JP7618448B2 - Intake manifold for a heat engine having an optimized recirculation gas mixer - Patents.com - Google Patents

Description

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

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

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

PRIOR ART The present invention relates to internal combustion engines, in particular intended to be equipped in motor vehicles, employing means for recirculating burnt gases.

The invention more particularly relates to means for recirculating the burnt gases of an internal combustion engine. The burnt gases may also be output by the exhaust circuit of the engine, and may be taken directly as close as possible to the exhaust manifold, in which case they are considered to be at high pressure, or may be taken in a pollution abatement system downstream of the exhaust manifold, in which case they are considered to be at low pressure, or may be output from an oil separation step passing through an oil separator, in which case they are known as blow-by gases.

The standards with regard to pollution and consumption, especially of internal combustion engines fitted in motor vehicles, are becoming increasingly stringent in industrialized countries. The automotive industry is therefore currently seeking technical solutions to meet these obligations without unduly sacrificing the performance of the heat engine or its cost. A known technique for reducing pollution in such internal combustion engines is to recirculate the burnt gases, i.e. to return a portion of the burnt gases to the intake air and mix it with the fresh air drawn in, in order to reduce the nitrogen oxides. This technique consists in reinjecting a portion of the exhaust gases into the combustion chamber of the engine, depending on the operating conditions of the engine, which has the effect of proportionally reducing the amount of oxidant gases and therefore lowering the combustion temperature and, as a result, reducing the production of NOx, i.e. nitrogen oxides.

For example, a commonly employed process involving low pressure burnt gases is "external recirculation" of exhaust gases using an EGR (exhaust gas recirculation) valve to recirculate the exhaust gases, opening and closing the line connecting the exhaust manifold to the intake manifold of the engine. The EGR valve allows a predetermined amount of gases taken from the exhaust to be injected at the intake depending on the engine operating conditions.

The burnt gases are typically injected into the engine intake manifold or directly into the engine intake duct between the engine intake manifold and the combustion chamber as the engine intakes.

Thus, publication EP 1 447 533-A1 proposes a direct injection of blow-by gases into an intake duct leading to the combustion chamber of the engine. The gases pass through a channel which leads into the intake duct.

The disadvantage of this type of injection is that the mixture formed by the blow-by gases and air is not optimal, which can limit engine performance.

As is known, the burnt gases can be collected in a recirculation ramp extending substantially parallel to the longitudinal axis X of the engine. An intake channel leads to the ramp, connecting the ramp to one of the intake ducts of the engine.

Thus, U.S. Patent Application Publication No. 20090301448(A1) proposes a lamp for collecting blow-by gases injected into the intake duct of an engine.

In the same way as the previous type of injection, the intake channel for the burnt gases leads directly to the intake duct leading to the combustion chamber, which means that the burnt gases and air cannot be mixed optimally before entering the combustion chamber, which can reduce the performance of the engine.

Publication FR 2946699-A1 discloses a lamp for collecting burnt gases, which runs parallel to the axis of the engine and is connected to an intake manifold plenum, which is arranged in the direction of air flow downstream of an air/water heat exchanger. The connection is made by a channel leading to the plenum.

The drawback of this type of burnt gas injection is also the mixing of the burnt gas and air, which is not optimal and tends to reduce engine performance.

US2015002078A1 proposes the injection of burnt gases into the plenum of a heat engine intake manifold by a duct penetrating upstream into the plenum of the intake manifold, the duct having a gas injection orifice facing the combustion chamber.

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

The object of the present invention is to propose an intake circuit with recirculation of burnt gases for a gasoline or diesel heat engine, which remedies the above-mentioned drawbacks and improves the intake circuits with mixing of burnt gases for heat engines known in the prior art, in order to provide an optimal mixing of the recirculated burnt gases with air before entering the combustion chamber, while at the same time causing little, if any, pressure drop in the gas flow.

The internal combustion engine according to the invention has a gas recirculation system. The system includes the extraction of burnt gases, which may be high pressure burnt gases from the exhaust circuit of the engine upstream of the pollution abatement system, for example from the exhaust manifold of the engine, or from the pollution abatement system or downstream of the system, or from oil vapors, which may be extracted downstream of the oil separator. The recirculation system allows the burnt gases to be drawn into the intake of the engine by injection of the gases into the intake manifold plenum, minimizing the pressure drop and optimizing the mixing of the gases with the fresh intake air.

The invention relates to an intake circuit for a heat engine, the intake circuit comprising a recirculation system for burnt gases or blow-by gases, positioned between an air compression element and at least one upper part of a combustion chamber that is part of the cylinder head of the engine, the intake circuit comprising a cylinder head, an intake manifold and at least one intake duct, the recirculation system comprising at least one burnt gas injection duct bounded by a side wall, an upper wall and a lower wall in the direction of air flow, leading to a plenum of the manifold, the duct being capable of transporting the gases in countercurrent to the intake flow.

Advantageously, the system comprises at least one burnt gas injection duct leading to the plenum of the manifold and capable of conveying gases countercurrent to the airflow so as to improve the mixing of the gases with the air before entering the combustion chamber of the engine. The gases are first directed countercurrent to the intake airflow and then directed back towards the intake duct, thereby improving the mixing of the gases with the intake air. The arrangement of the injection duct in the plenum is arranged so as to cause little pressure drop in the airflow.

According to a further feature of the invention,
At least one injection duct opens into the plenum coincident with the axis of at least one associated intake duct.

Advantageously, the injection duct extends substantially coincident with the axis of the at least one intake duct so as to convey the burnt gases which are mixed and led to the intake duct.
the outlet of at least one injection duct into the plenum is remote from the outlet of at least one associated intake duct into the plenum;

Advantageously, the outlet of the at least one injection duct into the plenum is remote from the outlet of the at least one associated intake duct into the plenum so that the burnt gases and the intake air are better mixed before entering the at least one associated intake duct.
At least one injection duct has a tubular channel penetrating into the plenum of the manifold.

Advantageously, the injection duct is cylindrical and straight to minimize pressure drop of the burnt gas flow, especially during injection into the manifold plenum.

Advantageously, the injection duct has a tubular channel penetrating into the plenum of the manifold, in order to obtain an optimal position for the injection of the burnt gases into the plenum, midway through the intake flow, improving mixing.
The tubular channels have openings facing upstream in the air flow.

Advantageously, the tubular channels have openings facing upstream in the airflow, allowing better injection of the burnt gases and better diffusion and mixing of the burnt gases within the airflow.
The tubular channel has an oblique opening facing upstream in the intake air flow.

Advantageously, the tubular channels have bevelled openings, the openings facing in the upstream direction of the airflow to allow optimal mixing of the burnt gases with the intake air.
The tubular channel extends in the upstream direction of the air flow from a deflection wall which is able to direct the air flow towards an opening connected to an intake duct.

Advantageously, to reduce the pressure drop when the mixture of air and burnt gases is introduced into the intake duct, the plenum is bounded by side walls, an upper wall, a lower wall, and a downstream airflow deflection wall capable of directing the airflow toward an opening connected to the intake duct.

The tubular channel extends from the deflecting wall in the upstream direction of the gas flow to direct the gas in the upstream direction of the intake air flow and thus as a counterflow to the intake air flow.
The deflection wall and the tubular channel are made in one piece.

Advantageously, the deflection wall and the tubular channel are made in one piece, for easier manufacturing as well as easier attachment to the cylinder head and formation of the plenum.
The recirculation system comprises a supply rail extending transversely to the air flow axis, the rail being connected to at least one gas injection duct.

Advantageously, the recirculation system comprises a supply rail connected to the burnt gas circuit, the rail extending transversely to the direction of air flow and parallel to the axis of the engine so as to be able to blow into all of the intake ducts of the engine.
The supply rail is either hollowed out in the cylinder head or is fixed to the lower wall of the plenum or is fixed to the upper wall of the plenum.

Advantageously, the supply rail, which extends transversely to the intake air flow, is hollowed out of the cylinder head or is fixed to the bottom wall or to one of the bottom or top walls of the plenum, which allows both simple circuitry and easy implementation.
The supply rail is connected to the outlet of the blow-by gas separator.

Preferably, the supply rail is connected to an outlet of the blow-by gas separator to return the blow-by gas to the intake.
The supply rail is connected to the exhaust gas circuit.

Preferably, the supply rail is connected to a circuit for burnt gases from the engine exhaust, the gases being capable of being high pressure burnt gases or low pressure burnt gases.

Further characteristics and advantages of the present invention will become apparent from reading the following description of particular embodiments of the invention, given as non-limiting examples and illustrated in the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of an intake circuit of a heat engine. 1 is a schematic cross-sectional view of a cylinder head and intake manifold according to a first embodiment of the present invention; 1 is a schematic top view of a cylinder head having an intake circuit according to the present invention; 4 is a schematic cross-sectional view of a cylinder head and intake manifold according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE FIGURES In the following description, the same reference numerals denote the same parts or parts having similar functions.

In this specification, the expression "opening" is understood to mean the surface of the duct for the gas to pass through, which part is, as the case may be, transverse to the axis of the duct or at an angle to the axis of the duct.

The terms "upstream/downstream" refer to the direction of air flow in the intake circuit.

The terms "upper/lower" refer to a vertical axis perpendicular to a horizontal plane parallel to the mating surfaces of the crankcase and cylinder head of the described engine.

Thermal engines or internal combustion engines of automobiles have both systems for reducing the pollution caused by burnt gases from the combustion chamber of the engine, and supercharging systems for improving the efficiency of the engine.

To reduce pollution, it is known to return at least a portion of the burnt gases to the intake air of the engine, which is then mixed with the fresh air before it enters the cylinders of the engine. Several types of recirculation of the burnt gases are distinguished: low-pressure recirculation, which involves taking off the burnt gases downstream of a pollution reduction device, such as a catalytic converter, in the direction of the exhaust gas flow, or high-pressure recirculation, in which the burnt gases are taken upstream of the pollution reduction device, preferably at the outlet of the cylinder head of the engine. The burnt gases, called high-pressure burnt gases, are thus taken off in an exhaust manifold fixed to the exhaust face of the cylinder head of the engine.

The burnt gases can therefore come from an oil vapour separator and are called blow-by gases. The separator is generally placed at the top of the engine. It allows the separation of the oil contained in the vapours from the gases. The oil is then returned by an oil return circuit to an oil sump, preferably located at the bottom of the engine, and the gases can be returned towards the intake of the engine.

Generally, according to FIG. 1, the heat engine 100 has a crankcase 101 with at least one cylinder 102 in which a piston can slide along the axis of at least one cylinder, and a cylinder head 20 covering the upper part of the crankcase and thus sealing at least one combustion chamber 11. The combustion chamber is delimited by the respective walls of the cylinder, the piston and the cylinder head 20. The intake ducts 21 and the exhaust lines connecting the combustion chamber 11 of each cylinder to the intake circuit 10 and the exhaust circuit, respectively, are hollowed out of the cylinder head. The intake circuit 10 is fixed to the cylinder head 20 by an intake face 23. The exhaust circuit is fixed to the cylinder head by an exhaust face (not shown) symmetrically facing 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 approximately parallel to the axis of the crankshaft housed in the engine.

Fresh air 40 is drawn in from outside the vehicle and then mixed with burnt gases 41 in an intake manifold 12 fixed to the intake wall 22 on the intake face 23 side of the cylinder head 20 of the engine. The mixture is then conveyed to the combustion chamber 11 of the engine via an intake duct 21. At the top of each cylinder of the crankcase 101, the mixture of air and burnt gases is injected into the combustion chamber where it is mixed with fuel to cause an explosion, thereby generating burnt gases. The burnt gases are then pushed out of the combustion chamber via an exhaust line towards 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 returning burnt gases to the intake of the engine.

Burnt gases are understood to be gases from the exhaust circuit or blow-by gases.

In the remaining description, the return of blow-by gases to the intake is described to make the invention easier to understand, but the burnt gases can also be high pressure or low pressure burnt gases or a mixture of burnt gases.

As is known, fresh intake air 40 is drawn in from the front of the vehicle and passes through an intake circuit in order to be injected into each combustion chamber 11 of the cylinders. The intake air is first filtered by an air filter to remove impurities and dust carried by the intake air. It is also known that the pressure of the drawn in gases can then be increased to better fill at least one cylinder of the engine with a fuel/air mixture in order to improve the engine's performance. Thus, the power density of the engine, together with its power, is increased and the engine's consumption is reduced. An intake compression stage is therefore arranged between the air filter and the engine. This compression stage (not shown) can be formed by a compression stage of a turbocharger or by an electric compressor.

Downstream of the compression stage, the compressed air is hot and its density is reduced, which is detrimental to the engine's performance. It is therefore useful to have an intake air cooling stage adjacent to the compressor (not shown), downstream of it in the direction of air circulation from the compressor. This cooling stage may consist of a cooler 14, more specifically an air/water heat exchanger. Water at a suitable temperature passes through the heat exchanger 14 to remove some of the heat from the compressed air.

The compressed and cooled air 40 is then directed to an intake manifold 12 for controlling the flow of air admitted to the combustion chambers. The manifold is fixed by a flange 13 to a fixed wall 22 on the intake face 23 of the engine's cylinder head 20 and directs the compressed and cooled air to an intake duct 21 hollowed out of the cylinder head. The cylinder head intake duct 21 has a particular shape and profile depending on the type of engine, e.g. diesel or spark ignition.

The cooler 14 is also known as WCAC, which stands for water charge air cooler. The manifold 12 is substantially characterized by a plenum 16 or charge chamber before entering the intake duct 21 of the cylinder head. The manifold 12 is downstream of the WCAC heat exchanger 14, and in our embodiment the manifold 12 and the WCAC heat exchanger 14 share the same casing. The casing is fixed to a fixed wall 22 of the cylinder head. The fixed wall 22 extends in a plane, for example inclined with respect to a horizontal plane that is parallel to the mating surface 25 between the cylinder head and the crankcase. This inclination allows easier installation of the cooler and more reliable retention.

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

As shown in Figures 1 to 4, the cooler 14 and the intake manifold 12 are integrated into one piece 15.

The following description is given for one cylinder for ease of understanding, however, the engine according to the invention has at least one cylinder and the invention proposes an injection duct for each cylinder.

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

Preferably, the intake rail 31 extends parallel to the longitudinal axis X of the engine. The rail can be obtained by drilling a hole in the cylinder head, which means that the rail is arranged inside the cylinder head, as shown in figures 1 and 2, or it can be fixed to an element of the intake circuit 10 of the engine, which means that the rail is arranged outside the engine, as shown in figure 4. The intake rail makes it possible to transport the burnt gases to the intake of the engine.

The injection duct 17 is fluidly connected to the intake rail 31 and the plenum 16. The duct is generally cylindrical and straight so as to minimize the pressure drop of the burnt gas flow. Preferably, the injection duct 17 is arranged to lead to the plenum 16 of the manifold upstream of the intake duct connected to the associated cylinder. The injection duct allows the injection of the burnt gas 41 to mix with the intake air, which is then 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 21 leads to two secondary intake branches (not shown) that lead to the combustion chamber of the cylinder.

According to Fig. 3, the intake circuit comprises an intake rail 31 which extends parallel to the longitudinal axis X of the engine and transverse to the direction E of the flow of intake air in the plenum 16 of the intake manifold. An injection duct 17, whose axis is substantially perpendicular to the axis of the intake rail 31, opens at a first end into the intake rail 31 and at a second opposite end into the plenum 16. The number of injection ducts 17 is preferably equal to the number of cylinders of the engine. Thus, the injection ducts 17 extend perpendicularly to the axis X of the engine from the injection rail 31 in 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 intake duct 21. More precisely, the projection of the outlet of the injection duct 17 into the plenum 16 in the horizontal plane is arranged within the projection of the axis of the associated intake duct in the same horizontal plane, as shown in Fig. 3. The outlet of the intake duct into the plenum is disposed substantially forward of the inlet of the associated intake duct 21. Each of the injection ducts 17 extends linearly and leads from the wall of the plenum 16 in the upstream direction _Am of the intake air flow for conveying the burnt gases in counterflow to the intake air flow direction.

Referring to Figures 2-4, the airflow is represented by arrows 32 and the injection of burnt gases into the plenum is represented by arrows 33.

The injection duct 17 preferably comprises a tubular channel 18 penetrating into the plenum along the intake duct 21, preferably away from the outlet of the intake duct 21 into the plenum 16, so as to optimally position the injection point of the burnt gases 41 in the flow of intake air 40. The tubular channel extends from the wall of the plenum in the upstream direction A _m of the flow of intake air. The distance may be, for example, greater than 20 mm, so as to allow optimal mixing of the burnt gases with the intake air before entering the intake duct 21 leading to the cylinder.

Preferably, the tubular channel 18 is substantially inclined along a vertical plane relative to the axis of flow E of the intake air 40, as shown in Figures 2 and 4.

The tubular channel 18 has at its free end 18' an opening oriented in the upstream direction A _m of the air flow. The opening may for example be bevelled and has an opening oriented in the upstream direction A _m of the air flow.

The burnt gases 41 are thus directed counter-currently to the flow of intake air 40 and then directed back in the direction of intake air into the intake duct 21, thereby substantially improving the mixing of the burnt gases with the air before they enter the intake duct 21.

According to FIG. 2, the tubular channel 18 extends from an inclined deflection wall 34 that downstream bounds the plenum 16. According to a preferred embodiment, the plenum 16 comprises a portion hollowed out from the cylinder head 20.

According to Figs. 1-4, the deflection wall 34 is inclined with respect to the axis of the flow of air E. More precisely, the axis perpendicular to the deflection wall intersects the axis of the flow of air E in a vertical plane. The tubular channel 18 can be inclined with respect to an axis perpendicular to the surface of the deflection wall 34, or can be approximately parallel to the axis so as to be inclined with respect to the axis of the flow of gas E.

Preferably, the tubular channel 18 and the deflection wall 34 are made as one piece, for example obtained by moulding. As the tubular channel 18 and the deflection wall 34 are not exposed to high temperatures, they can be made from a plastic material.

According to Fig. 4, the supply rail 31 is fixed under a lower wall 35 that bounds the plenum. The injection duct 17 passes through the lower wall 35 in the upstream direction of the air flow _Am at an angle to an axis substantially perpendicular to the inner surface of the wall. The injection duct 17 leads into a tubular channel 18 which preferably extends from the lower wall 35 at an angle in the upstream direction _Am of the intake air flow or in a direction directed towards the heat exchanger 12.

According to another embodiment, not shown, the injection rail 31 is fixed on the top wall 36 of the plenum. The injection duct 17 passes through the top wall 36 in the upstream direction of the air flow _Am at an angle to an axis substantially perpendicular to the inner surface of the wall. The injection duct 17 leads into a tubular channel 18 which preferably extends from the top wall 36 at an angle in the upstream direction _Am of the intake air flow or in a direction directed towards the heat exchanger 12.

The tubular channel 18 has at its free end 18' an opening which is preferably oriented in the upstream direction _Am of the gas flow.

The openings can be formed by angled cuts on the tubular channel, the openings facing the upstream direction A _m of the intake air flow, or in this case facing the heat exchanger 12 .

Preferably, the tubular channel 18 has a smaller cross-sectional area to reduce the pressure drop in the air flow.

The objective is achieved. The burnt gas recirculation system 10 of the intake circuit according to the present invention improves the mixing of gas and air without causing an excessive pressure drop in the intake flow.

Needless to say, the present invention is not limited to the embodiments described above by way of example, but includes all variants thereof.

For example, the tubular channels can be replaced by protrusions on the inner surface of the deflection wall or below the manifold.

The tubular channel 18 may also extend parallel to an axis perpendicular to the lower wall 36 or the deflection wall 34 and may have openings for the injection of burnt gases directed in the upstream direction _Am of the air flow.

Another exemplary embodiment may be one in which the tubular channel has a radial opening at its free end 18' facing the upstream direction _Am of the air flow.

Claims (10)

An intake circuit (10) for a heat engine, comprising:
a recirculation system (30) for gases output from said heat engine, adapted to be positioned between an intake compression stage and an upper portion of a combustion chamber (11) hollowed out in a cylinder head (20) of the engine,
the intake circuit (10) comprises the cylinder head, an intake manifold (12) with a plenum (16), and at least one intake duct (21);
In the intake circuit (10),
the recirculation system (30) comprises at least one injection duct (17) leading to the plenum (16);
the injection duct (17) is capable of conveying the gas in counterflow to the flow of intake air (32);
the at least one injection duct (17) leads to a tubular channel (18) penetrating the plenum (16) of the intake manifold (12);
The intake circuit (10), characterized in that the tubular channel (18) extends in an upstream direction of the flow of the intake air (32) from a deflection wall (34 ) capable of directing the flow of the intake air (32) towards the outlet of the at least one intake duct (21). 2. An intake circuit (10) according to claim 1 , characterized in that, in a top view, each of the at least one injection duct (17) is aligned with a central axis of one of the at least one intake ducts (21) in the flow direction of the intake air (32). An intake circuit (10) according to claim 1 or 2, characterized in that the outlet of the at least one injection duct (17) into the plenum is remote from the outlet of the at least one intake duct (21) into the plenum. 4. An intake circuit (10) according to any one of claims 1 to 3, characterized in that the tubular channel (18) has an opening facing in the upstream direction (Am) of the flow of the intake air (32) . 5. An intake circuit (10) according to any one of claims 1 to 4, characterized in that the tubular channel (18) has an oblique opening facing in the upstream direction (Am) of the flow of the intake air (32) . The intake circuit (10) according to any one of claims 1 to 5, characterized in that the deflection wall (34) and the tubular channel (18) are made in one piece. The intake circuit (10) according to any one of claims 1 to 6, characterized in that the recirculation system (30) comprises a supply rail (31) extending transversely to the air flow axis (E), the supply rail being connected to the at least one injection duct (17). The intake circuit (10) according to claim 7, characterized in that the supply rail (31) is hollowed out of the cylinder head (20) or is fixed to one of the lower wall (35) or the upper wall (36) of the plenum (16). An intake circuit (10) according to claim 7 or 8, characterized in that the supply rail (31) is connected to the outlet of a blow-by gas separator. An intake circuit (10) according to claim 7 or 8, characterized in that the supply rail (31) is connected to the exhaust gas circuit.

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