Claims:We claim:
1. A system (100) to deliver reducing agent for Selective Catalytic Reduction (SCR) in a vehicle, said vehicle comprising at least an air compressor (106) for an engine (122) and a pump (114) to deliver reducing agent in an exhaust path of said engine (122), said pump (114) comprising a chamber (202) with a flexible membrane (212), an inlet (206) and an outlet (204), characterized in that:
a spring (208) held in support of said flexible membrane (212) inside said chamber (202) of said pump (114), and
said air compressor (106) in fluid communication with said pump (114), in a manner such that pressurized fluid from said air compressor (106) is adapted to drive said pump (114).

2. The system (100) as claimed in claim 1, wherein said pump (114) delivers said reducing agent in said exhaust path through said outlet (204) when said flexible membrane (212) is moved from a first position (214) to a second position (216) upon supply of said pressurized fluid to said chamber (202).

3. The system (100) as claimed in claim 1, wherein said pump (114) intakes reducing agent through an inlet (206) when said flexible membrane (212) moves from said second position (216) to said first position (214) upon drop in pressure of said pressurized fluid.

4. The system (100) as claimed in claim 2, wherein said spring (208) is compressed and held in tension when said flexible membrane (212) is moved to said second position (216) under supply of said pressurized fluid.

5. The system (100) as claimed in claim 3, wherein said spring (208) expands and brings said flexible membrane (212) to said first position (214) when there is a drop in pressure of said pressurized fluid.

6. The system (100) as claimed in claim 1, wherein an inlet check valve and an outlet check valve is provided for said inlet (206) and said outlet (204) of said chamber (202), respectively.

7. The system (100) as claimed in claim 1, wherein said reducing agent is gravity fed to said chamber (202) through said inlet (206) of said pump (114).

8. The system (100) as claimed in claim 1, wherein flow of said pressurized fluid to said flexible membrane (212) of said pump (114) is opened and closed with a control valve (110) based on temperature of exhaust gas.

9. The system (100) as claimed in claim 1, wherein an injector (120) is integrated to said outlet (204) of said pump (114).

10. The system (100) as claimed in claim 1, wherein said air compressor (106) is at least one selected from a group comprising a supercharger and a reservoir filled with pressurized fluid. , Description:Field of the invention:
[0001] The present disclosure relates to Selective Catalytic Reduction (SCR) and particularly relates to a system to deliver reducing agent in exhaust path of a Diesel engine.

Background of the invention:
[0002] An air compressor such as a super charger is well-known in the art. The supercharger operates based on roots blower principle by rotation of two rotor lobes which compresses the intake air from an input port to an outlet port. In view of the current and future strict emission legislation in various countries such as India for the low price vehicle segment, air charging of the single cylinder engine is becoming mandatory to achieve the NOx reductions. It is foreseen to have a supercharger before the intake manifold of the engine and to boost by 200-300 mbar. This allows to apply higher Exhaust Gas Recirculation (EGR) rates (25%) and bring down the NOx emissions. But the measures on the engine combustion side is not sufficient, there is an additional need for NOx exhaust gas treatment.

[0003] As already known, there are two methods available, either a NOx Storage Catalyst (NSC) or Selective Catalyst Reduction (SCR). The first NSC methods stores the NOx in the catalyst and calls for frequent regeneration operating the combustion engine in rich mode (lambda < 1). This has to be considered critical for the single cylinder engines due to load cycles and missing closed particle filter (DPF) to restrict the high Particulate Matter (PM) emissions during regeneration cycle. NOx reduction by SCR happens by a frequent urea injection upstream to the SCR catalyst.

[0004] Problem is that the available market solution are designed for bigger engines with increased injection rates and are costly and difficult to package. The existing systems requires a tank, supply and dosing module and an electronic dosing control unit.

[0005] Hence, there is a need for a simple mechanical system for injecting reducing agent/ urea solution in the exhaust path to reduce NOx.

Brief description of the accompanying drawings:
[0006] An embodiment of the disclosure is described with reference to the following accompanying drawings,
[0007] Fig. 1 illustrates a block diagram of engine with a system to deliver reducing agent for a vehicle, according to an embodiment of the present invention;
[0008] Fig. 2 illustrates a state of a pump before a delivery phase and after an intake phase of reducing agent, according to an embodiment of the present invention, and
[0009] Fig. 3 illustrates the state of the pump after the delivery phase and before the intake phase of the reducing agent, according to an embodiment of the present invention.

Detailed description of the embodiments:
[0010] Fig. 1 illustrates a block diagram of engine with a system to deliver reducing agent for a vehicle, according to an embodiment of the present invention. The engine 122 is a diesel engine with at least one cylinder. The intake path of the engine 122 is disclosed to be comprising an air filter 104, an air compressor 106 and an intercooler 108. The exhaust path of the engine 122 comprises filters such as Diesel Oxidation Catalyst (DOC) 132 and/or Particle Oxidation Catalyst (POC) 130 and a silencer 124. An Exhaust Gas Recirculation (EGR) valve 116 is also provided for circulating exhaust gas into cylinder of the engine 122 to reduce NOx. A SCR mechanism helps in reducing the NOx emissions of the engine 122 furthermore. The SCR mechanism comprises a catalyst 126, a tank 102 storing urea solution or Diesel Exhaust Fluid (DEF) or reducing agent. Further, a pump 114 is provided, which intakes the reducing agent from the tank 102 and delivers into the exhaust path upstream of the catalyst 126 through an injector 120. The exhaust path further comprises a temperature sensor 128 to detect the optimal temperature to initiate injection of the reducing agent. A control unit 112 controls the EGR valve 116 and a control valve 110 and receives input from the temperature sensor 128. The control unit 112 is a microcontroller or a microprocessor. The pump 114 is a diaphragm pump.

[0011] In accordance to an embodiment of the present disclosure, a system 100 to deliver reducing agent for Selective Catalytic Reduction (SCR) of exhaust gas in a vehicle is provided. The vehicle comprises at least an air compressor 106 for the engine 122, and the pump 114 to deliver reducing agent in the exhaust path. With reference to Fig. 2, the pump 114 comprises a chamber 202 with a flexible membrane 212, an inlet 206 and an outlet 204. The pump 114 is characterized by a spring 208 held in support of the flexible membrane 212 inside the chamber 202 of the pump 114. Further, the air compressor 106 is in fluid communication with pump 114, in a manner such that pressurized fluid from the air compressor 106 is adapted to drive the pump 114.

[0012] The pump 114 also comprises an inlet check valve and an outlet check valve for the inlet 206 and the outlet 204 of the chamber 202, respectively. This ensures that during suction, fluid enters through the inlet 206 and exits during delivery through outlet 204 of the pump 114.

[0013] In accordance to an embodiment of the present disclosure, the reducing agent is gravity fed to the pump 114 which is actuated by the pressure of the fluid discharged by the air compressor 106. The air compressor 106 is mechanically driven by the combustion engine 122 with a fixed drive ratio. Hence, the volume of the fluid mass delivered by the air compressor 106 is directly synchronous/ proportional to the drive speed of the engine 122.

[0014] In accordance to an embodiment of the present invention, the air compressor 106 is a supercharger. The supercharger works based on two rotor lobes rotating and meshing against each other in a common casing with input and output port for the fluid. The rotors with different numbers of lobes as per requirement are used, such as but not limited to two, three and four lobes. The fluid such as air enters the casing of the supercharger through input port, is trapped between two adjacent lobes, transported and pushed out after exposure of the trapped volume to the output port. Pressurization of the fluid happens during delivery. The number of delivery events is depending on the number of lobes. For. Example: a three-lobe rotor yields six delivery events (three by each rotor). This signifies that at each delivery event an air pressure wave acts on the flexible membrane 212 i.e. the diaphragm. Hence, the number of lobe defines the delivery as well urea injection frequency.

[0015] The delivery characteristic of the supercharger is not continuous and there are pulsations depending on the number of lobes each rotor has. For example: total number of pressure peaks during one revolution for a supercharger comprising two rotors with three lobes each is six.

[0016] In accordance to another embodiment of the present disclosure, the air compressor 106 comprises a reservoir filled with pressurized fluid. The pressurized fluid is discharged operatively to drive the pump 114. The pressurized fluid is released/discharged through a control valve 110 by the control unit 112.

[0017] Fig. 2 illustrates a state of a pump before a delivery phase and after an intake phase of reducing agent, according to an embodiment of the present invention. In the delivery phase, the pump 114 delivers the reducing agent in the exhaust path through the outlet 204 when the flexible membrane 212 is moved from a first position 214 to a second position 216 upon supply of the pressurized fluid to the chamber 202. The flexible membrane 212 is shown in a first position 214, where the spring 208 is neutral (not in tension) and covers/closes an opening 210 of the chamber 202. The flexible membrane 212 has moved from a second position 216 (shown in dotted line) to the first position 214 during the intake phase. In intake phase, the spring 208 expands and pushes back the flexible membrane 212 to the first position 214 when there is a drop in pressure of the pressurized fluid. While the flexible membrane 212 moves to the first position 214, an inlet check valve at the inlet 206 is opened. The inlet check valve is a one way valve which opens only when a fluid flows into the chamber 202 from outside. The pump 114 is ready for the delivery phase, when the flexible membrane 212 is at the first position 214. The delivery phase of the pump 114 is initiated directly after the delivery event of the air compressor 106. The pressure wave of the pressurized fluid from the air compressor 106 is directed to the opening 210, which pushes the flexible membrane 212 against the force of the spring 208 toward the second position 216.

[0018] Fig. 3 illustrates the state of the pump after the delivery phase and before the intake phase of the reducing agent, according to an embodiment of the present invention. In suction phase, the pump 114 intakes reducing agent through the inlet 206 when the flexible membrane 212 moves from the second position 216 to the first position 214 upon drop in the pressure of the pressurized fluid. The flexible membrane 212 is shown in the second position 216, where the spring 208 is compressed. The flexible membrane 212 has moved from the first position 214 (shown in dotted line) under the force/ pressure of the pressurized fluid to the second position 216. While the flexible membrane 212 moves towards the second position 216, the pressure in the chamber 202 filled with reducing agent increases. As the flexible membrane 212 moves, an inlet check valve at the inlet 206 closes and an outlet check valve at the outlet 204 opens. The reducing agent is pushed out of the chamber 202 through the outlet 204 and finally through the injector 120 such as mechanical injector. The outlet check valve is a one way valve which opens when a fluid moves out of the chamber 202.

[0019] The spring 208 is compressed and held in tension when the flexible membrane 212 is moved to the second position 216 under supply of the pressurized fluid. The spring 208 remains in the same state unless the pressure of the pressurized fluid drops.

[0020] The spring 208 when compressed, is designed to withstand the maximum force exerted by the pressurized fluid in second position 216. After the pressure of the pressurized fluid drops, the spring 208 pushes back the flexible membrane 212 to the first position 214. During the suction phase, the inlet check valve opens and the reducing agent is sucked in assisted by gravity force.

[0021] The required urea injection pressure is achieved by selection of the dead volume in a connector 205 i.e. upstream of the injector 120. The volume of the connector 205 should be minimal to achieve a high injection pressure. Since the quantity of injection of the reducing agent to be considered is three to four percent of Diesel fuel consumption, which is feasible by the system 100.

[0022] The required quantity of urea injection is depending of NOx to be converted and hence depending on the exhaust mass flow. Since the air compressor 106, preferably the supercharger is driven by the crankshaft of the engine 122, there is a direct relation between inlet air mass flow, number of delivery and urea injection events and exhaust mass flow. An increase in the drive speed increases inlet and exhaust mass flow as well the number of injection of reducing agent and vice versa.

[0023] The injection of the reducing agent is performed through a simple injector 120 comprising a mechanical nozzle holder assembly. The nozzle opens the spray hole and releases the specific quantity of the reducing agent, only when the pressure of the reducing agent inside the injector 120 exceeds a threshold. The injector 120 is conventional pressure based injector.

[0024] In accordance to another embodiment of the present invention, the pump 114 and the injector 120 are integrated as a single unit, and forms a common distributor for the reducing agent. Alternatively, the pump 114 and the injector 120 are integrated but are removable. By this, the requirement of small dead volume downstream of the outlet 204 of the pump 114 is achieved easily.

[0025] In accordance to yet another embodiment of the present disclosure, a control valve 110 to open or close the flow of pressurized fluid to the pump 114 is provided. The control valve 110 is located in the fluid communication between the air compressor 106 and the pump 114. The control valve 110 is controlled by the control unit 112 based on the temperature detected in the exhaust path from a temperature sensor 128. Alternatively, the control valve 110 is provided with mechanical linkages to allow manual switching.

[0026] The control valve 110 is provided to mitigate deposit formation and fouling within the catalyst 126 caused by injection of the reducing agent not within the suitable temperature range. The injection of reducing agent during low temperature causes increase in the deposit formation. The control valve 110 is provided upstream of the pump 114. The temperature sensor 128 is located in proximity to the catalyst 126. The control unit 112 is adapted to monitor the exhaust temperature and depending on the temperature, opens or closes the path for the flow of the pressurized fluid. The control unit 112 is not limited to the functions described but is usable for other functions of the vehicle such as to control EGR valve, fuel injection and some additional monitor functions.

[0027] The present disclosure provides a low cost system 100 for SCR of exhaust gas/stream with a pump 114 driven by a supercharger. Further, the system 100 is mechanically operated. The pressurized fluid comprises ambient air or a combination of ambient air and recirculated exhaust gas. Due to this relation there will be no need of a separate urea injection control. A check valve 118 is also provided to prevent flow of the reducing agent back to the tank 102. The injector 120 is mechanically actuated by pressure pulsation generated at the outlet 204 of the pump 114 and injects the reducing agent upstream of the catalyst 126. The compressor 106 deliver both compressed fluid to the combustion engine 122 and to the low cost SCR system 100.

[0028] 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.