FR3087834A1 - INJECTOR FOR INJECTING A GAS REDUCING AGENT INTO AN EXHAUST GAS STREAM OF AN INTERNAL COMBUSTION ENGINE - Google Patents

Abstract

The injector (32) includes an injection nozzle (34), a metering system (36) for supplying a metered flow of the reducing agent to the injection nozzle, and an injection line (38) connecting the metering system (36) to the injection nozzle (34). The injector (32) comprises heating means arranged to heat at least part of the injector (32).

Description

The present invention relates to an injector for injecting a gaseous reducing agent into the exhaust gas stream of an internal combustion engine.

The invention further relates to an exhaust pipe for an internal combustion engine comprising an injector, and a motor vehicle comprising such an exhaust pipe.

The reducing agent comprises, for example, ammonia, a mixture of air and ammonia, or a mixture of ammonia and neutral gas such as helium.

Automotive internal combustion engines are known to produce oxides of nitrogen also referred to as "NOx".

These can be a significant source of air pollution since they contribute to the formation of fog and acid ads, and affect ground-level ozone. It is therefore desirable to remove NOx from the gas. exhaust 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 carry out this process is to inject 'into the exhaust line a liquid urea agent which will be mixed with the exhaust gas and subjected to thermal hydrolysis to turn into ammonia. , before the mixture of exhaust gas and ammonia passes through an SCR catalyst in which the ammonia reduces NOx to nitrogen.

However, it has been discovered that it is much more efficient to inject ammonia directly into the exhaust pipe, upstream of the RGS catalyst, rather than the aforementioned liquid urea-based agent.

In this way, the aforementioned first step is eliminated.

This observation has led to the development of injectors of the aforementioned type, which are known for example from document FR 2 994 455.

These injectors are commonly used as a replacement for liquid urea agent injectors.

However, these known injectors are not entirely satisfactory.

Indeed, it has been discovered that at the start of the injection of ammonia, ammoniacal salts can interfere with the correct operation of the injector.

For example, the injection nozzles of these injectors are usually clogged with ammonia salts, so ammonia cannot be injected into the mixture. It takes several hours before the injection nozzle is unclogged and the 'injector can work.

During this time, the exhaust gas cannot be decontaminated.

2 An objective of the invention is therefore to prevent the formation of salts formed by the reaction between the reducing agent and water and / or carbon dioxide, or to unclog the injector quickly when necessary and therefore to reduce the time before an injector of the aforementioned type is effective after starting the engine.

To this end, the invention relates to an injector for injecting a reducing agent into an exhaust gas flow of an internal combustion engine, the injector comprising an injection nozzle, a metering system for providing a metered flow reducing agent to the injection nozzle, and an injection line connecting the metering system to the injection nozzle, characterized in that the injector comprises heating means for heating at least part of the 'injector.

In this specification, the term "heating means" refers to any means promoting heating.

Such heating means can be active or passive.

More particularly, the active heating means emit heat and the passive heating means are intended to prevent heat loss.

The salts formed by the reaction between the reducing agent, water and carbon dioxide are created under cold conditions and they disappear under hot conditions.

Thus, the heating means are intended to accelerate the decomposition of ammoniacal salts, Sou prevent or reduce the creation of ammoniacal salts.

An injector according to the invention can include any of the following features, alone or in any possible combination. - The heating means comprise a heat exchanger arranged around the injection pipe, the heat exchanger comprising a thermal fluid circulating in a thermal circuit arranged to take calories from a heating source, the heating source being for example a second heat exchanger taking heat from the engine or from an exhaust gas. - The heating means comprise a heating element, for example an electric heating element, more particularly a heating resistor, arranged near the injection pipe, preferably near the injection nozzle. - The heating means comprise a heating element arranged inside the injection pipe, for example of a heating wire, and / or a heating element arranged inside the injection nozzle. - The heating means comprise a heating element arranged around the injection pipe, for example a heating wire wound around at least part of the injection pipe. 3 - The heating means comprise an insulating sleeve surrounding at least part of the injection pipe. - The heating means comprise a heat shield arranged near the injection pipe, preferably with an air gap between the exhaust pipe 5 and your injection pipe. - The heating means comprise a thickened nozzle, said thickened nozzle comprising an internal part extending inside the flow of exhaust gas and an external part extending outside the flow of exhaust gas, the internal part and / or the external part having a thickness greater than 2 mm. 10 - The injection pipe is made of a first material and the thickened nozzle is made of a second material, the thermal conductivity of the second material being greater than the thermal conductivity of the first material. - The heating means comprise a chemical heating element, arranged in the injection pipe or around the injection pipe. 15 - The injection pipe comprises a long portion, shaped to extend into a hot zone inside the exhaust pipe or outside the exhaust pipe. - The injection pipe comprises a non-return capet preventing backflow from the exhaust pipe to the injection pipe, the heating means 20 comprising a heating element arranged in the non-return valve.

The invention also relates to an exhaust pipe for an internal combustion engine comprising a mixer configured to be traversed by a flow of exhaust gas produced by the internal combustion engine and the injector described above for injecting the agent. reducing agent in said gas flow. exhaust.

The invention further relates to a motor vehicle comprising the exhaust pipe.

Other characteristics and advantages of the invention will become apparent from a detailed description which is provided below by way of indication and in no case of limitation, with reference to the appended figures, in which: Figure I is a general diagram of an exhaust pipe according to the invention, - Figure 2 is a sectional view of a section of the exhaust pipe of Figure I, according to a first embodiment of the invention, Figure 3 is a sectional view of a section of the exhaust duct 35 of Figure 1, according to a second embodiment of the invention, Figure 4 is a sectional view of a section of the exhaust pipe ia Figure 1, according to a third embodiment of the invention, Figure 5 is a sectional view of a section of the exhaust pipe of Figure 1, according to a fourth embodiment embodiment of the invention, FIG. 6 is a sectional view of a section of the exhaust duct of the invention. Figure 1, according to a fifth embodiment of the invention, - Figure 7 is a sectional view of a section of the exhaust pipe of Figure 1, according to a sixth embodiment of the invention, Figure 8 is a sectional view of a section of the exhaust pipe 10 of the figure. 1, according to a seventh embodiment of the invention, - Figures 9 and 10 are sectional views of a section of the exhaust pipe of Figure '1, according to two variants of a ninth embodiment of the invention, [a FIG. 11 is a sectional view of a section of the exhaust pipe 15 of FIG. 1, according to a tenth embodiment of the invention.

The exhaust pipe 10 shown in Figure 1 forms part of the internal combustion engine 12, for example, of a motor vehicle.

This exhaust line 10 carries a flow of exhaust gas generated by the engine 12 through various upstream exhaust components 14 to reduce remission and control noise from a gasket. known.

The various upstream exhaust components 14 may include one or more of the SuiYaAts elements: pipes, filters, valves, catalysts, mufflers etc.

In the exemplary configuration, the exhaust line 10 comprises a diesel oxidation catalyst (COD) 16 having an inlet 18 and an outlet 20 positioned downstream of the upstream exhaust pipes 14, so that these components upstream exhaust 14 direct the engine exhaust gases into COD 16.

In the example shown, the exhaust pipe 10 further comprises a diesel particulate filter (FPD) 21 positioned downstream of the COD 16.

This FPD is able to remove contaminants from the exhaust gas in a known manner.

The exhaust line 10 also includes a selective catalytic reduction (SCR) catalyst 22 having an inlet 24 and an outlet 26, and upstream exhaust components 28 positioned downstream of the RCS catalyst 22.

This RCS 22 catalyst is here positioned downstream of the COD 16 and the optional FPD 21.

The SCR catalyst 22 may optionally include a catalyst which is configured to perform a selective catalytic reduction function and a particulate filter function.

The various downstream exhaust components 28 include, for example, one or more of the following pipes, filters, valves, catalysts, mufflers, etc.

The upstream 14 and downstream 28 components can be mounted in various configurations and combinations depending on the vehicle application and the available packaging space.

The exhaust pipe 10 further comprises, upstream of the inlet 24 of the RCS catalyst 22, a mixer 30 configured to be traversed by the flow of exhaust gas before it enters the RCS catalyst 72.

This mixer 30 is here positioned downstream of the outlet 20 of the COD 16 and of the FEI) 21 as an option.

The mixer 30 is preferably configured to generate a swirling or rotary motion of the exhaust gas stream.

Alternatively, the mixer 30 consists of a single pipe.

The exhaust line 10 also includes an injector 32 for injecting a reducing agent into the flow of exhaust gas in the mixer 30 so that the mixer 30 can thoroughly mix the reducing agent and the exhaust gas.

The reducing agent comprises, for example, a mixture of air and ammonia, or a mixture of ammonia and neutral gas such as helium.

The injector 32 includes an injection nozzle 34 positioned inside the mixer 20 30 to direct the reducing agent injected into the mixer 30 to mix it with the engine exhaust gas, a metering system 36 to provide a flow. dosed of reducing agent to the injection nozzle 34, and an injection line 38 connecting the dosing system 34 to the injection nozzle 32.

The metering system 36 includes a source of reducing agent 40, a metering valve 42 for metering the amount of reducing agent supplied to the injection nozzle 34, and a control unit 44 for controlling the metering valve 32. so as to control the dosage of the reducing agent in a known manner. The source of reducing agent 40 here consists of a source of ammonia.

This source usually includes a reservoir (not shown) in which ammonia gas is stored under pressure.

Alternatively, the source comprises salts of urea or strontium chloride (SrCl2) intended to be heated to generate ammonia.

In order to accelerate the decomposition of ammoniacal salts, Wou to prevent or reduce the creation of ammoniacal salts, the injector 32 comprises heating means.

This is because ammoniacal salts are created under cold conditions and are broken down under hot conditions.

Thus, the heating means are intended to heat the injection line 38 so that the ammoniacal salts are decomposed as soon as possible when the engine 12 is used. As specified above, the term "Heating means" denotes any 5 what means favoring heating.

Such heating means can be active or passive. More particularly, active heating means emit heat and passive heating means are intended to prevent heat loss.

We will now describe certain examples of heating means with reference to FIGS. 2 to 10. It should be noted that these heating means are only examples and that it may therefore be possible to consider other heating means.

Furthermore, the heating means described below are not mutually exclusive.

Thus, any combination of several heating means can be considered.

A first example of heating means is shown in FIG. 2, In the first embodiment, the heating means comprise a first heat exchanger 46 arranged around the injection pipe 38.

Such a first heat exchanger 46 is an active heating means.

The first heat exchanger 46 comprises a thermal fluid 48 circulating in a thermal circuit 50 arranged to take calories from a heating source 52, via a second heat exchanger 54, The heat source 52 is a very hot element of the heat exchanger. vehicle, for example, the engine 12 or the exhaust pipe in which an exhaust gas circulates.

Indeed, the exhaust gas can reach a very high temperature (more than 25 350 ^ C) in a short time. Thus, in this first example, the heating means heat the injection pipe 38, and the salts ammonia which are in this injection line 38, in a short time after switching on the engine 12.

It should be noted that the first heat exchanger 46 can surround the whole of the injection line 38, from the metering unit 36 to the injection nozzle 34, thus, i | can decompose ammonia salts anywhere in this injection line 38.

On the other hand, this embodiment has the advantage that the heat is taken from the nearby very hot environment, thus, there is no need at all for another power consuming device.

The thermal fluid 48 can be any thermal fluid, for example, a gas or a liquid.

7 As a variant, the thermal fluid is an engine coolant also used to cool the engine 12.

This can be an advantage since the engine cooling system has a regulated temperature around 80 ° C.

A second example of heating means is shown in figure 3.

In this second embodiment, the heating means comprise a heating element 56, for example an electric heating element, more particularly a heating resistor, arranged near the injection pipe 38, preferably near the injection nozzle. i4.

Alternatively, the heating element 56 is arranged inside the injection line 38, preferably inside the injection nozzle 34.

Such a heating element 56 is an active heating means.

Such a heating element 56 allows local heating of the injection line 38, outside the exhaust line where an obstruction 58 is likely to be present.

It should be noted that the heating means can comprise a plurality of these heating elements 56 arranged along the injection line 38.

Such a heating element 56 allows rapid and efficient localized heating, which could accelerate the decomposition of the salt.

In the case of an electric heater 56, this electric heater 56 can be activated only when necessary.

The electric heating element 56 is powered by a battery, for example, a vehicle battery, via a power cable 60.

Alternatively, the electric heater 56 may be powered by an electric power source independent of the vehicle battery, so that it can be activated even when the vehicle is turned off.

For example, the electric heater 56 is energized by a controller which includes a thermometer and which is configured to activate the electric heater 56 when the temperature in the injection line 38 is below a predefined threshold. .

This is to prevent the formation of ammonia salt since the injection line 38 is never in the cold condition.

Alternatively, the controller is time programmable, and can be configured to activate heater 56 at a predetermined time.

This allows the decomposition of ammonia salts shortly before use of the vehicle. Alternatively, the controller can be manually activated, so that the user activates the heating element 56 when necessary.

8 It should be noted that such a heating element 56 can be temperature regulated, so that it heats only to a necessary temperature.

A third example of heating means is shown in Figure 4.

In this third embodiment, the heating means 62 are arranged inside the injection line 38.

For example, the heating element 62 is a heating wire.

Such a heating element 62 is an active heating means.

Such a heating wire 62 can extend throughout the injection line 38, from the metering unit 36 to the injection nozzle 34.

Such a heating element 62 provides rapid and efficient localized heating, which could accelerate the decomposition of the salt or prevent its formation.

In the case of an electric heating element 62, this electric heating element 62 can be activated only when necessary.

The electric heating element 62 is powered by a battery, for example, a vehicle battery.

Alternatively, the electric heater 62 may be powered by an electric power source independent of the vehicle battery, so that it can be activated even when the vehicle is turned off.

For example, the electric heater 62 is energized by a controller which includes a thermometer and which is configured to activate the electric heater 62 when the temperature in the injection line 38 is below a threshold. predefined.

This makes it possible to prevent the formation of ammonia salt since the injection line 38 is never in the cold condition.

Alternatively, the controller is time programmable, and can be configured to activate heater 62 at a predetermined time.

This allows the decomposition of ammonia salts shortly before the use of the vehicle.

Alternatively, the controller can be manually activated, so that the user activates the heating element 62 when necessary.

It should also be noted that such a heating element 62 can be temperature regulated, so that it heats only to a necessary temperature.

A fourth example of heating means is shown in Figure 5.

This fourth embodiment is similar to the third embodiment, except that a heating means 64 is arranged outside the injection pipe 38, for example, the heating means 64 is wound around this pipe 35. injection 38.

For example, in this embodiment, the heating means 64 is a wire, a heating hose or a heating sleeve.

The operation of the device according to the fourth embodiment is similar to the operation of the device according to the third embodiment and therefore will not be described again.

A fifth example of heating means is shown in Figure 6.

In this fifth embodiment, the heating means comprise an insulating sleeve 66 surrounding at least a part of the injection pipe 38, Such an insulating sleeve 66 is a passive heating means, it allows the injection pipe 10 38 to xnserver thermal energy for a longer period, and also allows the injection line 38 to heat up more quickly when it is in operation, It should be noted that the injection line 38 is for example heated by the exhaust pipe 52.

More particularly, the heat spreads by conduction from the exhaust pipe 30 into the injection pipe 38.

As a variant, the injection line 38 is heated by any other heating means.

Since the thermal energy is retained in the injection line 38, the formation of ammoniacal salts is slower when the engine 12 is not running.

On the other hand, since the injection line 38 is heated more quickly when the engine 12 is running, any ammoniacal salts are broken down more quickly.

The insulation sleeve 66 may be made of any suitable material such as a fiberglass mat.

A sixth example of heating means is shown in Figure 7, In this sixth embodiment, the heating means comprises a heat shield 68 arranged near the injection line 38, preferably with an air gap 70. between the heat shield 68 and the injection line 38.

The heat shield 68 (with the air gap 70) is arranged around the nozzle 34 e. At least a part of the injection line 38, to conserve thermal energy, promote heating and prevent cooling from external convection while driving.

The objective is to limit the effect of cooling convection around the injection pipe 38 linked to the movement of the vehicle.

This will help to conserve heat from the start of the driving phase where salt 58 is present in the injection line 38, in order to decompose it and allow the injection of NH3. presence between the exhaust pipe 30 and the injection pipe 38 of an air gap protected from the cooling convection during driving, aids the exchange of heat by convection and radiation from the exhaust pipe 30 towards the injection line 38.

In a seventh embodiment, shown in Fig. 8, the heating means comprises a thickened nozzle 34.

The thickened nozzle 34 includes an inner portion 34a extending inside the exhaust gas stream and an outer portion 34b extending outside the exhaust gas stream.

Preferably, the length of the outer part 34b is between 2 cm and 10 cm, for example, 5 cm.

The internal part 34a and / or the external part 34b have a thickness greater than 2 mm.

For example, the thickness is less than 10mm, preferably the thickness is between 2mm and 8mm, more preferably between 4mm and 6mm.

The thickness of the outer part 34b and the thickness of the inner part 34a may be different.

Advantageously, the injection pipe 38 is made of a first material, and the injection nozzle 34 is made of a second material.

Preferably, the thermal conductivity of the second material is greater than the thermal conductivity of the first material.

Through. example, the second material is steel.

Thus, the thickened nozzle 34 allows good heat conduction from the exhaust line 30 to the injection line 38, in order to quickly heat the parts when salts are formed in order to decompose them and ensure the availability of 25. injection of reducing agent.

In addition, when the engine is stopped, the thickened nozzle 34 remains very hot and therefore delays the formation of potential salts in this nozzle 34.

In an eighth embodiment, the heating means comprise a chemical heating element, arranged in the injection pipe 38 or around the injection pipe 38.

The chemical heating element comprises a substance which, when activated, produces an exothermic phenomenon.

For example, the chemical heating element is of the crystallization type, the same technology as a reusable hand heater.

After activation, the chemical heating element is reactivated by ambient heat, by conduction and / or invexion from the exhaust gas.

The next time the engine is started, the heating element can therefore be activated and release heat.

A ninth example of the heating means is shown in Figures 9 and 10.

In the ninth embodiment, the injection pipe 38 comprises a long portion 72, shaped to be placed in a hot zone 74 near the exhaust pipe 30.

This long portion 72 can be arranged outside the exhaust pipe 30 (Figure 9) or as a variant, inside the exhaust pipe 30 (Figure 109).

The length of the long portion 72 is preferably between 10cm and 2m, more preferably between 30cm and 2m.

For example, to increase the length of the portion 72 in the hot zone 74, the portion 72 is wrapped around the exhaust pipe 30.

The hot zone 74 is preferably the hottest zone near the exhaust duct 30.

Alternatively, the entire area near the exhaust duct 15 may be considered a hot area.

By "near" is meant that the distance between the portion 72 and the exhaust pipe 30 is less than 10 cm.

The use of a long portion 72 in the hot zone 74 makes it possible to keep the residual gases in this portion 72 hot.

This also makes it possible to reduce the 2D quantity of Ca, and of F-120 in the cold zone (limitation of reflux).

Thus, the formation of ammoniacal salts is reduced.

This long portion 72 forms a passive heating means.

A tenth example of heating means is shown in Figure 11.

In this tenth embodiment, the injection line 38 comprises a non-return valve 76 preventing backflow from the exhaust line 30 towards the injection line 38.

Preferably, the heating means comprise a heating element 78 arranged in the non-return valve 76.

The use of a heated check valve 76 allows the heating of the shingles around the valve 76 for the injection of ammonia, and prevents backflow of the exhaust gas into the injection line.

Thus, thanks to the heated valve, i-. there will be no obstruction of ammoniacal salts in the non-return valve 76 and upstream thereof.

It should be noted that other means of heating can be considered.

Furthermore, any combination of heating means, as described above, or not described,

Claims (14)

CLAIMS 1. Injector (32) for injecting a reducing agent into a gas stream. exhaust of an internal combustion engine (12), the injector (32) comprising an injection nozzle (34), a metering system (36) for supplying a metered flow of the reducing agent to the nozzle injection, and an injection line (38) connecting the metering system (36) to the injection nozzle (34), characterized in that the injector (32) comprises heating means arranged to heat at the minus part of the injector (32). 10 2. Injector (32) according to claim 1, wherein the heating means comprise a heat exchanger (46) arranged around the injection pipe (38), the heat exchanger comprising a thermal fluid (48) circulating. in a thermal circuit (50) arranged to take calories from a heating source (54), the heating source (54) being for example a second heat exchanger taking heat from the engine (12) or from a exhaust gas. 3. injector (32) according to claim 1 or 2, wherein the heating means comprise a heating element (56), for example an electric heating element, more particularly a heating resistor, arranged near the injection pipe (38 ), preferably near the injection nozzle (34). 4. Injector (32) according to any one of the preceding claims, wherein the heating means comprise a heating element (62) arranged inside the injection pipe, for example a heating wire, and / or a heating element (62) arranged inside the injection nozzle (34). 5. An injector (32) according to any preceding claim, wherein the heating means comprises a heating element (64) arranged around the injection pipe (38), for example, a heating wire wound around it. at least part of the injection line (35). 6. An injector (32) according to any preceding claim, wherein the heating means comprise an insulating sleeve (66) surrounding at least a part of the injection pipe (38). 7. An injector (32) according to any preceding claim, wherein the heating means comprises a heat shield (68) arranged near the injection line (38), preferably with an air gap. (70) between the exhaust pipe (30) and the injection pipe (38). 8. An injector (32) according to any preceding claim, wherein the heating means comprises a thickened nozzle (34), said thickened nozzle comprising an internal portion (34a) extending inside the gas stream. exhaust and an outer part (34b) extending outside the exhaust gas stream, the inner part and the outer part having a thickness greater than 2 mm. 9. An injector according to claim 8, wherein the injection pipe (38) is made of a first material and the thickened nozzle (34) is made of a second material, the thermal conductivity of the second material being greater than the thermal conductivity of the first material. 10. An injector (32) according to any preceding claim, wherein the heating means comprise a chemical heater, arranged in the injection line or around the injection line. 11. An injector (32) according to any one of the preceding claims, wherein the injection line (38) comprises a long portion (72), shaped to extend into a hot zone (74) within. the exhaust line (30) or outside the exhaust line (30). 12. An injector according to any preceding claim, wherein the injection line (38) comprises a non-return valve (76) preventing backflow from the exhaust line (30) to the exhaust line (30). injection (36), the heating means oemprenant a heating element (78) arranged in the non-return valve (76). 13. Exhaust pipe for an internal combustion engine (12) comprising a mixer configured to be traversed by a flow of exhaust gas produced by the internal combustion engine and the injector (32) according to any one of the following. preceding claims for injecting the reducing agent into said gas stream (the exhaust. 14. A motor vehicle, comprising the exhaust line according to claim 13.