WO2008031959A1

WO2008031959A1 - Device improving the operation of a supercharged engine with an exhaust gas recirculation circuit

Info

Publication number: WO2008031959A1
Application number: PCT/FR2007/051752
Authority: WO
Inventors: Stephane Guilain; Eric Magere; Johann William
Original assignee: Renault S.A.S.
Priority date: 2006-09-12
Filing date: 2007-07-30
Publication date: 2008-03-20
Also published as: FR2905735B1; FR2905735A1

Abstract

The invention relates to an exhaust gas recirculation circuit (B2) positioned between an exhaust manifold (1) and an air intake distributor (2) of a supercharged engine comprising an EGR regulating means (6) positioned between the exhaust manifold (1) and an EGR cooler (7), characterized in that the circuit (B2) has an obstruction means (8) that can be used to at least partially obstruct the circuit (B2) positioned between an upstream port of the EGR cooler (7) and the air intake distributor (2). Another subject of the invention is an engine comprising a recirculation circuit according to the invention.

Description

DEVICE IMPROVING THE OPERATION OF A

ENGINE SUPERCHARGED WITH A CIRCUIT OF

RECIRCULATION OF EXHAUST GAS

The present invention relates to a device improving the operation of a supercharged engine. More particularly, the invention relates to an exhaust gas recirculation circuit disposed between an exhaust manifold and an intake air distributor of a supercharged engine comprising means for regulating the amount of EGR.

Modern supercharged engines have to comply with increasingly stringent anti-pollution standards. For this, several techniques have been developed and one of them is the recirculation of a portion of the exhaust gas on admission (EGR). This technique, by the mixture of exhaust gas to air that is admitted into the engine, reduces the formation of nitrogen oxides (NOx) during the combustion phase by depleting the oxygen / fuel mixture. It is also expected to cool the exhaust before reintroduction to obtain an increased efficiency of the reduction of NOx formation. To preserve the maximum performance of the engine, the amount of recirculated gas is generally varied according to the engine load, so as not to deplete the oxygen / fuel mixture at full load of the engine. Generally, it is expected to be able to cut the EGR when the engine is fully loaded so as to achieve high oxygen / fuel mixtures. Usually, these recirculated gases are injected at a single point upstream of the intake air distributor and can come from a single recirculation circuit or from several recirculation circuits. In systems of the prior art such as that presented, for example, in patent WO 2004/04441 2, the EG R flow control valve is placed between the cooler EG R and the intake air distributor. This configuration presents reliability problems at the valve. More particularly, the location of the EGR control valve downstream of the EGR cooler can pose long-term problems of fouling and / or corrosion of the EG R valve due to the condensation of the exhaust gas comprising corrosive particles in and after the cooler EG R. As a result, the seal of the valve is degraded which results in a degradation of the performance of the engine at full load. Because of this phenomenon, this valve must be made with a material type and thickness determined to ensure satisfactory endurance. This has implications for the weight and price of such a valve.

Some systems have a valve placed upstream of the cooler EG R to overcome the aforementioned drawbacks of systems that have a control valve of the amount of EG R placed downstream of the cooler EGR. Generally, in these systems, a regulation valve of the amount of EG R is placed between an exhaust manifold and the cooler EG R. According to this configuration, there is a decrease in the performance of the engine that it important It is not possible to compensate, for example by changing the parameters of the turbocharger. This is explained by the fact that positioning the valve thus, problems of pressure pulsations appear in the air intake circuit, reducing the intake pressure in engine. This change in behavior is particularly noticeable during operating modes where the EGR is removed, especially at full load and for low engine speeds. The supercharging pressure is then reduced significantly, thereby reducing the torque and the dynamic behavior of the engine at these speeds.

The invention proposes to solve the problem of modifying the inlet gas pressure which leads to a reduction in engine performance and to solving the problem of the reliability of the valve regulating the amount of EGR.

For this purpose, there is provided a gas recirculation circuit comprising means for regulating the amount of EGR placed between the exhaust manifold and an EGR cooler, the circuit also comprising an obstruction means that can at least partially obstruct the circuit arranged between an upstream port of the EGR cooler and the air distributor at the intake. According to a characteristic of the invention, a duct of the supercharging circuit is connected at a damper box upstream of the intake air distributor. The obstruction means is then disposed in this housing. According to this characteristic, it does not change the pressure pulsations on admission while obtaining a better compactness of the system. It also reduces the number of connections on the recirculation circuit, which has the effect of limiting the risk of leaks from the circuit.

According to another characteristic, the obstruction means is a flap, a joint of which has a common pivot point with a damper flap, these flaps having respective independent movements. The addition of a flap in the housing is achieved by reusing the mechanical pivoting means of the damper flap, reducing the cost of production and study of the housing. The independent nature of the movements of these components makes it possible to separate the functions of each component.

Another feature is to place the obstruction means in the EG cooler R at the downstream port. This provides a compact recirculation circuit and having a reduced number of connections that can be a source of leaks. This also makes it possible to couple this obstruction means with means for selecting EG R "hot" or "cold".

According to another characteristic, the obstruction means is unique and is placed in a U-type EGR cooler. The configuration of the U-shaped cooler makes it possible to make the circuit adaptation to the motor more compact, and to make the system more reliable and less expensive because of the use of a single obstruction means, which in this configuration also makes it possible to operate the selection of EG R "hot" or "cold".

According to another characteristic, a conduit of the recirculation circuit is connected to a supercharging circuit at a supercharger. A higher integration is achieved with the obstruction function being able to be coupled with means already present in the supercharging cooler.

The invention also relates to a supercharged engine comprising an EGR circuit according to the invention. Other characteristics and advantages of the invention will become clear from reading the following description of the nonlimiting embodiment thereof, in conjunction with the appended drawings in which:

- Figure 1 is a diagram showing a first embodiment of the invention. A second valve regulating the amount of EGR is added between the cooler and the intake air distributor;

- Figure 2a is a diagram showing a second embodiment. An additional flap is added in the damper box to close the EGR circuit in "EGR operating" position; - Figure 2b is a diagram showing a second embodiment. An additional flap is added in the damper box to close the EG R circuit in the "full load" position;

- Figure 3a is a diagram showing a third embodiment of the invention. A system comprising two flaps is adapted to an EG cooler R I to allow the closure of the downstream duct EG R, represented in the "full load" position;

- Figure 3b is a diagram showing a third embodiment of the invention. A system comprising two flaps is adapted to an EG cooler R I to allow the closure of the downstream duct EG R, shown in position "cold operation EG R";

- Figure 3c is a diagram showing a third embodiment of the invention. A system comprising two flaps is adapted to an EG cooler R in I for allow the shut-off of the downstream duct EG R, represented in the "operating EG R hot"position;

FIG. 4a is a diagram showing a fourth embodiment. A system comprising two shutters is adapted to a U-shaped U-shaped cooler to allow the shut-off of the downstream duct EG R, represented in the "full load" position;

- Figure 4b is a diagram showing a fourth embodiment. A system comprising two flaps is adapted to a U-shaped cooler R R to allow the closure of the downstream duct EGR, represented in position "cold EGR operation";

- Figure 4c is a diagram showing a fourth embodiment. A system comprising two flaps is adapted to a U-shaped cooler R R to allow the closure of the downstream duct EGR, represented in position "hot EGR operation"; Figure 5 is a diagram showing a connection of the recirculation circuit at the booster.

In the following description, it qualifies a downstream position, the position being on the side of an element through which the fluid flowing through it springs out of it. An upstream position is referred to as the position on the side of an element through which the fluid passing through it enters the position. By extension, the downstream ports and the upstream ports will also be referred to as the input and output ports of an element, respectively. FIG. 1 shows an exhaust gas recirculation system for a supercharged engine according to a first embodiment.

This system is adapted to an engine comprising at least one exhaust manifold 1 and an intake air distributor 2 and having a boost circuit B1 and an exhaust gas recirculation circuit B2.

The supercharging circuit B1 comprises at least a first C1 and a second C2 circuit portions and at least one turbocharger or a mechanical compressor 3, possibly a charge cooler 4 and possibly a damper housing 5. The first portion of conduit C1 is arranged between the turbocharger 3 and the charge cooler 4 and the second portion of the duct C2 is arranged between the charge cooler 4 and the intake air distributor 2. This case 5 is arranged on the second portion of the duct C2 thereof. circuit B1. The housing 5 stops the engine by cutting off the air supply. This housing 5 can also be used to regulate quantities of EG R in certain modes of operation.

The recirculation circuit B2 comprises at least a first C3 and a second C4 duct portions, a flow control valve EGR 6, an EG cooler R 7 and an obstruction means 8 of the circuit B2. The first duct portion C3 is disposed between the exhaust manifold 1 and the cooler EG R 7 and the second duct portion C4 is disposed between the cooler EG R 7 and the intake air distributor 2. The valve EG R 6 flow control is placed on the first conduit portion C3 and the obstructing means 8 is placed on the second conduit portion C4. The EG R 6 flow control valve regulates the amount of exhaust gas that is recirculated at the intake. This means 8 makes it possible to at least partially obstruct the section of the second duct portion C4 for the operating modes of the engine for which a total or partial reduction of the quantity of EG R is desired, in particular at full load. Closing this means 8 makes it possible to reduce the volume seen from the intake, and to minimize the propagation of the wave fronts in the recirculation circuit which causes pressure losses on admission. By positioning the means 8 as close as possible to the inlet distributor 2, it is possible to optimize the reduction of the pressure losses since it is possible to adapt the volume seen from the admission remaining after the closure of this means 8. Surprisingly, a good operation of the system is obtained even for a medium level of sealing, that is to say from a quasi-total obstruction of the conduit C4 by the means 8. This ensures a good reliability of the system itself when the means 8 is fouled or corroded due to condensed exhaust gas after passing through the cooler EG R 7.

According to a second embodiment, the obstruction means 8 of the recirculation circuit B2 take place in the damper housing 5. This second embodiment is shown in FIGS. 2a and 2b which show the integration of the obstruction means 8 in the damper housing 5 respectively in a position corresponding to the mode of "EGR operation" and "full load".

According to this second embodiment, the second duct portion C4 of the recirculation circuit B2 is connected to the second duct portion C2 of the booster circuit B1 at the damper housing 5. The housing Damper 5 thus comprises at least three ports with an input port and an output of conduit C2 and an input port of conduit C4. This housing 5 further comprises a pair of obstruction means which may be flaps. A first obstruction means Vs is placed in the passage of the conduit portion C2 of the boost circuit B1 and regulates the amount of air from it. This means Vs makes it possible to stop the engine and to assist in regulating the flow rates of EG R. A second Vegr obstruction means is placed in the passage of the portion of the duct C4 of the recirculation circuit B2 and makes it possible to regulate the amount of exhaust gas recirculated at intake. These obstruction means Vs and Vegr are mobile and can be moved independently of one another. These means Vs and Vegr take determined positions as a function of the load, the engine speed and the desired amount of EGR.

FIG. 2a represents the position of these means Vs and Vegr when this damper box 5 is in the "operating EG R" position. In operation EG R, the means Vs can take a number of positions obstructing more or less the line C2 of the supercharging circuit B1. For its part, the Vegr means can take a number of positions between a position in which the conduit C4 of the recirculation circuit B2 is not obstructed at all and a position partially obstructing this conduit so as to regulate the amount of EGR on admission.

FIG. 2b represents the position of these means Vs and Vegr when this damper box 5 is in the "full load" position, that is to say with little or no EG R. At full load, we thus have the average Vs which is positioned as close as possible to the walls of the C2 conduit in order to obstruct the least possible this one. It will thus be possible to adapt the shape of this means Vs to the contour of the duct C2. The Vegr means is positioned so that the conduit C4 is almost completely obstructed when one is in "full load" operating mode.

This second embodiment makes it possible to limit the volume seen of the admission and thus to reduce the problems of loss of pressure on admission while obtaining a better compactness of the system. The number of connections present on the gas recirculation circuit is also reduced.

According to a third embodiment, represented in FIGS. 3a, 3b and 3c, the obstruction means 8 of the recirculation circuit B2 are located in the EGR cooler 7. This embodiment is applicable to an EGR cooler 7 comprising at least two types distinct passages and having a structure called I. An I-7 cooler has upstream and downstream ports on opposite sides, fluids flowing therethrough in a substantially rectilinear motion and in a single direction. The first passage C is called "EG R hot" and allows to let the exhaust gas to recirculate without being cooled. The second passage F referred to as "cold EGR" includes at least one cooling channel to obtain cooled recirculated exhaust gases to further reduce NOx formation. The hot EGR passage C is used to obtain exhaust gases that are warmer than those that have passed through the cold EG R passage F. Although an optimal reduction of NOx is not achieved, there is a reduction in other pollutants present when the engine has not yet been warmed up or for particular depollution methods. A first 8a and a second 8b average type shutter make it possible to choose the desired passage for the exhaust gases to be recirculated. In the embodiment shown, these means are placed at the outlet of the EGR cooler 7. These flaps make it possible to obstruct one or the other of the passages C, F according to the desired operation. The second component 8b is added to allow the exhaust gas recirculation to be eliminated at full load. This flap 8b may be disposed in the vicinity of the upstream port of the cooler 7 or in the vicinity of the downstream port. Preferably, as shown in Figure 3a, 3b and 3c, the second component 8b is disposed adjacent the first flap 8a and has the same axis of rotation as the latter.

Figure 3a shows the positioning of the flaps 8a, 8b when the EGR is off, operating mode that is used when the engine is used at full load. In this configuration, the flaps are arranged so that the passages EGR hot C and EGR cold F are obstructed.

Figure 3c shows the positioning of the flaps when the EGR is not cooled, operating mode that is used when the engine has not yet reached its operating temperature or for certain modes of combustion. According to this mode of operation, the flaps 8a, 8b are arranged so as to obstruct the cold EGR passage F. FIG. 3b shows the positioning of the flaps when the EGR is cooled, operating mode that is used when the engine has reached its end. operating temperature and that the motor is not used at full load. According to this mode of operation, the flaps 8a, 8b are arranged so as to obstruct the hot EGR passage C and to leave at least partially free passage EG R cold F.

FIGS. 4a, 4b and 4c show the integration of the function of obstruction of the EGR conduits C3, C4 in a U-shaped cooler 7 according to a fourth embodiment. A U-shaped cooler 7 has upstream and downstream ports on the same side, the fluids passing therethrough follow a looping movement to exit on the side where they entered the cooler 7. The use of this type of EGR cooler 7 has advantages in terms of integration and compactness of the system on an engine. As for the third embodiment, according to this embodiment, the EGR cooler 7 has two separate passages for the recirculated exhaust gas, a warm EG R passage C and a cold EGR passage F but the configuration and location of those These are different. The hot EGR passage C is located on the side of the end of the cooler 7 which has the upstream and downstream ports. The cold EGR passage F extends between this hot EGR circuit C and the end of the cooler 7 opposite the end which has the upstream and downstream ports. This cold EGR passage F comprises at least one cooling channel.

According to this embodiment, the configuration of this U-shaped cooler 7 makes it possible, thanks to a single flap 8, to perform the dual function of selecting between a hot EGR and a cold EG R and the obstruction function of the EGR circuit in order to suppress exhaust gas recirculation at full load. This flap 8 is located on the side of the cooler EG R 7 having the upstream and downstream ports. Thus, putting aside the reduced implementation costs of this system, the use of a U-shaped cooler 7, simplifies the EGR system and increases the level of reliability.

Figure 4a shows the positioning of the flap 8 when the gas recirculation is cut off, operating mode that is used when the engine is used at full load. In this configuration, the flap 8 obstructs the downstream port of the cooler 7. Thus, the recirculated gases can not leave the cooler 7, the engine operates without EGR at the intake. Figure 4b shows the positioning of the flap 8 when the EGR is not cooled, operating mode that is used when the engine has not yet reached its operating temperature. During this operating mode, the shutter 8 is placed in such a way that it does not obstruct any opening or driving. The hot EGR passage C being placed closer to the downstream and upstream ports than the cold EGR passage F and that the resistance is less important there, because of the absence of cooling channel, the gases preferentially circulate by the first city. Figure 4c shows the positioning of the flap when the EGR is cooled, the operating mode that is used when the engine has reached its operating temperature and the engine is not being used at full load. During this operating mode, the flap 8 is placed so as to obstruct the hot EGR passage C, the recirculated gases thus pass through the cold EGR passage F and the gases downstream of the cooler 7 are cooled.

FIG. 5 represents a fifth embodiment in which the recirculation circuit B2 is connected to the supercharging circuit B1 as close as possible to the charge-air cooler 4. According to this embodiment, the pressure loss phenomena in the intake circuit are little affected by the addition of the volume of the recirculation circuit B2. An obstruction means 8 may be added in the charge-air cooler 4. The recirculation circuit B2 may comprise an EGR cooler 7 according to the third or fourth embodiment.

According to a variant of the invention not shown, the exhaust gas recirculation system according to embodiment 4 is modified so as to integrate the damper means in the damper housing and place it close to the cooler of the overeating. This further reduces the elements by coupling the obstruction means and means for selecting the temperature and the charge air flow rate in the charge-air cooler.

1) Exhaust gas recirculation circuit (B2) arranged between an exhaust manifold (1) and an intake air distributor (2) of a supercharged engine comprising means for regulating the amount of exhaust gas EG R (6) placed between the exhaust manifold (1) and an EGR cooler (7) characterized in that the circuit (B2) has an obstruction means (8) which can at least partially block the circuit (B2) disposed between an upstream port of the cooler EG R (7) and the air distributor to the inlet (2).

2) exhaust gas recirculation circuit (B2) according to claim 1 characterized in that a conduit (C4) is connected to a supercharging circuit (B1) at a damper housing (5) and in that that the obstruction means (8) is disposed in this housing (5).

3) exhaust gas recirculation circuit (B2) according to claim 2 characterized in that the obstruction means (8) is a flap (Vegr), a joint has a common pivot point with a damper flap ( Vs) and in that their respective displacements are independent.

4) exhaust gas recirculation circuit (B2) according to claim 1 characterized in that the obstruction means (8) is placed in the EGR cooler (7) at its downstream port.

Claims

5) exhaust gas recirculation circuit (B2) according to claim 4 characterized in that the obstruction means (8) is placed in an EG cooler R (7) and comprises at least a first flap (8a) allowing to obstruct the passage EG R hot (C) and a second flap (8b) for obstructing the passage EG R cold (F), relative independent movement and that the first flap (8a) and the second flap ( 8b) are able to pivot about the same axis.

6) exhaust gas recirculation circuit (B2) according to claim 5 characterized in that in a first position, the first flap (8a) obstructs the passage EG R hot (C) and the second flap (8b) obstructs the cold EG R passage (F); in a second position, the first (8a) and second (8b) shutters obstruct the cold EGR passage (F); and in a third position, the first (8a) and second (8b) shutters obstruct the EG R hot passage (C).

7) EGR exhaust gas recirculation circuit (B2) according to claim 4 characterized in that the obstruction means (8) is placed in a U-type EG cooler (7) and comprises a flap (8) Unique to obstruct the hot EGR passage (C) and / or the cold EGR passage (F).

8) EGR exhaust gas recirculation circuit (B2) according to claim 4 characterized in that in a first position, the flap (8) obstructs the downstream port EG cooler R (7); in a second position, the flap (8) is placed in a position such that it does not obstruct any port or passage of the cooler (7); and in a third position, the flap (8) obstructs the EG R hot passage (C).

9) EGR exhaust gas recirculation circuit (B2) according to claim 1, 3, 4, 5 and 6 characterized in that a duct (C4) is connected to a supercharging circuit (B2) at the level of a charge cooler (4).

10) supercharged engine comprising an EGR circuit according to one of the preceding claims.