Patent Description:
This disclosure relates to exhaust recirculation (EGR) systems for internal combustion engines.

Exhaust gas recirculation, especially cooled EGR, can be added to internal combustion engine systems to reduce NOx emissions and reduce knock tendency. In such a system, an amount of exhaust gas is added to the air and/or fuel mixture within the air-intake manifold of the engine. The challenge is that there is a cost to deliver the cooled EGR (cEGR), especially for high efficiency engines which generally are most efficient when the exhaust manifold pressure is lower than the intake manifold pressure. The pressure difference creates a positive scavenging pressure difference across the engine which scavenges burn gas from the cylinder well and provides favorable pressure-volume pumping loop work. It is particularly challenging to deliver cEGR from its source at the exhaust manifold to the intake manifold without negatively impacting the residual gas scavenging and efficiency of the engine cycle via the pumping loop. The "classic" high pressure loop cEGR system plumbs the exhaust gas directly to the intake manifold, which requires either design or variable turbocharging to force the engine exhaust manifold pressure to be higher than the intake manifold, which in turn, unfavorably reduces scavenging of hot burned gases and engine P-V cycle and loses efficiency. It is particularly counterproductive since the purpose of the cEGR is to reduce the knock tendency to improve efficiency and power density. However, this classic method to drive EGR actually increases the knock tendency through residual gas retention and reduces efficiency thru negative pressure work on the engine - in a manner of diminishing returns, i.e., two steps forward to reduce knock with cEGR, but one step back due to how it is pumped, leading to a zero gain point where the cost of driving cEGR counteracts the benefits of delivering it.

<CIT> shows a conventional exhaust gas feedback system for an internal combustion engine. <CIT> shows conventional systems and methods for an exhaust gas recirculation mixer.

This disclosure describes technologies relating to recirculating exhaust gas. A mixer according to the present invention is defined by claim <NUM>. An engine system according to the present invention is defined by claim <NUM>. A method according to the present invention is defined by claim <NUM>. Further advantageous developments of the present invention are set out in the dependent claims.

Particular implementations of the subject matter described herein can have one or more of the following advantages. The exhaust gas recirculation mixer can allow recirculating exhaust gas into a pressurized engine intake, such as in a supercharged or turbocharged engine, when the exhaust gas source is at a lower pressure than the intake. In certain instances, the mixer can enable admission of exhaust gas even when the internal combustion engine is running under high-load and high boost. At such high-load high boost conditions, EGR is needed the most but it is also most difficult to supply the EGR, due to the higher pressure in the intake system over the exhaust. Moreover, the mixer can mitigate high back pressure in the exhaust system, which prevents burned gas from effectively leaving the combustion chamber and, itself, promotes knock. The mixer is a passive pump, relying on the area reduction of the primary gas stream to accelerate the gas to a high velocity. The accelerated gas causes a low pressure using the Bernoulli's effect, followed by the creation of a free jet of the gas into a receiver chamber. The free jet generated low pressure acts as a suction in the receiver chamber, which when connected to the EGR path, manifests as a pressure below the exhaust manifold creating a favorable pressure gradient for the EGR to flow to the lower pressure to admit exhaust gas into the mixer. Following the mixer, the reverse Bernoulli effect converts the high velocity gas mixture to a high pressure when it is decelerated into the engine intake manifold. Thus, it mitigates system efficiency losses attributable to the pumping work needed to operate more conventional EGR systems and the negative scavenging pressures across the engine. The mixer is also quite simple in construction, and needs no working parts to operate. The mixer can also be mechanically designed to have different primary flow nozzles which can be modular (e.g., threaded on/off the change out), interchangeably fitted for a wide range of engine displacement families. Further, the mixer creates internal turbulence that promotes mixing of the EGR, air and fuel. Further, the mixer can receive fuel, and operate to mix the fuel, air and EGR. Thus, some implementations <NUM>) reduce the pressure difference across the engine to drive EGR from the exhaust manifold to the intake manifold - under any back pressure to intake pressure ratio, <NUM>) including the special case when it is desirable to maintain the back pressure equal to or below the intake pressure - which (a) improves efficiency (due to the reduction of Pumping Mean Effective Pressure (PMEP) and (b) reduces the retention of hot burned gases trapped inside the combustion chamber which themselves increase the very knock tendency that the active cooled EGR is attempting to reduce, (<NUM>) the addition of high velocity fuel enhances the Jet and suction effect, (<NUM>) can simplify the fuel delivery system by eliminating the pressure regulator and preheater circuit since the mixer favors high pressure fuel and cold fuel to cool the EGR using the Joules-Thomson effect (fuel jetting will cause the temperature to drop - which is favorable since cooled EGR and cooled intake air are beneficial to engine operation). By using four barrels, a similar total inlet area and outlet area can be used as compared to a single-barrel exhaust gas recirculation mixer, while reducing the total length of the mixer to be substantially half that of a single-barrel mixer.

Exhaust gas recirculation (EGR) can have parasitic effects on an engine system, that is, it can reduce the effective power output of an engine system as energy is required to move exhaust gas from an exhaust manifold and into an intake manifold. This is especially problematic on forced induction engines where the intake manifold pressure can be higher than the exhaust manifold pressure. Ironically, EGR is most needed when the intake manifold pressure is high, such as when the engine is running at high load. In the case of a turbo-charged engine, increased back-pressure within the exhaust manifold can also contribute to knock under high loads.

The concepts herein relate to an EGR system that can be used on an internal combustion engine, including a forced induction internal combustion engine. A set of jet pumps arranged in parallel is added to the air intake system of the engine between the throttle and the intake manifold. If a compressor is provided in the intake system, the jet pumps can be placed downstream of the compressor (although it could alternatively be placed upstream of the compressor, too). Air, the primary fluid, flows through a central flow passage of each of the jet pumps from the throttle towards the intake manifold. In a low pressure receiver region within each jet pump, recirculated exhaust gas is added to each air stream from the exhaust manifold. The lower effective pressure in each receiver region allows for a pressure differential to form between the exhaust manifold and the receiver. The reverse Bernoulli Effect recovers the pressure by slowing down the high velocity/low pressure gas to create a pressure in the intake manifold that is equal to or higher than the exhaust manifold. So, at the system level, the jet pumps enable the exhaust gas to flow from the exhaust manifold to the intake manifold even when the exhaust manifold is at a lower pressure. Fuel can be added to the air stream upstream of the convergent end of the convergent nozzles. Turbulence is produced within the jet pumps and downstream of the jet pumps leading to a well-mixed, combustible mixture flowing into the manifold.

<FIG> shows an example engine system <NUM>. The engine system <NUM> includes an intake manifold <NUM> configured to receive a combustible mixture to be combusted within a combustion chamber of the engine <NUM>. That is, the intake manifold is fluidically coupled to a source of oxygen and a source of fuel. The combustible mixture can include air and any combustible fluid, such as natural gas, atomized gasoline, or diesel. While the illustrated implementation includes a four-cylinder engine <NUM>, any number of cylinders can be used. Also, while the illustrated implementation includes a piston engine <NUM>, aspects of this disclosure can be applied to other types of internal combustion engines, such as rotary engines or gas turbine engines.

A throttle <NUM> is positioned upstream of the intake manifold <NUM>. The throttle <NUM> is configured to at least partially or entirely regulate an air flow into the intake manifold from the ambient environment <NUM>, for example, by changing a cross-sectional area of a flow passage going through the throttle <NUM>. In some implementations, the throttle <NUM> can include a butterfly valve or a disc valve. Reducing the cross-sectional area of the flow passage through the throttle <NUM> reduces the flowrate of air flowing through the throttle <NUM> towards the intake manifold <NUM>.

An exhaust manifold <NUM> is configured to receive combustion products (exhaust) from a combustion chamber of the engine <NUM>. That is, the exhaust manifold <NUM> is fluidically coupled to an outlet of the combustion chamber. An EGR flow passage <NUM> or conduit fluidically connects the exhaust manifold <NUM> and the intake manifold <NUM>. In the illustrated implementation, an EGR throttle valve <NUM> is located within the EGR flow passage <NUM> between the exhaust manifold <NUM> and the intake manifold <NUM> and is used to regulate the EGR flow. The EGR throttle valve <NUM> regulates the EGR flow by adjusting a cross-sectional area of the EGR flow passage <NUM> going through the EGR throttle valve <NUM>. In some implementations, the EGR throttle valve <NUM> can include a butterfly valve, a disc valve, a needle valve, a globe valve, or another style of valve.

The EGR flow passage <NUM> feeds into an EGR mixer <NUM> that is located downstream of a throttle <NUM> and upstream of the intake manifold <NUM> in the illustrated implementation. The EGR mixer <NUM> is in the engine intake system, fluidically connected to the throttle <NUM>, the intake manifold <NUM>, and the EGR flow passage <NUM>. The fluid connections can be made with conduits containing flow passages that allow fluid flow. In some implementations, the EGR mixer <NUM> can be included within a conduit connecting the intake manifold <NUM> to the throttle <NUM>, within the intake manifold <NUM> itself, within the EGR flow passage <NUM>, integrated within the throttle <NUM>, or integrated into the EGR throttle valve <NUM>. Details about an example EGR mixer are described throughout this disclosure.

In some implementations, an exhaust gas cooler <NUM> is positioned in the EGR flow passage <NUM> between the exhaust manifold <NUM> and the EGR mixer <NUM>. The exhaust gas cooler <NUM> can operate to lower a temperature of the exhaust gas prior to the EGR mixer <NUM>. The exhaust gas cooler <NUM> is a heat exchanger, such as an air-air exchanger or an air-water exchanger. In some implementations, the exhaust gas cooler <NUM> is not included.

In some implementations, the engine system <NUM> includes a compressor <NUM> upstream of the throttle <NUM>. In an engine with a compressor <NUM> but no throttle, such as an un-throttled diesel engine, the throttle is not needed and the mixer can be down stream of the compressor. The compressor <NUM> can include a centrifugal compressor, a positive displacement compressor, or another type of compressor for increasing a pressure within the intake manifold <NUM> during engine operation. In some implementations, the engine system <NUM> can include an intercooler <NUM> that is configured to cool the compressed air prior to the air entering the manifold. In the illustrated implementation, the compressor <NUM> is a part of a turbocharger. That is, a turbine <NUM> is located downstream of the exhaust manifold <NUM> and rotates as the exhaust gas expands through the turbine <NUM>. The turbine <NUM> is coupled to the compressor <NUM>, for example, via a shaft <NUM>, and imparts rotation on the compressor <NUM>. In the illustrated implementation, the turbine <NUM> also increases a back-pressure within the exhaust manifold <NUM>, thereby increasing the pressure within the EGR flow passage <NUM>. While the illustrated implementation utilizes a turbocharger to increase the pressure within the intake manifold <NUM>, other methods of compression can be used, for example an electric or engine powered compressor (e.g., supercharger). In some implementations, a separate controller <NUM> or engine control unit (ECU) is used to control various aspects of the system operation. For example, the controller <NUM> can adjust air-fuel ratios, spark timing, and EGR flow rates based on current operating conditions.

<FIG> is a perspective view of the example exhaust gas recirculation mixer <NUM>. The exhaust gas recirculation mixer <NUM> includes four jet pumps, or barrels <NUM>, all arranged in parallel. In the illustrated perspective view, barrels 200a, 200b, 200c, and 200d are visible. By using four barrels, a similar total inlet area and outlet area can be used as compared to a single-barrel exhaust gas recirculation mixer, while reducing the total length of the exhaust gas recirculation mixer <NUM> to be substantially half that of a single-barrel mixer. An example single-barrel mixer is described in <CIT>. With the single barrel design, there is a fresh air core surrounded by mixed air/EGR. With the multi barrel design described herein, there are multiple fresh air cores, so the fresh air is better divided, distributed, mixed, or otherwise spread prior to entering the engine intake manifold <NUM>. The improved mixing results in a more even distribution of fresh air, EGR, and fuel being distributed among the engine cylinders.

<FIG> is a side half cross sectional view of the example exhaust gas recirculation mixer <NUM> of <FIG>. In this illustration, barrels 200a and 200c are visible. <FIG> is a half cross sectional view of the example exhaust gas recirculation mixer of <FIG>. This view is <NUM>° from the half cross sectional view shown in <FIG>. In this illustration barrels 200b and 200c are visible. It should be noted that the fourth barrel, 200d, is not visible in the present figures, but is structurally similar to the other barrels described herein. The following description is provided in reference to both <FIG> and <FIG> unless otherwise specified.

The EGR mixer <NUM> is made up of one or more housings or casings. Openings in the end walls of the casings define an air inlet <NUM> and an outlet <NUM> of multiple interior flow passages <NUM>, defined by each of the barrels <NUM>. The interior flow passages <NUM> direct flow from the air inlet <NUM> to the outlet <NUM> to allow flow through the EGR mixer <NUM>. Within a casing(s) <NUM>, the EGR mixer <NUM> includes multiple convergent nozzles <NUM>, each associated with a barrel <NUM>, that define interior flow passages <NUM> in a flow path from an air inlet <NUM> of the EGR mixer <NUM> to an outlet <NUM> of the EGR mixer <NUM>. The convergent nozzles <NUM> each converge toward the outlet of the EGR mixer <NUM>. That is, each of the convergent nozzles <NUM> converge in the direction of flow toward a convergent end <NUM>. That is, the downstream end (outlet) of the convergent nozzle <NUM> has a smaller cross-sectional area, i.e., a smaller flow area, than the upstream end (inlet) <NUM> of the convergent nozzle <NUM>. In some implementations, the inlets <NUM> of the convergent nozzles <NUM> are in a same, first plane <NUM>, and corresponding outlets of the convergent nozzles <NUM> are in a same, second plane <NUM>. In other words, the components of each barrel <NUM> are aligned in parallel such that each component receives fluid flow in parallel with one-another within standard manufacturing tolerances.

The EGR mixer <NUM> includes an exhaust gas receiver housing <NUM> and the exhaust gas receiver housing <NUM> includes one or more exhaust gas inlets <NUM> fed from and fluidically connected to the EGR flow passages <NUM>, and into an interior receiver cavity <NUM> of the exhaust gas receiver housing <NUM>. In the illustrated implementation, the exhaust gas receiver housing <NUM> surrounds the convergent nozzles <NUM>, such that a portion of the convergent nozzle <NUM> is within the interior receiver cavity <NUM>. In some implementations, convergent-divergent nozzles <NUM> of each barrel <NUM> can be within the interior receiver cavity <NUM> as well. The convergent nozzles <NUM> are positioned to each form a free jet of gas out of the convergent end <NUM> of each nozzle <NUM>. Also, the exhaust gas inlet <NUM> is upstream of an outlet <NUM>, of each convergent nozzle <NUM>. While the illustrated implementation shows an outlet <NUM> separate from a convergent end <NUM>, other arrangements can be used, for example, the outlet <NUM> and the convergent end <NUM> can both be in the second plane <NUM> in some implementations. While the illustrated implementation shows the outlet <NUM> to extend (at least partially or entirely) within the exhaust gas receiver housing <NUM>, other designs can be utilized. In some implementations, the air inlet <NUM> and the outlet <NUM> are provided with attachments or fittings to enable connection to the intake manifold <NUM> of the engine <NUM> and/or the EGR mixer <NUM>. In some instances, the convergent nozzles <NUM> can be modularly interchangeable with convergent nozzles of different the inlet area <NUM> and convergent area <NUM>, making the system readily changeable to fit multiple engine sizes. For example, the nozzles <NUM> can be provided with threads or another form of removable attachment to the remainder of the mixer casing <NUM>. In some implementation, the convergent nozzles <NUM> can be integrated into the mixer casing <NUM> as a single, unitary piece.

Within each barrel <NUM>, a convergent-divergent nozzle <NUM> is downstream of the convergent end <NUM> of a corresponding convergent nozzle <NUM> and is fluidically coupled to receive fluid flow from the outlet <NUM>, the exhaust gas inlet <NUM>, and, in certain instances, a fuel supply <NUM>. In other words, the convergent-divergent nozzle <NUM> can act as an air-fuel-exhaust gas inlet for the intake manifold <NUM> (<FIG>). The air-exhaust gas inlet <NUM> of each of the convergent-divergent nozzles <NUM> is in a same, third plane <NUM> that is perpendicular to the flow path. The corresponding outlet of each of the convergent-divergent nozzles <NUM> is in a same, fourth plane <NUM> that is perpendicular to the flow path and downstream of plane <NUM>, plane <NUM>, and plane <NUM>. In other words, the components of each barrel are aligned in parallel such that each component receives fluid flow in parallel with one-another within standard manufacturing tolerances. To help facilitate mixing, an air-exhaust gas inlet <NUM> of each convergent-divergent nozzle <NUM> has a greater area than corresponding outlet <NUM>. Each convergent-divergent nozzle <NUM> includes three parts: an air-exhaust gas inlet <NUM>, a throat <NUM>, and an outlet <NUM>. The throat <NUM> is the narrowest point of each of the convergent-divergent nozzles <NUM> and is located and fluidically connected downstream of the air-exhaust gas inlet <NUM> of each of the convergent-divergent nozzles <NUM>. The narrowing of the convergent-divergent nozzles <NUM> at the throat <NUM> increases a flow velocity of a fluid flow as it passes through each convergent-divergent nozzle <NUM>. The outlet <NUM> of each of the convergent-divergent nozzles <NUM> is fluidically connected to and upstream of the intake manifold <NUM>. Between the throat <NUM> and the outlet <NUM>, the cross-section of the flow passage through the convergent-divergent nozzle <NUM> increases. The increase in cross-sectional area slows the flow velocity and increases the pressure of the fluid flow. In certain instances, the increase in cross-sectional area can be sized to increase a pressure within the EGR mixer <NUM> so that the pressure drop across the EGR mixer <NUM> is zero, nominal, or otherwise small. In some implementations, a divergent portion 214b of each of the convergent-divergent nozzles <NUM> diverges no more than <NUM>°. The divergent portion 214b of each convergent-divergent nozzle <NUM> can diverge linearly or with a curve flaring outward. The convergent-divergent nozzle <NUM> can include threads or another form of removable attachment at the air-exhaust gas inlet <NUM>, the outlet <NUM>, or both to allow the convergent-divergent nozzle <NUM> to be installed and fluidically connected to the remainder of the intake of the engine system <NUM>. Like the convergent nozzle <NUM>, the convergent-divergent nozzle <NUM> can be modularly interchangeable with nozzles <NUM> of a different inlet <NUM>, throat <NUM>, and outlet <NUM> areas too make the system readily changeable to fit multiple engine sizes. In some implementation, multiple convergent-divergent nozzles <NUM> can be integrally formed into a single unitary piece.

In some implementations, the convergent nozzles <NUM> and the convergent-divergent nozzles <NUM> within each barrel <NUM> to be aligned at a same center axis <NUM>, but in some implementations, the center axis <NUM> of the convergent nozzle <NUM> and the convergent-divergent nozzle <NUM> within each barrel <NUM> might not be aligned or parallel. For example, space constraints may require the EGR mixer <NUM> to have an angle between the axis of each of the convergent nozzles <NUM> and their corresponding convergent-divergent nozzles <NUM>. In some implementations, rather than having a substantially straight flow passage as shown in <FIG>, the flow passage may be curved.

In some implementations, the fuel supply <NUM> includes a fuel manifold <NUM> and fuel supply ports <NUM> upstream of each of the convergent ends <NUM> of the convergent nozzles <NUM> within the air flow path. Each fuel supply port <NUM> is configured to supply fuel into the air flow path and upstream of a corresponding convergent nozzle <NUM>. In some implementations, the fuel supply port <NUM> can be a gaseous fuel supply port, coupled to a source of gaseous fuel; however, the fuel delivered by the fuel supply port <NUM> can include any combustible fluid, such as natural gas, gasoline, or diesel. The fuel supply port <NUM> supplies a fuel flow <NUM> from a fuel manifold <NUM>. Though illustrated with a single fuel port <NUM> within each barrel supplied by the common fuel manifold <NUM>, separate, discrete fuel supplies with separate, discrete ports can be used with similar effect. While shown as a single port within each barrel, the fuel supply ports <NUM> can be configured in other ways, for example, as multiple fuel supply ports along the perimeter of each barrel, or in another manner. While the illustrated implementation shows a fuel supply port <NUM> configured to inject fuel upstream of the convergent end <NUM> of the convergent nozzle <NUM>, fuel can also be added with a fuel supply port <NUM> upstream of the exhaust gas inlet <NUM>. Such a port can include a gaseous fuel supply port.

A pressure port <NUM> is positioned downstream the convergent portion <NUM> of each of the convergent nozzles <NUM>. The pressure port <NUM> provides a location to sense pressure downstream of a convergent end <NUM> of each of the convergent nozzles <NUM> by allowing fluid communication between the interior flow passage <NUM> and a common pressure sensing manifold <NUM>. A pressure sensor <NUM> senses a pressure within the common pressure sensing manifold <NUM> and sends a signal to the controller <NUM> indicative of the pressure within the common pressure sensing manifold <NUM>. Though illustrated with a single sensor on a common manifold, separate, discrete sensors with separate, discrete ports can be used with similar effect. Alternatively or in addition, a virtual sensor can be used in lieu of a discrete sensor. That is, the pressure can be calculated based on the known geometry of the convergent nozzles and other information received from various sensors throughout the system.

The pressure sensed by the pressure sensor <NUM> can be compared to a sensed pressure elsewhere either upstream or downstream of the EGR mixer <NUM> to determine a differential pressure. The determined differential pressure can be used to determine a mass air-flow (MAF) rate passing through the EGR mixer <NUM>. In certain instances, such a calculation can be performed by the controller <NUM> (<FIG>). The MAF rate can be used as an input for the controller to adjust a variety of parameters within the engine system <NUM>. In certain instances, the controller <NUM> is an engine control unit (ECU) that controls some or all aspects of the engine system <NUM> operations, such as fuel supply, air, ignition and/or other engine operational parameters. In certain instances, the controller <NUM> is a separate control unit from the engine system's ECU. The controller <NUM> also need not send actuation and/or control signals to the engine system <NUM>, but could instead provide information, such as the MAF and EGR flow rates, to an ECU for use by the ECU in controlling the engine system <NUM>.

<FIG> is a block diagram of an example controller <NUM> that can be used with aspects of this disclosure. The controller <NUM> can, among other things, monitor parameters of the system and send signals to actuate and/or adjust various operating parameters of the system. As shown in <FIG>, the controller <NUM> can include one or more processors <NUM> and non-transitory storage media (e.g., memory <NUM>) containing instructions that cause the processors <NUM> to perform operations described herein. The processors <NUM> are coupled to an input/output (I/O) interface <NUM> for sending and receiving communications with components in the system, including, for example, the pressure sensor <NUM>. In certain instances, the controller <NUM> can additionally communicate status with and send actuation and/or control signals to one or more of the various system components (including the throttle <NUM> and the EGR throttle valve <NUM>) of the engine system <NUM>, as well as other sensors (e.g., pressure sensors, temperature sensors, knock sensors, and other types of sensors) provided in the engine system <NUM>.

The illustrated implementation operates as follows. The first set of convergent nozzles <NUM> each increase a velocity and decrease a pressure of a portion of an air flow <NUM> in the EGR mixer <NUM> to form multiple free jets exiting a corresponding convergent nozzle <NUM>. An exhaust flow <NUM> is drawn into the EGR mixer <NUM> through the exhaust gas inlet <NUM> in response to (e.g., because of) the decreased pressure of each of the free jet air flows <NUM> exiting the convergent nozzles <NUM>. The exhaust flow <NUM> is directed from the exhaust manifold <NUM> eventually to the point downstream of the convergent nozzles <NUM>. The air flow <NUM>, the exhaust flow <NUM>, and a fuel flow <NUM> are mixed to form multiple mixed flows <NUM> that act as a combustion mixture. The mixed flows <NUM> are mixed with a second set of convergent nozzles 214a positioned downstream of the corresponding first convergent nozzles <NUM>. Each of the second set of convergent nozzles 214a corresponds to a different one of the first set of convergent nozzles <NUM>. A pressure of each of the mixed flows is increased, and a velocity of each of the mixed flows <NUM> is reduced with a set divergent nozzles 214b each corresponding to a different one of the second of convergent nozzles 214a. While each of the second set of convergent nozzles 214a and each of the set of divergent nozzles 214b are illustrated as unitary convergent-divergent nozzles <NUM>, each of the second set of convergent nozzles 214a and each of the set of divergent nozzles 214b can be separate and distinct parts.

In the illustrated implementation, the fuel flow <NUM> is supplied into the air flow <NUM> with a fuel supply port <NUM> located on the side of each of the convergent nozzles <NUM>. The fuel flow <NUM> is supplied upstream of the convergent end <NUM>. In some implementations, the fuel flow <NUM> is supplied into the exhaust flow <NUM> with a fuel supply port <NUM>. Regardless of the implementation used, the fuel flow <NUM> can include a gaseous fuel flow.

Claim 1:
An engine exhaust gas recirculation mixer (<NUM>) for an engine (<NUM>), the mixer (<NUM>) comprising:
a plurality of convergent nozzles (<NUM>) defining a plurality of flow passages (<NUM>) that extend alongside one another in a flow path from an engine intake air inlet (<NUM>) of the mixer (<NUM>) to an outlet (<NUM>) of the mixer (<NUM>), the plurality of convergent nozzles (<NUM>) each converging toward the outlet (<NUM>) of the mixer (<NUM>);
an exhaust gas receiver housing (<NUM>) comprising an exhaust gas inlet (<NUM>) into an interior of the exhaust gas receiver housing (<NUM>); and
a plurality of convergent-divergent nozzles (<NUM>) in the flow path each corresponding to one of the plurality of convergent nozzles (<NUM>), the plurality of convergent-divergent nozzles (<NUM>) extending alongside one another, the plurality of convergent-divergent nozzles (<NUM>) each comprising an air-exhaust gas inlet (<NUM>) in fluid communication to receive fluid flow from a corresponding convergent nozzle (<NUM>) and the interior of the exhaust gas receiver housing (<NUM>);
characterized in that:
the air-exhaust gas inlet (<NUM>) of each of the plurality of convergent-divergent nozzles (<NUM>) is an air-fuel-exhaust gas inlet in communication with a fuel supply (<NUM>) into the mixer (<NUM>), wherein
the fuel supply (<NUM>) comprises fuel supply ports (<NUM>) positioned upstream of the convergent-divergent nozzles (<NUM>), and
the fuel supply ports (<NUM>) are located on a side of each of the convergent nozzles (<NUM>) or downstream of a convergent end (<NUM>) of each of the convergent nozzles (<NUM>) and upstream of the exhaust gas inlet (<NUM>).