Claims:
We claim:
1. An exhaust gas treatment (EGT) apparatus (100) for an internal combustion engine (104) said EGT apparatus (100) comprising:
- A diesel oxidation catalyst (DOC) (102) disposed downstream of said engine (104) in an exhaust path (106)
- A particle oxidation catalyst (POC) (108) disposed downstream of said DOC (102)
- An exhaust gas re-circulation (EGR) valve (110) downstream of said POC (108), said EGR valve (110) guiding a portion of exhaust gases to said engine (104) for combustion
- A supercharger (112) to receive intake air and said portion of exhaust gases; said supercharger (112) compressing said air and said portion of exhaust gases to deliver to said engine (104)
- A dosing module (114) to inject reducing agent into said exhaust path downstream of said POC (108)
- A selective catalytic reduction (SCR) catalyst (116) disposed in said exhaust path downstream of said dosing module (114)
- A pair of oxygen sensors; first oxygen sensor disposed before said DOC (102) and second oxygen sensor disposed after said SCR catalyst (116)

2. An EGT apparatus (100) according to claim 1 wherein said EGR valve (110) is electronically controlled
3. An EGT apparatus (100) according to claim 1 wherein said EGR valve (110) is a proportional valve
4. An EGT apparatus (100) according to claim 1 wherein amount of opening of said EGR valve (110) depends upon the amount of oxygen detected by said oxygen sensors
5. An EGT apparatus (100) according to claim 1 wherein said EGR valve (110) is located on low pressure side of said supercharger (112).
6. An EGT apparatus (100) according to claim 1 wherein said EGR valve (110) is downstream of said POC (108).
7. An EGT apparatus (100) according to claim 1 wherein a single ECU 208 controls fuel injection apparatus and exhaust gas treatment apparatus.
8. An EGT apparatus (100) according to claim 1 wherein input to supercharger is controlled by a proportional valve (132).
9. A system for reducing harmful gases from exhaust gases of an internal combustion engine, said system comprising an EGT apparatus (100) and a lean electronic fuel injection apparatus (200); said EGT apparatus (100) comprising
- A diesel oxidation catalyst (DOC) (102) disposed downstream of an engine (104) in an exhaust path (106)
- A particle oxidation catalyst (POC) (108) disposed downstream of said DOC (102)
- An exhaust gas re-circulation (EGR) valve 110) downstream of said POC (108), said EGR valve 110) guiding a portion of exhaust gases to said engine 104) for combustion
- A supercharger (112) to receive intake air and said portion of exhaust gases; said supercharger (112) compressing said air and said portion of exhaust gases to deliver to said engine (104)
- A dosing module (114) to inject reducing agent into said exhaust path downstream of said POC (108)
- A selective catalytic reduction apparatus (118) disposed in said exhaust path downstream of said dosing module (114)
- A pair of oxygen sensors; first oxygen sensor disposed before said DOC (102) and second oxygen sensor disposed after said SCR apparatus (116)
and said lean electronic fuel injection apparatus (200) comprising a mechanical pump (205) and an electronic injector (206).
, Description:

Field of the invention:
[0001] This invention relates to the field of exhaust gas treatment for internal combustion engines in general. The invention, in specific, relates to the internal combustion engines having a single cylinder.

Background of the invention:
[0002] The US patent US patent application 20070163239 discloses an internal combustion engine with exhaust treatment system. The system disclosed in said prior art includes a reservoir containing an active ingredient a delivery device for delivering the active ingredient and an injection device for injecting the active ingredient into the exhaust. In the prior art the exhaust treatment system includes a pressure reservoir that is fed by the delivery device; this pressure reservoir is able to store the active ingredient under pressure and is directly connected to the injection device.

Brief description of the accompanying drawings:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0004] Fig. 1 illustrates an exhaust gas treatment apparatus
[0005] Fig. 2 a light fuel injection apparatus

Detailed description of the embodiments:
[0006] Shown in fig. 1 is an illustration of an exhaust gas treatment (EGT) apparatus 100 according to an embodiment of the invention. The EGT apparatus 100 comprises a diesel oxidation catalyst DOC 102 disposed downstream of an engine 104 in an exhaust path 106; a particle oxidation catalyst POC 108 disposed downstream of said DOC 102; an exhaust gas re-circulation (EGR) valve 110 downstream of POC 108, said EGR valve 110 guiding a portion of exhaust gases back to engine for combustion; a supercharger 112 to receive intake air and said portion of exhaust gases; said supercharger 112 compressing said air and portion of exhaust gases to deliver to said engine 104; a dosing module 114 to inject reducing agent into said exhaust path downstream of POC 108; a selective catalytic reduction (SCR) catalyst 116 disposed in exhaust path downstream of said dosing module 114; a pair of oxygen sensors 120, 122; first oxygen sensor 120 disposed before DOC 102 and second oxygen sensor 122 disposed after SCR catalyst 116. Also there are a couple of temperature sensors. Also there may be silencers 118 disposed in exhaust path.
[0007] The engine 104 receives the air and fuel mixture through the intake path 124 for the combustion. An air filter 126 disposed in the intake path 124 filters the air. A mass flow sensor and a temperature sensor 128 are also disposed in the intake path 124 to determine the amount of air entering into the engine 104 and the temperature of the air entering. These two parameters are used to determine the quantity of fuel to be injected into the cylinders of the engine 104 to maintain the required air-fuel ratio. After the mass flow sensor 128, the supercharger 112 is located in the intake path 124. The supercharger 112 compresses the incoming air thereby delivering more air to the engine 102. Availability of more air at the engine 102 results in injection of more fuel thereby delivery of more power by the engine 104. After the supercharger 112, an intercooler 130 is located to cool the compressed air being delivered to the engine 104.
[0008] The exhaust path 106 refers to the entire path through which exhaust gases flow from engine 104 till the exhaust gases are released into atmosphere. The intake path 124 refers to the path through which the atmospheric air passes till engine.
[0009] The engine 104 receives the air into the cylinders through an intake valve which is not shown in fig. The air in the cylinder is compressed by a piston and at a predefined position of the piston, the fuel is injected by an injector resulting in the combustion of air-fuel mixture in the cylinder. In the exhaust stroke the exhaust gases are sent out from the cylinder through the exhaust path 106.
[0010] The exhaust gases coming out of the engine 104 comprise various gases which may be harmful to the environment. As the vehicles have to meet legal requirements regarding the amount of harmful gases that are permitted to be released into the environment, the vehicles come with EGT in various forms. The invention discloses one of the EGT apparatuses.
[0011] The various components of the exhaust gas treatment apparatus 100 are explained below:
[0012] Diesel Oxidation Catalyst DOC 102: The Diesel Oxidation Catalyst converts exhaust gas pollutants into harmless gases by chemical oxidation. In case of diesel exhaust, the catalyst oxidizes CO and HCs which are present in the exhaust gases, to carbon dioxide and water. A diesel oxidation catalyst consists of a stainless steel canister that contains a honeycomb structure called a substrate. The substrate may be made of ceramic material or metal foil. The interior surfaces are coated with catalytic metals such as platinum and/or palladium. When the exhaust gases pass through the DOC, the chemical reaction takes place and the CO and HC are converted into CO2 and H2O. The exhaust gases then flow to the POC 108 which forms next stage of EGT.
[0013] Particle oxidation catalyst POC 108: The Particle Oxidation Catalyst 108 is a specialized diesel oxidation catalyst with a capacity to hold solid soot particles. The captured particles are removed through oxidation to gaseous products, in a process called regeneration. After removal of particle matter, the exhaust gases flow to the SCR apparatus which forms the next stage of EGT.
[0014] Selective Catalytic Reduction SCR apparatus: SCR is a technique of converting nitrogen oxides, into nitrogen (N2) and water (H2O). The SCR apparatus uses a catalyst. A reducing agent which is typically urea or ammonia solution is sprayed into the exhaust gases before the exhaust gases enter the catalyst in the SCR apparatus. When the exhaust gases are passing through the SCR apparatus, the chemical reaction takes place. In the chemical reaction the harmful nitrogen gases are converted into harmless N2 and H2O. SCR catalysts are made from various ceramic materials used as a carrier, such as titanium oxide. The SCR apparatus typically comprises an SCR catalyst 116, a tank 117 to store the reducing agent, a pump which is not shown, to draw the reducing agent from the tank 117, a dosing module 114 to spray the reducing agent into the exhaust path. There may be a separate Electronic Control Unit (ECU) 208 to control the SCR apparatus or the Engine Control Unit 208 which also controls the fuel injection, may control the SCR apparatus. The ECU 208 computes the quantity of the reducing agent to be sprayed into the exhaust path depending upon the engine operating conditions.
[0015] It is mandated by legal requirement that sufficient amount of reducing agent is maintained in the tank 117. When the quantity of the reducing agent falls below a threshold, the ECU 208 limits the torque generated by the engine 104 by reducing the quantity of fuel injected in the cylinders of the engine 104. Also the ECU 208 generates a visual warning to the user to indicate that the level of reducing agent is below required quantity and it needs to be refilled.
[0016] An oxygen sensor 140 disposed downstream of the SCR apparatus, measures the amount of oxygen available in the exhaust gases. The amount of oxygen provides an indication on the quality of the combustion in the engine which in turn provides an indication of the harmful gases present in the exhaust gases. If the oxygen level is above a predefined value, it indicates that enough fuel is not injected into the cylinder for the burning of the oxygen. This is called lean air fuel mixture. This leads to reduced torque generation and reduced performance of the engine. In some cases this may also lead to increased HC emissions. If the oxygen level is below a predefined value, it indicates that there was more fuel injected in the cylinder and there was not enough oxygen to burn the fuel completely. This is called rich air fuel mixture. This results in reduced fuel efficiency and increased HC emissions.
[0017] As lean or rich air fuel mixture burning in the cylinder is not advisable, the engine control unit (ECU) 208 continuously monitors the oxygen content in the exhaust gases and controls the fuel injection for the next cycles to achieve a standard air fuel ratio. There may be second oxygen sensor 142 before the DOC 102 for better control of air fuel mixture. The two oxygen sensors 140, 142 also provide the efficiency of the SCR apparatus in reducing nitrogen gases. The fuel injection is controlled by activating and de-activating the injector.
[0018] Exhaust Gas Recirculation EGR: The EGR technique involves recirculating a portion of the engine’s exhaust gases back into the intake path. In most systems, an intercooler lowers the temperature of the recirculated gases. The cooled recirculated gases, which have a higher heat capacity and lower oxygen content than air, lower the combustion temperature in the engine, thus reducing NOx formation. In Fig. 1, the exhaust gases are passed through an EGR valve 110 and then fed to the supercharger 112. The supercharger 112 also receives the air from the atmosphere through the intake path 124. The fresh air and the recirculated gases are compressed in the supercharger 112. The compressed air and recirculated gases are passed through the intercooler 130 to remove some of the heat. The mixture of air and recirculated gases are fed into the cylinders of the engine 104 for combustion. At the inlet of the supercharger 112, there is placed a second valve 132 to regulate the quantity of the air and recirculated gases depending upon the engine operating conditions. The ECU 208 controls both the valves 132, 110 to provide appropriate quantity of recirculated gases and the air for the combustion. The valves 110 and 132 are proportional valves comprising solenoids and controlled by the ECU.
[0019] The EGT apparatus according to the invention shown in fig. 1 reduces the harmful gases in the exhaust gases. The supercharger increases the air mass being delivered to the engine. The EGR path is located towards the low pressure side of the supercharger 112. The recirculated gases which are fed into supercharger 112 are free from particle matter as the POC is located upstream of the supercharger 112. This enhances the reduction of harmful gases from the exhaust. Positioning the EGR valve on the low pressure side of the supercharger increases the stability of the engine. This is specifically helpful for single cylinder engine. Also as the POC is upstream of EGR valve, the efficiency of the EGT apparatus increases as the EGR valve receives exhaust gases which are free from soot particles.
[0020] Fig. 2 illustrates a lean fuel injection apparatus 200. The lean fuel injection apparatus 200 comprises a fuel tank 202, a fuel filter 204, a pump 205, an injector 206 and an engine control unit (ECU) 208, apart from all the required sensors which are not shown. Here the pump 205 is a mechanical pump. The injector 206 is an electronically controlled injector which may be a common rail injector controlled by the ECU 208. This apparatus 200 is a hybrid fuel injection system where the pump 205 and the pump control logic are mechanical whereas the injector 206 and the injector controls are electronically operated. Here injector control refers to the ECU 208 and the other sensors and actuators. The pump control logic refers to the mechanism to operate the pump 205. The injector 206 typically has a solenoid which is controlled by the ECU 208. The power supplied to the injector 206 is controlled by the ECU 208 to inject the right quantity of fuel into the cylinders of the engine 104.
[0021] The EGT system comprises the lean fuel injection apparatus 200 and the EGT apparatus 100. In the lean fuel injection apparatus 200 the mechanical pump is used along with the electronically controlled injector. To make the whole system simple and cost effective, the same ECU is used to control the engine104, the valves 110, 132, dozing module 114 and all other actuators. The mechanical pump referred above is used to supply pressurized fuel to the injectors 206.
[0022] The invention proposes an efficient EGT system for a single cylinder engine 104. The EGT system proposed has advantages in fuel consumption due to avoidance of exhaust temperature generation by increasing the engine injection parameters or rich mode of operation where the single cylinder engine has problem in stable combustion due to its air system leading to problems in drivability. The proposed EGR system provides drivability and stability in combustion as the EGR is provided on the low pressure of the supercharger.
[0023] The EGT system along with the lean fuel injection apparatus makes it cost effective and helps in meeting all the regulations for the emission standards.
[0024] Even though the EGT apparatus 100 according to the invention increases the stability of the single cylinder engines, the same EGT apparatus also works for plurality of cylinders.
[0025] The EGT system proposed has cost advantage because a single ECU 208 is used to control the fuel injection as well as exhaust gas treatment.