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 14;
- an exhaust gas recirculation duct 16, and an exhaust gas recirculation valve 18 in flow communication with said exhaust gas recirculation duct 16;
- an air intake duct 20;
at least a part of said exhaust gas duct 14 and at least a part of said air intake duct 20 are in flow communication with said exhaust gas recirculation duct 16; characterized in that
- an exhaust gas recirculation bypass duct 22 is in flow communication with said exhaust gas recirculation duct 16 in a manner such that air entering said exhaust gas recirculation valve 18 is bypassed in at least one operating condition of said engine 12.

2. The air circulation system 10 for an engine 12 in accordance with Claim 1, wherein an upstream end of said exhaust gas recirculation bypass duct 22 is located at an inlet portion of said exhaust gas recirculation valve 18.

3. The air circulation system 10 for an engine 12 in accordance with Claim 1, wherein a downstream end of said exhaust gas recirculation bypass duct 22 is located at an outlet portion of said exhaust gas recirculation valve 18.

4. The air circulation system 10 for an engine 12 in accordance with Claim 1, wherein said exhaust gas recirculation valve 18 is closed during a full load operating condition of said engine 12 such that exhaust gas is channeled through said exhaust gas recirculation bypass duct 22 for the full load condition of said engine 12.

5. The air circulation system 10 for an engine 12 in accordance with Claim 1, wherein said exhaust gas recirculation valve 18 is opened during a partial load operating condition of said engine 12 such that exhaust gas is channeled through said exhaust gas recirculation bypass duct 22 and said exhaust gas recirculation valve 18 for the partial load operating condition of 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 valve that is integrated with a bypass flow path to an air intake duct of the engine.
Background of the invention:
[0002] U.S. Patent Publication Number 2006/0042608 A1 describes a method and device for operating an internal combustion engine having exhaust-gas recirculation. The method and device allowing a diagnosis of an exhaust-gas recirculation cooler during normal operation of the internal combustion engine. In this context, a variable characteristic of the functioning of the exhaust-gas recirculation cooler is monitored. The variable characteristic of the functioning of the cooling device is ascertained as a function of a measured value. The variable characteristic of the functioning of the exhaust-gas recirculation cooler is specified on the basis of an intact exhaust-gas recirculation cooler. The ascertained value of the variable characteristic of the functioning of the exhaust-gas recirculation cooler is compared to the predefined value. An error is detected when the ascertained value of the variable characteristic of the functioning of cooling device deviates from the specified value.

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] An air circulation system 10 for an engine 12 is described. The air circulation system 10 comprises at least an exhaust gas duct 14, an exhaust gas recirculation duct 16, and an exhaust gas recirculation valve 18 in flow communication with the exhaust gas recirculation duct 16, and an air intake duct 20. At least a part of the exhaust gas duct 14 and at least a part of the air intake duct 20 are in flow communication with the exhaust gas recirculation duct 16. A bypass duct 22 is located in the exhaust gas recirculation duct 16 in a manner such that air entering the exhaust gas recirculation valve 18 is bypassed in at least one operating condition of the engine 12.
[0006] Figure 1 illustrates a block diagram of an air circulation system 10 for an engine 12. The air circulation system 10 comprises an air filter 24. Fresh air from an inlet is channeled to the air filter 24 via an air intake duct 20, wherein the air filter 24 separates impurities from fresh air and supplies fresh air to an engine 12.

[0007] An exhaust gas recirculation (EGR) valve 18 is coupled to an exhaust gas recirculation duct 16. The exhaust gas recirculation valve 18 facilitates controlling a pressure and mass flow rate of exhaust gas that is channeled to the engine 12. An engine control unit is connected to the exhaust gas recirculation valve 18 and controls the operation of the exhaust gas recirculation valve 18and facilitates controlling the exhaust gas recirculation valve 18 to an “open” and “closed” position to facilitate controlling the opening pressure and flow rate of exhaust gas that is channeled to the engine 12. A silencer 28 is coupled downstream from the engine 12 and vents exhaust gas out of the exhaust gas circulation system 10. A diesel oxidation catalyst 26 is coupled downstream from the engine 12 and to the exhaust gas duct 14 and facilitates oxidizing the nitrous oxide gas and carbon monoxide gas that is discharged from the engine 12. An exhaust gas recirculation bypass duct 22 is coupled to the exhaust gas recirculation duct 16. An upstream end of the exhaust gas recirculation bypass duct 22 is in flow communication with an inlet portion of the exhaust gas recirculation valve 18, while a downstream end of the exhaust gas recirculation bypass duct 22 is in flow communication with an outlet portion of the exhaust gas recirculation valve 18. The exhaust gas recirculation bypass duct 22 facilitates bypassing the exhaust gas recirculation valve 18 during one operating condition of the engine 12.

[0008] The working of the exhaust gas circulation system 10 is described as an example. Fresh air is channeled to the engine 12 via the air filter 24. When the engine 12 is operating under full load, the exhaust gas recirculation valve 18 is closed by the engine control unit. Therefore, the exhaust gas flows through the exhaust gas recirculation bypass duct 22 and into the engine 12 via the air intake duct 20. During a partial load of the engine 12, the engine control unit opens the exhaust gas recirculation valve 18 to an “open” position. Therefore exhaust gas flows to the engine 12 via the exhaust gas recirculation valve 18 as well as the exhaust gas recirculation bypass duct 22, thereby increasing the pressure and mass flow rate of exhaust gas to the engine 12.
[0009] The application of the exhaust gas recirculation bypass duct 22 between an inlet and an outlet of the exhaust gas recirculation valve 18 allows for precise controlling of the exhaust gas recirculation rate in 1 cylinder engine applications as the engine load is predominantly at full load. The exhaust gas recirculation rate should be limited at full load by allowing the exhaust gas to flow through the exhaust gas recirculation bypass duct 22 while the exhaust gas recirculation valve 18 remains closed. At part load, the exhaust gas recirculation rate can be increased by opening the exhaust gas recirculation valve 18 to an “open” position. 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 16 and the air filter 24 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.

[00010] 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.