FR2994454A1 - Post-processing system for post-processing exhaust fumes produced by internal combustion engine of car, has main cartridges connected to main line through secondary line, and shedding line extending between main cartridges and main line - Google Patents

Abstract

The system (5) has a starter cartridge (6) connected to an exhaust line (2) by a main feed line (8). Main cartridges (6', 6'') are connected to the main line through a secondary feed line (11). A load shedding line (13) extends between the main cartridges and the main line. The secondary line and the load line are provided with two non-return valves (12, 15). The non-return valves are mounted parallel to each other between the main cartridges and the main line. One of the non-return valves is damages with a reference pressure (Pref) that is lower than another reference pressure (P'ref). An independent claim is also included for a method for applying a post-processing system.

Description

The invention relates to an exhaust aftertreatment system comprising means for purifying the exhaust gases by catalytic conversion of harmful components contained therein of these. It relates to an exhaust after-treatment system produced by an internal combustion engine of a motor vehicle. It also relates to a method of implementing such a system. The document DE102009060286 describes a motor vehicle equipped with an internal combustion engine. The latter is provided with an exhaust line for discharging exhaust gases produced by the internal combustion engine to an external environment. The exhaust gases contain harmful components that it is preferable to treat prior to their discharge to the external environment. The harmful components are in particular nitrogen oxides of the NO type, where x is equal to 1 or 2. To do this, the exhaust line is equipped with an exhaust aftertreatment system comprising an SCR catalyst. , according to the Anglo-Saxon acronym for Selective Catalytic Reduction, which is capable of reducing nitrogen oxides NO x prior to their discharge to the external environment. The SCR catalyst is in connection with a main supply line of ammonia which is provided with cartridges capable of delivering ammonia. Among these cartridges, there is a starter cartridge which is implemented at the start of the motor vehicle and at least one main cartridge that takes the relay of the starter cartridge after a certain period of time. Ammonia is stored inside a solid salt contained inside each cartridge. The cartridges are heated by a heating element to facilitate desorption of the ammonia for its evacuation to the exhaust line. Inside the SCR catalyst, the ammonia participates in a reduction reaction of the NO oxides of nitrogen. As the heating of each cartridge, a dead volume is formed inside the cartridge due to the desorption of ammonia. The more the dead volume increases, the more energy to bring to heat the cartridge is important. This results in an overpressure that is detrimental to the durability of the cartridge. Such overpressure occurs especially in the case where the motor vehicle is traveling at high speed at startup. In this case, the starter cartridge is heated to release ammonia. When stopping the motor vehicle, a thermal inertia of the starter cartridge induces a significant overpressure, for example of the order of 8 bars, inside the post-processing system which is detrimental. Such overpressure is likely to be varied according to characteristics of the cartridge, in particular depending on the nature of the solid salt that the cartridge contains. Such overpressure also varies according to stresses that the cartridge undergoes, such as vibration conditions, humidity, temperature, power supply in particular.

Such overpressure has a major drawback which lies in an excessive production of carbon dioxide by the motor vehicle. An object of the present to provide an exhaust gas after-treatment system produced by an internal combustion engine fitted to a motor vehicle, such a post-processing system being adapted to prevent an overpressure inside. said system, in particular after stopping the internal combustion engine. A system of the present invention is an exhaust after-treatment system produced by an internal combustion engine fitted to a motor vehicle. The post-processing system includes a starter cartridge which is connected to an exhaust line by a main supply line. The post-processing system comprises at least one main cartridge which is connected to the main power line via a secondary power line. According to the present invention, the post-processing system further comprises a load shedding line which extends between the main cartridge and the main supply line. The secondary supply line is advantageously equipped with a first non-return valve. The load shedding line is advantageously equipped with a second non-return valve. The first check valve and the second non-return valve are advantageously mounted in parallel with each other between the main cartridge and the main supply line. The first non-return valve and the second check valve are advantageously mounted in opposite directions from one another between the main cartridge and the main supply line. The first non-return valve is preferably calibrated at a first reference pressure which is less than a second reference pressure which is tared the second non-return valve. Preferably, the main cartridges are in plurality and are connected to the main supply line by a single unloading line which is common to them and which is provided with the second non-return valve. A motor vehicle of the present invention is mainly recognizable in that the motor vehicle is equipped with such a post-processing system. A method of implementing such a post-processing system is mainly characterized in that the method comprises a step of learning a pair of information comprising a general pressure within the system of post-processing and a respective filling coefficient of the main cartridges. The method advantageously comprises a step of storing a heating time associated with an overpressure measured inside the post-treatment system and a general pressure profile. Other features and advantages of the present invention will appear on reading the description which will be made of embodiments, in connection with the figures of the attached plates, in which [0020] Figures 1 to 3 are schematic representations of respective operating situations of a post-processing system of the present invention. Figure 4 is a schematic illustration of a general pressure within the post-processing system as a function of time. In the figures, a motor vehicle is equipped with an internal combustion engine 1 to allow movement of the motor vehicle. The internal combustion engine 1 is provided with an exhaust line 2 for discharging to an outside environment 3 exhaust gases 4 produced by the internal combustion engine 1. The exhaust gases 4 contain harmful components that it is desirable to treat them before they are discharged into the external environment 3. Among these harmful components, there are nitrogen oxides NO x (x being equal to 1, 2 or 3). To eliminate the NO oxides of nitrogen, the exhaust line 2 is provided with a reduction catalyst SCR, according to the acronym for Selective Catalytic Reduction, which is capable of reducing nitrogen oxides NO x prior to their rejection to the external environment. The SCR reduction catalyst is constitutive of a post-treatment system 5 nitrogen oxides NO x which also includes 6,6 'cartridges containing ammonia. More particularly, the cartridges 6.6 'contain a solid salt which is able to release ammonia by desorption after heating. Also each cartridge 6,6 'is equipped with a respective heating means 7, such as an external electrical resistance, a central heating bar or the like. The after-treatment system 5 comprises a main ammonia feed line 8 which opens out at an injection point 9 formed between the exhaust line 2 between the internal combustion engine 1 and the reduction catalyst SCR. The main supply line 8 is equipped with a metering unit 10 which controls a delivery of ammonia inside the exhaust line 2. Among the cartridges 6, 6 ', 6 ", distinguishes a starter cartridge 6 which is implemented during a start of the internal combustion engine 1. The main supply line 8 extends between the injection point 9 and the starter cartridge 6. [0025] Among the cartridges 6.6 ', 6 ", there is also at least one main cartridge 6' which is implemented a lapse of time after the start of the internal combustion engine 1. On the variant illustrated, the main cartridges 6 ' There are two of them. Each main cartridge 6 ', 6 "is connected to the main supply line 8 by a secondary supply line 11 which extends between the main cartridge and the main supply line 8. Each secondary supply line 11 is provided with a respective first non-return valve 12 which allows an ammonia passage from the main cartridge 6 ', 6 "to the main supply line 8, (Here the calibration of the valve 12 Pref is preferably a few millibars simply to perform its function of nonreturn valve) According to the present invention, each main cartridge 6 ', 6 "is provided with a load shedding line 13 which extends between the main cartridge 6', 6" and a bypass point 14 provided on the main supply line 8, upstream of the metering unit 10 in a flow direction of the ammonia inside the main supply line 8. The line of unloading 13 is provided with a second valve a back-flow 15 which allows a passage of ammonia from the branch point 14 to the main cartridge 6 ', 6 "when a second pressure P' inside the main supply line 8 is greater than a second reference pressure Pref, for example 6 bar. In the illustrated variant, the second non-return valve 15 is advantageously common for all the main cartridges 6 ', 6 ".The second reference pressure P'ref is greater than the first reference pressure Pref. [0027] FIG. 2 shows a first life situation of the motor vehicle in which the starter cartridge 6 is used, for example during a starting phase of the internal combustion engine 1. The starter cartridge 6 delivers a pressure P 1, which is for example 3 bars, inside the main supply line 8 and inside a first portion 16 of the line shedding 13 which is between the second check valve 15 and the derivation point 14. Is represented in dashed line, a first zone 8,13 inside which prevails the service pressure Pi. At the beginning of such a phase, a first filling coefficient C1 of the for example, the starting layer 6 is 50% while a second filling coefficient 02 of a first main cartridge 6 'is 50% and a third filling coefficient of a second main cartridge 6 "is 100%. %. At the end of such a phase, the first filling coefficient C1 of the starter cartridge 6 is for example 45% while the second filling coefficient 02 of the first main cartridge 6 'is still 50% and the third The filling factor of the second main cartridge 6 "is always 100%, because only the starter cartridge 6 has released ammonia, hence a decrease in the first filling coefficient Cl. [0028] In FIG. 2 is a second life situation of the internal combustion engine 1, which is consecutive to the first life situation, and in which the internal combustion engine 1 is at a standstill. ammonia within the main supply line 8. Due to a thermal inertia of the starter cartridge 6, an overpressure of ammonia appears within said first zone 8, 13, so that that a pressure r Gnant within said first area 8.13 is likely to exceed the second reference pressure Fret. This results in an opening of the second non-return valve 15 which allows a passage of ammonia through the latter. This results in an increase of a volume available for ammonia, represented in dashed line. This finally results in a lowering of the pressure inside said first zone 8, 13, from an ammonia refill of the first main cartridge 6. At the end of such a phase, the first filling factor Cl of the starter cartridge 6 is for example 50% while the second filling coefficient 02 of the first main cartridge 6 'is for example 51% and the third filling factor of the second main cartridge 6 "is still 100% As the pressure drop within said first zone 8,13, the pressure becomes lower than the second reference pressure P'ref, which causes a closure of the second non-return valve 15. Finally, the first filling coefficient C1 of the starter cartridge 6 is for example 55% while the second filling coefficient 02 of the first main cartridge 6 'is for example 53% and that the third filling coefficient of the second main cartridge 6 "is always 100%. FIG. 4 shows an evolution of a general pressure P "inside the aftertreatment system 5 as a function of time, after a stop A of the internal combustion engine 1. In a first case of Figure H1 where the post-processing system 5 is not equipped with a load shedding line 13 provided with the second non-return valve 15, the general pressure P "continues to increase after stopping A of the internal combustion engine 1, including after a lapse of time L. In a second case of figure H2 where the post-processing system 5 is a system of the present invention on a single cartridge 6 'or 6 "because the other cartridge is full the P "general pressure increases more slowly than in the case of Figure H1 after the lapse of time L after stopping A of the internal combustion engine 1. In a third case of Figure H3 where the two main cartridges 6 ', 6" neither are 100% fulfilled, there is a decrease in the general pressure P "within the post-processing system 5.A method of implementing such a post-processing system 5 comprises a learning step of a pair of information comprising the general pressure P "inside the after-treatment system 5 and a respective filling coefficient 02, 03 of the main cartridges 6 ', 6". According to this information, a heating time of the main cartridges 6 ', 6 "is mapped in the laboratory so as to minimize the heating time The general pressure P" is for example measured by a pressure sensor housed inside The filling coefficient C is for example determined by an integration of a quantity of ammonia injected inside the exhaust line 2, starting from the implementation of a integrated solenoid valve inside the metering unit 10. At each step of heating a main cartridge 6 ', 6 "with a known filling coefficient 02,03, the method comprises a step of setting memory of a heating time associated with the overpressure measured inside the post-treatment system 5 and a general pressure profile P ". In a subsequent start-up step of the same main cartridge 6 ', 6 "with the same filling coefficient 02.03, the method allows optimization of the heating time to avoid overpressure. This method is advantageously self-adaptive in the sense that, during a subsequent start of the main cartridge 6 ', 6 ", a possible excess pressure is proved due to aging of components for example, the method uses the maps relating to this state of loading to adapt accordingly the heating time and prevent an occurrence of a new overpressure.

Claims (10)

1. After-treatment system (5) of exhaust gas (4) produced by an internal combustion engine (1) fitted to a motor vehicle, the post-processing system (5) comprising a starter cartridge ( 6) which is connected to an exhaust line (2) by a main supply line (8), the after-treatment system (5) comprising at least one main cartridge (6 ', 6 ") which is connected at the main supply line (8) via a secondary supply line (11), characterized in that the post-treatment system (5) further comprises a load shedding line (13) which extends between the main cartridge (6 `, 6") and the main supply line (8). 2. post-processing system (5) according to the preceding claim, characterized in that the secondary supply line (11) is equipped with a first non-return valve (12). 3. post-processing system (5) according to any one of the preceding claims, characterized in that the load shedding line (13) is equipped with a second non-return valve (15). 4. After-treatment system (5) according to claims 2 and 3, characterized in that the first non-return valve (12) and the second non-return valve (15) are connected in parallel with one of the another between the main cartridge (6 ', 6 ") and the main supply line (8). 5. Aftertreatment system (5) according to claims 2 to 4, characterized in that the first non-return valve (12) and the second non-return valve (15) are mounted in opposite directions one of the another between the main cartridge (6 ', 6 ") and the main supply line (8). 6. post-treatment system (5) according to claims 2 to 5, characterized in that the first non-return valve (12) is calibrated at a first reference pressure (Pref) which is less than a second reference pressure (P'ref) according to which is tared the second check valve (15). 7. post-processing system (5) according to any one of the preceding claims, characterized in that the main cartridges (6 ', 6 ") are in plurality and are connected to the main supply line (8) by a single unloading line (13) which is common to them and which is provided with the second non-return valve (15). 8. Motor vehicle equipped with a post-processing system according to any one of the preceding claims. 9. A method of implementing a post-processing system (5) according to any one of claims 1 to 8, characterized in that the method comprises a learning step of a pair of information comprising a general pressure (P ") within the after-treatment system (5) and a respective filling coefficient (02, C3) of the main cartridges (6 ', 6"). 10. Method according to claim 9, characterized in that the method comprises a step of storing a heating time associated with an overpressure measured inside the post-treatment system (5) and a pressure profile. general (P ").