FR3102684A1 - Exhaust gas purification device, exhaust line and associated vehicle - Google Patents

Abstract

Exhaust gas purification device, associated exhaust line and vehicle This exhaust gas purification device (16) comprises: - a duct (18), defining a passage (26) for the circulation of gas. exhaust; and - an injector (20) for injecting a reducing agent, the injector (20) extending into the circulation passage (26) and comprising: - an injection nozzle (28) comprising at least one injection orifice (42) gaseous reducing agent; and - a plurality of deflection pairs (32), each deflection pair (32) being formed of two deflectors (44) each extending radially between the injection nozzle (28) and a radial end (46) and having each a radial height (H). The deflectors (44) of each deflection pair (32) have a radial height (H) different from that of the deflectors of the deflection pairs (32) which are adjacent to it. Figure for abstract: figure 1

Description

Exhaust gas purification device, associated exhaust line and vehicle

The present invention relates to an exhaust gas purification device, comprising:

- a duct, extending along a central axis, defining a passage for the circulation of exhaust gases from an internal combustion engine; And

- an injector for injecting a reducing agent into the exhaust gas stream, the injector extending into the exhaust gas circulation passage and comprising:

- a nozzle for injecting the gaseous reducing agent, extending along the central axis longitudinally in the flow of exhaust gas, between an upstream end and a downstream end, the injection nozzle comprising at least one orifice injection of the gaseous reducing agent, provided between the upstream end and the downstream end; And

- a plurality of deflection pairs, each deflection pair being formed of two deflectors each extending radially between the injection nozzle and a radial end and each having a radial height defined by the radial distance between the injection nozzle and its radial end, the two deflectors of each deflection pair being symmetrical with respect to the central axis.

Exhaust gas purification devices are mainly used in vehicles comprising internal combustion engines, such as, for example, motor vehicles.

Automotive internal combustion engines are known to produce nitrogen oxides also referred to as "NOx". These can be a significant source of air pollution as they contribute to the formation of acid fog and rain, and affect ground-level ozone. It is therefore desirable to eliminate the NOx contained in the exhaust gas from these engines.

To this end, a process known as "selective catalytic reduction" (SCR) has been developed, in which ammonia is used to reduce NOx to harmless nitrogen. The most common way to implement this process is to inject a liquid urea-based agent into the exhaust pipe which will be mixed with the exhaust gas and subjected to thermal hydrolysis to transform into ammonia, before that the mixture of exhaust gas and ammonia passes through an SCR catalyst in which the ammonia reduces the NOx to nitrogen.

In order to optimize the mixing of the ammonia with the exhaust gases, it is known to use deflectors arranged in the flow of exhaust gases upstream of the injection nozzles. Such deflectors ensure in particular a turbulent flow of exhaust gases close to the injection orifices of the gaseous reducing agent, improving the mixing of the gaseous reducing agent with the exhaust gases.

A purification device using such deflectors does not, however, give complete satisfaction. Indeed, the reducing agent is not optimally mixed with the exhaust gases, which reduces the purification performance of the device, and the deflectors generate a significant pressure drop.

An object of the invention is therefore to provide an exhaust gas purification device whose exhaust gas purification performance is improved and generates a reduced pressure drop.

To this end, the subject of the invention is an exhaust gas purification device comprising:

- a duct, extending along a central axis, defining a passage for the circulation of exhaust gases from an internal combustion engine; And

- an injector for injecting a reducing agent into the exhaust gas stream, the injector extending into the exhaust gas circulation passage and comprising:

- a nozzle for injecting the gaseous reducing agent, extending along the central axis longitudinally in the flow of exhaust gas, between an upstream end and a downstream end, the injection nozzle comprising at least one orifice injection of the gaseous reducing agent, provided between the upstream end and the downstream end; And

- a plurality of deflection pairs, each deflection pair being formed of two deflectors each extending radially between the injection nozzle and a radial end and each having a radial height defined by the radial distance between the injection nozzle and its radial end, the two deflectors of each deflection pair being symmetrical with respect to the central axis; characterized in that the deflectors of each deflection pair have a different radial height from that of the deflectors of the deflection pairs adjacent to it.

The deflection couples of the aforementioned purification device are particularly advantageous since they ensure a turbulent flow at the level of the injection orifices, improving the mixing between reducing agent and exhaust gas, and thus making it possible to obtain a purification device of exhaust gases whose performance is improved. The deflection torques as described above also make it possible to ensure a high level of turbulence at the level of the injection ports while maximizing the exhaust gas passage section, thus limiting pressure drops. The deflection couples also make it possible to protect the introduction of the reducer into the duct by allowing it to occupy a larger section and then facilitating its mixing.

According to particular embodiments of the invention, the purification device comprises one or more of the following characteristics, taken in isolation or in any technically possible combination:

- the deflectors are attached to the injection nozzle between the upstream end and the at least one injection port;

- each deflector extends substantially along a plane normal to the central axis;

- each injection orifice extends over a peripheral face of the injection nozzle, the normal of each injection orifice extending radially with respect to the central axis;

- each deflector has a symmetrical shape with respect to a median radial plane, each injection orifice is arranged opposite a deflector, the normal of each orifice extending substantially in the median radial plane of the corresponding deflector;

- the injector comprises a connector connected to the upstream end of the injection nozzle, the connector being intended to be fluidically connected to a reservoir of reducing agent;

- the injector comprises two long deflection pairs and two short deflection pairs, the deflectors of the long deflection pairs having a first radial height, and the deflectors of the short deflection pairs having a second radial height less than the first radial height;

- each deflector is in one piece and comprises a base connected to the injection nozzle, the width of the deflector, considered perpendicular to the median radial plane, decreasing from the base of the deflector towards the radial end of the deflector, this radial end preferably being cutting edge ;

- each deflector comprises a support rod and a deflection plate, the support rod radially connecting the deflection plate to the injection nozzle;

- the device comprises a mixer fixed to the injection nozzle between the at least one injection orifice and the downstream end, the mixer comprising a casing defining a passage for mixing exhaust gases, the mixer comprising a plurality vanes connecting the casing to the injection nozzle, the set of vanes being adapted to generate a swirl of exhaust gases around the central axis.

The invention further relates to an exhaust line comprising an exhaust gas purification device as defined above.

The invention also relates to a vehicle comprising an exhaust line as defined previously.

Other characteristics and advantages of the invention will appear on reading the following description, given solely by way of example and made with reference to the appended drawings, in which:

FIG. 1 is a schematic profile representation of a vehicle comprising an exhaust line according to the invention;

FIG. 2 is a schematic profile representation of an injector of the exhaust line shown in FIG. 1;

FIG. 3 is a representation similar to FIG. 2, in which the injector comprises a mixer;

FIG. 4 is a schematic front view of an injector according to a first embodiment of the invention;

FIG. 5 is a schematic front view of an injector according to a second embodiment of the invention; And

FIG. 6 is a schematic front view of a mixer of a purification device according to the invention.

In the rest of the description, the terms upstream and downstream are defined according to a direction of flow of a fluid from a source, an upstream point being closer to the source of the flow than a downstream point.

There is shown in Figure 1 a vehicle 10 comprising an exhaust line 12. The exhaust line 12 is for example adapted to treat the exhaust gases of an internal combustion engine 14, for example a diesel engine .

The exhaust line 12 is for example a vehicle exhaust line 10, and in particular of a motor vehicle such as a car, a bus or a truck. As a variant, the exhaust line 12 is an exhaust line of a fixed installation.

The exhaust line 12 comprises a device 16 for purifying exhaust gases.

The exhaust gas purification device 16 is adapted to treat the exhaust gases from the internal combustion engine 14 and for example adapted to eliminate the NOx contained in the exhaust gases from the engine 14.

The exhaust gas purification device 16 is advantageously placed upstream of an SCR catalyst.

The exhaust gas purification device 16 comprises a conduit 18 and an injector 20.

The duct 18 extends along a central axis A-A'. Duct 18 has an inlet end 22, corresponding to an upstream end of duct 18, and an exhaust end 24 corresponding to a downstream end of the duct. Conduit 18 is preferably cylindrical.

The conduit 18 defines an exhaust gas circulation passage 26 extending between the intake end 22 and the exhaust end 24. The circulation passage 26 is configured to ensure the circulation of exhaust gases from inlet end 22 of conduit 18 to exhaust end 24 of conduit 18.

The injector 20 is adapted to inject a reducing agent into the exhaust gas stream. The injector 20 is preferably adapted to inject ammonia to reduce the NOx contained in the flow of exhaust gases into harmless nitrogen.

The gaseous reducing agent is represented schematically by a set of clouds 27 in Figures 2 to 5.

The injector 20 extends into the exhaust gas circulation passage 26.

As illustrated in Figure 2, the injector 20 comprises an injection nozzle 28, a connector 30 and a plurality of deflection pairs 32. The injector 20 preferably comprises, as shown in Figure 3, a mixer 34.

The connector 30 preferably extends from the conduit 18 towards the central axis A-A'. The connector 30 extends for example radially with respect to the central axis A-A' in the conduit 18.

The connector 30 is for example fluidically connected on the one hand to a reservoir of reducing agent (not shown) and on the other hand to the injection nozzle 28. The connector 30 is preferably adapted to supply the injection nozzle 28 in reducing agent.

The injection nozzle 28 extends along the central axis A-A', longitudinally in the flow of exhaust gas between an upstream end 36 and a downstream end 38. The injection nozzle comprises a peripheral face 40 connecting upstream end 36 to downstream end 38.

Injection nozzle 28 is preferably connected to fitting 30 at upstream end 36.

The injection nozzle 28 is preferably closed off at the downstream end 38.

The injection nozzle 28 comprises at least one orifice 42 for injecting the gaseous reducing agent. In the variants shown in Figures 1 to 5, the injection nozzle comprises a plurality of injection orifices 42.

Injection nozzle 28 fluidly connects fitting 30 to each injection port 42.

The injection nozzle 28 is for example substantially in the shape of a cylindrical tube.

Each injection orifice 42 is for example formed between the upstream end 36 and the downstream end 38. Each injection orifice 42 preferably extends over the peripheral face 40 of the injection nozzle.

The normal of each injection orifice 42 preferably extends radially with respect to the central axis A-A'.

The angle formed by the normals of two adjacent injection orifices 42 is for example substantially equal for any pair of adjacent orifices 42 of the set of orifices 42.

All the injection orifices 42 extend for example at the same distance from the downstream end 38.

The purification device 16 comprises at least two deflection pairs 32 and, in the variant illustrated in FIG. 4, the purification device 16 comprises four deflection pairs 32.

Each deflection pair 32 is formed by two deflectors 44. In particular, each deflection pair 32 is formed by two deflectors 44 arranged symmetrically with respect to the central axis A-A'.

Each deflector 44 comprises a radial end 46 and extends radially between the injection nozzle 28 and this radial end 46. Each deflector 44 has a radial height H defined by the radial distance between the injection nozzle 28 and the end radial 46 of said deflector 44.

Each deflector 44 is attached to the injection nozzle 28 between the upstream end 36 and the at least one injection port 42 in the direction of the axis A-A'. Each deflector 44 is for example welded to the injection nozzle 28.

Each deflector 44 preferably extends substantially along a plane normal to the central axis A-A'.

Each deflector 44 has a symmetrical shape with respect to a median radial plane, the central axis A-A' being included in said median radial plane. In the embodiment of FIG. 4, each deflector 44 is placed upstream of an injection orifice 42, so that each injection orifice 42 is arranged facing a deflector 44. Thus, in the direction of the axis A-A', the normal of each injection orifice 42 extends substantially in the median radial plane of the deflector 44 corresponding thereto.

In the variant shown in Figure 4, each deflector 44 is in one piece and comprises a base 48 connected to the injection nozzle 28. The width L of each deflector 44, considered in the median radial plane and perpendicular to a radial axis, is decreasing from the base 48 of the deflector 44 towards the radial end 46 of the deflector 44. The radial end 46 of each deflector 44 is preferably pointed. Each deflector 44 preferably has a substantially triangular shape, the base 48 of each deflector 44 marrying the peripheral face 40 of the injection nozzle 28. As illustrated in FIGS. 2 and 3, the thickness E of each deflector 44, taken according to the direction defined by the central axis A-A', is preferably decreasing from the base 48 of the deflector 44 towards the radial end 46 of the deflector 44.

Each deflection pair 32 extends in the same radial direction as that of the deflectors 44 of which it is formed. The angle formed between the radial direction of two adjacent deflection pairs 32 is for example substantially equal for all the adjacent deflection pairs 32. In the example presented in FIG. 4, the angle formed between the radial direction of two adjacent deflection pairs 32 is substantially equal to 45°.

Each deflection pair 32 includes deflectors 44 having a radial height H different from that of the deflectors 44 of the deflection pairs 32 which are adjacent to it.

The injector 44 preferably comprises two long deflection pairs 50 and two short deflection pairs 52 arranged alternately around the central axis A-A'. The deflectors 44 of the long deflection pairs 50 have a first radial height H1 and the deflectors of the short deflection pairs 52 have a second radial height H2 . The second radial height H2 of the short deflection pairs 52 is lower than the first radial height H1 of the long deflection pairs 50.

As illustrated in Figure 3, the mixer 34 is attached to the injection nozzle 28 between the at least one injection port 42 and the downstream end 38, in the direction of the central axis A-A'.

Mixer 34 includes a plurality of vanes 54 and a housing 56.

The plurality of blades 54 is fixed to the injection nozzle 28. In particular, the mixer 34 comprises between 6 and 10 vanes.

Each vane 54 extends radially around the injection nozzle 28, between this injection nozzle and the casing 56. The vanes 54 of the mixer 34 are preferably distributed at regular intervals around the central axis A-A' .

Each vane 54 is for example fixed on the injection nozzle 28 so that the mean angle of attack of each vane with respect to the flow of exhaust gases is between 0° and 60°.

The set of vanes 54 is adapted to generate a swirl of exhaust gases around the central axis A-A'.

The casing 56 extends in the direction of the central axis A-A'. The housing 56 defines an exhaust gas mixing passage 58. The 56 casing is for example of tubular shape defined around the central axis A-A'.

The operation of an exhaust gas purification device 16 will now be described.

Connection 30 supplies injection nozzle 28 with reducing agent. The connector is for example connected to a reservoir of reducing agent (not shown) located away from the conduit 18. The injection nozzle 28 guides the reducing agent to the injection ports 42, the reducing agent being injected into the circulation passage 26 of exhaust gases and therefore into the exhaust gases, via the injection ports 42.

The exhaust gases flow in the conduit 18 from the intake end 22 towards the exhaust end 24. The exhaust gases are deflected by each of the deflectors 44 upstream of the injection ports 42. In particular, the exhaust gases are deflected away from the injection ports 42 by the deflectors 44. The exhaust gases are more strongly deflected by the long deflection couples 50 than by the short deflection couples 52.

As the exhaust gases are deflected away from the injection ports 42, the reducing agent is injected into a region sheltered from the flow of exhaust gases by the deflectors. The reducing agent is then dispersed further radially than in the absence of deflectors 44.

Following the dispersion of the reducing agent in the exhaust gases, the mixture is mixed by the mixer 34, ensuring a good homogenization of the mixture between the exhaust gases and the reducing agent when it reaches the exhaust end 24.

The use of a set of deflection pairs 32 having different radial heights is particularly advantageous since it makes it possible to ensure better dispersion of the reducing agent while limiting pressure drops. Indeed, such deflection couples 32 make it possible to ensure a high level of turbulence at the level of the injection orifices 42 while maximizing the exhaust gas passage section, thus limiting pressure drops.

Fixing the deflectors 44 upstream of the injection orifices ensures better dispersion of the reducing agent in the passage 26.

The orientation of the deflectors 44 perpendicular to the central axis A-A' makes it possible to increase the turbulence generated by the deflectors 44.

The orientation of the injection ports 42 on the injection nozzle 28 ensures radial dispersion of the reducing agent which improves the mixing between the reducing agent and the exhaust gases, thus improving the efficiency of the device 16 exhaust gas purification.

The use of a deflector 44 upstream of each injection orifice 42 is particularly advantageous for improving the dispersion of the reducing agent.

The connector 30 connected to the upstream end 36 of the injection nozzle 28 ensures a good flow of the reducing agent in the injection nozzle 28.

The use of long deflection pairs 50 and short deflection pairs 52 ensures a highly turbulent flow, improving the performance of the purification device 16, while leaving a high passage section for the exhaust gases 24, in particular limiting the losses dump.

The deflectors 44, the width of which decreases from their base 48 towards their radial end 46, ensure good dispersion of the reducing agent while improving the robustness of the purification device 16.

The mixer 34 located downstream of the injection ports 42 improves the mixing between the exhaust gases and the reducing agent, thus improving the performance of the device 16 for purifying exhaust gases.

In Figure 5 is shown an alternative embodiment of the device 16 for purifying exhaust gases. This embodiment differs from the embodiment shown in Figure 4 only in the following. Similar elements bear the same references.

The deflectors 44 are not one-piece but each deflector 44 comprises a retaining rod 60 and a deflection plate 62.

The retaining rod 60 radially connects the deflection plate 62 to the injection nozzle 28.

The deflection plate 62, carried away from the injection nozzle 28 is for example substantially trapezoidal.

Such deflectors 44 are particularly advantageous in that their geometry, or in other words the position of the deflection plates 62 in the circulation passage 26, can be optimized to improve the performance of the purification device 16.

Claims (12)

Device (16) for purifying exhaust gases, comprising:
- a duct (18), extending along a central axis (A-A'), defining a passage (26) for the circulation of exhaust gases from an internal combustion engine (14); And
- an injector (20) for injecting a reducing agent into the exhaust gas stream, the injector (20) extending into the exhaust gas flow passage (26) and comprising:

• an injection nozzle (28) for the gaseous reducing agent, extending along the central axis (A-A') longitudinally in the flow of exhaust gas, between an upstream end (36) and a downstream end (38), the injection nozzle (28) comprising at least one injection orifice (42) of the gaseous reducing agent, arranged between the upstream end (36) and the downstream end (38); And
• a plurality of deflection pairs (32), each deflection pair (32) being formed of two deflectors (44) each extending radially between the injection nozzle (28) and a radial end (46) and each having a radial height ( H ) defined by the radial distance between the injection nozzle (28) and its radial end (46), the two deflectors (46) of each deflection couple (32) being symmetrical with respect to the central axis (A-A');

characterized in that the deflectors (44) of each deflection pair (32) have a radial height (H) different from that of the deflectors of the deflection pairs (32) which are adjacent to it. A purification device (16) according to claim 1, wherein the baffles (44) are attached to the injection nozzle (28) between the upstream end (36) and the at least one injection port (42) . A purification device (16) according to claim 1 or 2, wherein each baffle (44) extends substantially along a plane normal to the central axis (A-A'). A purification device (16) according to any preceding claim, wherein each injection orifice (42) extends over a peripheral face (40) of the injection nozzle (28), a normal of each orifice injection nozzle (42) extending radially with respect to the central axis (A-A'). Purification device (16) according to claim 4, in which each deflector (44) has a symmetrical shape with respect to a median radial plane, each injection orifice (42) is arranged facing a deflector (44), the normal of each orifice (42) extending substantially in the median radial plane of the corresponding deflector (44). A purification device (16) according to any preceding claim, wherein the injector (20) includes a fitting (30) connected to the upstream end (36) of the injection nozzle (28), the fitting (30) being intended to be fluidly connected to a reservoir of reducing agent. Purification device (16) according to any one of the preceding claims, in which the injector (20) comprises two long deflection pairs (50) and two short deflection pairs (52), the deflectors (44) of the pairs of long deflection (50) having a first radial height ( H1 ), and the deflectors of the short deflection pairs (52) having a second radial height ( H2 ) less than the first radial height ( H1 ). A purification device (16) according to any one of claims 1 to 7, wherein each deflector (44) is integral and includes a base (48) connected to the injection nozzle (28), the width of the deflector (44 ), considered perpendicular to the median radial plane, decreasing from the base (48) of the deflector (44) towards the radial end (46) of the deflector (44), this radial end (46) preferably being pointed. A purification device (16) according to any one of claims 1 to 7, wherein each deflector (44) comprises a retaining rod (60) and a deflector plate (62), the retaining rod (60) connecting radially the deflection plate (62) to the injection nozzle (28). A purification device (16) according to any preceding claim, wherein the device (16) comprises a mixer (34) attached to the injection nozzle (28) between the at least one injection port (42 ) and the downstream end (38), the mixer (34) comprising a housing (58) defining an exhaust gas mixing passage (58), the mixer (34) comprising a plurality of vanes (54) connecting the casing (56) to the injection nozzle (28), the set of vanes (54) being adapted to generate a swirl of exhaust gases around the central axis (A-A'). Exhaust line (12), comprising an exhaust gas purification device (16) according to any one of the preceding claims. Vehicle comprising an exhaust line (12) according to claim 11.