METHOD FOR DISTINGUISHING BETWEEN NITROGEN OXIDE EMISSIONS AND AMMONIA EMISSIONS IN AN EXHAUST LINE OF AN INTERNAL COMBUSTION ENGINE

Abstract

The invention relates to a method for distinguishing between nitrogen oxide emissions and ammonia emissions after treatment by a catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle comprising a step of controlling the voltage (E1) of the sensor for measuring the nitrogen oxide concentration; a step of controlling a voltage gradient (E2) and the oxygen voltage of the catalytic converter; an ammonia detection step (E3); a step of measuring the temperature (E4) of the catalytic converter by the temperature determination means; a step of controlling the oxygen concentration (E5) in the catalytic converter; a step of correcting the nitrogen oxide concentration (E6); a step of determining a correction factor (E7); a step of correcting the ammonia concentration (E8). Figure 1

Description

Title of the invention: METHOD FOR DISTINGUISHING BETWEEN NITROGEN OXIDE EMISSIONS AND EMISSIONS OF AMMONIA IN AN EXHAUST LINE OF AN INTERNAL COMBUSTION ENGINE

[0001] The invention relates to thermal motor vehicles, and more particularly to the treatment of exhaust gases from the internal combustion engines of these vehicles.

[0002] Known from the prior art is a patent application KR20180026112 which describes a method for controlling an oxygen-lean nitrogen oxide trap for a motor vehicle. The method comprises a first step of detecting a temperature upstream of said nitrogen oxide trap when the engine is in operating condition, a second step of determining the need to perform a rich mode, i.e. an increase in the quantity of fuel entering the internal combustion engine of the vehicle, as a function of the temperature detected during the first step, a third step of reading data from a nitrogen oxide sensor when the rich mode is activated during the second step. Subsequently, the variation of the value of the data from the nitrogen oxide sensor with respect to time is determined. It is checked whether the variation of the data is positive. In other words, it is checked whether the values ​​increase as a function of time.If this is the case, when the rich mode is deactivated, the data values ​​initially considered as being values ​​attributed to nitrogen oxides are reassigned as being values ​​attributed to ammonia. However, a disadvantage remains. Indeed, the parameters specific to the vehicle's exhaust line, such as the quantity of oxygen present for example, are not interpreted even though this information is fundamental for assigning the values ​​to nitrogen oxides or ammonia. For example, in the presence of a large quantity of oxygen, the production of ammonia is residual, or even zero. Thus, there is a high probability that values ​​will be mistakenly assigned to ammonia, when they are actually nitrogen oxides. This therefore distorts the results.

[0003] The objective of the present invention is to overcome these drawbacks and to enable the distinction between nitrogen oxide emissions and ammonia emissions in a precise manner.

[0004] To achieve this objective, the invention proposes a method for distinguishing between nitrogen oxide emissions and ammonia emissions after treatment by a catalytic converter of an exhaust line of an internal combustion engine. of a thermal motor vehicle, said catalytic converter comprising a means for determining the temperature and a sensor for measuring the oxygen concentration comprising a oxygen electrode, said exhaust line comprising a sensor for measuring the nitrogen oxide concentration positioned downstream of the catalytic converter, remarkable in that said method comprises the following steps: - a voltage control step at the electrode level; - a step of controlling a voltage gradient at the electrode; - a step of detecting ammonia at a first predetermined time when the voltage of the electrode is greater than a first threshold value or when the voltage of the electrode is greater than a second threshold value and the voltage gradient at the electrode is greater than a third threshold value; - a step of measuring the temperature of the catalytic converter by the temperature determination means; - a step of controlling the oxygen concentration in the catalytic converter; - a step of correcting the nitrogen oxide concentration during which it is considered that the nitrogen oxide concentration decreases from the first predetermined time until the nitrogen oxide concentration is zero at a second predetermined time; - a step of determining a correction factor corresponding to the decrease in the concentration of nitrogen oxides between the first predetermined time and the second predetermined time, the correction factor being determined as a function of the temperature of the catalytic converter; - a step of correcting the ammonia concentration based on the inverse of the correction factor determined during the determination step from the first predetermined time.

[0005] Thanks to the invention, it is possible to precisely differentiate between nitrogen oxide emissions and ammonia emissions.

[0006] Advantageously, during said ammonia detection step, said first threshold value is 780 mV.

[0007] Advantageously, during said step of controlling the oxygen concentration, the ammonia concentration is considered to be zero when the oxygen concentration is greater than a fourth threshold value.

[0008] In the presence of a large quantity of oxygen, the production of ammonia is residual, or even zero.

[0009] Advantageously, during the temperature measurement step, the ammonia concentration is considered to be zero when the temperature is greater than 800°C.

[0010] When the temperature of the catalytic converter is higher than 800°C, the production of ammonia is residual, or even zero.

[0011] Preferably, said catalytic converter is a three-way catalyst.

[0012] Preferably, said temperature determining means is a temperature measuring sensor or a temperature model.

[0013] The invention also relates to a computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of the method for distinguishing between nitrogen oxide emissions and ammonia emissions after treatment by a gasoline catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle described above.

[0014] Furthermore, the invention relates to a thermal motor vehicle comprising an electronic control unit configured to implement said method of distinguishing between nitrogen oxide emissions and ammonia emissions after treatment by a gasoline catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle previously described.

[0015] The invention will be further detailed by the description of non-limiting embodiments, and on the basis of the appended figures illustrating variants of the invention, in which: [Fig.l] schematically illustrates, in the form of a flowchart, a method for distinguishing between nitrogen oxide emissions and ammonia emissions after treatment by a catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle according to one embodiment of the invention; [Fig.2] schematically illustrates a plurality of graphs illustrating the concentration of nitrogen oxides and / or ammonia over time during the various stages of the process.

[0016] [Fig.l] is schematically illustrated in the form of a flowchart, a method for distinguishing between nitrogen oxide emissions and ammonia emissions after treatment by a catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle. The role of the catalytic converter is to implement a chemical reaction transforming the nitrogen oxides into nitrogen and water. The reaction takes place aerobically, that is to say in the presence of oxygen. A reaction intermediate of the reaction described above is ammonia. The catalytic converter therefore produces a quantity of ammonia depending on the composition of the exhaust gases and the first temperature. Thus, the nitrogen oxides are transformed into ammonia, nitrogen and water. The presence of ammonia is temporary because, when the reaction is carried out in an oxygen-rich environment, the reaction continues until the nitrogen oxides and ammonia are completely converted into nitrogen and water. However, a large portion of the oxygen is consumed in the internal combustion engine. The catalytic converter is therefore likely to have a partial oxygen deficiency causing ammonia to accumulate in the exhaust line. Preferably, the catalytic converter is a three-way catalyst. The three-way catalyst works in three phases to reduce harmful exhaust emissions. The three-way catalyst converts both carbon monoxide and hydrocarbons into carbon dioxide and water vapor. In addition, the catalyst causes the conversion of nitrogen oxides into nitrogen and water.This process effectively reduces harmful exhaust gas emissions that contribute to air pollution. The catalytic converter includes a temperature determination means and a sensor for measuring the oxygen concentration. The temperature determination means is a temperature measurement sensor or a temperature model. A temperature model is a mathematical representation that is used to predict or estimate the temperature based on several parameters, such as the composition of the exhaust gas, the temperature of the incoming exhaust gas, or the vehicle speed. The oxygen concentration measurement sensor includes a oxygen electrode. The oxygen electrode is an electrochemical device for measuring the concentration of oxygen dissolved in a fluid, whether liquid or gas.The electrode comprises a cathode that catalyzes the reduction of oxygen into ions on the surface of the electrode, an anode polarized at a constant potential that is an interface for the oxygen dissolved in the fluid to be measured and an electrolyte that allows the transport of ions between the cathode and the anode. The exhaust line comprises a sensor for measuring the concentration of nitrogen oxides. The sensor for measuring the concentration of nitrogen oxides does not make it possible to distinguish between nitrogen oxide emissions and ammonia emissions. However, this information is interesting for knowing the performance of the catalytic converter. Indeed, said sensor for measuring the concentration of nitrogen oxides is positioned downstream of the catalytic converter. Therefore, the emissions of nitrogen oxides and ammonia are good indicators of the capacity of said catalytic converter to treat fluid emissions.During a voltage control step E1, the oxygen voltage is measured at said electrode. During a voltage gradient control step E2, the oxygen voltage gradient is measured at the electrode. In electrochemistry, the voltage gradient is the variation of the electrical voltage at the interface between said electrode and the medium in which the electrode. evolves. In an ammonia detection step E3, ammonia is considered to be emitted when the oxygen voltage at the electrode measured during the voltage control step E1 is greater than a first threshold value or when the electrode voltage is greater than a second threshold value and the oxygen voltage gradient at the electrode measured during the voltage gradient control step E2 is greater than a third threshold value. The chemical reaction is favored in a specific voltage range called the catalytic window. The first threshold value corresponds to a voltage greater than a catalytic window voltage. Preferably, the first threshold value is 780 mV. When all of these conditions are met, ammonia is considered to be emitted at a first predetermined time TL In [Fig.2], graph A illustrates the concentration of nitrogen oxides NOX and the concentration of ammonia NH3 over time t. A peak in the concentration of nitrogen oxides NOX is illustrated, followed by a peak in the concentration of ammonia NH3. Ammonia NH3 is detected from the first predetermined time TL. During a temperature measurement step E4, the temperature of the catalytic converter greatly influences the treatment of gaseous emissions from the internal combustion engine of the vehicle. Preferably, above 800°C, the ammonia concentration is considered to be zero. Emissions detected when the temperature is above 800°C are therefore attributed to nitrogen oxide emissions. During a dioxygen concentration control step E5, the dioxygen concentration at the catalytic converter is measured.As mentioned previously, the lack of oxygen induces an incomplete reaction of the transformation of nitrogen oxides into nitrogen and water, resulting in the production of ammonia. Conversely, in the presence of a large quantity of oxygen, the reaction is complete. The reaction intermediate, i.e. ammonia, is therefore eliminated. Thus, preferably, the ammonia concentration is considered to be zero when the oxygen concentration is greater than a fourth threshold value. During a step of correction of the nitrogen oxide concentration E6, the nitrogen oxide concentration is considered to decrease from the first predetermined time T1, i.e. from the detection of ammonia during the ammonia detection step E3. Indeed, if ammonia is detected, this means that a portion of the nitrogen oxides is transformed into ammonia.Therefore, if the ammonia concentration increases, then the concentration of nitrogen oxides, the reactant of the reaction, decreases. The decrease progresses until the concentration of nitrogen oxides is considered to be zero, at a second predetermined time T2. During a step of determining a correction factor E7, the correction factor corresponds to the decrease in the concentration of nitrogen oxides between the first predetermined time and the second. predetermined time. The correction factor is dependent on the catalytic converter temperature measured during the temperature measurement step E4. In graph B of [Fig.2], the correction factor FC is illustrated between the first predetermined time T1 and the second predetermined time T2. The ammonia concentration NH3 is not shown in graph B for clarity. In an ammonia concentration correction step E8, the ammonia concentration NH3 is corrected by applying the inverse of the correction factor previously determined in the correction factor determination step E7. The ammonia concentration correction NH3 is implemented from the first predetermined time TL In [Fig.2], graph C illustrates the implementation of the ammonia concentration correction step E8.The correction factor FC shown in graph C is the inverse of the correction factor FC shown in graph B. The correction factor FC is applied from the first predetermined time TL. The concentration of nitrogen oxides NOX is not shown in graph C for clarity. Thus, the emissions of nitrogen oxides NOX and the emissions of ammonia NH3 can be studied separately. In graph D of [Fig.2], the corrected ammonia NH3 concentration is shown after applying the correction factor FC during the ammonia concentration correction step E8.

[0017] Furthermore, the invention relates to a computer program configured to implement said previously described method. The invention also relates to a thermal motor vehicle configured to implement said previously described method.

Claims

Claims

1. Method for distinguishing between nitrogen oxide (NOX) emissions and ammonia (NH3) emissions after treatment by a catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle, said catalytic converter comprising a means for determining the temperature and a sensor for measuring the oxygen concentration comprising a oxygen electrode, said exhaust line comprising a sensor for measuring the nitrogen oxide (NOX) concentration positioned downstream of the catalytic converter, characterized in that said method comprises the following steps: - a step of controlling the voltage (El) at the electrode; - a step of controlling a voltage gradient (E2) at the electrode; - an ammonia detection step (E3) at a first predetermined time (Tl) when the electrode voltage is greater than a first threshold value or when the electrode voltage is greater than a second threshold value and the voltage gradient at the electrode is greater than a third threshold value; - a step of measuring the temperature (E4) of the catalytic converter by the temperature determination means; - a step of controlling the oxygen concentration (E5) in the catalytic converter; - a step of correcting the nitrogen oxide concentration (E6) during which it is considered that the nitrogen oxide (NOX) concentration decreases from the first predetermined time (T1) until the nitrogen oxide (NOX) concentration is zero at a second predetermined time (T2); - a step of determining a correction factor (E7) corresponding to the decrease in the concentration of nitrogen oxides (NOX) between the first predetermined time (T1) and the second predetermined time (T2), the correction factor (FC) being determined as a function of the temperature of the catalytic converter; - a step of correcting the ammonia concentration (E8) as a function of the inverse of the correction factor (FC) determined during the determination step from the first predetermined time (Tl).

2. Method according to claim 1 characterized in that, during said ammonia detection step (E3), said first threshold value is 780 mV.

3. Method according to claim 1 or 2 characterized in that, during said step of controlling the dioxygen concentration (E5), the ammonia concentration (NH3) is considered to be zero when the dioxygen concentration is greater than a fourth threshold value.

4. Method according to any one of claims 1 to 3 characterized in that, during the temperature measurement step (E4), the ammonia (NH3) concentration is considered to be zero when the temperature is greater than 800°C.

5. Method according to any one of claims 1 to 4 characterized in that said catalytic converter is a three-way catalyst.

6. Method according to any one of claims 1 to 5 characterized in that said temperature determining means is a temperature measuring sensor or a temperature model.

7. Computer program comprising instructions which, when the program is executed by a computer, cause the latter to implement the steps of the method for distinguishing between nitrogen oxide (NOX) emissions and ammonia (NH3) emissions after treatment by a gasoline catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle according to any one of claims 1 to 6.

8. Thermal motor vehicle comprising an electronic control unit configured to implement said method of distinguishing between nitrogen oxide (NOX) emissions and ammonia (NH3) emissions after treatment by a gasoline catalytic converter of an exhaust line of an internal combustion engine of a thermal motor vehicle according to any one of claims 1 to 6.

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