Claims:We Claim:

1. A method (20) of improving exhaust gas treatment during regeneration of a diesel particulate filter (115) in a vehicle, the method (20) comprising:
sensing (205) a start of regeneration process of the diesel particulate filter (115) by an electronic control unit (160);
actuating (210) a valve (155) on an output line (150) of an air tank (135) by the electronic control unit (160), the output line (150) enabling flow of air from the air tank (135) to a mixer (125) of a selective catalytic reduction module (120), the diesel particulate filter (115) and the selective catalytic reduction module (120) located in the exhaust pipe (105) of the vehicle; and
closing (215) the valve (155) on the output line (150) of the air tank (135) by the electronic control unit (160), upon completion of the regeneration process of the diesel particulate filter (115).

2. An electronic control unit (160) for improving exhaust gas treatment during regeneration of a diesel particulate filter (115) in a vehicle, the control unit (160) adapted to:
sense a start of regeneration process of the diesel particulate filter (115);
actuate a valve (155) on an output line (150) of an air tank (135), the output line (150) enabling flow of air from the air tank (135) to a mixer (125) of a selective catalytic reduction module (120), the diesel particulate filter (115) and the selective catalytic reduction module (120) located in the exhaust pipe (105) of the vehicle; and
close the valve (155) on the output line (150) of the air tank (135), upon completion of the regeneration process of the diesel particulate filter (115).

3. An exhaust system (102) for improving exhaust gas treatment during regeneration of a diesel particulate filter (115) in a vehicle, the exhaust system (102) comprising:
a diesel oxidation catalyst (110) located in an exhaust pipe (105);
a diesel particulate filter (115) located downstream the diesel oxidation catalyst (110) in the exhaust pipe (105);
a selective catalytic reduction module (120) located downstream the diesel particulate filter (115); and
a mixer (125) for the selective catalytic reduction module (120) disposed between the diesel particulate filter (115) and the selective catalytic reduction module (120);
characterized in that:
an air tank (135) containing air connected to the mixer (125) through an output line (150), for introducing air to the mixer (125) during a regeneration process of the DPF (115).
, Description:Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[0001] This invention relates to a method of improving exhaust gas treatment in general, and more specifically during regeneration of a diesel particulate filter.

Background of the invention
[0002] Emissions from automobiles have been in focus for quite a long time now and with the recent implementation of emission norms and regulations, improvements are being made to the components of exhaust for optimal and improved performance. The diesel particulate filter, diesel oxidation catalyst and the selective catalytic reduction module work at optimum levels only if the working conditions are within limits. The selective catalytic reduction module works at an optimum temperature only. Therefore, as the temperature of the exhaust upstream to the selective catalytic reduction module increases, the catalytic reduction module may not work efficiently. Therefore, there is a need to improve the working environment of the selective catalytic reduction module. CN101321575B discloses a multi-stage system for selective catalytic reduction systems.

Brief description of the accompanying drawing
[0003] Figure 1 shows a schematic of an exhaust system comprising a diesel oxidation catalyst, a diesel particulate filter and a selective catalytic reduction module;

[0004] Figure 2 shows a schematic of a mixer of the selective catalytic reduction module; and

[0005] Figure 3 shows a method of improving exhaust gas treatment during regeneration of a diesel particulate filter.

Detailed description of the embodiments
[0006] Figure 1 shows a schematic of an exhaust system comprising a diesel oxidation catalyst, a diesel particulate filter (DPF) and a selective catalytic reduction module (SCR). The exhaust system is connected to an engine 100. The exhaust system contains an exhaust pipe 105 on which the diesel oxidation catalyst module (DOC) 110, the diesel particulate filter 115 and the selective catalytic reduction module 120 is located in the same order. Each of the DOC, DPF and SCR perform different functions as is understood by a person of ordinary skill in the art to reduce pollutants and emissions entering the atmosphere. Between the DPF 115 and the SCR 120 is an SCR mixer 125. It is understood that the SCR mixer 125 serves the function of optimally mixing the exhaust and diesel exhaust fluid. The exhaust system further comprises a tank 130 for containing the diesel exhaust fluid (DEF) and a compressed air tank 135 for holding compressed air. The tank 130 is connected to a conduit 140 and a nozzle 145 for spraying DEF into the mixer 125. The tank 135 is connected to an output line 150 which ends in a nozzle to introduce air into the SCR mixer 125, which will be described hereinafter. The conduit 150 is controlled by a valve 155 controlled by an electronic control unit 160, which again will be described hereinafter.

[0007] Figure 3 shows a method 20 of improving exhaust gas treatment during regeneration of a diesel particulate filter. The method 20 of improving exhaust gas treatment during regeneration of a diesel particulate filter (DPF) 115 in the vehicle comprises a first step 205 of sensing a start of regeneration process of the DPF 115 by the electronic control unit 160, a second step 110 of actuating the valve 155 on the output line 150 of the air tank 135 by the electronic control unit 160, the output line 150 enabling flow of air from the air tank 135 to the mixer 125 of the SCR 120, the DPF 115 and the SCR 120 located in the exhaust pipe 105 of the vehicle.

[0008] It is common knowledge that the diesel particulate filter is for removing diesel particulate matter or soot from the exhaust gas of a diesel engine. The particulate matter or soot gets deposited in the components of the filter, thereby gradually choking the flow path and increasing pressure at the filter entry. The DPF is regenerated by subjecting the DPF to temperatures as high as 600°C, which burns the soot or particulate matter in the DPF. Removal of soot from the DPF reduces the inlet pressure at the entry of the DPF also.

[0009] As the process of DPF regeneration involves higher temperatures, the temperatures of the exhaust leaving the DPF is higher than normal working temperatures as well. The next stage in the exhaust gas treatment apparatus is the selective catalytic reduction module (SCR). The exhaust flows from the DPF to the SCR and if the temperature of the exhaust exiting the DPF is higher, the SCR will be subjected to higher temperatures as well. The SCR work efficiently at a temperature range of 250°C – 450°C. During regeneration, the temperature of the exhaust entering the SCR can be in the range of 450°C to 600°C, thereby reducing the efficiency of the SCR.

[0010] The electronic control unit 160 for improving exhaust gas treatment during regeneration of the DPF 115 in the vehicle, the control unit 160 adapted to sense a start of regeneration process of the DPF 115, actuate the valve 155 on the output line 150 of the air tank 135, the output line 150 enabling flow of air from the air tank 135 to the mixer 125 of the SCR module 120, the DPF 115 and the SCR 120 located in the exhaust pipe 105 of the vehicle, and close the valve 155 on the output line 150 of the air tank 135, upon completion of the regeneration process of the DPF 115.

[0011] Figure 2 shows a schematic of the mixer 125 of the SCR module 120. It can be seen from Figure 2 that the nozzle of the output line 150 of the air tank 135 and the nozzle 145 from the DEF tank 130 are introduced into the mixer 125. The working of the method 20 and the arrangement is described hereinafter.

[0012] The exhaust system 102 for improving exhaust gas treatment during regeneration of a diesel particulate filter in the vehicle comprises the diesel oxidation catalyst 110 located in the exhaust pipe 105, the diesel particulate filter 115 located downstream the diesel oxidation catalyst 110 in the exhaust pipe 105, the selective catalytic reduction module 120 located downstream the diesel particulate filter 115 and the mixer 125 for the SCR module 120 disposed between the DPF 115 and the SCR module 120. The exhaust system further comprises an air tank 135 containing air and connected to the mixer 125 through an output line 150 for introducing air to the mixer 125 during the regeneration process of the DPF 115.

[0013] When the regeneration process starts, the status of the flag or counter in the control unit 160 is set or changed to reflect the start of regeneration. The control unit controlling the regeneration process may be the same or a different control unit. In the event of a different control unit, the control unit 160 communicates with the other control unit. Once the start of regeneration is sensed, the control unit 160 actuates the valve 155 to open the same, such that compressed air flows from the tank 135 to the mixer 125 through the nozzle. As the compressed air is discharged from the nozzle, the expansion causes the temperature of the air to drop. The low temperature air mixes with the hot exhaust from the DPF 115 that is being regenerated and this results in reduction of the temperature of the exhaust that enters the SCR 120. The temperature of the exhaust that enters the SCR 120 is in the range of 250°C to 450°C. Once the regeneration of the DPF 115 stops, the valve 155 is also closed by the control unit 160. The valve is any conventionally available valve that is controllable electronically.

[0014] The tank 135 contains compressed air and when the air is released from the nozzle, the air expands.

[0015] This can find application in passenger and commercial vehicles, and in general in engines conforming to stringent emission regulations such as BS VI or Euro 6 or any equivalent standard. In BS VI engines, the regeneration adjustment factor Ki is also maintained with the above methodology. The advantage of this invention is that the reduction of efficiency of SCR module is reduced and optimal working conditions of the emission control system is maintained.

[0016] It should be understood that embodiments explained in the description above are only illustrative and do not limit the scope of this invention. Many such embodiments and other modifications and changes in the embodiment explained in the description are envisaged. The scope of the invention is only limited by the scope of the claims.