Claims:We claim:
1. An air circulation system 10 for an engine 12, said air circulation system 10 comprising at least:
- an exhaust gas duct 27;
- an exhaust gas recirculation duct 25;
- an air intake duct 29;
at least a part of said exhaust gas duct 27 and at least a part of said air intake duct 29 are in flow communication with said exhaust gas recirculation duct 25; characterized in that
- a supercharger 16 located in the air intake duct 29 upstream from a junction of the exhaust gas recirculation duct 25 and the air intake duct 29
- a bypass duct 19 located in said air intake duct 29 in a manner such that air entering said supercharger 16 is bypassed in at least one operating condition of said engine 12;
- a bypass valve 20 located in said bypass duct 19 and adapted to be operated in a manner such as to control a mass flow rate of air entering the supercharger 16 in said at least one operating condition of said engine 12.

2. The air circulation system 10 for an engine 12 in accordance with Claim 1 further comprising an exhaust gas recirculation valve 28 coupled downstream from an exhaust gas recirculation cooler 24 and adapted to control a flow rate of exhaust gas to said engine 12.

3. The air circulation system 10 for an engine 12 in accordance with Claim 1 further comprising:
an intercooler 14 in flow communication with said engine 12, said intercooler 14 located upstream from said engine 12;
said supercharger 16 in flow communication with said intercooler 14, said supercharger 16 located upstream from said intercooler 14, said supercharger 16 adapted to control a pressure and flow rate of fresh air to said intercooler 14.

4. The air circulation system 10 for an engine 12 in accordance with Claim 4 further comprising a throttle valve 34 coupled in flow communication downstream from said intercooler 14, said throttle valve 34 adapted to control a flow rate of fresh air to said engine 12. , Description:Field of the invention:
[0001] This disclosure relates to an air circulation system for an engine and more particularly to an EGR path to an air intake of an engine that is positioned downstream from a supercharger, intercooler and throttle valve.
Background of the invention:
[0002] E.P. Patent Application Number 1193388 A2 describes an exhaust gas purifying apparatus for an internal combustion engine with a turbocharger is provided with an introduction port for EGR gas disposed upstream of a compressor and a throttle valve disposed upstream of the introduction port, and comprised of a failsafe means that the portion on the upstream side of the compressor does not have any excessive negative pressure even if a malfunction occurs in the throttle valve. The exhaust gas purifying apparatus for an internal combustion engine with a turbocharger is provided with a supercharger having a turbine disposed in an exhaust passage and a compressor disposed in an intake passage and having an exhaust gas recirculation system for connecting the exhaust passage downstream of the turbine and the intake passage with each other and for recirculating a part of exhaust gas back to an intake system of the internal combustion engine, wherein an introduction port for recirculating the part of the exhaust gas and a throttle valve for opening/closing the intake passage as desired are arranged in this order. A fail safe unit for allowing a predetermined flow rate of intake air to flow to the compressor and giving a load, when the throttle valve is fully closed, is provided in the intake passage upstream of the compressor.

Brief description of the accompanying drawing:
[0003] An embodiment of the disclosure is described with reference to the following accompanying drawing:
[0004] Figure 1 illustrates a block diagram of an air circulation system for an engine.

Detailed description of the embodiments:
[0005] Figure 1 illustrates a block diagram of an air circulation system 10 for an engine 12. The air circulation system 10 comprises at least an exhaust gas duct 27, an exhaust gas recirculation duct 25, and an air intake duct 29. At least a part of the exhaust gas duct 27 and at least a part of the air intake duct 29 are in flow communication with the exhaust gas recirculation duct 25. A supercharger 16 is located in the air intake duct 29 upstream from a junction of the exhaust gas recirculation duct 25 and the air intake duct 29. A bypass duct 19 is located in the air intake duct 29 in a manner such that air entering the supercharger 16 is bypassed in at least one operating condition of the engine 12. A bypass valve 20 is located in the bypass duct 19 and adapted to be operated in a manner such as to control a mass flow rate of air entering the supercharger 16 in at least one operating condition of the engine 12.
[0006] The air circulation system 10 comprises an air filter 18. Fresh air from an inlet is channeled to the air filter 18, wherein the air filter 18 separates impurities from fresh air and supplies fresh air to a supercharger 16. The supercharger 16 is coupled downstream from the air filter 18 and receives fresh air that is supplied from the air filter 18. The supercharger 16 facilitates pressurizing and delivering fresh air to an intercooler 14. The cooled fresh air is channeled from the intercooler 14 to a throttle valve 34. The throttle valve 34 facilitates decreasing a pressure of fresh air that is supplied from the intercooler 14 to the engine 12.
[0007] A bypass duct 19 is in flow communication with a bypass valve 20 and is coupled between an inlet and an outlet of the supercharger 16. The bypass valve 20 facilitates channeling fresh air from an inlet of the supercharger 16 to an outlet of the supercharger 16. The engine control unit is coupled to the bypass valve 20. The engine control unit controls an opening percentage of the bypass valve 20 to reduce a quantity of fresh air that is channeled through the supercharger 16 in accordance with an engine operating condition. The throttle valve 34, and the bypass valve 20 that are used in combination with each other facilitate decreasing a pressure of fresh air that needs to be supplied to the engine 12 at a specific engine operating condition.
[0008] An exhaust gas recirculation cooler 24 is coupled between the throttle valve 34 and the engine 12 and supplies exhaust gas to the engine 12 that is drawn from an exhaust manifold of the engine 12. A bypass valve 26 is coupled between an inlet of the exhaust gas recirculation cooler 24 and an outlet of the exhaust gas recirculation cooler 24 and bypasses exhaust gas that is not required to be channeled to the exhaust gas recirculation cooler 24. An engine control unit (not shown) is in electronic communication with the bypass valve 26 and controls an opening percentage of the bypass valve 26 to facilitate bypassing exhaust gas away from the exhaust gas recirculation cooler 24. An exhaust gas recirculation (EGR) valve 28 is coupled to the exhaust gas recirculation duct 25 and is located downstream from the exhaust gas recirculation cooler 24. The exhaust gas recirculation valve 28 facilitates controlling a pressure and mass flow rate of exhaust gas that is channeled to the engine 12. The engine control unit is coupled to the exhaust gas recirculation valve 28 and facilitates controlling an opening percentage of the exhaust gas recirculation valve 28 and the bypass valve 26 simultaneously to facilitate controlling the opening pressure and flow rate of exhaust gas that is channeled to the engine 12. A silencer 36 is coupled downstream from the engine 12 and vents exhaust gas out of the exhaust gas recirculation system 10. A diesel particulate filter 30 is coupled downstream from the engine 12 and to the exhaust gas duct 27. The diesel particulate filter 30 facilitates absorbing soot particles from the exhaust gases that are discharged from the engine 12 before discharging the exhaust gas to the silencer 36. A diesel oxidation catalyst 32 is positioned upstream from the diesel particulate filter 30 and facilitates oxidizing the nitrous oxide gas and carbon monoxide gas that is discharged from the engine 12.
[0009] The working of the exhaust gas recirculation system 10 is described as an example. Fresh air is channeled to the supercharger 16 via the air filter 18. Depending on an engine operating condition such as but not limited to engine speed and engine torque, the engine control unit operates the bypass valve 20 to channel fresh air from an inlet of the supercharger 16 to an outlet of the supercharger 16. Due to a reduced mass flow rate of fresh air that is allowed to flow through the supercharger 16, a smaller quantity of fresh air gets pressurized and delivered from the outlet of the supercharger 16 to the engine 12. When it is required to increase the mass flow rate of fresh air that is to be delivered from the supercharger 16, the engine control unit closes the bypass valve 20. Therefore, a higher mass flow rate of fresh air is allowed to flow to the supercharger 16. Due to an increased mass flow rate of fresh air that is allowed to flow through the supercharger 16, a greater quantity of fresh air gets pressurized and delivered from the outlet of the supercharger 16 to the engine 12.
[00010] Exhaust gas is channeled to the exhaust gas recirculation cooler 24 from the engine 12. Depending on an engine operating condition such as but not limited to engine speed and engine torque, the engine control unit operates the bypass valve 26 to channel exhaust gas from an inlet of the exhaust gas recirculation cooler 24 to an outlet of the exhaust gas recirculation cooler 24. Due to a reduced mass flow rate of exhaust gas that is allowed to flow through the exhaust gas recirculation cooler 24, a smaller quantity of exhaust gas gets pressurized and delivered from the outlet of the exhaust gas recirculation cooler 24 to the engine 12. When it is required to cool a greater mass flow of exhaust gas, the engine control unit closes the bypass valve 26. Therefore, a higher mass flow rate of exhaust gas is allowed to flow to the exhaust gas recirculation cooler 24. Due to an increased mass flow rate of exhaust gas that is allowed to flow through the exhaust gas recirculation cooler 24, a greater quantity of cooled exhaust gas is delivered from the outlet of the exhaust gas recirculation cooler 24 to the engine 12. An exhaust gas recirculation valve 28 is positioned downstream from the exhaust gas recirculation cooler 24 and coupled to the exhaust gas recirculation duct 25. The engine control unit is in electronic communication with the exhaust gas recirculation valve 28 and controls an opening percentage of the exhaust gas recirculation valve 28 depending on a pressure and mass flow rate of exhaust gas that is required to be delivered from the exhaust gas recirculation valve 28 to the engine 12. The pressure of the exhaust gas that flows from the exhaust gas recirculation valve 28 must be equal to the pressure of the fresh air that flows from the throttle valve 34. Therefore the engine control unit has to control an opening percentage of the bypass valve 20, the throttle valve 34, the bypass valve 26, and the exhaust gas recirculation valve 28 simultaneously to ensure that the pressure of fresh air that is supplied from the throttle valve 34 is equal to the pressure of the exhaust gas that is supplied from the exhaust gas recirculation valve 28 for a given mass flow rate of fresh air and exhaust gas that is required to be supplied to the engine 12. Owing to the regulation of the mass flow rate of exhaust gas and fresh air that is supplied to the engine 12 from the exhaust gas recirculation duct 25 and the supercharger 16 respectively, the engine 12 can be used in every operating condition with respect to engine speed and engine torque while at the same time meeting the EU5 / BS5 emission norms. Specifically, positioning of the supercharger 16 and the exhaust gas recirculation valve 28 can be used to regulate the mass flow rate of exhaust gas and fresh air that is supplied to 1 cylinder engines and hence meet the BS5 and BS6 emission norms for 1 cylinder engines.
[00011] 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.