Method and device for estimating a nitrogen oxide mass stored in a catalytic trapping device of a motor vehicle

3:

• The method according to claim 2, wherein the mass of nitrogen oxide instantaneously adsorbed (dNS_i/dt) by the catalytic trapping device of each individual reactor i (i=1 to n) is calculated using the following relationship:
• ⅆ
• NS_i
• ⅆ
• t
• =
• NOx_i
• *
• Eff_i
• in which:
• NOx_i:
• mass flow of nitrogen oxides at the inlet of the individual reactor i, in g/s, NOx—1 calculated;
• Eff_i:
• instantaneous storage efficiency in the individual reactor i, a predetermined function of NS_i/NSC_i and of T_i, obtained by looping the calculation of NS_i/NSC_i;
• NS_i:
• nitrogen oxide mass present in the reactor i, in g;
• NSC_i:
• maximum nitrogen oxide mass being able to be stored by the reactor i, in g;
• T_i:
• temperature of the catalytic phase at the inlet of the individual reactor i, calculated by the thermal model, in K.

4:

• The method according to the claim 3, wherein the nitrogen oxide mass (NS_i) present in the individual reactor i is calculated using the following relationship:
• NS_i
• =
• ∫
• t
• 0
• t
• ⁢
• (
• ⅆ
• NS_i
• ⅆ
• t
• )
• ⁢
• ⁢
• ⅆ
• t
• +
• NS_i
• ⁢
• (
• t
• 0
• )
• in which:
• interval t0 to t:
• interval of time between the end (t0) of the last of regeneration phase of the catalytic trapping device and the present time (t), in s;
• and
• NS_i:
• nitrogen oxide mass present in the reactor i, in g.
• NS_i (t0):
• estimated nitrogen oxide mass present in the reactor i at time t0 corresponding to the end of the last regeneration phase of the catalytic device, in g.

5:

• The method according to claim 4, wherein the total mass (NS) of nitrogen oxides stored in the entire catalytic trapping device is calculated using the following relationship:
• NS
• =
• ∑
• i
• =
• n
• n
• ⁢
• NS_I
• in which:
• NS:
• total mass of nitrogen oxides stored in the entire catalytic trapping device, in g;
• and
• NS_i:
• nitrogen oxide mass present in the individual reactor i, in g.

6:

• The method according to claim 5, wherein the flow of untreated nitrogen oxides leaving the last reactor n is calculated using the following relationship:
• NOx_exhaust outlet=NOx_n*(1−Eff_n)
• in which:
• NOx_exhaust outlet:
• mass flow of untreated nitrogen oxides, at the exhaust outlet after traversing the catalytic trapping device, in g/s;
• NOx_n:
• mass flow of nitrogen oxides at the inlet of the last reactor n, in g/s;
• and
• Eff_n:
• instantaneous storage efficiency in the last reactor n.

8:

• A device for estimating a nitrogen oxide mass stored in a nitrogen oxide catalytic trapping device, comprising a catalytic phase, and traversed by the exhaust gases of an internal combustion engine of a motor vehicle, comprising an electronic control unit, wherein the device comprises:
• means for splitting the geometry of the catalytic trapping device into several (n) perfectly-stirred, successive individual reactors;
• and
• means for estimating the nitrogen oxide mass present in the catalytic trapping device by combining a thermal model allowing calculation of the temperature variation of the catalytic phase of the catalytic trapping device when it is traversed by the exhaust gases, and an adsorption model allowing calculation at any time of the nitrogen oxide mass stored in the catalytic trapping device as a function of the characteristics of the catalytic trapping device, the temperatures from the thermal model for each individual reactor, and the mass flow of exhaust gas from the engine.