阅读说明：本技术 具有优化再循环气体混合设备的热力发动机进气歧管 (Heat engine intake manifold with optimized recirculated gas mixing device ) 是由 T·维尼齐亚尼 于 2019-04-16 设计创作，主要内容包括：一种用于热力发动机的进气回路(10),该进气回路包括已燃烧气体再循环系统(30),该已燃烧气体再循环系统旨在被定位在空气压缩元件与燃烧室(11)的从该发动机的气缸盖(20)挖出的上部部分之间,所述空气进气回路包括该气缸盖、包含集气室(16)的进气歧管(12)、以及空气进气管道(22),其特征在于,该再循环系统(30)包括以开口方式进入该集气室(16)的已燃烧气体注入管道(17),所述管道(17)能够以与进气空气流(32)逆流的方式输送所述已燃烧气体。(An intake circuit (10) for a heat engine, comprising a burnt gas recirculation system (30) intended to be positioned between air compression elements and an upper portion of a combustion chamber (11) hollowed out of a cylinder head (20) of the engine, said intake circuit comprising the cylinder head, an intake manifold (12) containing a plenum (16), and an air intake duct (22), characterized in that the recirculation system (30) comprises a burnt gas injection duct (17) that enters the plenum (16) in an open manner, said duct (17) being able to convey said burnt gas in counterflow to an intake air flow (32).)

1. An intake circuit (10) for a heat engine, comprising a recirculation system (30) for burnt gases intended to be positioned between air compression elements and an upper portion of a combustion chamber (11) hollowed out of a cylinder head (20) of the engine, said intake circuit comprising the cylinder head, an intake manifold (12) containing a plenum (16), and an air intake duct (22), characterized in that the recirculation system (30) comprises at least one burnt gas injection duct (17) opening into the plenum (16) delimited in the direction of the air flow by a side wall, an upper wall and a lower wall, said duct (17) being able to convey said burnt gases in counterflow to the intake air flow (32).

2. An intake circuit (10) according to claim 1, characterized in that the at least one injection duct (17) opens into the plenum (16) in line with the axis of at least one associated intake duct (21).

3. An air inlet circuit (10) according to claim 2, characterized in that the air outlet of the at least one injection duct (17) into the plenum is at a distance from the air outlet of the at least one associated inlet duct (21) into said plenum.

4. The intake circuit (10) according to any one of claims 1 to 3, characterized in that the at least one injection duct (17) is continued by a tubular passage (18) penetrating into the plenum (16) of the manifold (12).

5. An air inlet circuit (10) as claimed in claim 4, characterized in that the tubular passage (18) has an upstream direction (A) facing the air flow_m) Is provided.

6. An air inlet circuit (10) as claimed in claim 4 or 5, characterized in that the tubular passage (18) has an upstream direction (A) facing the air flow_m) Is cut obliquely.

7. An air inlet circuit (10) according to any one of claims 4 to 6, characterized in that the tubular passage (18) extends in an upstream direction of the air flow from a redirecting wall (34) capable of directing the air flow towards an opening connected to the air inlet duct (22).

8. An intake circuit (10) according to claim 7, characterized in that the redirecting wall (34) and the tubular passage (18) are made in one piece.

9. The intake circuit (10) of any one of claims 1 to 9, wherein the recirculation system (30) comprises a plenum rail (31) extending transversely to the axis (E) of the air flow, said rail being connected to the at least one gas injection duct (17).

10. The intake circuit (10) of claim 9, wherein the air rail (31) is hollowed out of the cylinder head (20) or is fixed to one of a lower wall (35) or an upper wall (36) of the plenum (16).

11. The intake circuit (10) according to claim 9 or 10, characterized in that the gas feed rail (31) is connected to the outlet of the blow-by separator.

12. An intake circuit (10) according to claim 9 or 10, characterized in that the supply rail (31) is connected to an exhaust circuit.

Technical Field

The present invention relates to an internal combustion engine or heat engine of a motor vehicle.

The invention relates more particularly to a heat engine intake manifold having a device for mixing combusted gases.

The invention also relates to a recirculation system of burnt gas for a heat engine.

Background

The present invention relates to internal combustion engines, particularly intended for motor vehicles, of the type that employ means for recirculating the burnt gases.

The invention relates more particularly to an arrangement for recirculating combusted gases of an internal combustion engine. The combusted gases are output by the exhaust circuit of the engine and may be discharged directly from as close to the exhaust manifold as possible (in this case referred to as high pressure combusted gases), or at a pollution reduction system downstream of the exhaust manifold (in this case referred to as low pressure combusted gases), or from an oil separation stage when passing through an oil separator (in this case referred to as blow-by gas).

In industrialized countries, standards relating to pollution and consumption of internal combustion engines, particularly those with which motor vehicles are equipped, are becoming more and more stringent. The automotive industry is therefore currently seeking technical solutions that satisfy these obligations without excessively compromising the performance of the heat engine or its cost price. One known technique for reducing the pollution of said internal combustion engines consists in recirculating burnt gases to the intake in order to reduce the nitrogen oxides, that is to say returning some burnt gases to the intake and mixing them with the fresh air taken in. This technique consists in re-injecting some of the exhaust gases into the combustion chamber of the engine according to the operating conditions of the engine, which has the effect of reducing the quantity of combustion-supporting gases, and therefore the combustion temperature, proportionally, so as to reduce the production of NOx or nitrogen oxides.

For example, a commonly employed process involving low-pressure combusted gases is "external recirculation" of exhaust gases by means of an EGR (exhaust gas recirculation) valve for recirculating the exhaust gases, closing or opening a line connecting the exhaust manifold of the engine to the intake manifold. The EGR valve makes it possible to inject a given amount of gas discharged from the exhaust port at the intake port according to the operating conditions of the engine.

Combusted gases are injected at an intake port of the engine, typically into an intake manifold of the engine or directly into an engine intake conduit between the intake manifold and the combustion chamber of the engine.

Thus, publication EP 1447533-a1 proposes injecting the blow-by gas directly into an air intake duct that faces a combustion chamber of the engine. The gas passes through a passage leading into the gas inlet duct.

A disadvantage of this injection is that the mixture formed by blow-by gas and air is not optimal and this may limit the performance of the engine.

It is known to collect said burnt gases in a recirculation chute extending substantially parallel to the longitudinal axis X of the engine. An intake passage connecting the chute to one of the engine's air intake ducts opens into the chute.

Thus, publication US 20090301448-a1 proposes a chute for collecting blow-by gas to be injected into an air intake duct of an engine.

In the same manner as the former injection, the intake passage of the burnt gas leads directly into the air intake duct leading to the combustion chamber and does not allow the burnt gas and air to form an optimum mixture before entering the combustion chamber, which may reduce the performance of the engine.

Publication FR 2946699-a1 discloses a chute for collecting the burnt gases, which chute extends parallel to the axis of the engine and is connected to an air intake manifold plenum arranged downstream of the air-water heat exchanger in the direction of the air flow. The connection is achieved by means of a channel leading into the plenum.

The disadvantages of this injection of burnt gas are also: the mixture of combusted gases and air is not optimal and tends to impair engine performance.

Publication US 2015002078-a1 proposes to inject the burnt gas into the plenum of the heat engine air intake manifold by means of a duct penetrating upstream into the plenum of the intake manifold, said duct having gas injection holes facing the combustion chamber.

The disadvantage of this injection is not only that the penetrating duct causes a pressure drop in the air flow to the combustion chamber, but also that the mixture is not optimal and tends to impair the engine performance.

The object of the present invention is to propose an air intake circuit with recirculation of burnt gas for a gasoline or diesel heat engine, to remedy the above drawbacks and to improve the air intake circuit for a heat engine known from the prior art with respect to the burnt gas mixture, so as to provide an optimal mixture of recirculated burnt gas and air before they enter the combustion chamber, while hardly causing a pressure drop (if any) in the gas flow.

The internal combustion engine according to the invention has a gas recirculation system, that is to say the system involves the extraction of burnt gases, which may be high-pressure burnt gases coming from the exhaust circuit of the engine upstream of the pollution reduction system (for example from the exhaust manifold of the engine), or from the pollution reduction system or downstream of said system, or from the oil vapours emitted from the oil separator downstream. The recirculation system allows the intake of the combusted gases at the intake of the engine by injecting the gases into the intake manifold plenum, thereby minimizing pressure drop and optimizing the mixture of these gases and fresh intake air.

Disclosure of Invention

The invention relates to an air intake circuit for a heat engine, said air intake circuit comprising a recirculation system for burnt gases or blow-by gases and being positioned between an air compression element and at least one upper portion of a combustion chamber, the at least one upper portion being part of a cylinder head of the engine, said air intake circuit comprising the cylinder head, an air intake manifold, and at least one air intake duct,

characterized in that it comprises at least one burnt gas injection duct opening into a plenum of the manifold, which plenum is delimited in the direction of the air flow by a side wall, an upper wall and a lower wall, said duct being able to convey said gases in counterflow to the intake air flow.

Advantageously, the system comprises at least one burnt gas injection duct which opens into the plenum of the manifold and is able to convey the gases in counterflow to the air flow, improving their mixture before the air and gases enter the combustion chamber of the engine. The gases are initially directed in counterflow to the intake air flow and then returned toward the intake duct, improving the mixture of the gases and the intake air. The arrangement of the injection duct within the plenum is such that it causes little or no pressure drop in the air stream.

According to a further feature of the present invention:

the at least one injection duct opens into the plenum in line with the axis of at least one associated intake duct.

Advantageously, the injection duct extends substantially in line with the axis of at least one intake duct, so as to convey the burnt gases to be mixed and directed into said intake duct.

The air outlet opening of the at least one injection duct into the plenum is at a distance from the air outlet opening of the at least one associated inlet duct into said plenum.

Advantageously, the distance between the air outlet of the at least one injection duct into the plenum and the air outlet of the at least one associated inlet duct into said plenum is such that the combusted gases form a better mixture with the inlet air before entering the at least one associated inlet duct.

-the at least one injection conduit has a tubular passage penetrating into the plenum of the manifold.

Advantageously, the injection duct is cylindrical and rectilinear, so as to cause a minimum pressure drop in the flow of burnt gases, and in particular during injection into the plenum of the manifold.

Advantageously, the injection duct has a tubular passage that penetrates into the plenum of the manifold, so as to obtain an optimal position for injecting the burnt gas into the plenum in the middle of the intake air flow and improve the mixture.

The tubular passage has an opening facing in the upstream direction of the air flow.

Advantageously, the tubular passage has an opening facing in the upstream direction of the air flow, allowing better injection of the burnt gases and better diffusion and mixing of the burnt gases in the air flow.

The tubular passage comprises a chamfered opening facing in the upstream direction of the intake air flow.

Advantageously, the tubular passage has an opening cut with a slope, said opening portion facing in the upstream direction of the air flow, to allow the formation of an optimal mixture of burnt gases and intake air.

The tubular passage extends in the upstream direction of the air flow from a redirecting wall able to direct the air flow towards an opening connected to the air intake duct.

Advantageously, the plenum is delimited by a side wall, an upper wall, a lower wall and a deflector wall downstream of the air flow, capable of directing the air flow towards an opening connected to the air intake duct to reduce the pressure drop at the inlet of the air and burnt gases mixture into the intake duct.

The tubular passage extends from said redirecting wall in the upstream direction of the gas flow so as to direct the gas in the upstream direction of the flow of intake air and therefore in counter-flow to the flow of intake air.

The redirecting wall and the tubular passage are made in one piece.

Advantageously, the deflector wall and the tubular channel are made in one piece, which not only makes manufacture easier, but also makes installation in the cylinder head and formation of the air collecting chamber easier.

-the recirculation system comprises a gas delivery rail extending transversely to the axis of the air flow, said rail being connected to the at least one gas injection duct.

Advantageously, the recirculation system comprises a delivery rail connected to the burnt gas circuit, said rail extending transversely to the direction of the air flow and parallel to the axis of the engine, so as to enable injection through all the intake ducts of the engine.

The plenum rail is hollowed out from the cylinder head, or fixed to the lower wall of the plenum, or fixed to the upper wall of the plenum.

Advantageously, the plenum rail extending transversely to the flow of intake air is hollowed out from the cylinder head or fixed to the lower wall, or to one of the lower or upper walls of the plenum, so as to make the circuit compact and easy to implement.

The plenum rail is connected to an outlet of the blow-by separator.

Preferably, the gas supply rail is connected to an outlet of the blow-by gas separator so as to return the blow-by gas to the gas inlet.

The supply rail is connected to an exhaust circuit.

Preferably, the plenum rail is connected to a circuit for combusted gases from the exhaust of the engine, said gases being able to be high pressure combusted gases or low pressure combusted gases.

Drawings

Further characteristics and advantages of the invention will become apparent from reading the following description of a particular embodiment of the invention, given by way of non-limiting example and illustrated in the accompanying drawings, wherein:

fig. 1 is a schematic cross-sectional view of an intake circuit of a heat engine.

Fig. 2 is a schematic cross-sectional view of a cylinder head and an intake manifold according to a first embodiment of the invention.

Fig. 3 is a schematic top view of a cylinder head with an intake circuit according to the invention.

Fig. 4 is a schematic cross-sectional view of a cylinder head and an intake manifold according to another embodiment of the invention.

Detailed Description

In the following description, like reference numbers indicate identical or functionally similar elements.

In this context, the expression "open portion" is understood to mean a surface of the duct for the passage of the gas, said portion possibly being transverse to the axis of the duct or at an angle to the axis of the duct.

The term upstream/downstream relates to the direction of flow of air in the intake circuit.

The term up/down refers to a vertical axis perpendicular to a horizontal plane parallel to the mating surfaces of the crankcase and cylinder head of the engine of the present specification.

A heat engine or an internal combustion engine of a motor vehicle has a system for reducing pollution caused by burnt gases from the combustion chambers of the engine and a supercharging system in order to increase the efficiency of the engine.

To reduce pollution, it is known to return at least a portion of the burnt gas to the intake of the engine, said portion then being mixed with fresh air before entering the cylinders of the engine. The recirculation of combusted gases is divided into several types: low pressure recirculation, which involves discharging combusted gases downstream of a pollution reduction device, such as a catalytic converter, in the direction of exhaust flow; or high-pressure recirculation, in which the burnt gases are taken in upstream of the pollution-reduction device and preferably at the outlet of the cylinder head of the engine. Therefore, the burnt gas, which is referred to as high-pressure burnt gas, is discharged at an exhaust manifold fixed to an exhaust face of a cylinder head of the engine.

As such, the burnt gas may come from the oil vapor separator, and is referred to as blow-by gas. The separator is typically arranged in the upper part of the engine. This separator allows the separation of the oil contained in the vapour from the gas. Next, the oil return circuit returns the oil, preferably to an oil sump provided at the bottom of the engine, and the gas may return towards the air intake of the engine.

Generally, according to fig. 1, a heat engine 100 has: a crankcase 101 comprising at least one cylinder 102 in which a piston is able to slide along the axis of the at least one cylinder; and a cylinder head 20 covering an upper portion of the crankcase, thereby closing at least one combustion chamber 11. The combustion chamber is delimited by the walls of each cylinder, the piston and the cylinder head 20. An intake pipe 21 and an exhaust line connecting the combustion chamber 11 of each cylinder to the intake circuit 10 and the exhaust circuit, respectively, are hollowed out from the cylinder head. The intake circuit 10 is fixed to the cylinder head 20 through an intake face 23. The exhaust circuit is fixed to the cylinder head by its exhaust face (not shown) which is symmetrically opposite to the intake face with respect to a vertical median plane passing through the longitudinal axis X of the engine.

The longitudinal axis X of the engine is substantially parallel to the axis of the crankshaft housed in the engine.

Fresh air 40 is taken in from the outside of the vehicle and then mixed with burnt gas 41 at the intake manifold 12, which is fixed to the intake wall 22 on the side of the intake face 23 of the cylinder head 20 of the engine. The mixture is then delivered to the combustion chamber 11 of the engine via the intake conduit 21. A mixture of air and burnt gas is injected into the combustion chamber, in the top part of each cylinder of the crankcase 101, and mixed with fuel in order to cause an explosion in said chamber, producing burnt gas. Then, the burned gas is pushed out from the combustion chamber via an exhaust line toward an exhaust circuit fixed to the cylinder head on the exhaust face side of the engine.

The present invention relates to an intake circuit 10 for a heat engine, comprising a recirculation system 30 for burnt gas to be returned to the intake of the engine.

Burnt gas is understood to be gas from the exhaust circuit or blow-by gas.

In the remainder of this description, the return of blow-by gas to the intake port will be described to facilitate understanding of the invention, but the burnt gas may also be high pressure burnt gas or low pressure burnt gas or a mixture of burnt gases.

As is known, fresh intake air 40 is drawn in from the front face of the vehicle and then through the intake circuit to be injected into the combustion chamber 11 in each cylinder. First, the intake air is filtered by means of an air filter to remove impurities and dust carried by the intake air. Next, in order to improve the performance of the engine, it is also known to increase the pressure of the intake gases and to make the fuel/air mixture fill better at least one cylinder of the engine. In this way, the power density of the engine increases as its power increases, while the consumption of the engine decreases. Thus, an intake air compression stage is provided between the air filter and the engine. This compression stage (not shown) may be formed by a compression stage of a turbocharger or by an electric compressor.

Downstream of the compression stage, the compressed air is at a high temperature and its density is reduced, which is detrimental to the performance of the engine. It is therefore useful to provide a charge air cooling stage adjacent to the compressor (not shown), downstream of the compressor in the direction of circulation of the air from the compressor. This cooling stage may consist of a cooler 14, and more specifically an air-to-water heat exchanger. The water, which is at a moderate temperature, passes through the heat exchanger 14 and removes some heat from the compressed air.

The compressed and cooled air 40 is then directed toward the air intake manifold 12 to control the flow of air into the combustion chambers. The manifold is fixed by means of a flange 13 to a fixed wall 22 of an intake face 23 of a cylinder head 20 of the engine and directs compressed and cooled air towards an intake duct 21 hollowed out of the cylinder head. Said intake duct 21 in the cylinder head has a particular shape and profile, depending on the type of engine (for example diesel engine or spark-ignition engine).

The cooler 14, also referred to as WCAC, represents a water-cooled charge air cooler. The manifold 12 differs essentially in the air collection chamber 16 or air supply chamber before the inlet of the intake duct 21 of the cylinder head. The manifold 12 is located downstream of the WCAC heat exchanger 14 and in our embodiment they share the same housing. The housing is fixed to a fixed wall 22 of the cylinder head. The fixed wall 22 extends in a plane and exhibits an inclination with respect to a horizontal plane parallel to, for example, a mating surface 25 between the cylinder head and the crankcase. The inclination makes the installation of the cooler easier and it remains more reliable.

The plenum 16 is bounded in the direction of airflow by side walls, an upper wall 36 and a lower wall 35.

According to fig. 1 to 4, the cooler 14 and the air intake manifold 12 are integrated 15.

For ease of understanding, the following description is made with respect to one cylinder, but an engine according to the present invention has at least one cylinder, and the present invention proposes an injection conduit for each cylinder.

According to fig. 1 to 4, the recirculation system 30 comprises a gas feed rail 31 for burnt gas, which is connected to the exhaust circuit or to an outlet for gas from an oil vapor separator (not shown).

Preferably, the intake rail 31 extends parallel to the longitudinal axis X of the engine. The rail may be obtained by piercing the cylinder head (which means that it is arranged inside the cylinder head), as shown in fig. 1 and 2, or may be fixed to an element of the intake circuit 10 of the engine (which means that it is arranged outside the engine), as shown in fig. 4. The intake rail makes it possible to deliver burnt gas to the intake port of the engine.

The injection conduit 17 fluidly connects the intake rail 31 and the plenum 16. The duct is substantially cylindrical and rectilinear, so as to cause a minimum pressure drop in the flow of the burnt gas. Preferably, the injection duct 17 is arranged to open into the plenum 16 of the manifold upstream of the intake duct connected to the associated cylinder. Said injection duct allows the injection of burnt gases 41 to be mixed with the intake air, said mixture then being led to the associated intake duct leading to the cylinder. In this description, there is one intake duct 21 for each cylinder of the engine. Typically, the intake duct 17 is then continued by two secondary intake branches (not shown) leading into the combustion chambers of the cylinders.

According to fig. 3, the intake circuit comprises an intake rail 31 extending parallel to the longitudinal axis X of the engine and transversely to the direction E of the intake air flow in the plenum 16 of the intake manifold. The injection duct 17 (the axis of which is substantially orthogonal to the axis of said intake rail 31) opens into the intake rail 31 at a first end and into the plenum 16 at a second opposite end. The number of injection ducts 17 is preferably equal to the number of cylinders of the engine. In this way, the injection duct 17 extends perpendicularly to the axis X of the engine from the injection rail 31 at the associated cylinder along the axis X of the engine. Each injection duct opens into the plenum 16 in line with the axis of the inlet duct 21. More specifically, as shown in fig. 3, the projection of the outlet opening of the injection duct 17 entering the plenum 16 on a horizontal plane is set in the projection of the axis of the associated intake duct on the same horizontal plane. The air outlet of an inlet duct into the plenum is disposed substantially in front of the inlet portion of the associated inlet duct 21. Each of the injection ducts 17 extends linearly and in the upstream direction a of the intake air flow_mAnd out of the walls of the plenum 16 to deliver combusted gases in a counter-current manner to the direction of the intake air flow.

According to fig. 2-4, the airflow is represented by arrows 32 and the injection of the combusted gases into the plenum is represented by arrows 33.

The injection duct 17 comprises a tubular passage 18 penetrating the plenum in order to optimally position in the intake air flow 40 an injection point of the burnt gases 41, preferably in line with the intake duct 21 and preferably at a distance from the outlet of said intake duct 21 into the plenum 16. The tubular passages are from the wall of the plenum in the upstream direction A of the intake air flow_mAnd (4) extending. This distance may be larger than, for example, 20mm in order to achieve an optimum mixing of the burnt gas and the intake air before entering the intake duct 21 leading to the cylinder.

Preferably, as shown in fig. 2 and 4, the tubular passage 18 is inclined with respect to the axis E of the intake air flow 40 substantially along a vertical plane.

The tubular passage 18 has at its free end 18' an upstream direction A directed towards the air flow_mIs provided. The opening may be, for example, a cut having a slope and may have an upstream direction a directed towards the air flow_mThe opening portion of (2).

Thus, the burnt gas 41 is directed in counter-current to the intake air flow 40 and then returns towards the intake conduit 21 in the direction of the intake port, thereby greatly improving the mixing of the burnt gas with air before entering the intake conduit 21.

According to fig. 2, the tubular channels 18 extend from an inclined deviator wall 34 which defines downstream the plenum 16. According to a preferred embodiment, the plenum 16 includes a portion that is hollowed out of the cylinder head 20.

According to fig. 1 to 4, the redirecting wall 34 is inclined with respect to the axis E of the air flow; more specifically, the axis orthogonal to the deviator wall intersects, in a vertical plane, the axis E of the air flow. The tubular passage 18 can exhibit an inclination with respect to an axis orthogonal to the surface of the redirecting wall 34, or substantially parallel to said axis, so as to exhibit an inclination with respect to the axis E of the gas flow.

Preferably, the tubular passage 18 and the redirection wall 34 are made in one piece, obtained for example by moulding. They may be made of plastic materials because they are not exposed to high temperatures.

According to fig. 4, the plenum rail 31 is fixed below a lower wall 35 delimiting the plenum. The injection duct 17 is in the upstream direction a of the air flow_mPasses through the inner surface of said lower wall 35 substantially at an angle with respect to an axis orthogonal to this wall. The injection duct is continued by a tubular passage 18, preferably from the lower wall 35 in an upstream direction a directed towards the intake air flow_mOr extend at an angle in a direction towards the heat exchanger 12.

According to another embodiment (not shown), the air delivery rails 31 are fixed above the upper wall 36 of the plenum. The injection duct 17 is in the upstream direction a of the air flow_mAbout an axis orthogonal to the inner surface of said upper wall 36Substantially at an angle through the wall. The injection duct is continued by a tubular passage 18, preferably from the upper wall 36 in an upstream direction a directed towards the intake air flow_mOr extend at an angle in a direction towards the heat exchanger 12.

The tubular passage 18 preferably has at its free end 18' an upstream direction a directed towards the gas flow_mIs provided.

The opening may be formed by a chamfered cut on the tubular passage, the opening portion facing in the upstream direction A of the intake air flow_mOr in this case, faces the heat exchanger 12.

Preferably, the tubular passage 18 has a smaller cross-sectional area, thereby causing a lower pressure drop in the air flow.

The object is achieved as follows: the burnt gas recirculation system 10 of the air intake circuit according to the invention achieves an improved mixture of said gas and air without causing an excessive pressure drop in the intake air flow.

It goes without saying that the invention is not limited to the embodiments described above by way of example only, but encompasses all variants thereof.

For example, the tubular channels may be replaced with protrusions on the inner surface of the redirecting wall or below the manifold.

The tubular passage 18 may also extend parallel to an axis orthogonal to the lower wall 36 or to the redirecting wall 34 and may have an upstream direction a directed towards the air flow_mOpening for injecting combusted gases.

Another exemplary embodiment may be that the tubular passage has at its free end 18' an upstream direction A facing the air flow_mIs open in the radial direction.