually a build-up of carbon (and possibly other deposits) around these worn engine parts. The piston rings of the worn engine 10 could allow oil from the main engine sump to pass into a combustion chamber(s) 11. The use of an aspirator 26 as described above can have a large impact on these worn areas of the engine 10 (as well as exhaust system 24). In particular, such use can clean and remove the carbon and other deposits from the worn engine parts, even in a relatively short period of time. As a result the problem of engine wear may be highlighted; because more oil may be allowed into the combustion chamber(s) 11 after the carbon or other deposit is cleared away by the use of the above described method. Accordingly, where the aspirator 26 is fitted to an engine 10, replacement of the engine’s piston rings and/or refurbishment of valves and/or seatings may be advantageous, as this can counter the negative effects (if any) of ‘cleaning’ the engine 10 using the aspirator 26 and method above.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

Various modifications may be made to the apparatus described whilst enabling the methods of the invention to be performed. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

Claims

1. A method of operating an internal combustion engine, including: combusting primary fuel and primary air in a combustion chamber to produce combustion products; exhausting the combustion products to an exhaust system for exhausting the combustion products to atmosphere; and introducing into the exhaust system secondary air and mechanically acting upon the secondary air and the combustion products in the exhaust system in the presence of a catalyst to produce an oxidising agent.
2. A method according to claim 1, wherein the oxidising agent is molecular oxygen (O2).
3. A method according to claim 2, wherein the molecular oxygen is produced by a steam reforming reaction:
4. A method according to any preceding claim, wherein the secondary air is introduced into the exhaust system via an exhaust aspirator which draws air into the exhaust system during low pressure or partial vacuum conditions occurring during the cycle of pressure changes which occur in the exhaust system during normal operation of the engine.
5. A method according to claim 4, wherein the catalyst is provided by materials from which the aspirator is at least partly made.
6. A method according to claim 5, wherein the aspirator is connected to the exhaust system by a connector and the catalyst is provided by materials from which the connector is at least partly made.
7. A method according to claim 6, wherein the exhaust system and the connector of the aspirator include complementary tapered threads.
8. A method according to any of claims 4 to 7, wherein the aspirator is tuned to draw air into the exhaust system and mechanically act upon the secondary air and products of combustion by means of pressure pulses in a manner to optimise production of the oxidising agent.
9. A method according to any of claims 4 to 8, wherein the aspirator includes a control valve assembly including: a valve seat member having an annular valve seat; a valve disc for engaging the valve seat, wherein the valve disc includes a non-metal material; and a resilient biasing element for biasing the valve disc towards the valve seat.
10. A method according to claim 9, wherein the valve disc includes a plastics material and/or a polymer material.
11. A method according to any of claims 4 to 10, wherein the internal combustion engine has a plurality of combustion chambers each having an exhaust port, each exhaust port opening into an exhaust manifold, and wherein the aspirator is connected to the exhaust manifold.
12. A method according to claim 11, wherein the aspirator does not protrude into the exhaust manifold.
13. A method according to claims 11 or 12, wherein the aspirator is attached to the position where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.
14. A method according to any of claims 4 to 13, wherein the aspirator is secured to the engine block so as to reduce vibration of the aspirator.
15. A method of adapting an internal combustion engine for operation in accordance with any one of the preceding claims, the method including providing the internal combustion engine with an exhaust aspirator for introducing into the exhaust system secondary air, mechanically acting upon the secondary air and products of combustion in the exhaust system in the presence of a catalyst to produce an oxidising agent.
16. A method according to claim 15 wherein the engine which is to be adapted includes an engine management system, the method including derating and/or detuning the engine management system to provide less fuel and/or air in response to a power demand.
17. An exhaust aspirator for admitting air to the exhaust system of an internal combustion engine including: an air admission tube; a connector at one end of the tube for connecting the tube to an exhaust system; and a control valve assembly at the other end of the tube for controlling the passage of air into the air admission tube, wherein the control valve assembly includes: a valve seat member having an annular valve seat; a valve disc for engaging the valve seat, wherein the valve disc includes a non-metal material; and a biasing element for biasing the valve disc towards the valve seat.
18. An exhaust aspirator according to claim 17, wherein the valve disc includes a plastics material and/or a polymer material.
19. An exhaust aspirator according to claim 17 or 18, wherein the connector includes a portion lined with a catalytic material.
20. An exhaust aspirator for admitting air to the exhaust system of an internal combustion engine including: an air admission tube; a connector at one end of the tube for connecting the tube to an exhaust system; and a control valve assembly at the other end of the tube for controlling the passage of air into the air admission tube, wherein the connector includes a portion lined with a catalytic material.
21. An exhaust aspirator according to claim 19 or 20, wherein the catalytic material includes a material selected from the group consisting of copper, cerium, platinum, rhodium, and combinations thereof.
22. An internal combustion engine including an exhaust aspirator according to any of claims 17 to 21.
23. An internal combustion engine according to claim 22, including: at least one combustion chamber for combusting primary fuel and primary air to produce combustion products; and an exhaust system including at least one exhaust manifold connected to the or each combustion chamber for receiving the combustion products, wherein the exhaust aspirator is connected to the exhaust system for introducing secondary air into the exhaust system.
25. An internal combustion engine according to claim 23, wherein the exhaust system and the connector of the aspirator include complementary tapered threads.

25. An internal combustion engine according to claim 23 or 24, wherein the aspirator is connected to the exhaust manifold.
26. An internal combustion engine according to claim 25, wherein the aspirator does not protrude into the exhaust manifold.
27. An internal combustion engine according to claims 25 or 26, wherein the aspirator is attached to the position where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.
28. An internal combustion engine including an exhaust aspirator for admitting air to the exhaust manifold of an internal combustion engine, the aspirator including: an air admission tube; a connector at one end of the tube for connecting the tube to an exhaust manifold; and a control valve assembly at the other end of the tube for controlling the passage of air into the air admission tube, wherein the aspirator does not protrude into the exhaust manifold.
29. A method of determining an optimum location for positioning an aspirator for admitting air to the exhaust manifold of an internal combustion engine, the method including: operating the internal combustion engine and scanning an ultrasonic probe across the exhaust manifold to determine a location where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.
30. An internal combustion engine including: at least one combustion chamber for combusting primary fuel and primary air to produce combustion products; an exhaust manifold connected to the or each combustion chamber for receiving the combustion products; and an exhaust aspirator for introducing secondary air into the exhaust manifold, wherein the exhaust aspirator is attached to the position where the pressure waves of the combustion products in the exhaust manifold which result from operation of the engine have the largest amplitude.
31. A method, an aspirator or an engine substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
32. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.