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 motor vehicle, comprising a voltage control step (E1) of the nitrogen oxide concentration measurement sensor; a voltage gradient control step (E2) and of the oxygen voltage of the catalytic converter; an ammonia detection step (E3); a temperature measurement step (E4) of the catalytic converter by means of temperature determination; an oxygen concentration control step (E5) in the catalytic converter; a nitrogen oxide concentration correction step (E6); a correction factor determination step (E7); and an ammonia concentration correction step (E8). Figure 1

Description

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

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

[0002] Prior art patent application KR20180026112 is known, describing a method for controlling a low-oxygen 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 running; a second step of determining the need to operate in a rich mode, i.e., an increase in the amount of fuel entering the vehicle's internal combustion engine, based on the temperature detected in the first step; and a third step of reading data from a nitrogen oxide sensor when the rich mode is activated in the second step. Subsequently, the change in the nitrogen oxide sensor data value with respect to time is determined. It is verified whether the change in data is positive. In other words, it is verified whether the values ​​increase over time.If this is the case, when the rich mode is deactivated, the data values ​​initially attributed to nitrogen oxides are reassigned as ammonia values. However, a drawback remains. Indeed, parameters specific to the vehicle's exhaust system, such as the amount of oxygen present, are not interpreted, even though this information is fundamental for assigning values ​​to nitrogen oxides or ammonia. For example, in the presence of a large amount of oxygen, ammonia production is minimal or even nonexistent. Thus, there is a high probability that values ​​will be mistakenly attributed to ammonia when they are actually nitrogen oxides. This skews the results.

[0003] The objective of the present invention is to remedy these drawbacks and to allow 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 an oxygen electrode, said exhaust line comprising a sensor for measuring the concentration of nitrogen oxides positioned downstream of the catalytic converter, notable in that said process comprises the following steps: - a step of checking the voltage at the electrode; - a step of controlling a voltage gradient at the electrode; - an ammonia detection step at a predetermined first time 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 of the catalytic converter by means of temperature determination; - a step to control the concentration of dioxygen in the catalytic converter; - a nitrogen oxide concentration correction step during which the nitrogen oxide concentration is considered to decrease 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 according to 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 differentiate precisely 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 oxygen concentration control step, 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 dioxygen, 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 above 800°C.

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

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

[0012] Preferably, said means for determining the temperature 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, lead the latter to implement the steps of the process 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 previously described thermal motor vehicle.

[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 previously described thermal motor vehicle.

[0015] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: [Fig.1] schematically illustrates, in the form of a logic diagram, 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 an embodiment of the invention; [Fig.2] schematically illustrates a plurality of graphs showing the concentration of nitrogen oxides and / or ammonia over time during the various stages of the process.

[0016] A process for distinguishing between nitrogen oxide emissions and ammonia emissions after treatment of the exhaust line of an internal combustion engine of a motor vehicle by a catalytic converter is schematically illustrated in [Fig. 1] in the form of a flowchart. The catalytic converter's role is to carry out a chemical reaction transforming nitrogen oxides into nitrogen and water. The reaction takes place aerobically, that is, in the presence of dioxygen. 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 initial temperature. Thus, nitrogen oxides are transformed into ammonia, into 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 complete conversion of nitrogen oxides and ammonia to nitrogen and water. However, a large portion of the oxygen is consumed in the internal combustion engine. The catalytic converter is therefore susceptible to a partial oxygen deficiency, causing ammonia to accumulate in the exhaust system. Preferably, the catalytic converter is a three-way catalyst. The three-way catalyst operates in three phases to reduce harmful emissions from the exhaust system. The three-way catalyst converts both carbon monoxide and hydrocarbons into carbon dioxide and water vapor. In addition, the catalyst facilitates the conversion of nitrogen oxides into nitrogen and water.This process effectively reduces harmful exhaust emissions that contribute to air pollution. The catalytic converter includes a temperature determination system and an oxygen concentration sensor. The temperature determination system is a temperature sensor or a temperature model. A temperature model is a mathematical representation used to predict or estimate the temperature based on several parameters, such as the composition of the exhaust gases, the temperature of the incoming exhaust gases, or the vehicle speed. The oxygen concentration sensor includes an oxygen electrode. The oxygen electrode is an electrochemical device used to measure the concentration of dissolved oxygen in a fluid, whether liquid or gas.The electrode comprises a cathode that catalyzes the reduction of oxygen to ions at its surface, an anode polarized at a constant potential that serves as an interface for the oxygen dissolved in the fluid being measured, and an electrolyte that enables the transport of ions between the cathode and the anode. The exhaust line includes a nitrogen oxide concentration sensor. This sensor cannot distinguish between nitrogen oxide and ammonia emissions. However, this information is useful for assessing the performance of the catalytic converter. This is because the nitrogen oxide concentration sensor is located downstream of the catalytic converter. Therefore, nitrogen oxide and ammonia emissions are good indicators of the catalytic converter's ability to treat fluid emissions.During a voltage control step E1, the oxygen voltage is measured at the electrode. During a voltage gradient control step E2, the oxygen voltage gradient is measured at the electrode. In electrochemistry, the voltage gradient is the change in electrical potential at the interface between the electrode and the medium in which the electrode is immersed. evolves. During 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 voltage in the catalytic window. Preferably, the first threshold value is 780 mV. When all these conditions are met, ammonia is considered to be emitted at a first predetermined time TL. [Fig.[2], Graph A illustrates the nitrogen oxide (NOx) and ammonia (NH3) concentrations over time t. A peak in NOx concentration is shown, followed by a peak in ammonia (NH3) concentration. Ammonia (NH3) is detected from the first predetermined time TL. During a temperature measurement step E4, the catalytic converter temperature greatly influences the treatment of the vehicle's internal combustion engine emissions. 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 an oxygen concentration control step E5, the oxygen concentration at the catalytic converter is measured.As mentioned previously, a lack of oxygen leads to an incomplete reaction in the transformation of nitrogen oxides into nitrogen and water, resulting in the production of ammonia. Conversely, in the presence of a large amount of oxygen, the reaction is complete. The reaction intermediate, ammonia, is therefore eliminated. Thus, it is preferable to consider the ammonia concentration to be zero when the oxygen concentration is above a fourth threshold value. During a nitrogen oxide concentration correction step E6, the nitrogen oxide concentration is considered to decrease from the first predetermined time T1, that is, from the detection of ammonia during the ammonia detection step E3. Indeed, if ammonia is detected, it means that some of the nitrogen oxides have been transformed into ammonia.Therefore, if the ammonia concentration increases, the concentration of nitrogen oxides, a reactant in the reaction, decreases. This decrease continues until the nitrogen oxide concentration is considered to be zero at a second predetermined time T2. In a step to determine a correction factor E7, the correction factor corresponds to the decrease in nitrogen oxide concentration between the first predetermined time and the second. predetermined time. The correction factor depends on the catalytic converter temperature measured during the temperature measurement step E4. In graph B of [Fig. 2], the correction factor FC is shown between the first predetermined time T1 and the second predetermined time T2. The ammonia concentration NH3 is not shown in graph B for clarity. During 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 starting 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 starting from the first predetermined time TL. The nitrogen oxide concentration NOx is not shown in graph C for clarity. Thus, nitrogen oxide emissions NOx and ammonia emissions NH3 can be studied separately. Graph D in [Fig. 2] shows the ammonia concentration NH3 corrected after the application of the correction factor FC during the ammonia concentration correction step E8.

[0017] Furthermore, the invention relates to a computer program configured to implement the aforementioned method. The invention also relates to a combustion engine motor vehicle configured to implement the aforementioned method.

Claims

Demands

1. A 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 dioxygen concentration comprising a dioxygen electrode, said exhaust line comprising a sensor for measuring the concentration of nitrogen oxides (NOx) positioned downstream of the catalytic converter, characterized in that said method comprises the following steps: - a voltage control step (El) at the electrode; - a voltage gradient control step (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 means of temperature determination; - a step to control the concentration of dioxygen (E5) in the catalytic converter; - a nitrogen oxide concentration correction step (E6) during which the nitrogen oxide (NOX) concentration is considered to decrease 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. A method according to claim 1 characterized in that, during said ammonia detection step (E3), said first threshold value is 780 mV.

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

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

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

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

7. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the process 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. Internal combustion 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 an internal combustion motor vehicle according to any one of claims 1 to 6.

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