FR3060664A1 - EXHAUST GAS CIRCULATION ASSEMBLY OF A THERMAL ENGINE - Google Patents

Abstract

An exhaust gas circulation assembly of a heat engine (1) comprises an exhaust gas recirculation circuit (12) configured to allow the removal of at least a portion of the exhaust gases of the combustion engine for combustion. reinject them into the intake circuit (4) of the engine. The recirculation circuit (12) has an energy recovery turbine (20) and the recirculation circuit (12) opens onto the intake circuit in a throttling portion (100) thereof.

Description

© Publication no .: 3,060,664 (to be used only for reproduction orders)

©) National registration number: 16 63021 ® FRENCH REPUBLIC

NATIONAL INSTITUTE OF INDUSTRIAL PROPERTY

COURBEVOIE

©) IntCI ⁸ : F 02 M 26/10 (2017.01), F 02 M 26/19

A1 PATENT APPLICATION

©) Date of filing: 21.12.16. ©) Applicant (s): VALEO CONTROL SYSTEMS (30) Priority: ENGINE Simplified joint-stock company - FR. ©) Inventor (s): COPPIN THOMAS. @) Date of public availability of the request: 22.06.18 Bulletin 18/25. (56) List of documents cited in the report preliminary research: Refer to end of present booklet (© References to other national documents ©) Holder (s): VALEO CONTROL SYSTEMS related: ENGINE Simplified joint-stock company. ©) Extension request (s): ©) Agent (s): VALEO CONTROL SYSTEMS ENGINE Simplified joint-stock company.

(04) EXHAUST GAS CIRCULATION ASSEMBLY OF A THERMAL ENGINE.

FR 3 060 664 - A1 _ An exhaust gas circulation assembly of a heat engine (1) comprises an exhaust gas recirculation circuit (12) configured to allow the sampling of at least part of the gases of the combustion engine to reinject them into the intake circuit (4) of the combustion engine.

The recirculation circuit (12) includes an energy recovery turbine (20) and the recirculation circuit (12) opens onto the intake circuit in a throttling portion (100) thereof.

110

120 î, ,,, <y O h tifi, A \ <11 • 6

i

ENGINE EXHAUST GAS CIRCULATION ASSEMBLY

THERMAL

The invention relates to the field of thermal engines of a motor vehicle, and more particularly it relates to engines equipped with an exhaust gas recirculation circuit.

A heat engine can consist of an atmospheric engine in which the gas mixture supplied into the engine cylinders is at atmospheric pressure, or a turbocharged engine, in which the gas mixture is compressed to increase the quantity of gas admitted into the cylinders. In each of these cases, the engine is supplied by an air intake circuit and rejects the gases from combustion in an exhaust circuit at the engine outlet.

Turbocharged engines have a compressor and a turbine, connected by a common shaft. The turbine, arranged across the exhaust gas exhaust circuit, is rotated under the effect of the exhaust gases passing through it, and this movement is transmitted to the compressor which supplies the engine with fresh gas. at a pressure higher than atmospheric pressure at which air is taken in an intake circuit.

In the case of a heat engine, nitrogen oxides and particles can be released into the exhaust gases. In order to reduce these emissions, it is known to set up an exhaust gas recirculation circuit, also known by the acronym EGR for "Exhaust Gas Recirculation". The EGR circuit is tapped on the exhaust circuit to direct the exhaust gases to the intake of the engine block. An EGR valve is provided to modulate the quantity of exhaust gas recycled in the intake manifold.

Such recirculation of the exhaust gases has the effect on the one hand of lowering the oxygen content in the gases admitted into the heat engine, and on the other hand of reducing the temperature of the gases during combustion. Burning these recirculated gases again has the effect of cooling them, it being understood that at a lower temperature, the exhaust gases emit less nitrogen oxides.

Furthermore, there are known exhaust gas recirculation circuits equipped with a turbine, additional in that it is distinct from the turbine of the turbocharger when the recirculation circuits are applied to turbocharged engines, configured to be implemented. works under the effect of the passage of these exhaust gases and to allow a production of useful energy to assist the operation of the vehicle, for example by relieving the alternator in the production of electricity and / or by providing mechanical assistance to the engine or to elements of the engine arbitration such as the turbocharger for example. This additional energy recovery turbine can, for example, be mechanically coupled to an electric machine, capable of generating electrical energy. The electrical energy thus produced can be redistributed elsewhere or stored in an energy storage system.

The present invention is part of this context and it aims to improve energy recovery within the EGR circuit by improving the operation of this additional turbine mounted on an exhaust gas recirculation circuit.

An exhaust gas circulation assembly of a heat engine according to the invention comprises an exhaust gas recirculation circuit configured to allow the sampling of at least a portion of the exhaust gases of the heat engine to reinject them in the intake circuit of the heat engine, and this recirculation circuit on the one hand comprises an energy recovery turbine and on the other hand opens onto the intake circuit in a throttling portion thereof.

Thus, the recirculated gases are introduced into the intake circuit at a low pressure zone, which makes it possible to increase the pressure difference between the outlet and the inlet of the recirculation duct for these gases and thus d 'increase the expansion rate at the terminals of the additional turbine arranged on this recirculation duct and increase the power recovered from the additional turbine.

According to other characteristics of the invention, taken alone or in combination, it can be provided that:

- The recirculation circuit opens into the throttling portion by defining a first upstream part whose section evolves by reducing from the intake circuit and a second downstream part whose section evolves by increasing towards the part of the intake circuit connected to the intake manifold; by changing the respective section of the first upstream part and the second downstream part, the aim is to protect the fact that the section variations are progressive and without straight bearings, in order to avoid or at least limit the pressure losses ;

- A first passage section of the intake circuit upstream of the throttling portion is equal or substantially equal to a second passage section of the intake circuit downstream of the throttling portion; it is estimated that the passage sections are equal or substantially equal when they have a deviation of less than 20% of the dimension of the largest of the passage sections;

- The recirculation circuit opens into the intake circuit at the center of the throttle portion relative to the direction of circulation of the intake gases in the intake circuit;

- The first upstream portion has a minimum passage section in the vicinity of the junction with the recirculation circuit which is less than the minimum passage section of the second downstream portion in the vicinity of said junction;

- The exhaust gas circulation assembly comprises means for adjusting the minimum passage section of at least one part from the first upstream part and the second downstream part;

- a bypass circuit is arranged in parallel with the throttling portion;

- the bypass circuit is equipped with a flow control valve passing through this bypass circuit;

- the energy recovery turbine is coupled to an electric machine.

The invention also relates to a heat engine comprising an exhaust gas circulation assembly as described above, and in particular a turbocharged engine, the exhaust gas recirculation circuit being a high pressure circuit, configured to allow the sampling of exhaust gas at the outlet of the heat engine, upstream of a turbocharger.

The invention may also relate to a heat engine comprising an exhaust gas circulation assembly as described above, and in particular a turbocharged engine, the exhaust gas recirculation circuit being a low pressure circuit, configured to allow sampling. of exhaust gas at the outlet of the engine, downstream of a turbocharger.

The invention can also relate to an internal combustion engine comprising an exhaust gas circulation assembly as described above, and in particular an atmospheric engine.

The invention further relates to a motor vehicle equipped with a heat engine in accordance with what has just been described.

Furthermore, the invention aims to protect a method of implementing an exhaust gas circulation assembly of a heat engine, during which at least part of the exhaust gases are passed through a circuit. recirculation, through an energy recovery turbine.

According to a characteristic of the process, the size of at least part of the throttling portion into which the recirculation circuit opens is controlled as a function of the quantity of recirculated gases and / or of inlet gas arriving on this portion d strangulation.

According to other characteristics, it is also possible to control the dimension of the throttling portion as a function of information on the state of the recovery system associated with the turbine present on the exhaust gas recirculation circuit, and it is possible to pilot a branch circuit mounted in parallel with the throttle portion to allow maximum engine flow despite the presence of the throttle portion.

Other characteristics and advantages of the present invention will appear more clearly with the aid of the description and the figures, among which:

- Figure 1 is a schematic representation of an architecture of a turbocharged engine equipped with a gas circulation assembly according to a first embodiment, arranged in a high pressure mode;

- Figure 2 is a representation of a detail of the gas circulation assembly of Figure 1, in which we have made visible a throttling portion into which opens the gas recirculation circuit;

- Figure 3 is a representation, similar to that of Figure 2, of a gas circulation assembly according to a second embodiment;

- Figure 4 is a representation, similar to that of Figure 2, of a gas circulation assembly according to a third embodiment;

- Figure 5 is a representation, similar to that of Figure 2, of a gas circulation assembly according to a fourth embodiment;

- Figure 6 is a representation, similar to that of Figure 2, of a gas circulation assembly according to a fifth embodiment;

- Figure 7 is a schematic representation of an architecture of a turbocharged engine 10 equipped with a gas circulation assembly according to the invention, arranged in a low pressure mode; and

- Figure 8 is a schematic representation of an architecture of an atmospheric engine equipped with a gas circulation assembly according to the invention.

In the description which follows, the terms upstream and downstream will be used, in particular to qualify the position of such or such element of the recirculation circuit. These terms will be understood as a function of the direction of circulation of the gases in the corresponding circuit. Thus, when it will be specified that a first element of the recirculation circuit is upstream of a second element of the recirculation circuit, it will be a matter of understanding that the gases circulating in this recirculation circuit pass through the first element before cross the second element.

A heat engine 1 comprises an engine block 2 defining combustion chambers provided with pistons which rotate an output shaft. The combustion chambers of the engine block 2 are connected via an intake distributor 3 to a fresh air intake circuit 4, taken from the exterior of the vehicle, and via an exhaust manifold

5 to an exhaust circuit 6 of the gases burned during combustion, or exhaust gases.

In the example illustrated in FIG. 1, the heat engine 1 is a turbocharged engine in which a turbocharger 110 is formed by the cooperation of a compressor 8, arranged on the intake circuit 4, and of a turbine 10, placed on the exhaust circuit 6 so as to recover part of the energy of the exhaust gases and drive the compressor 8 in rotation. In particular, the compressor 8 and the turbine 10 can be mounted on a common shaft 810.

The intake circuit 4 here comprises, in addition to the compressor 8, an air filter 7 placed upstream of the compressor 8 and a heat exchanger 9 placed downstream thereof and intended to cool the air supplying the chambers combustion of the engine block 2. It is understood that without departing from the context of the invention, provision could be made to equip the intake circuit with any type of filter and any type of exchanger. Furthermore, the intake circuit 4 may have, downstream of the compressor 8, a controlled regulation device for controlling the supply of fresh air to the combustion chambers of the engine block 2.

The exhaust circuit 6 may comprise downstream of the turbine 10 a device for treating pollutants of the exhaust gases 11 and which may in particular consist, by way of example, in a catalyst or a particulate filter. The exhaust circuit can also include an exhaust back pressure device not shown here.

The engine according to the invention further comprises an exhaust gas recirculation circuit 12, which makes it possible to re-inject part of the exhaust gases into the intake, in particular to the intake manifold. This contributes to the cooling of the combustion in the cylinders and the reduction of the oxygen rate, which makes it possible to reduce the quantity of nitrogen oxides (NOx) in the exhaust gases from combustion in the engine block, harmful nitrogen oxides being mainly developed at high temperatures and high oxygen concentrations. The circulation circuit is thus configured to allow the sampling of at least part of the exhaust gases from the heat engine to be reinjected into the intake circuit.

The recirculation circuit 12 is here a high pressure circuit in that it is connected, at a first end 14, to the exhaust circuit 6 upstream of the turbine 10 and, at the opposite end 16, or second end , to the intake circuit 4 downstream of the compressor 8.

We will now describe in more detail the recirculation circuit 12 and the various elements which compose it, and more particularly their specific arrangement according to the invention.

From the first end 14 to the second end 16, the gases recirculated from the exhaust circuit 6 to the intake circuit 4 meet at least one energy recovery turbine 20. In the example illustrated, the recirculated gases are brought to pass through a heat exchange device 22, without this being necessary for the implementation of the invention.

The energy recovery turbine 20 is driven in rotation by the passage of the exhaust gases circulating in the recirculation circuit 12, and this rotation is used to assist the operation of the vehicle, for example by relieving the alternator in the production of electricity and / or by providing mechanical assistance to the engine or to elements of the engine architecture such as the turbocharger for example. The energy recovery turbine can in particular be mechanically coupled to an electric machine, capable of generating and / or storing the electric energy thus produced so as to redistribute it elsewhere. It is according to the examples detailed above that the turbine 20 is qualified as energy recuperator of the recirculated gases. This turbine 20 can also be qualified as an additional turbine in that it is distinct from the turbine of the turbocharger.

The heat exchange device 22 is disposed on the recirculation circuit 12, here downstream, in the direction of gas recirculation, of the energy recovery turbine 20, so as to cool the recirculated gases before their reinsertion into the intake circuit 4.

The heat exchange device may in particular consist of an air-air type or air-water type heat exchanger, the choice being made in particular according to space constraints, without departing from the context of the invention.

A regulation valve 120, arranged on the recirculation circuit, makes it possible to control the percentage of exhaust gas in the air admitted into the combustion chamber of the engine block 2. In the context of the invention, any type of valve can be implemented. It is understood that the regulation valve is associated with a control means configured to control the passage of recirculated gases as a function of the desired operating characteristics of the engine. In the example illustrated, and as can be seen in particular in FIG. 2, provision may be made for placing the control valve 120 directly upstream from the connection point, called the second end 16, of the recirculation circuit 12 with the circuit d admission 4, without however being restrictive.

According to the invention, the recirculation circuit 12 leads to the intake circuit 4 in a throttling portion 100, that is to say a section of the intake circuit reduced relative to sections respectively upstream and downstream of this throttling portion 100. Such a throttling portion is particularly visible in FIG. 2 and it is understood that in this zone of smaller section, the gas mixture present in the intake circuit accelerates and there is produced point depression, on which, advantageously, the recirculation circuit 12 opens.

As will be specified below, the vacuum thus formed punctually at the point of introduction of the recirculation circuit is greater than that necessary to create a pressure differential for the sole circulation of the exhaust gases in the recirculation circuit. The vacuum, i.e. the shape and dimensions of the throttle portion, is determined by calculation in order to significantly increase the pressure ratio between the turbine terminals and allow the increase energy recovery potential.

It is understood that valves arranged on the intake circuit and / or on the exhaust circuit could create an equally significant depression, but which would consist almost entirely of pressure drops, which would generate an increase in the pressure differential between the engine block exhaust and intake. This problem would also be present if the flow in the choke portion were to be sonic or supersonic, and the choke portion must be defined for this purpose to avoid such flow conditions.

We will give in the following paragraphs calculation elements for determining the appropriate dimensioning of the choke portion.

The energy recovery potential of the additional turbine can be expressed as follows:

^ îurb.ref P turb ^C P exh QeGR exh

1P exh. P adm, ι-y A 1 /

With

P _tur b: Mechanical power recovered at the energy recovery turbine Vturb ^: Efficiency of the energy recovery turbine Cpexh ^: heat capacity at constant pressure of the exhaust gas Qegr · Mass flow of recirculated gases

Γ _A ^: Exhaust gas temperature

Pexh ^: Exhaust gas pressure

Padm ^: Intake gas pressure

The exhaust / intake pressure ratio is determined by the characteristics of the exhaust and intake lines, the turbocharger and the calibration choices.

The introduction of recirculated gases into the intake circuit at a throttle portion 100 allows the pressure to be reduced at the outlet of the recirculation circuit. Indeed, the flow at the neck of the venturi can be expressed in the following way (neglecting the kinetic energy of the fluid in section Al, assumed to be sufficiently large):

Or

Qcoi ~ CdS _co i

HT f

max PR _cr , ^ l P Al.

I) f (x)

2γ / -I λ z-i

1-x

PR r

\ / - l / + l _z

With:

Qcol

CdS col pcol pAl: Mass flow of gases at the junction zone in the choke portion Effective section at the junction zone in the choke portion: Pressure at the junction zone in the choke portion: Pressure at level of the first passage section Al

PRcr: Critical pressure report

7741: Gas temperature at the level of the first passage section Al

P: Specific constant of the gas considered

And /: Adiabatic index of the gas considered

As a result, the power recovered by the turbine on the exhaust gas recirculation circuit is then increased due to the increase in the pressure ratio, according to the following equation:

^ îurb dîurb exh QeGR exh

1P exh P adm. P adm P col ι-y A) /

We will be able to define the passage sections in the throttling portion to recover maximum power from the turbine.

Referring again to FIG. 2, it is notable that the recirculation circuit 12 opens into the throttle portion 100 by defining a first upstream part 101 forming a bottleneck and a second downstream part 102 flaring in s moving away from this choke portion. In other words, the first upstream part 101 has a section which evolves by reducing from the intake circuit 4 towards the throttling portion and the second downstream part 102 has a section which evolves inversely, increasing from the portion throttle 100 to the intake circuit 4.

We can define a first passage section A1 of the intake circuit 4 before the dimension of this circuit decreases by approaching the throttling portion 100 and the junction zone with the recirculation circuit 12, as well as a second passage section A4 of this same intake circuit 4 downstream of the throttling portion, in an area where the dimension of the intake circuit has become constant. It is notable that according to the invention, the first passage section A1 is substantially equal to the second passage section A4. This avoids significant pressure drop on intake which could penalize the operation of the engine.

The junction area of the intake circuit 4 and the recirculation circuit 12 is such that the recirculation circuit opens into the intake circuit 4 at the center of the throttling portion 100, that is to say so forming a downstream part and an upstream part between the first passage section A1 and the second passage section A4 of the intake circuit 4 which are of length, in the direction of flow of the air in the intake circuit , substantially equal.

Furthermore, in the example illustrated, the recirculation circuit 12 opens into the throttling portion 100 of the intake circuit 4, at the periphery thereof, by a tap on the wall delimiting the conduit of the circuit. admission. It will be possible, in a variant not shown here, for the recirculation circuit to pass through the wall delimiting the intake circuit conduit and extend inside the intake circuit to open out substantially at the level of the axis defining the intake circuit duct.

Other variants could be implemented, in particular by tilting the recirculation circuit in the junction zone, in order to inject the recirculated gases with an angle OL, advantageously between 0 and 90 °, relative to the main flow. in the intake circuit, and / or by providing several junction zones at the periphery of the intake circuit.

In each of these cases, it is remarkable that the recirculated gases are injected into a vacuum zone, generated by the conformation of the throttling portion 100 on the intake circuit 4. The pressure at the second end 16 of the recirculation circuit 12 is therefore greatly reduced relative to the pressure at the first end 14, and the pressure differential thus created is favorable to the operation of the energy recovery turbine 20 formed on the recirculation circuit .

According to the invention, an energy recovery turbine is thus positioned on a recirculation circuit at the terminals of which a pressure differential is generated for the optimal operation of this turbine, the pressure differential being implemented other than by a valve. which would generate a high pressure drop.

Due to the configuration of the throttling portion, this pressure differential is created by maintaining an equivalent pressure between the first passage section A1 and the second passage section A4 of the intake circuit, which makes it possible to do not change the pressure difference ratio between the intake and the engine exhaust. This ensures the optimal operation of the energy recovery turbine without penalizing the operation of the heat engine. According to the invention, the aim is not to modify the flow rate of the gaseous mixture admitted into the engine block and the flow rate of the recirculated gases, but rather to increase the pressure ratio between the connection of the recirculation circuit to the intake circuit and the connection of the recirculation circuit at the other end to the exhaust circuit.

In this first embodiment, it should be noted that the passage section immediately downstream A3 from the arrival of recirculated gases, that is to say the minimum passage section in the vicinity of the junction with the recirculation circuit , is identical to the passage section immediately upstream A2 of this recirculated gas inlet, that is to say the minimum passage section in the vicinity of this junction.

The dimension of these minimum passage sections must be determined precisely by calculation so as to be able to adapt to the recirculated gas supplies. After the injection of these gases, the flow is accelerated in this case and, in the case of a passage section immediately downstream A3 too low or in the event of too large a flow of recirculated gases, this embodiment presents the risk of generating sonic or supersonic flow conditions.

In order to ensure that it does not enter into such operating characteristics, it is possible to implement a second embodiment which illustrated in FIG. 3 and which differs from the embodiment previously presented in that the first upstream portion 101 has a minimum passage section A2 in the vicinity of the junction with the recirculation circuit 12 which is less than the minimum passage section A3 of the second downstream portion 102 in the vicinity of said junction. In other words, the passage section immediately downstream of the recirculated gas inlet is larger than the passage section immediately upstream of this gas inlet. The increase in the passage section downstream of the connection is defined as a function of an average injection rate of recirculated gases, so that the pressure at the outlet of the throttling portion is very close to that which there would be in the intake circuit in the absence of a throttle portion.

In this case, the aim is not to propose a passage section immediately downstream A3 which is too large, which could lead, in cases where the supply of recirculated gases is minimal, a pressure drop on the circuit. admission. This second embodiment makes it possible in particular to take account of a high motor flow rate while the recirculation circuit operates at low flow rate.

A third embodiment, illustrated in FIG. 4, differs from the second embodiment previously described in that it further comprises a bypass circuit 103 disposed in parallel with the throttle portion 100. In this way, we overcomes the reduction in passage cross-section for at least part of the gas mixture arriving in the intake circuit 4 upstream of the junction zone with the recirculation circuit 12.

This bypass circuit 103 is equipped with a flow regulating valve 104, which makes it possible to control the quantity of gaseous mixture coming from the intake authorized to bypass the throttling portion, in order to allow a maximum engine flow.

In this third embodiment, it is therefore possible to size the passage sections immediately upstream and downstream smaller than in the second embodiment and to authorize via the throttling portion lower maximum flows, since 'Beyond the maximum flow authorized by the throttling portion, the valve associated with the bypass circuit may be partially or completely open and allow the gas mixture to pass. Such an embodiment has the advantage of dimensioning the throttling portion on low flow rates and therefore of increasing the pressure differential between the inlet of the gas recirculation circuit and its outlet at the throttling portion on the intake circuit. It is understood that it is advisable to associate with the regulating valve 104 a control module configured to control this valve as a function of the flow rate of recirculated gases reinjected into the intake circuit and as a function of the engine requirement in fresh gas mixture.

This type of embodiment with a throttling portion of variable section is particularly advantageous in the case of application to low pressure recirculation circuits, as will be described below with reference to FIG. 7. It is possible to indeed reduce the passage section to obtain the desired pressure differential for the operation of the energy recovery turbine and increase this section to pass the maximum engine flow.

We will now describe, with reference to FIGS. 5 and 6, two particular embodiments in that at least one passage section of the throttle portion has a variable dimension depending on the operating conditions of the assembly of exhaust gas circulation. In these two embodiments, means 50 for adjusting the minimum passage cross section A2, A3 are provided for at least one part from the first upstream part 101 and the second downstream part 102, that is to say d at least one part immediately adjacent to the junction zone with the recirculation circuit 12. More particularly, the adjustment means 50 comprise a control module configured to define a passage section to be targeted as a function of the initial passage section, the quantity of recirculated gas to be reinjected, the quantity of fresh air to be supplied to the intake distributor and the maximum pressure differential that can be generated to make the energy recovery turbine operate at its best. It can also be provided to configure the adjustment means so that they can receive information relating to the operation of the energy recovery system, and in particular the operation of the turbine 20 and / or the state of the associated electrical machine and / or the state of charge of the associated storage system.

A fourth embodiment is thus illustrated in FIG. 5 in which the adjustment means 50 control a simultaneous variation of the minimum passage section A2 of the first upstream part 101 and of the minimum passage section A3 of the second downstream part 102 The adjustment means 50 allow in a first case to reduce the passage section over the entire throttling portion when the flow rates are low, which makes it possible to increase the pressure ratio at the terminals of the energy recovery turbine. , and in a second case to increase this passage section when the flow rates are greater, in order to avoid a sonic or supersonic flow.

There is shown diagrammatically in FIG. 5 an adjustment means 50 equipped with an actuator rod 51 bearing on a peripheral wall of the duct delimiting the throttling portion, and it is understood that in this example example, the means of adjustment is configured to generate a defined displacement in advance of the actuator rod so that it pushes on the wall, in order to bring it into the position shown in dotted lines in the figure, or to generate a defined displacement in withdrawal of the cylinder rod so that it causes the separation of the wall, in order to bring it into the position shown in solid lines in the figure.

The adjustment means 50 can in particular be arranged at the center of the throttling portion, in the same way as the second end 16 of the recirculation circuit 12, opposite the latter. In this way, an action on the wall defining the duct of the throttling portion 100 symmetrically impacts the first upstream part 101 and the second downstream part 102.

Like what could have been presented in a previous embodiment, a bypass circuit 103 can be implemented to short-circuit this throttling portion, in order to compensate for possible failures of the adjustment means, or to overcome the dimensional limitations of the choke portion.

A fifth embodiment is illustrated in FIG. 6 in which adjustment means 50, 52 independently control a variation of the minimum passage section A2 of the first upstream part 101 and a variation of the minimum passage section A3 of the second downstream part 102. In the example illustrated, two adjustment means are provided, among which an adjustment means 50 is similar to that previously described in the context of the description of the fourth embodiment, and in particular positioned in the center of the portion. throttle 100, and an additional adjustment means 52 is arranged specifically in the vicinity of the second end of the recirculation circuit 16, bearing on the second downstream part 102.

In this way, the difference which originally existed between the dimensions of these two passage sections may vary if the additional adjustment means 52 is activated. It is thus possible to adapt the junction zone to the amount of recirculated gas to be reinjected, by adapting as best as possible the different passage sections of the throttling portion 100 to the flows passing through them. In this way it is possible to maximize the increase in the pressure ratio at the terminals of the turbine, while allowing a rise in pressure of the flow between the passage section immediately downstream A3 of the second portion 102 and the second passage section A4 of the intake circuit, which avoids pressure losses that are detrimental to engine operation.

Like what could have been presented in a previous embodiment, a bypass circuit can be implemented to short-circuit this throttling portion, in order to compensate for possible failures of the adjustment means, or to overcome the limitations dimensions of the choke portion.

It will be understood from reading the above that the connection of a recirculation circuit equipped with a recovery turbine is particularly advantageous when it is carried out in a throttling portion, in order to benefit from a vacuum zone at the outlet of the recirculation circuit to optimize the performance of the energy recovery turbine.

This advantage is equally obtained in the case of application illustrated in FIG. 7, in which the energy recovery turbine 20 is mounted on a low pressure recirculation circuit, whereas previously a high recirculation circuit was described. pressure. The recirculation circuit is said to be low pressure as soon as the circuit enters the exhaust circuit is made downstream of the turbocharger turbine, and the circuit leaves the intake circuit is made upstream of the compressor. turbocharger. As before, the recirculation circuit equipped with an energy recovery turbine leads to the intake circuit at a throttle portion 100. This avoids the presence of flap or valve at the intake in upstream of the recirculation circuit connection and the presence of a flap or back pressure valve downstream of the recirculation circuit connection on the exhaust circuit.

As illustrated in FIG. 8, a recirculation circuit equipped with an energy recovery turbine 20 can also be installed in an atmospheric engine and connected to the intake circuit according to the principle of the invention, c '' ie at a throttling portion which facilitates the pressure differential necessary for the proper functioning of the energy recovery turbine.

Of course, various modifications can be made by a person skilled in the art to the exhaust gas circulation assembly without departing from the context of the invention, it being understood that the invention cannot be limited to the embodiment specifically described. in this document, and that it extends in particular to all equivalent means and to any technically operating combination of these means, as soon as a gas recirculation circuit simultaneously has an energy recovery turbine and a connected end to the intake circuit at a throttling portion forming a pressure differential adapted to the proper functioning of the turbine.

Claims (15)

1. Exhaust gas circulation assembly of a heat engine (l) comprising an exhaust gas recirculation circuit (12) configured to allow the sampling of at least part of the exhaust gases of the heat engine to re-inject them into the intake circuit (4) of the heat engine, in which the recirculation circuit (12) comprises an energy recovery turbine (20), characterized in that the recirculation circuit (12) leads to the intake circuit in a throttle portion (100) thereof. 2. exhaust gas circulation assembly according to claim 1, characterized in that the recirculation circuit (12) opens into the throttling portion (100) by defining a first upstream part (lOl) whose section changes in reducing from the intake circuit (4) and a second downstream part (102) whose section changes by increasing towards the intake circuit. 3. Exhaust gas circulation assembly according to the preceding claim, characterized in that a first passage section (Al) of the intake circuit (4) upstream of the throttling portion (100) is equal or substantially equal to a second passage section (A4) of the intake circuit (4) downstream of the throttling portion. 4. exhaust gas circulation assembly according to claim 2 or 3, characterized in that the recirculation circuit (12) opens into the intake circuit (4) at the center of the throttling portion (100), with respect to the direction of circulation of the intake gases in the intake circuit. 5. exhaust gas circulation assembly according to one of claims 2 to 4, characterized in that the first upstream portion (lOl) has a minimum passage section (A2) in the vicinity of the junction with the recirculation circuit (12) which is less than or equal to the minimum passage section (A3) of the second downstream portion (102) in the vicinity of said junction. 6. exhaust gas circulation assembly according to one of the preceding claims, characterized in that it comprises adjustment means (50) of the minimum passage section (A2, A3) of at least one of the first upstream part (10l) and the second downstream part (102). 7. Exhaust gas circulation assembly according to one of the preceding claims, characterized in that a bypass circuit (lO3) is arranged in parallel with the throttling portion (lOO). 8. An exhaust gas circulation assembly according to the preceding claim, characterized in that the bypass circuit (103) is equipped with a valve (104) for controlling the flow passing through this bypass circuit. 9- exhaust gas circulation assembly according to one of the preceding claims, characterized in that the energy recovery turbine (20) is coupled to an electric machine. 10. Heat engine comprising an exhaust gas circulation assembly according to one of the preceding claims, characterized in that it is of the turbocharged engine type, and in that the exhaust gas recirculation circuit (12) is a high pressure circuit, configured to allow the sampling of exhaust gases at the outlet of the heat engine (l), upstream of a turbocharger (110). 11. A heat engine comprising an exhaust gas circulation assembly according to one of claims 1 to 9, characterized in that it is of the turbocharged engine type, and in that the recirculation circuit (12) of the gases d The exhaust is a low pressure circuit, configured to allow the sampling of exhaust gases at the outlet of the heat engine (l), downstream of a turbocharger (no). 12. A heat engine comprising an exhaust gas circulation assembly according to one of claims 1 to 9, characterized in that it is of the atmospheric type. 13. Motor vehicle equipped with a heat engine in accordance with one of claims 10 to 12. 14 · A method of implementing an exhaust gas circulation assembly of a heat engine according to one of claims 1 to 9, during which at least part of the exhaust gas is passed through a recirculation circuit (12), through an energy recovery turbine (20). 15- Method according to the preceding claim in which one controls the dimension of at least part of the choke portion (100) in which the 5 recirculation circuit (12) depending on the amount of recirculated gas and / or intake gas arriving on this throttling portion. 1/3