Method for estimating the quantity of polluting species in the exhaust gases of an internal combustion engine, equipped with at least one three-way catalyst.

Abstract

A method for estimating the quantity of polluting species in the exhaust gases of a motor vehicle equipped with an internal combustion engine and at least one three-way catalytic converter. The estimation method allows for estimating the quantity of polluting species in the exhaust gases, particularly before any concentration sensor has become sufficiently hot to perform measurements. The method comprises the following steps: a. identifying (1) the chemical reactions in the at least one three-way catalytic converter having the polluting species as reactants or products; b. determining (2) the reaction rates of each identified chemical reaction; c. performing (3) a mass balance in the at least one catalytic converter, considered as an open system, for each polluting species; and d. determining (4) the quantity of polluting species in the exhaust gases based on the mass balance. Figure for abstract: No figure

Claims

Claims

1. Method for estimating the quantity of polluting species in the exhaust gases of a motor vehicle equipped with an internal combustion engine and at least one first three-way catalyst, the estimation method making it possible to estimate the quantity of polluting species in the exhaust gases, in particular before a possible concentration sensor is sufficiently hot to carry out measurements, the method comprising the following steps: a. the chemical reactions involved in the first three-way catalyst having as reactant or product the polluting species whose quantity in the exhaust gases must be estimated are identified, b. the reaction rates of each identified chemical reaction are determined, c. a mass balance is carried out in the first catalyst considered as an open system, for each of the polluting species whose quantity must be determined, and d. the quantity of polluting species in the exhaust gases is determined based on the mass balance.

2. The estimation method of claim 1, wherein the polluting species are nitrogen monoxide and ammonia, the estimation method comprising the following steps: a. the temperature in the first catalyst, the flow rate in the first catalyst, and the torque of the internal combustion engine are determined, b. the molar fraction of nitrogen monoxide in the gases leaving the internal combustion engine is determined by applying an initial map based on the estimated torque of the engine, c. the molar fraction of nitrogen oxides in the gases leaving the first catalyst, located downstream of the internal combustion engine, is determined as a function of the molar fraction of nitrogen monoxide produced by the engine, the flow rate in the first catalyst and the volume of the first catalyst, as well as a second 1D map dependent on the temperature. temperature in the first catalyst and a third 1D map dependent on the flow rate in the first catalyst, d. the molar fraction of ammonia in the gases leaving the first catalyst is also determined, as a function of a fourth 1D map dependent on the temperature in the first catalyst and the molar fraction of nitrogen oxides in the gases emitted by the internal combustion engine.

3. Estimation method according to claim 2, wherein, when the motor vehicle is equipped with a second three-way catalyst upstream of the first three-way catalyst, the method comprises the following steps: a. determining the molar fraction of ammonia in the gases leaving a second catalyst, as a function of a fifth 1D map dependent on the temperature in the second catalyst and as a function of the value of the number of ammonia adsorption sites, b. determining the molar fraction of nitrogen monoxide in the gases leaving the second catalyst as a function of the molar fraction of nitrogen monoxide in the gases leaving the first catalyst, the flow rate in the second catalyst and the volume of the second catalyst, as well as a sixth 1D map dependent on the temperature in the second catalyst and a seventh 1D map dependent on the flow rate in the second catalyst.

4. Estimation method according to claim 2 or 3, in which the maps are calibrated according to measurements made during tests.

5. Estimation method according to claim 1, wherein the pollutant species are carbon dioxide CO2, carbon monoxide CO, hydrocarbons HC, ammonia, nitrogen monoxide NO, nitrogen dioxide NO2 or nitrous oxide N2O.

6. Motor vehicle equipped with an estimation system configured so as to carry out the estimation method according to any one of claims 1 to 5, in particular within an on-board diagnosis.

7. A motor vehicle according to claim 6, further comprising a partial exhaust gas recirculation circuit at the intake.

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