BE1028445A1 - Device and method for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle - Google Patents

Abstract

The invention relates to a process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle (1) and a device capable of implementing said process. According to the invention, such said method (1) comprises: • a step of determining a pressure, P1, in a burnt gas exhaust system upstream of at least one turbo (10); • a step of determining a pressure, P2, in a line for injecting a reducing agent (11); • a step of controlling a means of pressurizing the injection line when the pressure difference, P2 – P1, is less than a first reference value (12); • a step of injecting the reducing agent upstream of the at least one turbo in a burnt gas exhaust system by opening and closing a first injector, said injection step being carried out when the pressure difference, P2 – P1, is greater than or equal to a second reference value (13).

Description

Device and process for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle The invention relates to the field of motor vehicles with internal combustion heat engines such as cars for example The invention relates more particularly a process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle and a device implementing said process.

The invention is intended to be used in particular in the field of the injection of a reducing agent, such as urea, into the exhaust system of a turbocharged internal combustion heat engine on board a motor vehicle . In the case of the injection of a reducing agent, this reducing agent mixes with the exhaust gases and makes it possible to reduce the emissions of pollutants called NO.

Various techniques have already been proposed for reducing the emissions of polluting elements released into the atmosphere with the exhaust gases of motor vehicles equipped with an internal combustion heat engine. This is particularly the case for emissions of nitrogen oxides NOx which are treated by catalytic reduction. One technique for this is to mix a reducing agent, such as gaseous ammonia, with the exhaust gases and pass the mixture through or over a catalyst placed in the exhaust system. This technique is known by the abbreviation RCS (for Selective Catalytic Reduction) or the English abbreviation SCR (for Selective Catalytic Reduction). It is therefore necessary to have in the exhaust system a gaseous ammonia injector and a catalyst. The catalyst may have been deposited, for example by impregnation, on the walls of the channels of a ceramic block composed of a multitude of channels substantially parallel to the direction of flow of the exhaust gases. The reducing agent converts nitrogen oxides into nitrogen and water.

When the reducing agent is ammonia NH: the reaction is as follows: 4 NO+4 NH3 +02 — 4 N2+ 6H20 (D According to another form of implementation of this technique, an aqueous solution of urea (and therefore a liquid), which is transformed into ammonia under the effect of the heat of the exhaust gases.

The aqueous urea solution is injected into the exhaust line at a relatively high pressure (approximately 5 bars) and, the solution being an incompressible liquid, the flow rate of the aqueous urea solution injected is relatively insensitive to fluctuations. exhaust gas pressure.

In other words, the flow rate of the injected aqueous urea solution is practically independent of the pressure prevailing in the exhaust line.

A problem linked to these processes for treating the nitrogen oxides present in the exhaust gases of an internal combustion heat engine on board a motor vehicle is linked to the temperature that the selective catalytic reduction catalyst must reach. in order to catalyze the reduction reaction of NO(I) efficiently.

It is generally considered that said temperature should ideally be around 250° C., in this case we speak of standard SCR conditions.

At lower temperatures, of at least 160°C, preferably at least 180°C, a reduction of nitrogen oxides can also be carried out according to the reaction (ID), we will then speak of fast SCR 4 NH3 + 2 NO +2 NO2 —>> 4N2+6H0 (ID) In all cases, it is therefore observed that it is essential to reach a certain temperature in order to be able to carry out the reduction of nitrogen oxides.

The aim of the invention is in particular to overcome these drawbacks of the prior art.

More specifically, one objective of the invention, in at least one of its embodiments, is to implement a method for treating the exhaust gases of a turbocharged internal combustion heat engine on board a motor vehicle with optimized performance.

Another object of the invention, in at least one of its embodiments, is to provide a device for treating the exhaust gases of a turbocharged internal combustion heat engine on board a motor vehicle.

The invention, in at least one of its embodiments, also aims to provide a motor vehicle comprising a device for treating the burnt gases of a turbocharged internal combustion heat engine according to the invention.

In accordance with a particular embodiment, the invention relates to a process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle. According to the invention, such a process comprises: e a step of determination of a pressure, Pi, in a burnt gas exhaust system upstream of at least one turbo; e a step for determining a pressure, P2, in a line for injecting a reducing agent; e a step of controlling a means of pressurizing the injection line when the pressure difference, Pa — P1, is less than a first reference value;

e a step of injecting the reducing agent upstream of the at least one turbo in a burnt gas exhaust system by opening and closing a first injector, said injection step being carried out when the pressure difference, P2 — P1, is greater than or equal to a second reference value; The general principle of the invention is based on the injection of a reducing agent upstream of at least one turbo in a burnt gas exhaust system of a turbocharged internal combustion heat engine.

Thus, the invention is based on an entirely new and inventive approach for injecting a reducing agent upstream of at least one turbo of a reducing agent into a burnt gas exhaust system of a heat engine. turbocharged internal combustion. This injection makes it possible to carry out a treatment of the burnt gases at a higher temperature compared to an injection carried out downstream of at least one turbo. In order to obtain good treatment of the burnt gases, this injection via the first injector must be carried out with a pressure differential between the exhaust system and the injection line sufficient to obtain an optimum droplet size. This size is linked to the characteristics of the first injector.

The first reference value is approximately at least equal to or greater than 5 bars, more preferably is approximately less than or equal to 8 bars, more preferably approximately less than or equal to 7 bars. The second reference value is approximately at least equal to or greater than 5 bars, more preferably is approximately less than or equal to 8 bars, more preferably approximately less than or equal to 7 bars. Such values of first and second reference value make it possible to obtain at any time a sufficient pressure differential to obtain a good nebulization of the reducing agent in the exhaust system upstream of the at least one turbo but also to avoid a deposit on the walls of the exhaust system when the pressure differential is too high. The injection carried out with a high pressure differential leads to the projection of the droplets formed by nebulization on the walls of the exhaust system and the formation of deposits.

By the expressions "approximately at least equal to or greater than", "approximately less than or equal to"; is meant to denote the fact that a tolerance is applied to this pressure value, said tolerance being of the order of 0.5 bar.

The pressure values are relative values expressed with respect to atmospheric pressure. Atmospheric pressure can be measured using a third sensor located outside the exhaust system or located in the exhaust pipe. In the case of a third pressure sensor located in the exhaust pipe, the measured value can be corrected by calculation using vehicle data.

Advantageously, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle according to the invention is such that it comprises a pressure reduction step in the injection line when the difference pressure, P»-P1, is greater than the second reference value. Said second reference value is approximately less than or equal to 8 bars, more preferably approximately less than or equal to 7 bars.

Thus, such a step of pressure reduction in the injection line of the reducing agent makes it possible to guarantee the preservation of a good quality of nebulization of the reducing agent.

According to a preferred embodiment or in accordance with the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the step of injecting the reducing agent upstream of the turbo is carried out when the pressure difference, Pa — P1, is equal to a third reference value,

preferably when 80% of the pressure difference, 0.8 (P2 — P1, is equal to the third reference value.

Said third reference value being between 5 and 7 bars expressed as a relative pressure value.

Thus, a stage of injection of the reducing agent carried out with this difference makes it possible to guarantee a good quality of nebulization of the optimum reducing agent.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the step of determining the pressure, Pa, in the injection line of a reducing agent is carried out by measuring said pressure, Pa, by a first pressure sensor.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the step of determining the pressure, P1, in the exhaust system the flue gases upstream of the turbo is carried out by measuring the pressure by a second pressure sensor or is calculated on the basis of the exhaust gas temperature, the intake temperature and the pressure intake into the cylinder.

Preferably, the step of determining the pressure, P1, in the burnt gas exhaust system upstream of the turbo is carried out by measuring the pressure by a second pressure sensor.

The use of a second pressure sensor provides a more precise pressure value than that obtained by calculation.

More preferably, the second pressure sensor is located on the first injector.

Such an arrangement makes it possible to obtain a more precise pressure value and thus ensure better control of the nebulization.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the reducing agent is ammonia or a precursor of ammonia such as urea, preferentially the reducing agent is ammonia.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the means for pressurizing the line of injection is a gear pump.

The use of a gear pump allows better regulation of the pressure in the injection line.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the first reference value is greater than or equal to 5 bars , preferably greater than or equal to 6 bars.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that the second reference value is greater than or equal to 5 bars , preferably greater than or equal to 6 bars.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that it comprises a step of injecting reducing agent upstream of the turbo in the burnt gas exhaust system by opening and closing an injector, said injection step being carried out when the pressure difference, P2 — P1, is greater than or equal to a fourth value of reference, said fourth value being less than said second reference value.

Preferably, the fourth reference value is approximately equal to 3 bars.

Thus an injection step carried out when the pressure difference, Pa—P1, is greater than or equal to a fourth reference value, said fourth value being less than said second reference value makes it possible to take account of a possible change in the point of engine operation.

By the term "engine operating point" is meant the engine rotational speed and the engine load.

Thus, such an injection step makes it possible to optimize the injection of reducing agent into the burnt gas exhaust system and to prevent the formation of deposits on the walls of the exhaust system.

An engine with a lower operating point results in a lower burnt gas exhaust velocity.

It is therefore advantageous to inject the reducing agent with a lower pressure differential.

According to an advantageous implementation or variant of the invention, the process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle is such that it comprises a step of injecting reducing agent downstream of the turbo into the burnt gas exhaust system by opening and closing a second injector.

Thus, such a step of injection downstream of the turbo into the burnt gas exhaust system by opening and closing a second injector makes it possible to optimize the injection of reducing agent into the burnt gas exhaust system.

The invention also relates to a device for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle capable of implementing the method for treating the burnt gases of a turbocharged heat engine according to the invention. , said processing device comprising:

e a reducing agent reservoir connected to at least one first injector via an injection line, said at least one first injector of the injection line being located upstream of at least one turbo in the exhaust system of the burnt gases, e a first pressure sensor capable of measuring the pressure in the injection line e a gear pump fluidly connected to the injection line, said pump being capable of injecting the reducing agent contained in the reservoir into the injection line, and a second pressure sensor located in the burnt gas exhaust system upstream of the at least one turbo, preferably said second sensor is located on the head of the at least one first injector, said second sensor being capable of measuring the pressure in the burnt gas exhaust system, e a first control unit controlling the starting or stopping of the gear pump as well as its speed as a function of the pressures measured by the first and the second c pressure fitter.

Finally, the invention also relates to a motor vehicle comprising a device for treating the burnt gases of a turbocharged heat engine according to the invention.

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a preferred embodiment, given by way of a simple illustrative and non-limiting example, and the appended drawings, among which:

° Figure 1 presents a block diagram of a mode of implementation of a process for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle according to the invention.

° Figure 2 illustrates an embodiment of a device for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle according to the invention.

In relation to FIG. 1, a mode of implementation of a process for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle (1) according to the invention is presented. Said process for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle (1) comprises: e a step of determining a pressure, P1, in a burnt gas exhaust system in upstream of at least one turbo (10); e a step of determining a pressure, P2, in a line for injecting a reducing agent (11); e a step of controlling a means of pressurizing the injection line when the pressure difference, P2 — P1, is less than a first reference value (12); e a step of injecting the reducing agent upstream of the at least one turbo in a burnt gas exhaust system by opening and closing a first injector, said injection step being carried out when the pressure difference, P2 — Pi, is greater than or equal to a second reference value (13).

The first reference value is approximately at least equal to or greater than 5 bars, more preferably is approximately less than or equal to 8 bars, more preferably approximately less than or equal to 7 bars. The second reference value is approximately at least equal to or greater than 5 bars, more preferably is approximately less than or equal to 8 bars, more preferably approximately less than or equal to 7 bars. Such values of first and second reference value make it possible to obtain at any time a sufficient pressure differential to obtain a good nebulization of the reducing agent in the exhaust system upstream of the at least one turbo but also to avoid a deposit on the walls of the exhaust system when the pressure differential is too high. The injection carried out with a high pressure differential leads to the projection of the droplets formed by nebulization on the walls of the exhaust system and the formation of deposits.

FIG. 2 illustrates an embodiment of a device for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle according to the invention. The device for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle (2) comprises: e a reducing agent tank (20) connected to at least one first injector (21) via a injection line (22), said at least one first injector (21) of the injection line (22) being located upstream of the turbo (30) in the burnt gas exhaust system (3), and a first pressure sensor capable of measuring the pressure in the injection line (22), and a gear pump fluidly connected to the injection line (22), said pump being capable of injecting the reducing agent contained in the reservoir (20) in the injection line (22), the gear pump located in a module (23) and a second pressure sensor located in the burnt gas exhaust system (3) upstream of the at least one turbo (30), preferably said second sensor is located on the head of the at least one first injector (21), said second sensor r being able to measure the pressure in the burnt gas exhaust system (3), e a first control unit (24) controlling the starting or stopping of the gear pump as well as its speed as a function of the measured pressures by the first and the second pressure sensor. Preferably, the first control unit (24) records the system data including in particular the pressures measured by the first and the second pressure sensor and controls a second control unit (25) which controls the gear pump. This arrangement makes it possible to optimize the control of the various components present in the module (23) such as the gear pump or the drivers (26). The first control unit (24) can also be connected to a NOXx/NHz sensor (28) fixed at the outlet or close to the outlet of the exhaust system (3).

e The injection line (22) may also include a second injector (27) located downstream of the at least one turbo (30).

e The exhaust system (3) comprises a so-called SCRF unit (31) located upstream of the at least one turbo (30) and an SCR UF unit (32) coupled with an ASC unit (33). Said unit

SCRF (31) is located between the at least one turbo (30) and the at least one first injector, said SCR units UF (32) and ASC (33) being located downstream of the second injector (27). The SCRF unit (31) incorporates Selective Catalytic Reduction (SCR) with a soot filter.

The SCR UF and ASC units are respectively a selective catalytic reduction of NO unit, and a unit containing an ammonia slip catalyst.

Claims (15)

1. Method for treating the burnt gases from a turbocharged internal combustion heat engine on board a motor vehicle (1), said method (1) comprising: e a step of determining a pressure, P1, in a system exhaust of burnt gases upstream of at least one turbo (10); e a step of determining a pressure, P2, in a line for injecting a reducing agent (11); e a step of controlling a means for pressurizing the injection line when the pressure difference, Pa — P1, is less than a first reference value (12); e a step of injecting the reducing agent upstream of the at least one turbo in a burnt gas exhaust system by opening and closing a first injector, said injection step being carried out when the pressure difference, P2 — P1, is greater than or equal to a second reference value (13). 2. Method (1) according to claim 1, such that it comprises a pressure reduction step in the injection line when the pressure difference, P2-P1, is greater than the second reference value. 3. Method (1) according to any one of the preceding claims, such as the step of injecting the reducing agent upstream of the turbo into a burnt gas exhaust system (13), said step being carried out when the difference of pressure, P2—P1, is equal to a third reference value, preferably when 80% of the pressure difference, 0.8 (P2—P1), is equal to the third reference value. 4. Method (1) according to claim 1, such that the step of determining the pressure, P2, in the injection line of a reducing agent (11) is carried out by measuring said pressure, Pz, by a first pressure sensor. 5. Method according to any one of the preceding claims 1, such that the step of determining the pressure, Pi, in the burnt gas exhaust system upstream of the turbo (10) is carried out by measuring the pressure by a second pressure sensor or is calculated on the basis of the exhaust gas temperature, the intake temperature and the intake pressure in the cylinder. 6. Method (1) according to claim 5, such that the step of determining the pressure, P1, in the burnt gas exhaust system upstream of the turbo (10) is carried out by measuring the pressure by a second Pressure sensor. 7. Method according to claim 6, such that the second pressure sensor is located on the first injector. 8. Method according to any one of the preceding claims, such that the reducing agent is ammonia or a precursor of ammonia such as urea, preferably the reducing agent is ammonia. 9. Method according to any one of the preceding claims, such that the pressurizing means of the injection line is a gear pump. 10. - Method according to any one of the preceding claims, such that the first reference value is greater than or equal to 5 bar, preferably greater than or equal to 6 bar. 11. …— Method according to any one of the preceding claims, such that the second reference value is greater than or equal to 5 bars, preferably greater than or equal to 6 bar. 12. Method according to any one of the preceding claims, such that it comprises a step of injecting the reducing agent upstream of the turbo into the burnt gas exhaust system by opening and closing a \1njector, said step injection being performed when the pressure difference, P2 — Pi, is greater than or equal to a fourth reference value, said fourth value being less than said second reference value. 13. — Method according to any one of the preceding claims, such that it comprises a step of injecting the reducing agent downstream of the turbo into the burnt gas exhaust system by opening and closing a second injector. 14. — Device for treating the burnt gases of a turbocharged internal combustion heat engine on board a motor vehicle (2) capable of implementing the process for treating the burnt gases of a turbocharged heat engine (1) according to any one of claims 1 to 12, said treatment device comprising: e a reservoir of reducing agent (20) connected to at least one first injector (21) via an injection line (22), said at least one first injector (21) of the injection line (22) being located upstream of at least one turbo (30) in the burnt gas exhaust system (3), e a first pressure sensor capable of measuring the pressure in the injection line, e a gear pump fluidly connected to the injection line, said pump being capable of injecting the reducing agent contained in the reservoir into the injection line, e a second pressure sensor located in the burnt gas exhaust system upstream of the at least one turbo (30), preferably said second sensor is located on the head of the at least one first injector, e a first control unit (23) controlling the starting or stopping of the gear pump as well as its speed according to the pressures measured by the first and second pressure sensor. 15. — Motor vehicle comprising a device for treating the burnt gases of a turbocharged heat engine according to claim 16.