Claims:We claim:
1. An Exhaust Gas Recirculation (EGR) system (100) for an engine (120), said system (100) comprises:
an intake conduit (104);
a circulation conduit (106) positioned inside said intake conduit (104) in coaxial manner, forming an annular space (112) with said intake conduit (104), said circulation conduit (106) fluidly coupled to an exhaust conduit (114) of said engine (120), characterized by
a fan (110) positioned at an open end of said circulation conduit (106), said fan (110) rotates by air coming through said intake conduit (104) and draws exhaust gas from said circulation conduit (106).

2. The EGR system (100) as claimed in claim 1, wherein said fan (110) comprises two sets of blades formed on two concentric rings, an outer ring (116) and an inner ring (118).

3. The EGR system (100) as claimed in claim 2, wherein said inner ring (118) has a radius equal to a radius of said circulation conduit (106) and said outer ring (116) has a radius equal to cover said annular space (112).

4. The EGR system (100) as claimed in claim 2, wherein a first set of blades (124) are provided inside said inner ring (118) and positioned at an interface of said open end of said circulation conduit (106).

5. The EGR system (100) as claimed in claim 2, wherein a second set of blades (122) are positioned between said outer ring (116) and said inner ring (118) within said annular space (112).

6. The EGR system (100) as claimed in claim 1, wherein said fan (110) comprises two sets of blades mounted to an inner ring (118).

7. The EGR system (100) as claimed in claim 1, wherein said a first set of blades (124) are mounted on inner periphery of said inner ring (118), and a second set of blades (122) mounted to an outer surface of said inner ring (118).
, 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] The present invention relates to an Exhaust Gas Recirculation (EGR) system for an engine.

Background of the invention:
[0002] The EGR is used in diesel engines for controlling NOx emissions. When the pressure difference between intake air and exhaust gases are less (i.e. PIn>PEx), the exhaust gases does not flow. The exhaust gas is sent into the intake manifold from exhaust pipe by opening an EGR valve. For the exhaust gas to flow into the intake manifold, the pressure at the intake manifold needs to be at least 120 mbar less than that of exhaust gases. If the delta pressure is less (pressure at intake manifold is more than exhaust gas or else the pressure difference is less than 120 mbar), exhaust gases cannot flow to intake manifold. In such cases, if EGR is required, then various actuators are used such as a throttle valve. Use of throttle valve increases cost of the system, calibration efforts and the maintenance.

[0003] According to a patent literature CN204458107, a mixing device for exhaust gas recirculation system is disclosed. The mixing device for the exhaust gas recirculation system comprises an air inlet pipe and an EGR pipe, the end of the EGR pipe extends into the air inlet pipe, and a connection end of the EGR pipe sequentially comprises a connection pipe and a mixing pipe, wherein the connection pipe is inserted into the air inlet pipe and arranged to be perpendicular to the air inlet pipe, the mixing pipe and the air inlet pipe are arranged in a coaxial-line mode, and the mixing pipe is composed of a narrowing section and an expanding section; the mixing pipe is arranged in the air inlet pipe in the flow direction of airflow, the narrowing section of the mixing pipe is connected with the connection pipe, the inner diameter of the narrowing section of the mixing pipe is smaller than that of the connection pipe, the expanding section of the mixing pipe gradually expands from the joint of the expanding section and the narrowing section to the tail end of the mixing pipe, multiple air outlet holes are formed in the pipe wall of the portion, with the maximum diameter, of the expanding section in an annular mode, and the tail end of the mixing pipe is closed. By means of the mixing device for the exhaust gas recirculation system, fresh intake air is changed to be the annular airflow, exhaust gas in EGR evenly enters the annular fresh air through the air outlet holes, the high uniformity of the EGR rate is achieved, and the mixing device for the exhaust gas recirculation system is of an integral type structure and is simple in structure and convenient to assemble or disassemble integrally.

[0004] Hence, this invention is to make EGR flow when the pressure difference is less without any complicated actuators.

Brief description of the accompanying drawings:
[0005] An embodiment of the disclosure is described with reference to the following accompanying drawing,
[0006] Fig. 1 illustrates the Exhaust Gas Recirculation (EGR) system for an engine, according to an embodiment of the present invention.

Detailed description of the embodiments:
[0007] Fig. 1 illustrates the Exhaust Gas Recirculation (EGR) system for an engine, according to an embodiment of the present invention. The system 100 comprises an intake conduit 104. A circulation conduit 106 is positioned inside the intake conduit 104 in coaxial manner, forming an annular space 112 with the intake conduit 104. The circulation conduit 106 is fluidly coupled to an exhaust conduit 114 of the engine 120. The system 100 is characterized by a fan 110 positioned at an open end of the circulation conduit 106. The fan 110 rotates because of the air coming in (shown by arrow) through the intake conduit 104 and draws exhaust gases from the circulation conduit 106. The rotation of fan 110 causes suction of exhaust gases from the exhaust conduit 114 through the circulation conduit 106. The intake conduit 104 is shown connected to a filter 102, however the same is optional.

[0008] The fan 110 comprises two sets of blades formed on two concentric rings. The rings are an outer ring 116 and an inner ring 118. The inner ring 118 has a radius equal to the radius of the circulation conduit 106, and the outer ring 116 has a radius enough to cover the annular space 112. The radius is considered from the center of the concentric rings.

[0009] In accordance to an embodiment of the present invention, the fan 110 is coupled to the periphery of the open end of the circulation conduit 106, in a rotatable manner. In another embodiment, the fan 110 is mounted to a shaft (not shown), and the shaft is mounted either to a surface of the circulation conduit 106 or the intake conduit 104.

[0010] A first set of blades 124 are provided inside the inner ring 118 and positioned at an interface of the open end of the circulation conduit 106. A second set of blades 122 are positioned between the outer ring 116 and the inner ring 118 within the annular space 112. Further, a valve 108 is provided to control the passage of exhaust gases through the circulation conduit 106. The valve 108 is electronically controllable through a controller (not shown) or mechanically controllable.

[0011] According to the present invention, a working of the EGR system 100 is explained. When the engine 120 is operating, the air is induced inside the intake conduit 104 through the filter 102. The incoming air flows through the annular space 112 due to the presence of a part of the circulation conduit 106 within the intake conduit 104. The air flow strikes or hits the second set of blades 122 and rotates the fan 110. The rotation of the fan 110 causes the first set of blades 124 to rotate, as both the set of blades are concentric and mounted to each other. The first set of blades 124 are designed in such a manner, that rotation causes suction from the circulation conduit 106 to the intake conduit 104. In other words, when the engine 120 is working, the air flow from intake conduit 104 drives the second set of blades 122. The first set of blades 124 starts rotating along with the second set of blades 122. The first set of blades 124 is designed similar to an exhaust fan. Therefore, the rotation of first set of blades 124 creates a suction force inside the circulation conduit 106. The suction force generated, draws the exhaust gas and then pushes towards the engine 120. When the load/speed is high, intake airflow is also high, thus applying more force on the fan 110. In low load conditions, the air flow is less creating less force on the fan 110. However, at low load/speed condition, as per the present invention, the pressure difference is available for the exhaust gas to be driven into the intake conduit 104. A precise control of the recirculated exhaust gases is performed by using the valve 108.

[0012] Now, two cases are provided for clarity in understanding, and the same must not be understood in limiting manner. In a first case, consider the engine 120 operating in low idle condition. In the low idle condition, if there is requirement of the exhaust gases, the valve 108 is opened and part of exhaust gas (based on the percentage of opening) from exhaust conduit 114 starts flowing towards the intake conduit 104 (only if sufficient difference in pressure is available). However, if the required pressure difference is not present, the fan 110 of the present invention assists in drawing the exhaust gases into the intake conduit 104.

[0013] In a second case, when the load/speed is high, the fuel injected is more for engine 120 to take more load. Due to this, the airflow to the engine 120 also increases. As the airflow increases, the force on the fan 110 increases, thereby increasing the speed of rotation of the same. With this phenomenon, more exhaust gases are drawn from the circulation conduit 106 and is supplied to the intake conduit 104.

[0014] In accordance to another embodiment of the present invention, the fan 110 comprises two sets of blades mounted to the inner ring 118, i.e. only one ring is used. The first set of blades 124 are mounted on inner periphery of the inner ring 118, and the second set of blades 122 are mounted to the outer surface of the inner ring 118. The outer ring (116) is not provided in this embodiment.

[0015] According to the present invention, the EGR system 100 is equipped with the fan 110 which assists in drawing exhaust gases to flow from exhaust conduit 114 to the intake conduit 104, even when the pressure difference (i.e. PIn>PEx) is less. A use of actuator such as throttle valve, is eliminated in those applications where the actuator is used solely to recirculate exhaust gases because of insufficient pressure difference. The present invention is cost effective, involves minimum maintenance costs, and provides simple and robust design for natural aspirated engines 120. Also, no separate calibration of the component is required unless and until the design of blades are as per the requirement to generate sufficient suction force. Further scope of improvement possible easily by introducing electronics.

[0016] 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.