FR2907163A1 - DEVICE AND METHOD FOR ESTIMATING THE INSTANTANEOUS EFFICIENCY OF STORING NITROGEN OXIDES FROM A CATALYTIC TRAPPING SYSTEM OF NITROGEN OXIDES - Google Patents

Abstract

The device (1) estimates the instantaneous storage efficiency of nitrogen oxides of a catalytic catalyst system of nitrogen oxides comprising a catalytic phase and through which the exhaust gases of an internal combustion engine of a motor vehicle. The estimating device (1) comprises means (15) for estimating the instantaneous storage efficiency of nitrogen oxides of said catalytic trap system from a previously calculated sum of the mass of nitrogen oxides adsorbed by said catalytic phase and an equivalent mass of nitrogen oxides corresponding to a mass of sulfur oxides blocking sites of adsorption of said catalytic phase.

Description

1 Apparatus and method for estimating the instantaneous efficiency of

  The present invention relates to a device and a method for estimating the instantaneous storage efficiency of nitrogen oxides of a nitrogen oxidation system. catalytic trapping of nitrogen oxides, comprising a catalytic phase, and through which the exhaust gases of an internal combustion engine of a motor vehicle.

  Internal combustion engines produce exhaust gases that contain regulated pollutants, such as NOS nitrogen oxides, HC unburned hydrocarbons, carbon monoxide CO and particles that need to be treated.

  The thresholds allowed for the emission of gaseous pollutants from motor vehicles are regularly revised downwards in the context of the evolution of the regulation on the depollution. Conventionally, the treatment of nitrogen oxides NOS emitted by the engine in the exhaust gas, are treated by a nitrogen oxide trapping system implanted in the exhaust line of the engine. Under normal exhaust conditions, ie when the fuel richness at the exhaust is low, the nitrogen oxide trapping system stores nitrogen oxides in the form of nitrates at adsorption, conventionally barium salt. Since the maximum storage capacity of such a trapping system is limited, it is necessary to regenerate it regularly, by increasing the fuel richness at the exhaust by controlling the operation of the engine, to a value slightly greater than 1.

Under these conditions NOX nitrogen oxides are desorbed from the storage sites and removed as nitrogen by a catalyst. The sulfur contained in the engine exhaust gases from the engine lubricating oil and the fuel supplying the engine can be fixed at the adsorption sites of the nitrogen oxides of the catalytic trapping system of the engine. oxides of nitrogen, and modify the instantaneous storage efficiency of nitrogen oxides in the trapping system, by decreasing the number of available adsorption sites for nitrogen oxides.

Also, it is important to take into account sulfur poisoning in estimating the nitrogen oxide loading of the catalytic nitrogen oxide capture system, particularly in the calculation of the instantaneous storage efficiency of nitrogen oxides. oxides of nitrogen from the catalytic trap system.

French patent application FR 2,856,741 describes an on-board estimator of the quantity of nitrogen oxides adsorbed in a device for catalytic trapping of nitrogen oxides of the exhaust gases of an internal combustion engine powered by a lean fuel mixture. The method used does not take into account the poisoning of the catalyst for catalytic capture of nitrogen oxides by the sulfur oxides. German patent application DE 100 38 461 describes the calculation of an instantaneous storage efficiency of nitrogen oxides of a catalytic nitrogen oxide trap system, corrected several times successively to take account of the sulfur poisoning. The disclosed calculation is complex and of limited accuracy, and requires a large onboard memory size to provide sufficient accuracy, yet the size of the on-board memory is limited, the accuracy is limited.

An object of the invention is to propose an alternative to the calculation of the instantaneous storage efficiency of nitrogen oxides of a catalytic system for the oxidation of nitrogen oxides, having improved accuracy, and of which the embedded software implementation is reduced in size. Also, it is proposed, according to one aspect of the invention, a device for estimating the instantaneous efficiency of storage of nitrogen oxides of a catalytic capture system of nitrogen oxides comprising a catalytic phase and traversed by the exhaust gas of an internal combustion engine of a motor vehicle. The estimation device comprises means for estimating the instantaneous storage efficiency of nitrogen oxides of said catalytic capture system from a sum of a mass of nitrogen oxides adsorbed by said catalytic phase. and an equivalent mass of nitrogen oxides corresponding to a mass of sulfur oxides blocking sites of adsorption of said catalytic phase. The presence of sulfur oxides blocking adsorption sites of the catalytic phase of the nitrogen oxide scavenging system is thus taken into account. This equivalent mass of nitrogen oxides, corresponding to the mass of sulfur oxides blocking adsorption sites of the catalytic phase, is used in the calculation of the mass of nitrogen oxides trapped in the trapping system. catalytic, used to estimate the instantaneous nitrogen oxide storage efficiency of the catalytic trap system. Also, the accuracy of the calculation of the instantaneous storage efficiency of nitrogen oxides is improved, and its software implementation is small, because the consideration of sulfur poisoning takes place upstream of the calculation of 2907163 4 the instantaneous storage efficiency, or, in other words, comes into input means for calculating the instantaneous storage efficiency. According to one embodiment, the device comprises first means for calculating the mass of sulfur oxides blocking adsorption sites of the catalytic phase. The device further comprises second means for calculating the equivalent mass of nitrogen oxides, corresponding to said mass of sulfur oxides calculated by the first calculation means, taking into account the temperature of the substrate on which it is based. said catalytic phase.

The equivalent mass of nitrogen oxides produced by the second calculation means being dependent on the temperature of the substrate, the taking into account of the latter makes it possible to obtain an improved accuracy of the calculation of the equivalent weight of oxides of nitrogen. nitrogen.

According to one embodiment, said estimation means are, furthermore, adapted to take into account the maximum nitrogen oxide storage capacity of the catalytic trap system when estimating said instant storage efficiency. nitrogen oxides.

According to one embodiment, the estimation device further comprises third means for calculating the maximum storage capacity for nitrogen oxides of the catalytic capture system taking into account the temperature of the substrate. Since the maximum nitrogen oxide storage capacity of said catalytic trapping system is sensitive to the temperature of the substrate, the calculation of the maximum storage capacity of nitrogen oxides of said catalytic trapping system has improved accuracy.

According to one embodiment, the estimation means are, furthermore, adapted to take into account the hourly volume velocity of the gases passing through the catalytic trap system when estimating said instantaneous storage efficiency of oxides of carbon dioxide. nitrogen from the catalytic trapping system. The instantaneous storage efficiency of nitrogen oxides depending on the hourly volume velocity of the gases passing through the catalytic trapping system, its estimation is of improved accuracy.

According to one embodiment, said means for estimating the instantaneous storage efficiency of nitrogen oxides are, furthermore, adapted to take account of the temperature of the substrate during the estimation of said instantaneous storage efficiency. nitrogen oxides of said catalytic trapping system.

Since the instantaneous nitrogen oxide storage efficiency of the catalytic trap system is dependent on the temperature of the substrate, taking the latter into account makes it possible to obtain an improved accuracy of the estimation of the instantaneous efficiency. According to another aspect of the invention, there is also provided a system for estimating a mass of nitrogen oxides stored in a catalytic nitrogen oxide capture system, comprising a device for estimating nitrogen oxides. the instantaneous storage efficiency of nitrogen oxides as described above. Such a system for estimating a mass of nitrogen oxides stored in a catalytic nitrogen oxide capture system is of improved accuracy, and its software implementation is reduced in size. It is furthermore proposed, according to another aspect of the invention, a system for periodically regenerating a catalytic nitrogen oxidation catalyst system comprising a device for estimating the instantaneous storage efficiency of a reactor. nitrogen oxides as previously described. Such a system of periodic regeneration of catalytic nitrogen oxide capture system can more accurately determine the trigger times of a regeneration phase of the catalytic trapping system, and a reduced size software implementation. It is also proposed, according to another aspect of the invention, a method for estimating the instantaneous storage efficiency of nitrogen oxides of a catalytic capture system of nitrogen oxides comprising a catalytic phase. and traversed by the exhaust gases of an internal combustion engine of a motor vehicle. The instantaneous storage efficiency of nitrogen oxides of said catalytic trap system is estimated from a sum of a mass of nitrogen oxides adsorbed by said catalytic phase and an equivalent mass of oxides. nitrogen corresponding to a mass of sulfur oxides blocking adsorption sites of said catalytic phase.

Other objects, features and advantages of the invention will appear on reading the following description of some non-limiting examples and with reference to the appended drawings, in which: FIG. 1 is a block diagram of a embodiment of a device for estimating the instantaneous storage efficiency of nitrogen oxides of a catalytic nitrogen oxide capture system according to one aspect of the invention; and FIG. 2 is a block diagram of an embodiment of a system for estimating a mass of nitrogen oxides stored in a catalyst for catalyzing nitrogen oxides in one aspect. of the invention. FIG. 1 shows a device 1 for estimating the instantaneous storage efficiency of nitrogen oxides of a catalytic catalyst system for the oxidation of nitrogen, comprising a catalytic phase and through which gas is passed through. exhaust of an internal combustion engine of a motor vehicle. The instantaneous storage efficiency of nitrogen oxides makes it possible to know at any time the adsorption capacity of the catalytic nitrogen oxide trapping system, and is defined by the following relation: Eff = 100 × 1 × Flow rate _N0 x _sortant Flow _ NOx _entrant in which: Eff is the instantaneous storage efficiency of the catalytic capture system of oxides of nitrogen, in percentage; Outgoing NO flow is the nitrogen oxide flow rate exiting the catalytic nitrogen oxide capture system, in g / s; and Incoming NO flow is the flow rate of nitrogen oxides entering the catalytic nitrogen oxide capture system, in g / s.

A first calculation module 2 makes it possible to determine a mass of sulfur oxides mso blocking the adsorption sites of the catalytic phase of the catalytic system for the capture of nitrogen oxides. The mass of sulfur oxides blocking adsorption sites of the catalytic phase is transmitted to a second calculation module 3 via a connection 4. The second calculation module 3 additionally receives, as input, the temperature T of the substrate by a connection 5. The second calculation module 3 determines an equivalent mass of nitrogen oxides pseudo_NOX corresponding to said mass of oxides of sulfur mso. The equivalent mass of nitrogen oxides pseudo_NOX is transmitted by a connection 6 to an addition module 7 also receiving as input an NF mass of nitrogen oxides trapped by the catalytic capture system of nitrogen oxides, via a connection 8. The addition module 7 delivers, at the outlet, a mass of nitrogen oxides NS 'corresponding to the sum of the mass of nitrogen oxides NS and the mass equivalent of pseudo_NOX nitrogen oxides by a connection 9, to a division module 10.

The division module 10 also receives as input, via a connection 11, a maximum NSC storage capacity of nitrogen oxides of the catalytic trapping system delivered by a third calculation module 12 as a function of the temperature T of the substrate received. The maximum NSC storage capacity of the catalytic trap system corresponds to the maximum mass of nitrogen oxides that can be stored by the catalytic phase. The division module 10 delivers at output, via a connection 14, the ratio of the sum NS 'and the maximum storage capacity NSC of nitrogen oxides of the catalytic trapping system, to a module of estimate 15 of the instantaneous storage efficiency of nitrogen oxides of the catalytic trapping system. The estimation module 15 also optionally receives, as an input, the temperature T of the substrate via a connection 16, and the hourly space velocity VVH representative of the residence time of the gases 25 in the catalytic trapping device, via a connection 17. The estimation module 15 of the instantaneous storage efficiency outputs, through a connection 18, the instantaneous efficiency of the storage of nitrogen oxides Eff of the catalytic nitrogen oxide capture system. This instantaneous efficiency takes into account the poisoning of the catalytic catalyst system by sulfur oxides, in a simplified manner. Also, the software implementation of this computing device can easily be embedded on board an electronic control unit of a motor vehicle, because of reduced size, whether it is implemented in software form or by integrated circuit. FIG. 2 shows a system for estimating a mass of nitrogen oxides stored in a catalytic nitrogen oxide capture system comprising a device for estimating the instantaneous storage efficiency. of nitrogen oxides as shown in Figure 1. The estimation device 1 outputs, through the connection 18, the instantaneous efficiency of nitrogen oxide storage Eff of the catalytic trapping system, to destination of a multiplication module 19 also receiving as input, through a connection 20, 15 the flow of nitrogen oxides incoming flow rate NO entering the catalytic trapping system, and a predetermined value dt through a connection 21. The value dt represents the step of calculation or integration time. The multiplication module 19 outputs, via a connection 22, the flow rate of stored nitrogen NO flow oxides stored in the catalytic trapping system, to an addition module 23. The addition module 23 also receives, as input, a cumulative mass NS of nitrogen oxides trapped by the catalytic trapping system, via a connection 24 from a storage module 25. the cumulative mass NS of nitrogen oxides trapped in the catalytic system of nitrogen oxides. The addition module 23 outputs, via a connection 26, a cumulative mass NS of nitrogen oxides trapped in the updated catalytic trapping system, which is also transmitted via a connection 27 to the storage module. 25 that memorizes this update. The storage module 25 further transmits, through the connection 8, forming a feedback loop, the mass of nitrogen oxides NS trapped in the updated catalytic trapping system, at the input of the device. estimate 1. Such a system can be used for a periodic regeneration system of the catalytic trapping system. The invention makes it possible to improve the calculation of the instantaneous storage efficiency of nitrogen oxides with improved precision, and to implement its software implementation so as to occupy a reduced space in the memory.

Claims (9)

  1. Apparatus for estimating (1) the instantaneous storage efficiency of nitrogen oxides of a catalytic capture system of nitrogen oxides comprising a catalytic phase and through which the exhaust gases of a internal combustion engine of a motor vehicle, characterized in that it comprises means (15) for estimating the instantaneous storage efficiency of nitrogen oxides of said catalytic trapping system from a sum of one mass of nitrogen oxides adsorbed by said catalytic phase and of an equivalent mass of nitrogen oxides corresponding to a mass of sulfur oxides blocking sites for adsorption of said catalytic phase.   2. Device (1) according to claim 1, comprising first calculating means (2) of said mass of sulfur oxides blocking adsorption sites of said catalytic phase, and second calculating means (3) of said equivalent mass of nitrogen oxides, corresponding to said mass of sulfur oxides calculated by said first calculation means (2), taking into account the temperature of the substrate on which said catalytic phase is based.   3. Device (1) according to one of the preceding claims, wherein said estimating means (15) are further adapted to take account of the maximum storage capacity nitrogen oxides of said catalytic trapping system when estimating said instantaneous efficiency of storing nitrogen oxides.   4. Device (1) according to claim 3, further comprising third calculation means (12) of the maximum nitrogen oxide storage capacity of said catalytic trapping system taking into account the temperature of the substrate. 2907163 12   5. Device (1) according to one of the preceding claims, wherein said estimating means (15) are further adapted to take account of the hourly volume velocity of the gas passing through said catalytic trapping system in 5 l estimating said instant nitrogen oxide storage efficiency of said catalytic trapping system.   6. Device (1) according to one of the preceding claims, wherein said estimating means (15) are further adapted to take account of the temperature of the substrate when estimating said instantaneous storage efficiency. nitrogen oxides of said catalytic trapping system.   7. System for estimating a mass of nitrogen oxides stored in a catalytic nitrogen oxide capture system, characterized in that it comprises a device for estimating (1) the efficiency instant storage nitrogen oxides according to one of claims 1 to 6.   8. Periodic regeneration system of a catalytic capture system of nitrogen oxides, characterized in that it comprises a device (1) for estimating the instantaneous storage efficiency of nitrogen oxides according to one of claims 1 to 6.   9. A method for estimating the instantaneous storage efficiency of nitrogen oxides of a catalytic capture system of nitrogen oxides comprising a catalytic phase and through which the exhaust gas of a combustion engine passes through in which the instantaneous nitrogen oxide storage efficiency of said catalytic trapping system is estimated from a sum of a mass of nitrogen oxides adsorbed by said catalytic phase and an equivalent mass of nitrogen oxides corresponding to a mass of sulfur oxides blocking sites of adsorption of said catalytic phase.