Claims:We Claim:

1. An exhaust gas system (100) for an engine (102), comprising:
an exhaust throttle device (106) disposed in fluid communication with and downstream from the engine (102) on the fluid passageway in exhaust path (103) and adapted to adjust a cross sectional area of the exhaust passage be variable to control the flow of exhaust gas recirculation to the engine (102);
a differential pressure sensor (112) disposed at inlet and outlet of a diesel particulate filter (110) is adapted to determine pressure differential between upstream and downstream of the diesel particulate filter (110), wherein the determined differential pressure is used to trigger the exhaust throttle device (106) to throttle the inlet air, based on pressure and temperature conditions in the exhaust gas system (100).

2. The exhaust gas system (100) as claimed in claim 1, wherein the exhaust throttle device (106) comprises an electrically powered intake throttle valve and an angular-position sensor for position feedback.

3. The exhaust gas system (100) as claimed in claim 2, the intake throttle valve further adapted to be throttled based on required exhaust temperature increase, to reduce the excess air ratio and subsequently increasing the exhaust gas system (100) temperature to the needful extend to foster the particulate burning via continuous regeneration technology (CRT) effect.

4. The exhaust gas system (100) as claimed in claim 1, wherein the system (100) functions when the engine is idling and/or under a low load operation mode, for an extended period.

5. The exhaust gas system (100) as claimed in claim 1, wherein the exhaust throttle device (106) is further adapted to perform thermal management in the system (100) under low-load operation mode and enable continuous regeneration technology (CRT) Effect in the exhaust gas system (100).
, 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] Present invention relates to the field of exhaust gas treatment systems in combustion engine of a vehicle. The invention relates in specific to an exhaust gas treatment system for Conventional Diesel Fuel Injection Systems.

Background of the invention
[0002] Exhaust gas treatment for internal combustion engines are known in the prior arts. The exhaust gas treatment (EGT) systems are used to reduce the exhaust emissions coming out of the internal combustion engine. The EGT system of diesel engines typically reduces hydro carbons, carbon monoxide, nitrogen oxide and particulate matter.

[0003] In internal combustion engines, a process known as exhaust gas recirculation (EGR) is used to reduce the amount of nitric oxide (NO X) emissions. In general, EGR involves routing a portion of the exhaust gas back into the intake air flow. In an engine where exhaust back pressure is greater than intake air pressure, an EGR flow can be realized simply by connecting a conduit between the exhaust and intake ducts. The flow from the exhaust manifold is drawn to the lower pressure of the intake because of the negative pressure differential. However during low or lower part load operation (?40% Load), the exhaust gas temperature sucks down below the minimum threshold temperature for the CRT®-Effect. During those operation conditions particulates get trapped in the DPF and collected. As a result, the backpressure of the exhaust gas treatment system increases and reaches a critical level after about 30h low load operation, and adversely affect fuel economy. Also, if an excessive amount of particulate matter is trapped, the filter may melt as a result of abnormal burning of the particulate matter.

[0004] Existing solutions for the above-mentioned problems includes electronically controlled fuel injection systems here typically Common Rail Systems (CRS). However, conventional fuel injection systems in contradiction to electronically controlled fuel injection systems, typically do not offer the opportunity of injection pattern variation hence the thermodynamic efficiency of the engine cannot be influenced by the conventional fuel injection systems. As a result, a necessary increase in exhaust temperature cannot be enabled and the system may collapse by increased backpressure.

[0005] The prior art US20080034737 discloses an exhaust gas purification system and method for an internal combustion engine that has a filter disposed in an exhaust passage that traps PM discharged from the engine. An exhaust throttle valve disposed downstream of the filter in the exhaust and a differential pressure sensor that detects the differential pressure between a portion of the exhaust passage upstream of the filter and a portion of the exhaust passage downstream of the filter. The exhaust throttle valve is operated based upon the differential pressure to aid the burning of the PM trapped by the filter so as to regenerate the filter. The exhaust gas purification system includes a determining section that determines whether there is a malfunction of the exhaust throttle valve based upon changes in the differential pressure that occur when the exhaust throttle valve is operated. However, the exhaust gas purification system and method disclose in the prior art is implemented in an electronically controlled fuel injection system.

Brief description of the accompanying drawing
[0006] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[0007] Fig. 1 illustrates an exhaust gas treatment (EGT) system, for Conventional Fuel Injection Systems, according to one embodiment of the invention.

Detailed description of the embodiments
[0008] FIG. 1 illustrates an exhaust gas treatment (hereinafter EGT) system 100, for conventional fuel Injection systems. Shown in fig. 1 is an internal combustion engine 102, an air filter 104, an exhaust throttle device 106, a diesel oxidation catalyst (hereinafter DOC) 108, a diesel particulate filter (hereinafter DPF) 110 and a differential pressure sensor 112. In one embodiment the EGT system 100 functions when the engine 102 is idling and/or under a low load operation mode, for an extended period.

[0009] The internal combustion engine 102 shown in fig. 1. In operation, during the suction stroke, the air enters into the cylinder after getting filtered from the air filter 104. During the compression stroke, the air gets pressurized and when the piston is close to top dead center, the fuel is injected into the cylinder. The fuel and air combust in the cylinder and the combustion generates exhaust gases and during the exhaust stroke, the exhaust gases are pushed out of the engine through the exhaust port of the engine into the exhaust path 103. The exhaust gases coming out of the engine comprise like NOx, HC, Sulphur oxide etc. The exhaust gases also contain particulate matter and soot. All of these are harmful if released into the atmosphere. These need to be reduced to meet the emission standards before the exhaust is released into the atmosphere.

[0010] The DPF 110 captures and stores exhaust soot in order to reduce harmful emissions from the exhaust gases. The trapped soot periodically needs to be emptied by the way of burning it. The burning of the soot is called regeneration process EGR. The DPF 110 regeneration comprises collecting particulate matter in a DPF from exhaust gas that is released from an engine. The DOC 108 is disposed at downstream of the engine 102 and upstream of the DPF 110, in the exhaust path 103. More specifically, the exhaust gases from DOC 108 is channeled into the diesel particulate filter for filtering the particulate matter that is present in the exhaust gases, before the exhaust gases are released into the environment. Over a period of time, the particulate matter is collected in the diesel particulate filter, and clogs an inner sidewall of the diesel particulate filter. Therefore, in order to prevent a substantial back-pressure of exhaust gases from building up on the engine due to the clogging of the diesel particulate filter, the diesel particulate filter needs to be periodically regenerated to burn away the particulate matter that is collected therein. Once the diesel particulate filter is regenerated and the particulate matter is burnt away, the clean diesel particulate filter can be reused once more to collect particulate matter from the exhaust gas that is released from the engine.

[0011] The exhaust throttle device 106 is disposed in fluid communication with and downstream from the engine 102 on the fluid passageway in the exhaust path 103 and adapted to adjust a cross sectional area of the exhaust passage be variable to control the flow of exhaust gas recirculation through EGR cooler 114 to the engine 102. The exhaust throttle device 106 includes an electrically powered intake throttle valve and an angular-position sensor for position feedback. The intake throttle valve obstructs the flow of exhaust gas through the exhaust path 103. The electronic control unit triggers the intake throttle valve.

[0012] The differential pressure sensor 112 disposed at inlet and outlet of the DPF 110. Further, the differential pressure sensor 112 is adapted to determine pressure differential between upstream and downstream of the DPF 110. The differential pressure sensor 112 senses the differential pressure at the DPF 110 and communicates to the exhaust throttle device 106. The determined differential pressure is used to trigger the exhaust throttle device 106 to throttle the inlet air, based on pressure and temperature conditions in the exhaust gas system 100. Specifically, the differential pressure determined by the differential pressure sensor 112 is used to trigger the intake throttle valve by the control unit to throttle the inlet air by engaging or disengaging the intake throttle valve. When the pressure differential between the outlet of the DPF 110 and the inlet of the DPF 110 increases above a threshold value, thereby causing regeneration of the DPF, depending on pressure and temperature conditions in the exhaust gas system 100. That is, the intake throttle valve is operated to increase the exhaust temperature to foster the particulate burning, thus reducing backpressure of exhaust gases in DPF 110.

[0013] In one embodiment, in case of longer low load operation and subsequent increase in differential pressure the intake throttle valve will be engaged and dependent on the required exhaust temperature increase, the inlet air duct will be throttled to reduce the excess air ratio and subsequently increase the EGT Temperature to a needful extend to foster the particulate burning via Continuous Regeneration Technique CRT®. A system under CRT effect has a filter coated with catalyst as well as having a Diesel oxidation catalyst (DOC) in front of the filter and this extends the operating window of the filter system to allow reliable regeneration with lower exhaust temperatures or lower NOx to particulate ratio in the exhaust gas.

[0014] In one embodiment, by varying intake throttle valve of the exhaust throttle device 106, during low and lower load operation, causes a significant increase in the exhaust temperature. In this embodiment, the intake throttle valve may be used to perform Exhaust Thermal Management during low load operation and enable CRT® -Effect in the EGT system (100).

[0015] 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.