GB2428465A

GB2428465A - A system for dispensing EGR in a reciprocating internal combustion engine

Info

Publication number: GB2428465A
Application number: GB0609674A
Authority: GB
Inventors: Thomas Tsoi Hei Ma
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-07-19
Filing date: 2006-05-16
Publication date: 2007-01-31
Also published as: GB0609674D0

Abstract

A system for dispensing EGR in a reciprocating internal combustion engine comprises a rotating matrix 10 having a plurality of flow passages 20 in communication with a first set of entry 22 and exit 22' ducts that communicate with an engine exhaust to the ambient atmosphere, and a second set of entry 24 and exit 24' ducts that communicate with an air intake air stream from the ambient atmosphere to the engine. Matrix 10 may be rotated at a variable speed by an electric motor or an engine drive train and walls of the passages 20 made from stainless steel or ceramic. Exhaust gases may communicate through a bifurcated pipe 30 and a diverter valve 36 proportions the amount of exhaust passing through the matrix 10. Exhaust gas and air flow may be in counter or contra flow directions. A third set of entry and exit ducts (26, 26' fig 4) for additional cooling of the matrix 10 may be provided whereby additional air is not contaminated with exhaust gas. A fuel dispensing unit (40, fig 6) may be provided so that the matrix evaporates fuel, passages 20 may be coated with a fuel reforming catalytic coating, and a fuel cell consuming some of EGR reformed fuel may be provided to generate electricity. Matrix 10 may operate as a self cleaning particulate filter (fig 8). Secondary air drawn from the intake air may be burnt in combination with fuel rich exhaust gas in a catalytic converter (140, fig 9) to rapidly heat it up during cold starts.

Description

EGR DISPENSING SYSTEM IN IC ENGINE

Field of the invention

The present invention relates to a dispensing system for Exhaust Gas Recirculation (EGR) in a reciprocating internal combustion engine.

Background of the invention

In a conventional reciprocating internal combustion engine EGR system, a metered proportion of the exhaust gas stream from the engine exhaust system is diverted to enter the engine intake system by an EGR pipe connected between the two. In order to drive a sufficient flow of recirculated exhaust gases from the exhaust system to the intake system of the engine, a substantial pressure drop (delta-P) in the desired direction along the EGR pipe is required. However this delta-P is not always available in the desired direction especially when the engine is operated in an unthrottled or in a boosted mode where the local pressure in the intake system could be substantially the same or higher than the local pressure in the exhaust system. In such cases, it is necessary to apply partial throttling of the intake system to reduce the air induction pressure or partial throttling of the exhaust system to increase the exhaust back pressure, neither of which is desirable because of the reduced volumetric efficiency and increased pumping work in the engine as a result. It is therefore common practice to keep delta-P as small as possible in such cases, but this would limit the maximum flow of EGR that can be delivered by the conventional EGR system which may fall short of the EGR demand in some advanced technology engines where more and more EGR is used for NOx control under highly boosted conditions and for initiation and regulation of special combustion modes such as controlled auto-ignition (CAl) and homogeneous charge compression ignition (HCCI) In attempting to provide high EGP. under highly boosted conditions in a turbo-charged engine, partially throttling the intake to reduce the air induction pressure or partially throttling the exhaust to increase the exhaust back pressure in order to produce sufficient delta-P across the EGR pipe could risk stalling the turbo-charger.

There is also increasing demand for the EGR gases to be cooled before they are delivered to the intake system of the engine. This is conventionally provided by an EGR cooler connected along the EGR pipe and this further increases the demand for delta-P to drive the EGR through the system.

Hot EGR may also be used for fuel reforming where some of the engine fuel is mixed with exhaust gases drawn along an EGR pipe which includes a catalytic reactor on the way to the engine intake system. This again further increases the demand for delta-P to drive the EGR.

Summary of the invention

with the aim of mitigating at least some of the above problems, there is provided according to the present invention a system for dispensing EGR in a reciprocating internal combustion engine comprising the engine with exhaust and intake ducts, a housing containing a rotating matrix, a first set of entry and exit ducts in the housing forming part of the engine exhaust duct connecting an engine exhaust gas stream from the engine through the housing and matrix to the ambient atmosphere, and a second set of entry and exit ducts in the housing forming part of the engine intake duct connecting an engine intake air stream from the ambient atmosphere through the housing and matrix to the engine, the system further characterised in that the rotating matrix is of thin wall structure having a plurality of flow passages aligned substantially parallel with the axis of rotation of the matrix for guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix, the housing contains and supports the rotating matrix and seals the unexposed ends of the matrix, and the respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the entry and exit ducts of the other set.

In the invention, each set of entry and exit ducts in the housing can only make through flow connection via a passing group of flow passages of the matrix which are instantaneously aligned with the flow cross-sections of the said ducts as the matrix rotates, such that the passing flow passages are sequentially exposed to the exhaust gas stream in the first set of ducts and then to the intake air stream in the second set of ducts, thereby intercepting and isolating a quantity of exhaust gases trapped within the lengths of the passing flow passages from the exhaust gas stream in the first set of ducts and carrying and depositing the said exhaust gases into the intake air stream in the second set of ducts as the matrix rotates.

The flow passages in the matrix may have porous walls allowing seepage of gases from one passage to an adjacent passage while guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix.

A very small minimum clearance is maintained between the end faces of the rotating matrix butting with the end walls of the housing in order to prevent to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the respective sets of ducts. The rotating matrix may be driven by an electric motor or by the engine drive train which may be stopped or disengaged when no EGR is required.

The above configuration of engine exhaust and intake ducts connected directly to separate parts of a rotary mass exchanger constitutes a system for dispensing EGR in the present invention with the conspicuous absence of an EGR pipe connecting between the exhaust duct and the intake duct of the engine as in a conventional EGR system. In the invention, there is no direct connection (such as an EGR pipe) between the exhaust system and the intake system of the engine. The exhaust gas stream and intake air stream are completely separate from one another, the former flowing from the engine through the housing and matrix to the ambient atmosphere, the latter flowing from the ambient atmosphere through the housing and matrix to the engine, the two streams flowing adjacent to one another within the housing but are kept apart by the matrix with no lateral connection between the two that would allow connecting flow from one stream to the other.

Thus the invention is also a method for connecting a rotating mass exchanger having a housing and rotating matrix described in the above system to a reciprocating internal combustion engine, comprising steps of connecting the first set of entry and exit ducts of the mass exchanger for through flow of gases along the exhaust duct of the engine, and connecting the second set of entry and exit ducts of the mass exchanger for through flow of gases along the intake duct of the engine.

The present invention is to be distinguished from the system described in GB1136122 in which a rotary regenerative heat exchanger is used across the inlet and outlet of a flame burner supplying combustion heat to a hot- gas engine which is an external combustion engine. Unlike an internal combustion engine where exhaust gas recirculation EGR is used to introduce inert exhaust gases of higher thermal capacity to dilute the combustible charge and lower the peak combustion temperature, there is no similar requirement in an external combustion flame burner and the design of the rotary heat exchanger shown in GB1136122 takes no account of internal mass exchange in any significant amount which might take place between the flue gas and the supply air in the flame burner. Hence there is no teaching in the prior art of a rotary mass exchanger connected for dispensing EGR in a reciprocating internal combustion engine.

A unique feature of the present invention as a consequence of the absence of the EGR pipe is that the dispensing of EGR gases into the intake air stream is not dependent on the pressure drop (delta-P) between the exhaust and intake systems of the engine. Indeed, the invention will work equally well in cases where the local pressure in the intake system is lower or higher than the local pressure in the exhaust system. EGR is delivered from the exhaust pipe to the intake pipe, not by a connecting flow, but by transport of discrete packages of exhaust gases trapped within the flow guiding passages of the matrix from one part of the housing to another part of the housing as the matrix rotates. The quantity of EGR gases transferred in this manner is determined by the passing train of discrete packages which is dependent on the volume of the passing flow passages in the matrix and the speed of rotation of the matrix, and independent of the delta-P between the exhaust gas and intake air streams. Very large quantities of EGR gases may be transferred to the engine intake air using the present invention without increasing the engine exhaust back pressure or decreasing the engine intake air induction pressure, thus maintaining high volumetric efficiency and low pumping work in the engine.

Preferably a bifurcated exhaust pipe coming from the engine is provided having a first branch connected to the first set of entry and exit ducts in the housing, and a second branch bypassing the first set of entry and exit ducts, and a diverter valve at the bifurcated junction of the exhaust pipe for proportioning the flow of exhaust gases between the two branches. This enables the dispensing of EGP.

to be controlled quantitatively in two ways: 1) diverting a predetermined proportion of the engine exhaust gas stream to the first entry and exit ducts and rotating the matrix at a sufficient speed to transfer all the diverted gas stream to the intake air stream in which case the diverter valve will set the quantity of EGR, or 2) diverting an arbitrary proportion of the engine exhaust gas stream to the first entry and exit ducts and rotating the matrix at a variable slower speed so that only a fraction of the diverted gas stream is transferred to the intake air stream while the remaining is discharged from the first exit duct in which case the rotating speed of the matrix will set the quantity of EGR. Of course when no EGR is required, the diverter valve may be moved to divert all the exhaust gases along the second branch completely bypassing the housing, or the rotation of the matrix may be stopped.

An inherent feature of the invention is that the exhaust gas stream leaving the first exit duct will have ambient air carried across and deposited into it in the same way as the intake air stream leaving the second exit duct will have EGR gases carried across and deposited into it as the matrix rotates. Thus in the first control method described above, the gas stream discharged from the first exit duct will be entirely air which could be released directly to the ambient atmosphere. In the second control method, the gas stream discharged from the first exit duct will be exhaust gases diluted with air and this may be treated in the variety of ways for cleaning up the exhaust before being discharged to the ambient atmosphere.

Another inherent feature of the invention is that the rotating matrix will inevitably attain different wall temperatures as it is exposed to different gas streams having different gas temperatures. This is a recuperative heating effect which is intrinsic to the working system of the invention, and could be exploited to useful advantage for heat exchange between gas streams in combination with EGR dispensing.

The above two inherent features are simultaneously effective in both the exhaust and intake gas streams flowing through the housing, so that whilst the exhaust gas stream loses heat to the matrix and gains some intake air mass as the matrix rotates, the intake air stream will gain heat from the matrix and gain some exhaust gases mass as EGR at the same time. So if an EGR cooler is required to cool the EGR gases before delivering them to the engine, the present invention will not be effective because most of the exhaust heat (including the heat of the EGR gases) is rejected to the intake air going into the engine, and only a small proportion of the heat stored within the matrix is rejected to the ambient atmosphere by the transferred air mass carried across to the outgoing exhaust gas stream as the matrix rotates. In fact, to all intents and purposes, the present invention heats up the intake air by soaking into the matrix most of the exhaust heat and then rejecting the heat to the intake air stream thus constituting an very efficient exhaust heat recovery system.

Fortuitously, the above heating effect may be used to aavantage in a combined system for dispensing EGR and heating the intake air. In this case, a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature such that, when the said flow passages pass across the second set of ducts again as the matrix rotates, the engine intake air stream is exposed to substantially hotter wall surfaces and is rapidly heated. The heated intake air and hot EGR will be ideal for operating an engine in controlled auto-ignition (CAT) or s homogeneous charge compression ignition (HCCI) combustion modes relying on compression heat within a pre-mixed charge for inducing ignition and eliminates the need of a separate air heater.

If an EGR cooler is required combined with the present invention, a third stream of ambient cooling air will be necessary for absorbing and rejecting most of the exhaust heat to the ambient atmosphere and this cooling air must not be contaminated by any exhaust gas transferred to it as the matrix rotates. The latter is important because otherwise additional after-treatment will be necessary to remove any undesirable gas and particulate emission in the cooling air and this is expensive and inefficient because of the low temperature of the stream. In the present invention, contamination of the cooling air may be avoided by positioning the cooling air stream after the engine intake air stream in rotational sequence of the rotating matrix so that any transferred exhaust gas (EGR) will be completely purged into the engine by the intake air stream, and further transfer of gases between the intake air stream and the cooling air stream as the matrix rotates will be clean air containing no exhaust gas.

Thus, in order to exploit the cooling using with ambient air without contaminating the air, the EGR dispensing system further comprises a third set of entry and exit ducts connecting an ambient air stream drawn from the ambient atmosphere to pass through the housing and matrix and out again to the ambient atmosphere, the system further characterised in that the entry and exit ducts are disposed in the housing opposite one another facing the ends of the rotating matrix and positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence after the first and second sets of entry and exit ducts.

The ambient air stream may be driven by an external air blower drawing ambient air and forcing it through the third set of entry and exit ducts.

In the above system in the case where the engine is supercharged or turbocharged, it is inevitable that pressurised air within the passing flow passages carried from the second set of ducts will join the third set of ducts with a sudden expansion into both the entry and exit ducts as the matrix rotates. This is undesirable and could counteract the through flow of air induced by the external air blower. On the other hand, the pressurised air within the passing flow passages before reaching the third set of ducts may be used to advantage for generating a cooling flow stream driven indirectly by the supercharger or turbocharger if this air is allowed to expand out of the matrix in a controlled manner and cool during the process, serving as a continuous air source to any external or internal device.

To this effect, the system further comprises an expansion port disposed at the end of the housing and positioned to release the pressurised air within the passing flow passages carried from the second set of ducts before reaching the third set of ducts as the matrix rotates, and this expansion port may be connected to the entry duct of the third set of ducts for supplying a continuous stream of cooling air through the rotating matrix along the third set of ducts. Thus, the supercharger or turbocharger could be used for boosting the engine via the second set of ducts as well as supplying cooling air via the expansion port and the third set of ducts. The quantity of cooling air may be controlled by the rotating speed of the matrix.

In this case, a combined system for dispensing EGR and cooling the EGR is provided in which an engine exhaust gas - 10 - stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix along the third set of ducts for cooling the walls of the passing flow passages and soaking them to a cold sink temperature such that, when the said flow passages pass across the first set of ducts again as the matrix rotates, the exhaust gas stream and the transferred exhaust gases (EGR) are exposed to substantially colder wall surfaces and are rapidly cooled. The cooled EGR will be ideal for NOx control without causing engine knock and eliminates the need of a separate EGR cooler.

The above EGR cooler should be distinguished from the less effective EGR coolers described in US6161528 and EP1586842 installed along an EGR pipe of the engine for cooling the connected EGR flow between the exhaust and intake systems of the engine. Such previous coolers have many shortcomings which are completely circumvented in the present invention. For example, the EGR flow through the cooler into the intake of the engine will be limited by the available delta-P across the EGR pipe and because some external cooling air will inevitably be transferred into the EGR stream replacing some of the EGR, the actual EGR flow into the engine will be less and further limited. In another example, the cooling air stream blown through the cooler will inevitably be contaminated with some exhaust gases transferred to it by the rotating matrix and this should not be discharged directly to the ambient atmosphere because of the untreated pollutants it contains. In contrast in the present invention as is already highlighted in the earlier paragraph, the EGR gases are transferred by the rotating matrix laterally to the intake air stream in the absence of an EGR pipe and not relying on delta-P, and the intake air - 11 - stream to the engine is positioned between the exhaust gas stream and the cooling air stream in rotational sequence of the matrix, thus purging the exhaust gases immediately into the engine as EGR and ensuring the cooling air stream is not contaminated when discharged to the ambient atmosphere.

Finally, the main exhaust gas stream will be diluted with some cooling air and this will safely pass through the main after-treatment system of the engine including a catalytic converter and particulate filter.

In a variation of the above combined EGR dispensing and cooling system of the invention, a combined system for dispensing EGR and cooling the intake air in a boosted engine is provided in which an engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with a hot intake air stream to the engine along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix along the third set of ducts for cooling the walls of the passing flow passages and soaking them to a cold sink temperature such that, when the said flow passages pass across the second sets of ducts again as the matrix rotates, the hot intake air stream is exposed to substantially colder wall surfaces and is rapidly cooled. The cooled intake air improves the thermodynamic efficiency of a boosted engine and eliminates the need of a separate air inter-cooler.

The EGR dispensing system of the present invention may also be used additionally as a fuel vaporiser and dispenser by introducing fuel into the exhaust gas stream to take advantage of the available high temperature and residence time within the passing flow passages to evaporate the fuel as the matrix rotates. In this case, the system further comprises a fuel dispensing unit for introducing fuel into the housing and matrix via the first entry duct.

- 12 - Thus, a combined system for dispensing EGR and dispensing fuel is provided in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be evaporated within the hot passing flow passages, and the evaporated fuel is carried and deposited into the intake air stream as the matrix rotates. The evaporated fuel will be ideal for providing a combustible pre-mixed fuel/air charge in a CAl or HCCI engine. It also eliminates the need of a separate fuel evaporator. This is particular useful in an engine supplied with diesel type fuel which is difficult to vaporise on account of the high boiling point of the heavier fraction of the fuel. Furthermore the evaporation of the dispensed fuel would contribute to the cooling of the EGR by absorbing the latent heat of evaporation of the fuel from the exhaust gases and from the walls of the rotating matrix.

The above combined system may further be used as a fuel reformer by introducing fuel into the exhaust gas stream to take advantage of the available high temperature and residence time within the passing flow passages to perform catalytic reforming of the fuel as the matrix rotates. In this case, the system further comprises a fuel reforming catalytic coating deposited on the surfaces of the flow passages within the rotating matrix.

Thus, a combined system for dispensing EGR and reforming fuel is provided in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and - 13 - carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be reformed by catalytic reaction with the exhaust gases within the hot passing flow passages, and the reformed fuel is carried and deposited into the intake air stream as the matrix rotates. The reformed fuel will be ideal for improving the combustion efficiency and enhancing ignition in a CAl or HCCI engine. It also eliminates the need of a separate fuel reformer.

A fuel cell may also be connected along the engine intake air stream after the fuel reformer, consuming some of the EGR reformed fuel while discharging its effluence to the engine cylinder for further aftertreatment within the engine if necessary, and generating electricity to power any external device thus serving as an Auxiliary Power Unit.

In the above applications as fuel dispenser and fuel reformer, preferably a bifurcated exhaust pipe coming from the engine is provided having a first branch connected to the first set of entry and exit ducts in the housing, and a second branch bypassing the first set of entry and exit ducts, and a diverter valve at the bifurcated junction of the exhaust pipe for proportioning the flow of exhaust gases between the two branches. This enables the dispensing of the fuel and EGR to be controlled quantitatively in two ways: 1) diverting a predetermined proportion of the engine exhaust gas stream to the first entry duct, introducing a predetermined flow of fuel into the first entry duct, and rotating the matrix at a sufficient speed to transfer all the diverted gases and fuel to the intake air stream in which case the diverter valve will set the quantities of dispensed fuel and EGR, or 2) diverting an arbitrary - 14 proportion of the engine exhaust gas stream to the first entry duct, introducing a predetermined flow of fuel into the first entry duct, and rotating the matrix at a variable slower speed so that only a fraction of the diverted gases and fuel is transferred to the intake air stream while the remaining exhaust gases and fuel are discharged from the first exit duct to join with the exhaust pipe. In this case, the rotating speed of the matrix will set the quantities of dispensed fuel and EGR. Preferably, a partition is provided to guide the dispensed fuel and directed it only towards those passing flow passage which are immediately leaving the first set of entry and exit ducts moving in a direction towards the second set of entry and exit ducts as the matrix rotates. This ensures substantially all the dispensed fuel will be transferred with the EGR to the intake air stream even at a slow rotating speed of the matrix.

In the first control method, only the heat of the transferred EGP. is available for supporting the evaporation of the fuel and/or the endothermjc reactions in the fuel reforming process. In the second control method, on the other hand, substantially all the exhaust heat from the full exhaust gas stream could be stored within the matrix and used to support the evaporation of the fuel and/or the endothermic reactions in the fuel reforming process. The quantity of exhaust gases involved in the evaporation and/or reforming process could be the flow quantity delivered as EGP. to the intake air stream along with a predetermined flow of fuel. Alternatively, more fuel could be introduced and some of the evaporated and/or reformed fuel in excess of the EGR flow quantity could be discharged from the first exit duct with the remaining exhaust gas stream. This could be used to supply suitable reductants to a Selective Catalytic Reactor (SCR) downstream in the engine exhaust system for reducing NOx emissions in the exhaust gases.

- 15 - The flow passages in the matrix may have porous walls allowing seepage of gases from one passage to an adjacent passage while guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix.

Furthermore, the ends of alternate flow passages may be blocked at one end of the matrix and the ends of the other flow passages blocked at the other end of the matrix in a construction similar to that of a diesel particulate filter DPF. In this case, a combined system for dispensing EGR and filtering particulate matter in the exhaust gases is provided in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of engine exhaust gas stream seeps across the porous walls of the passing flow passages while beingguided to flow from one exposed end of the matrix to the other exposed end of the matrix and particulate matter is filtered and deposited on the entry side walls of the passing flow passages.

By arranging the exhaust gas stream and the intake air stream to flow in counter directions through the rotating matrix, the combined EGR and DPF system of the present invention will be self-cleaning by the strong action of the full flow of the intake air stream dislodging the particulate matter from the walls of the passing flow passages and carrying it back into the engine as the matrix rotates. This eliminates the need of a separate DPF in the engine exhaust system and further eliminates the need to regenerate the DPF by heating to burn off the deposits.

Such self-cleaning DPF will be adequate for application in light-duty engines where the presence of particulate matters in the intake air may be tolerated at the expense of long term durability.

- 16 - As mentioned earlier, an inherent feature of the invention is that the exhaust gas stream leaving the first exit duct will have ambient air carried across and deposited into it in the same way as the intake air stream leaving the second exit duct will have EGR gases carried across and deposited into it as the matrix rotates. This may be exploited to advantage for automatically providing secondary air to a catalytic converter in the engine exhaust without relying on a separate secondary air pump while using the system of the invention for dispensing air into the exhaust gas stream at the same time as EGR is dispensed into the intake air stream. Thus a combined system is provided for dispensing EGR and providing secondary air to a catalytic converter in the exhaust gas stream downstream of the housing, in which the engine is provided with a predetermined volume flow of EGR and the catalytic converter is provided with a corresponding volume flow of air transferred from the intake air stream to the exhaust gas stream by the rotating matrix and mixed with the exhaust gas stream, characterised in that the engine is calibrated at a richer than stoichiometric fuel/air ratio in order to produce fuel-rich exhaust gases and an igniter is provided upstream of the catalytic converter for igniting the mixture of fuel-rich exhaust gases and secondary air in order to burn the fuel in the mixture and heat up the catalytic converter rapidly during cold start.

Preferably, the engine is supplied with nominally 50% EGR and briefly calibrated with a very rich fuel/air mixture of nominally lambda 0.5 during cold start in order to produce a sufficiently high concentration of hydrogen in the fuel-rich exhaust gases for the mixture to be easily ignitable when supplied with additional air and burn smoothly as a flame in front of a catalytic converter thus rapidly heating up the converter. Under these conditions, the corresponding flow of secondary air transferred to the exhaust gas stream by the rotating matrix will be nominally - 17 - correct for complete combustion of all the fuel in the exhaust mixture. Such a system for rapid light-off of a catalytic converter has been described in US5425233 in which the additional air was provided by a separate air pump made unnecessary in the present invention. The hydrogen- rich EGR dispensed to the engine also helps combustion during the cold start and the rotating matrix acts as an HC absorber recycling any condensed fuel discharged from the engine during cold cranking, thus improving US5425233.

Brief description of the drawings

The invention will now be described further by way of example with reference to the accompanying drawings in which Figure 1 is a schematic view of a system for dispensing EGR according to the present invention, Figure la is a schematic view of an alternative system for dispensing EGR according to the invention, Figure 2 is a schematic axial cross-section of a rotating matrix within a housing forming part of the EGR dispensing system of Figure 1, Figures 2a and 2b are developed views of the rotating matrix of Figure 2, Figure 3 is a schematic lateral cross-section of the rotating matrix and housing of Figure 2, Figure 4 is a schematic developed view of the rotating matrix within a different housing with additional cooling air entry and exit ducts, Figure 5 is a schematic lateral cross-section of the rotating matrix and housing of Figure 4, Figures 4a and 5a show an alternative system similar to that of Figures 4 and 5, with the addition of an expansion port, Figure 6 and 7 are schematic cross-sections of a rotating matrix within a housing similar to Figures 2 and 3 with the addition of a fuel dispensing unit for a fuel evaporator and/or a fuel reformer, - 18 - Figure 8 is a schematic cross-section of a rotating matrix within a housing similar to Figure 2 or Figure 6, constructed to operate as a particulate filter, and Figure 9 is a schematic view of a system similar to that of Figure 1, including a catalytic converter supplied with secondary air derived from the EGR dispensing system.

Detailed description of the preferred embodiment

Figure 1 (also Figure la) shows a reciprocating internal combustion engine 100 with intake manifold 114 admitting intake air from the ambient atmosphere through an air blower 124 and a housing 14 containing a flow guiding matrix 10 to the engine cylinders along an intake duct comprising elements 124, 24, 14, 10, 24', 114 in the flow direction indicated by arrows, and exhaust manifold 112 discharging exhaust gases from the engine cylinders through the housing 14 and matrix 10 to the ambient atmosphere via an exhaust turbine 122 along an exhaust duct comprising elements 112, 22, 14, 10, 22', 122 in the flow direction also indicated by arrows. The matrix 10 is supported for rotation within the housing 14 with good seals at each end of the matrix 10 butting against the end walls of the housing 14.

The above configuration of engine exhaust and intake ducts 112, 22, 22' and 24, 24', 114 respectively, connected directly to separate parts of a rotary mass exchanger 14, 10 (with or without the turbo-charger 122, 124) constitutes a system for dispensing EGR in the present invention with the conspicuous absence of an EGR pipe connecting between the exhaust duct and the intake duct of the engine as in a conventional EGR system. In the invention, EGR is delivered from the exhaust duct to the intake duct, not by a connecting flow, but by transport of discrete packages of - 19 exhaust gases trapped within the flow guiding passages of the matrix from one part of the housing to another part of the housing as the matrix rotates. When the matrix 10 is stationary, no package is transferred and the exhaust and intake streams will simply flow past one another along separate parts of the matrix 10. When the matrix 10 is rotated at a variable speed by an electric motor (not shown), discrete packages of exhaust gases will be intercepted from the exhaust gas stream 22, 22', trapped locally within part of the matrix 10, carried across to the intake air stream 24, 24' as the matrix rotates, and deposited into the intake air stream. Thus EGR is dispensed according to the rotating speed of the matrix and this could take place at any exhaust or intake pressure, not relying on delta-P to drive a connecting flow as in a conventional EGR system. Very large quantities of EGR gases may to transferred to the engine intake air using the present invention without increasing the engine exhaust back pressure or decreasing the engine intake air induction pressure, thus maintaining high volumetric efficiency and low pumping work in the engine.

Figures 2 and 3 show a rotating matrix 10 of thin wall structure forming a plurality of flow passages aligned substantially parallel with the axis of rotation of the matrix for guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix. A flow passage element 20 fed with an advancing column of exhaust gases is highlighted as example in Figure 2. The matrix 10 is contained within a housing 14 which seals the ends of the unconnected part of the matrix and supports the matrix for rotation about an axis 12 driven by a variable speed motor or by the engine drive train (not shown) . This assembly constitutes a rotary mass exchanger and is a key part of the EGR dispensing system of Figure 1 (also Figure la) with like components annotated by the same numerals.

- 20 - The housing 14 has two sets of entry and exits ducts labelled generally 22, 24 in Figure 3. A first set of entry and exit ducts 22, 22' respectively in the housing 14 connects an engine exhaust gas stream from the engine s exhaust system (112) through the housing 14 and matrix 10 to the ambient atmosphere. A second set of entry and exit ducts 24, 24' respectively in the housing 14 connects an engine intake air stream from the ambient atmosphere through the housing 14 and matrix 10 to the engine intake system (114) . In the invention, the respective sets of ducts are disposed in the housing 14 with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix 10 and positioned eccentrically to the axis of rotation of the matrix 10 apart from and in rotational sequence with the other set of entry and exit ducts. Each set of entry and exit ducts in the housing 14 can only make through flow connection via a passing group of flow passages in the matrix 10 which are instantaneously aligned with the flow cross-sections of the said ducts as the matrix rotates, such that the passing flow passages are sequentially exposed to the exhaust gas stream in the ducts 22, 22' and then to the intake air stream in the ducts 24, 24', thereby intercepting and isolating a quantity of exhaust gases trapped within the lengths of the passing flow passages in the matrix 10 from the exhaust gas stream in the ducts 22, 22', and carrying and depositing the said exhaust gases into the intake air stream in the ducts 24, 24' as the matrix rotates. For example the flow passage element 20 containing a trapped package of a column of exhaust gases is carried laterally from the duct 22 to the duct 24 along a locus indicated by the rotation arrow in Figure 3.

A very small minimum clearance is maintained between the end faces of the rotating matrix 10 butting with the end walls of the housing 14 in order to stop to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts 22, 22' and 24, 24', and to maintain different 21 - gas pressures within each set of ducts. The walls of the flow passages in the matrix 10 may be constructed of thin foils of stainless steel or extruded ceramic in a honeycomb flow guiding structure. The walls may also be porous allowing seepage of gases from one passage to an adjacent passage while guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix.

Figure 2 also shows a bifurcated exhaust pipe 30 coming from the engine exhaust system (112) with one branch connected to the entry and exit ducts 22, 22' and another branch 32 bypassing the entry and exit ducts 22, 22'. A diverter valve 36 is provided at the bifurcated junction for proportioning the flow of exhaust gases between the two branches. In the position shown, the diverter valve 36 diverts substantially the full flow of exhaust gases towards the duct 22. When the valve 36 is moved in the direction of the arrow, a smaller proportion of the exhaust gas flow will be diverted to the duct 22.

This enables the dispensing of EGR to be controlled quantitatively in two ways: 1) diverting a predetermined proportion of the engine exhaust gas stream to the entry duct 22 and rotating the matrix 10 at a sufficient speed to transfer all the diverted gases to the intake air stream in which case the diverter valve 36 will set the quantity of EGR, or 2) diverting an arbitrary proportion of the engine exhaust gas stream to the entry duct 22 and rotating the matrix 10 at a variable slower speed so that only a fraction of the diverted gases is transferred to the intake air stream while the remaining is discharged from the exit duct 22' to join with the exhaust pipe 30' in which case the rotating speed of the matrix will set the quantity of EGR.

Of course when no EGR is required, the diverter valve 36 may be moved to divert all the exhaust gases along the branch 32 completely bypassing the housing 14, or the rotation of the matrix 10 may be stopped.

- 22 - It should be noted that an inherent feature of the system in Figure 1 (also Figure la) is that the exhaust gas stream leaving the exit duct 22' will have ambient air carried across and deposited into it in the same way as the intake air stream leaving the exit duct 24' will have EGR gases carried across and deposited into it as the matrix 10 rotates, in Figure 2, in the first control method described in the previous paragraph, the gas stream discharged from the exit duct 22' will be entirely air, whereas in the second control method, the gas stream discharged from the exit duct 22' will be exhaust gases diluted with air. In the first case, the air discharge from the exit duct 22' may be released immediately to the ambient atmosphere without diluting the exhaust gas flow in the bypass branch 32, 30' connected to the exhaust after-treatment system of the engine including a catalytic converter. Accordingly, a two-position valve 38 is shown for releasing the air via a separate discharge duct 30".

The above two cases are further illustrated in Figures 2a and 2b respectively, which are developed views of the rotating matrix shown in Figure 1 moving in the direction of the dashed arrows and carrying the flow passages past the entry and exit ducts 22, 22' which take the exhaust gases from the engine, and then past the entry and exit ducts 24, 24' which take the intake air to the engine. Following one flow passage element moving from left to right, it has initially a column of air trapped between the sealed ends.

When this flow passage element is carried past the cross- section of the entry and exit ducts 22, 22', exhaust gases (shown shaded) will enter the passage as an advancing column pushing the air content out of the passage. The extent by which the exhaust gas column fills the length of the flow passage element would depend on the speed of the gas flow along the element and time available for element to traverse laterally the cross-section of the entry and exit ducts 22, 22'. In Figure 2a where the speed of the gas flow is - 23 - relatively low and the speed of rotation of the matrix 10 is relatively high, there is no breakthrough of the exhaust gas column reaching the exit duct 22' in the time available so that the gases leaving the exit duct 22' will be entirely air. On the other hand, in Figure 2b where the speed of the gas flow is relatively high and the speed of rotation of the matrix 10 is relatively low, there is breakthrough of the exhaust gas column reaching the exit duct 22' in the time available and the gases leaving the exit duct 22' will be a mixture of exhaust gases and air.

When the flow passage element is carried completely past the crosssection of the entry and exit ducts 22, 22', the column is sealed again at both ends and transported laterally until it reaches the cross-section of the entry and exit ducts 24, 24' where intake air will enter the passage as an advancing column and push the exhaust gas content out of the flow passage element into the exit duct 24'. These exhaust gases would join with more air breaking through the flow passage element and reaching the exit duct 24' in the time available according to the speed of rotation of the matrix 10, and the mixture is delivered to the engine as EGR mixed with intake air, thus achieving the objective of the invention for dispensing EGR by means of a system comprising the engine exhaust and intake ducts connected directly to separate parts of a rotary mass exchanger, without relying on flow along an EGR pipe.

It should be noted that whilst Figure 2a and 2b show the exhaust gas stream and intake air stream arranged in counter-flow directions as in Figure 1, the EGR dispensing system will operate to similar effectiveness when the two streams are arranged in the same flow direction as shown in Figure la.

Another inherent feature of the system in Figure 1 (also Figure la) is that the rotating matrix 10 will - 24 - inevitably attain different wall temperatures as it is exposed to different gas streams having different gas temperatures. This is a recuperative heating effect which is intrinsic to the working system of the invention, and could be exploited to useful advantage in combination with the EGR dispensing.

Fortuitously, the above heating effect may be used to advantage in a combined system for dispensing EGR and heating the intake air, shown in Figures 2 and 3 in combination with the system in Figure 1 (similarly in Figure la) . In this case, a flow of engine exhaust gas stream is passed through the matrix 10 along the ducts 22, 22' and a quantity of the exhaust gases is trapped and carried by the passing flow passages in the matrix 10 to join with an engine intake air stream along the ducts 24, 24' as the matrix rotates thereby providing EGR, characterised in that - 25 the flow of the engine exhaust gas stream heats the walls of the passing flow passages in the matrix 10 and soaks them to a hot sink temperature such that, when the said flow passages pass across the ducts 24, 24' again as the matrix S rotates, the engine intake air stream is exposed to substantially hotter wall surfaces and is rapidly heated.

The heated intake air and hot EGR will be ideal for operating an engine in controlled auto-ignition (CAl) or homogeneous charge compression ignition (HCCI) and eliminates the need of a separate air heater.

If an EGR cooler is required combined with the present invention, a third stream of ambient cooling air will be necessary for absorbing and rejecting most of the exhaust heat to the ambient atmosphere and this cooling air must not be contaminated by any exhaust gas transferred to it as the matrix rotates. The latter is important because otherwise additional after-treatment will be necessary to remove any undesirable gas and particulate emission in the cooling air and this is expensive and inefficient because of the low temperature of the stream. In Figure 4 which shows a developed view of a rotating matrix 10, opened out along the plane of the rotation arrow in Figure 5 and contained within a different housing 14 having additional ambient air entry and exit ducts 26, 26', contamination of the cooling air is avoided by positioning the ambient air stream 26, 26' after the engine intake air stream 24, 24' in rotational sequence of the matrix 10 in the direction of the rotation arrow, so that any transferred exhaust gas (EGR) will be completely purged into the engine by the intake air stream 24, 24', and further transfer of gases between the intake air stream 24, 24' and the ambient air stream 26, 26' as the matrix rotates will be clean air containing no exhaust gas. Again in Figure 4 and 5, like components are annotated with the same numerals as in Figure 1 (also Figure la) . The ambient air stream may be driven by an external air blower (not shown) blowing ambient air through the ducts 26, 26'.

- 26 - In the above system in the case where the engine is supercharged or turbocharged, it is inevitable that pressurised air within the passing flow passages carried from the ducts 24, 24' will join the ducts 26, 26' with a sudden expansion into both the entry and exit ducts 26, 26' as the matrix rotates. This is undesirable and could counteract the through flow of air induced by the external air blower. On the other hand, the pressurised air within the passing flow passages before reaching the ducts 26, 26' io may be used to advantage for generating a cooling flow stream driven indirectly by the supercharger or turbocharger if this air is allowed to expand out of the matrix 10 in a controlled manner and cool during the process, serving as a continuous air source to any external or internal device.

To this effect, Figures 4a and 5a show an alternative system further comprising an expansion port 28 disposed at the end of the housing 14 and positioned to release the pressurised air within the passing flow passages carried from the ducts 24, 24' before reaching the ducts 26, 26' as the matrix 10 rotates, and this expansion port 28 is connected to the entry duct 26 for supplying a continuous stream of cooling air through the rotating matrix 10 along the ducts 26, 26'. Thus, the supercharger or turbocharger has extra capacity supplying pressurised air for boosting the engine via the ducts 24, 24' as well as re-expanded air for cooling the rotating matrix 10 via the expansion port 28 and the ducts 26, 26'. The quantity of cooling air may be controlled by the rotating speed of the matrix 10.

In operation, the combined system for dispensing and cooling the EGR is shown in Figures 4 and 5 (or in Figures 4a and 5a), in which an engine exhaust gas stream is passed through the matrix 10 along the ducts 22, 22' and a quantity of the exhaust gases is trapped and carried by the passing flow passages in the matrix 10 to join with an engine intake air stream along the ducts 24, 24' as the matrix rotates - 27 - thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix 10 along the ducts 26, 26' for cooling the walls of the passing flow passages in the matrix 10 and soaking them to a cold sink temperature such that, when the said flow passages pass across the ducts 22, 22' again as the matrix rotates, the exhaust gas stream and the transferred exhaust gases (EGR) are exposed to substantially colder wall surfaces and are rapidly cooled. The cooled EGR will be ideal for NOx control and eliminates the need of a separate EGR cooler.

In a variation of the above EGR dispensing and cooling system, a combined system for dispensing EGR and cooling the intake air in a boosted engine is shown in Figures 4 and 5 (or in Figures 4a and 5a) in combination with the system in Figure 1 (similarly in Figure la), in which an engine exhaust gas stream is passed through the matrix 10 along the ducts 22, 22' and a quantity of the exhaust gases is trapped and carried by the passing flow passages in the matrix 10 to join with a hot intake air stream to the engine along the ducts 24, 24' as the matrix rotates thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix 10 along the ducts 26, 26' for cooling the walls of the passing flow passages in the matrix 10 and soaking them to a cold sink temperature such that, when the said flow passages pass across the ducts 24, 24' again as the matrix rotates, the hot intake air stream is exposed to substantially colder wall surfaces and is rapidly cooled.

The cooled intake air will be ideal for improving the thermodynamic efficiency of a boosted engine and eliminates the need of a separate air inter-cooler.

The EGR dispensing system of Figure 1 (also Figure la) may also be used additionally as a fuel evaporator and dispenser by introducing fuel into the exhaust gas stream to take advantage of the available high temperature and residence time within the passing flow passages to perform - 28 catalytic reforming of the fuel as the matrix rotates. For this purpose, Figures 6 and 7 show the system further comprising a fuel dispensing unit 40 for introducing fuel into the housing 14 and matrix 10 via the entry duct 22.

Again in Figures 6 and 7, like components are annotated with the same numerals as in Figures 2 and 3, and in Figure 1 (also Figure la) Thus a combined system for dispensing EGR and dispensing fuel is shown in Figures 6 and 7 in which a flow of engine exhaust gas stream is passed through the matrix 10 along the ducts 22, 22' and a quantity of the exhaust gases is trapped and carried by the passing flow passages in the matrix 10 to join with an engine intake air stream along the ducts 24, 24' as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be evaporated within the hot passing flow passages in the ducts 22, 22', and the evaporated fuel is carried and deposited into the intake air stream in the ducts 24, 24' as the matrix rotates. The evaporated fuel will be ideal for providing a combustible pre-mixed fuel/air charge in a CAl or HCCI engine. It also eliminates the need of a separate fuel evaporator. This is particular useful in an engine supplied with diesel type fuel which is difficult to vaporise on account of the high boiling point of the heavier fraction of the fuel. Furthermore the evaporation of the dispensed fuel would contribute to the cooling of the EGR by absorbing the latent heat of evaporation of the fuel from the exhaust gases and from the walls of the matrix 10.

The above combined system shown in Figures 6 and 7 may further be used as a fuel reformer by introducing fuel into the exhaust gas stream to take advantage of the available high temperature and residence time within the passing flow - 29 - passages to perform catalytic reforming of the fuel as the matrix rotates. In this case, the system further comprises a fuel reforming catalytic coating deposited on the surfaces of the flow passages within the rotating matrix 10.

Thus a combined system for dispensing EGR and reforming fuel is shown again including the fuel reforming catalytic coating in Figures 6 and 7 in which a flow of engine exhaust gas stream is passed through the matrix 10 along the ducts 22, 22' and a quantity of the exhaust gases is trapped and carried by the passing flow passages in the matrix 10 to join with an engine intake air stream along the ducts 24, 24' as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be reformed by catalytic reaction with the exhaust gases within the hot passing flow passages in the ducts 22, 22', and the reformed fuel is carried and deposited into the intake air stream in the ducts 24, 24' as the matrix rotates. The reformed fuel will be ideal for improving the combustion efficiency of the engine and eliminates the need of a separate fuel reformer.

Figure 6 also shows a bifurcated exhaust pipe 30 coming from the engine exhaust system (112) with one branch connected to the entry and exit ducts 22, 22' and another branch 32 bypassing the entry and exit ducts 22, 22'. A diverter valve 36 is provided at the bifurcated junction for proportioning the flow of exhaust gases between the two branches. This enables the dispensing of the fuel and EGR to be controlled quantitatively in two ways: 1) diverting a predetermined proportion of the engine exhaust gas stream to the entry duct 22, introducing a predetermined flow of fuelinto the entry duct 22, and rotating the matrix 10 at a sufficient speed to transfer all the diverted gases and fuel - 30 - to the intake air stream in which case the diverter valve 36 will set the quantities of dispensed fuel and EGR, or 2) diverting an arbitrary proportion of the engine exhaust gas stream to the entry duct 22, introducing a predetermined flow of fuel into the entry duct 22, and rotating the matrix at a variable slower speed so that only a fraction of the diverted gases and fuel is transferred to the intake air stream while the remaining exhaust gases and fuel are discharged from the exit duct 22' to join with the exhaust pipe 30' . In this case, the rotating speed of the matrix will set the quantities of dispensed fuel and EGR.

Preferably, a partition 42 is provided to guide the dispensed fuel and directed it only towards those passing flow passage which are immediately leaving the ducts 22, 22' moving in a direction towards the ducts 24, 24' as the matrix rotates. This ensures substantially all the dispensed fuel will be transferred with the predetermined EGR to the intake air even at a slow rotating speed of the matrix 10.

In the first control method, only the heat of the transferred EGR is available for supporting the evaporation of the fuel and/or the endothermjc reactions in the fuel reforming process. In the second control method, on the other hand, substantially all the exhaust heat from the full exhaust gas stream could be stored within the matrix 10 and used to support the evaporation of the fuel and/or the endothermic reactions in the fuel reforming process. The quantity of exhaust gases involved in the evaporation and/or reforming process could be the flow quantity delivered as EGR to the intake air stream 24, 24' along with a predetermined flow of fuel. Alternatively, more fuel could be introduced and some of the evaporated and/or reformed fuel in excess of the EGR flow quantity could be discharged from the first exit duct 22' with the remaining exhaust gas stream. This could be used to supply suitable reductants to a Selective Catalytic Reactor (SCR) downstream in the engine - 31 - exhaust system (not shown) for reducing NOx emissions in the exhaust gases.

A fuel cell 50 is also shown in Figure 6 connected schematically along the engine intake air stream after the fuel reformer, consuming some of the EGR reformed fuel while discharging its effluence to the engine cylinder for further aftertreatment within the engine if necessary, and generating electricity to power any external device thus serving as an Auxiliary Power Unit (APU) The EGR dispensing system of Figure 1 may also be used additionally as a particulate filter by constructing the flow passages in the rotating matrix 10 with porous walls allowing seepage of gases from one passage to an adjacent passage while guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix. The ends of alternate flow passages may be blocked at one end of the matrix 10 and the ends of the other flow passages blocked at the other end of the matrix 10 in a construction similar to that of a diesel particulate filter DPF. This is shown in Figure 8 where like components are annotated with the same numerals as in Figures 2 and 6, and in Figure 1.

Thus a combined system for dispensing EGR and filtering particulate matter in the exhaust gases is shown in Figure 8 in which a flow of engine exhaust gas stream is passed through the matrix 10 along the ducts 22, 22' and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the ducts 24, 24' as the matrix 10 rotates thereby providing EGR, characterised in that the flow of engine exhaust gas stream seeps across the porous walls of the passing flow passages while being guided to flow from one exposed end of the matrix 10 to the opposite exposed end of the matrix 10 and particulate matter is filtered and deposited on the entry side walls of the passing flow passages.

- 32 - In Figure 8, the exhaust gas stream and the intake air stream are arranged to flow in counter directions through the rotating matrix 10 as in Figure 1. This makes the combined EGR and DPF system of the present invention self- cleaning by the strong action of the full flow of the intake air stream dislodging the particulate matter from the walls of the passing flow passages and carrying it back into the engine as the matrix 10 rotates. This eliminates the need of a separate DPF in the engine exhaust system and further eliminates the need to regenerate the DPF by heating to burn off the particulate deposits. Such self-cleaning DPF will be adequate for application in light-duty engines where the presence of particulate matters in the intake air may be tolerated at the expense of long term durability.

The EGR dispensing system is shown again in Figure 9 in which like components are annotated with the same numerals as in Figure 1 (also Figure la) . In Figure 9, secondary air is automatically provide to a catalytic converter 140 without relying on a separate secondary air pump while using the system of the invention for dispensing air into the exhaust gas stream 22' at the same time as EGR is dispensed into the intake air stream 24'. In this case, the engine is provided with a predetermined volume flow of EGR and the catalytic converter 140 is provided with a corresponding volume flow of air transferred from the intake air stream 24 to the exhaust gas stream 22' by the rotating matrix 10 and mixed with the exhaust gas stream 22'. The engine 100 is calibrated at a richer than stoichiometric fuel/air ratio in order to produce fuel-rich exhaust gases, and an igniter 142 such as a spark plug or a glow plug is provided upstream of the catalytic converter 140 for igniting the mixture of fuel-rich exhaust gases and secondary air in order to burn the fuel in the mixture and heat up the catalytic converter 140 rapidly during cold start.

- 33 - Preferably, the engine 100 is supplied with EGR in the range of 40% to 60% and briefly calibrated with a very rich fuel/air mixture of lambda in the range of 0.6 to 0.4 respectively during cold start in order to produce a s sufficiently high concentration of hydrogen in addition to other partially burnt combustion products in the fuel-rich exhaust gases for the exhaust mixture to be easily ignitable when supplied with additional air and burn smoothly as a flame in front of the catalytic converter 140 thus rapidly heating up the catalytic converter. Under these conditions, the corresponding flow of secondary air transferred to the exhaust gas stream 22' will provide the additional air for complete combustion of all the fuel in the exhaust mixture.

Furthermore, the hydrogen-rich EGR dispensed to the engine will help combustion during the cold start and the rotating matrix acts as an HC absorber recycling any condensed fuel discharged from the engine during cold cranking. To enhance the fuel absorbing properties of the matrix over and above that of its naturally condensing surfaces, a fuel absorption coating may be provided on the walls of the flow passages.

In all the above examples of individual and combined systems for dispensing EGR, very large quantities of EGR may be transferred to the intake system of the engine and this is independent of the delta-P between the any connecting points in the exhaust and intake systems, and is limited only by the EGR tolerance characteristics of the engine combustion system accepting the EGR. The invention is to be contrasted with the conventional EGR system where the quantity of EGR is often limited by the delta-P available, in which case if more EGR is required than can be delivered by the available delta-P, various methods of adjustable valve timing of the engine intake and exhaust valves may have to be used to introduce additional internal EGR to supplement the deficiency of the conventional EGR system.

Such methods include positive valve overlap, exhaust valve re-open, negative valve overlap etc designed to trap, re- - 34 - breathe or re-shuffle some exhaust or burnt gases internally within the engine cylinder without letting them escape into the exhaust system. These methods have been used successfully in some CAT and HCCI engines where the overall EGR could be in the order of 70% of engine cylinder displacement and may go even higher, but they require special valve train systems which are expensive to make and complicated to control, hence the EGR dispensing system of the present invention could provide a simpler and more costeffective solution by supplying all the EGR that is needed.

Moreover, modern IC engines are commonly operated at high boost from a turbocharger or supercharger at the same time with high EGR in order to produce high power and reduced NOx emissions. The EGR dispensing system of the present invention is effective operating under such conditions as shown in Figures 1 and la connected in different configurations to a turbo-charger 122, 124 even against a rising delta-P.

Claims

- 35 - CLAIMS

1. A system for dispensing EGR in a reciprocating internal combustion engine comprising the engine with exhaust and intake ducts, a housing containing a rotating matrix, a first set of entry and exit ducts in the housing forming part of the engine exhaust duct connecting an engine exhaust gas stream from the engine through the housing and matrix to the ambient atmosphere, and a second set of entry and exit ducts in the housing forming part of the engine intake duct connecting an engine intake air stream from the ambient atmosphere through the housing and matrix to the engine, the system further characterised in that the rotating matrix is of thin wall structure having a plurality of flow passages aligned substantially parallel with the axis of rotation of the matrix for guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix, the housing contains and supports the rotating matrix and seals the unexposed ends of the matrix, and the respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the entry and exit ducts of the other set.

2. A method for connecting a rotating mass exchanger having a housing and rotating matrix as claimed in claim 1 to a reciprocating internal combustion engine, comprising steps of connecting the first set of entry and exit ducts of the mass exchanger for through flow of gases along the exhaust duct of the engine, and connecting the second set of entry and exit ducts of the mass exchanger for through flow of gases along the intake duct of the engine.

3. A system as claimed in claim 1, wherein a very small minimum clearance is maintained between the end faces - 36 - of the rotating matrix butting with the end walls of the housing in order to prevent to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the respective sets of ducts.

4. A system as claimed in claim 1 or 3, further comprising a bifurcated exhaust pipe coming from the engine having a first branch connected to the first set of entry and exit ducts in the housing, and a second branch bypassing the first set of entry and exit ducts, and a diverter valve at the bifurcated junction of the exhaust pipe for proportioning the flow of exhaust gases between the two branches.

5. A combined system for dispensing EGR and heating the intake air as claimed in any one of claims 1, 3 and 4, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature such that, when the said flow passages pass across the second set of ducts again as the matrix rotates, the engine intake air stream is exposed to substantially hotter wall surfaces and is rapidly heated.

6. A system as claimed in any one of claims 1, 3 and 4, further comprising a third set of entry and exit ducts connecting an ambient air stream drawn from the ambient atmosphere to pass through the housing and matrix and out again to the ambient atmosphere, the system further characterised in that the entry and exit ducts are disposed in the housing opposite one another facing the ends of the - 37 - rotating matrix and positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence after the first and second sets of entry and exit ducts.

7. A system as claimed in claim 6 in which the engine is supercharged or turbocharged, further comprising an expansion port disposed at the end of the housing and positioned to release the pressurised air within the passing flow passages carried from the second set of ducts before reaching the third set of ducts as the matrix rotates.

8. A system as claimed in claim 7, wherein the expansion port is connected to the entry duct of the third set of ducts.

9. A combined system for dispensing EGR and cooling the EGR as claimed in any one of claims 6 to 8, in which an engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix along the third set of ducts for cooling the walls of the passing flow passages and soaking them to a cold sink temperature such that, when the said flow passages pass across the first set of ducts again as the matrix rotates, the exhaust gas stream and the transferred exhaust gases (EGR) are exposed to substantially colder wall surfaces and are rapidly cooled.

10. A combined system for dispensing EGR and cooling the intake air in a boosted engine as claimed in any one of claims 6 to 8, in which an engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with a hot intake air stream - 38 - to the engine along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix along the third set of ducts for cooling the walls of the passing flow passages and soaking them to a cold sink temperature such that, when the said flow passages pass across the second sets of ducts again as the matrix rotates, the hot intake air stream is exposed to substantially colder wall surfaces and is rapidly cooled.

11. A system as claimed in any preceding claim, further comprising a fuel dispensing unit for introducing fuel into the housing and matrix via the first entry duct.

12. A combined system for dispensing EGR and dispensing fuel as claimed in claim 11, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be evaporated within the hot passing flow passages, and the evaporated fuel is carried and deposited into the intake air stream as the matrix rotates.

13. A system as claimed in claim 11, further comprising a fuel reforming catalytic coating deposited on the surfaces of the flow passages within the rotating matrix.

14. A combined system for dispensing EGR and reforming fuel as claimed in claim 13, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is 39 - trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be reformed by catalytic reaction with the exhaust gases within the hot passing flow passages, and the reformed fuel is carried and deposited into the intake air stream as the matrix rotates.

15. A combined system for dispensing EGR and reforming fuel as claimed in claim 14, wherein a fuel cell is connected along the engine intake air stream after the fuel reformer, consuming some of the EGR reformed fuel while discharging its effluence to the engine cylinder for further aftertreatment within the engine if necessary, and generating electricity to power any external device.

16. A system as claimed in any preceding claim, wherein the flow passages in the rotating matrix have porous walls and the ends of alternate flow passages are blocked at one end of the matrix and the ends of the other flow passages are blocked at the other end of the matrix, and wherein the exhaust gas stream and the intake air stream are arranged to flow in counter directions through the rotating matrix.

17. A combined system for dispensing EGR and filtering particulate matter in the exhaust gases as claimed in claim 16, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of - 40 - exhaust gas stream seeps across the porous walls of the passing flow passages while being guided to flow from one exposed end of the matrix to the other exposed end of the matrix and particulate matter is filtered and deposited on the entry side walls of the passing flow passages, and further characterised in that the filtered particulate matter is subsequently carried and purged into the intake air stream as the matrix rotates.

18. A combined system as claimed in any preceding claim, for dispensing EGR and providing secondary air to a catalytic converter in the exhaust gas stream downstream of the housing, in which the engine is provided with a predetermined volume flow of EGR and the catalytic converter is provided with a corresponding volume flow of air transferred from the intake air stream to the exhaust gas stream by the rotating matrix and mixed with the exhaust gas stream, characterised in that the engine is calibrated at a richer than stoichiometric fuel/air ratio in order to produce fuel-rich exhaust gases arid an igniter is provided upstream of the catalytic converter for igniting the mixture of fuel-rich exhaust gases and secondary air in order to burn the fuel in the mixture and heat up the catalytic converter rapidly during cold start.

19. A system as claimed in any preceding claim, wherein a fuel absorption coating is provided on the walls of the flow passages in the rotating matrix.

20. A combined system for dispensing EGR and recirculating unburnt fuel to the engine as claimed in claim 19, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that unburnt fuel - 41 - escaping with the exhaust gases from the engine is absorbed on the walls of the passing flow passages and is subsequently carried and purged into the intake air stream as the matrix rotates.

21. A rotary mass exchanger constructed for connection with the exhaust and intake ducts of a reciprocating internal combustion engine, constituting a system as claimed in claim 1 and according to a method as claimed in claims 2.

Amendmen to the claims have been made as follows 1. An EGR dispensing system comprising a reciprocating piston internal combustion engine having exhaust and intake ducts, a rotary gas exchanger having a housing containing a rotating matrix, and first and second sets of entry and exit ducts in the housing, characterised in that the first set of entry and exit ducts forms part of the engine exhaust duct connecting an engine exhaust gas stream from the engine through the housing and matrix to the ambient atmosphere, and the second set of entry and exit ducts forms part of the engine intake duct connecting an engine intake air stream from the ambient atmosphere through the housing and matrix to the engine, and means for rotating the matrix at a sufficient speed for a substantial volumetric gas exchange to occur between the engine exhaust gas stream and the intake air stream.

2. Asystem as claimed in claim 1, wherein the rotating matrix is of thin wall structure having a plurality of flow passages aligned substantially parallel with the axis of rotation of the matrix for guiding a flow of gases from one exposed end of the matrix to the other exposed end of the matrix, the housing contains and supports the rotating matrix and seals the unexposed ends of the matrix, and the respective sets of ducts are disposed in the housing with the entry and exit ducts of each set opposite one another facing the ends of the rotating matrix and positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence with the entry and exit ducts of the other set.

3. A system as claimed in claim 1 or 2, wherein a very small minimum clearance is maintained between the end faces of the rotating matrix butting with the end walls of the housing in order to prevent to all intents and purposes any gas leakage at the perimeters of the entry and exit ducts and to maintain different gas pressures within the respective sets of ducts.

4. A system aS claimed in any preceding claim, further comprising a bifurcated exhaust pipe coming from the engine having a first branch connected to the first set of entry and exit ducts in the housing, and a second branch bypassing the first set of entry and exit ducts, and a diverter valve at the bifurcated junction of the exhaust pipe for proportioning the flow of exhaust gases between the two branches.

5. A combined system for dispensing EGR and heating the intake air as claimed in any preceding claim, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature such that, when the said flow passages pass across the second set of ducts again as the matrix rotates, the engine intake air stream is exposed to substantially hotter wall surfaces and is rapidly heated.

6. A system as claimed in any preceding claim, further comprising a third set of entry and exit ducts connecting an ambient air stream drawn from the ambient atmosphere to pass through the housing and matrix and out again to the ambient atmosphere, the system further characterised in that the entry and exit ducts are disposed in the housing opposite one another facing the ends of the rotating matrix and positioned eccentrically to the axis of rotation of the matrix apart from and in rotational sequence after the first and second sets of entry and exit ducts.

7. A system as claimed in claim 6 in which the engine is supercharged or turbocharged, further comprising an expansion port disposed at the end of the housing and positioned to release the pressurised air within the passing flow passages carried from the second set of ducts before reachino- the third set of ducts as the matrix rotates.

10. A combined system for dispensing EGR and cooling the intake air in a boosted engine as claimed in any one of claims 6 to 8, in which an engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with a hot intake air stream to the engine along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that a flow of ambient air stream is passed through the matrix along the third set of ducts for cooling the walls of the passing flow passages and soaking them to a cold sink temperature such that, when the said flow passages pass across the second sets of ducts again as the matrix rotates, the hot intake air stream is exposed to substantially colder wall surfaces and is rapidly cooled.

14. A combined system for dispensing EGR and reforming fuel as claimed in claim 13, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of the engine exhaust gas stream heats the walls of the passing flow passages and soaks them to a hot sink temperature, a predetermined flow of fuel is introduced into the exhaust gas stream to be reformed by catalytic reaction with the exhaust gases within the hot passing flow passages, and the reformed fuel is carried and deposited into the intake air stream as the matrix rotates.

15. A combined system for disPensing EGR and reforming fuel as claimed in claim 14, wherein a fuel cell is connected along the engine intake air stream after the fuel reformer, consuming some of the EC-R reformed fuel while discharging its effluence to the engine cylinder for further aftertreatment within the engine if necessary, and generating electricity to power any external device.

17. A combined system for dispensing EGR and filtering particulate matter in the exhaust gases as claimed in claim 16, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped arid carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that the flow of exhaust gas stream seeps across the porous walls of the passing flow passages while being guided to flow from one exposed end of the matrix to the other exposed end of the matrix and particulate matter is filtered and deposited on the entry side walls of the passing flow passages, and further characterised in that the filtered particulate matter is subsequently carried and purged into the intake air stream as the matrix rotates.

18. A combined system as claimed in any preceding claim, for dispensing EGR and providing secondary air to a catalytic converter in the exhaust gas stream downstream of the housing, in which the engine is provided with a predetermined volume flow of EGR and the catalytic converter is provided with a

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corresponding volume flow: air transferred from the intake air stream to the exhaust gas stream by the rotating matrix and mixed with the exhaust gas stream, characterised in that the engine is calibrated at a richer than stoichiometrjc fuel/air ratio in order to produce fuel-rich exhaust gases and an igniter is provided upstream of the catalytic converter for igniting the mixture of fuel-rich exhaust gases and secondary air in order to burn the fuel in the mixture and heat up the catalytic converter rapidly during cold start.

20. A combined system for dispensing EGR and recirculating unburnt fuel to the engine as claimed in claim 19, in which a flow of engine exhaust gas stream is passed through the matrix along the first set of ducts and a quantity of the exhaust gases is trapped and carried by the passing flow passages to join with an engine intake air stream along the second set of ducts as the matrix rotates thereby providing EGR, characterised in that unburnt fuel escaping with the exhaust gases from the engine is absorbed on the walls of the passing flow passages and is subsequently carried and purged into the intake air stream as the matrix rotates.

21. A method for dispensing EGR in a system as claimed in any preceding claim, comprising the steps of connecting the first set of entry and exit ducts of the gas exchanger for through flow of gases along the exhaust duct of the engine, connecting the second set of entry and exit ducts of the gas exchanger for through flow of gases along the intake duct of the engine, and rotating the matrix at a sufficient speed such that there is substantial volumetric gas exchange between the flows in the engine exhaust and intake ducts.

22. A rotary gas exchanger constructed for connection with the exhaust and intake ducts of a reciprocating internal combustion engine, constituting a system as claimed in claim 1 and according to a method as claimed in claim 21.