The invention relates to exhaust gas recirculation (EGR) ejectors and a system for EGR.
There are many previously known automotive vehicles that utilize internal combustion engines such as diesel, gas or two stroke engines to propel the vehicle. In some constructions EGR (exhaust gas recirculation) recirculates the exhaust gas into the engine for mixture with the cylinder charge. The EGR that is intermixed with the air and fuel to the engine enhances the overall combustion of the fuel. This, in turn reduces exhaust gas emissions.
Various prior art systems ay use an EGR valve and a standard venturi to measure EGR to an intake manifold. However, such systems typically operate at undesired pressures and result in a loss of fuel economy. There is therefore a need in the art for an improved EGR system that operates over various engine operating conditions.
In one aspect, there is disclosed an exhaust gas recirculation ejector system for an engine that includes an air conduit coupled to an engine providing charge air to the engine. The air conduit includes at least one bend formed therein. The at least one bend includes a port formed therein. An EGR conduit is coupled to an exhaust manifold of the engine at a first end of the EGR conduit. A second end of the EGR conduit passes through the port and extends into the air conduit at the bend defining an ejector mixing the charge air and exhaust gas before entry into the engine A pressure sensor is positioned in the bend indicating a pressure of EGR gas exiting the bend.
In another aspect there is disclosed, a method of providing EGR flow to an engine including the steps of: providing an air conduit coupled to an engine providing charge air to the engine, the air conduit includes at least one bend formed therein and having a port formed therein; providing an EGR conduit coupled to an exhaust manifold of the engine at a first end of the EGR conduit, a second end of the EGR conduit passes through the port and extends into the air conduit at the bend defining an ejector mixing the charge air and exhaust gas before entry into the engine; providing a pressure sensor positioned in the bend indicating a pressure of EGR gas exiting the bend.
Referring to
The EGR conduit 24 may be coupled to additional components including an EGR cooler, pressure sensor and EGR control valve (not shown). The EGR conduit 24 is connected at the second end 17 to the air conduit 20. In one aspect, the EGR conduit is connected at a bend 26 of the air conduit 20 to define an ejector or injector 25 for the EGR gases into the air conduit 20 to define a mixing device that mixes charge air and exhaust gases for EGR.
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The EGR conduit 124 may be coupled to additional components including an EGR cooler, pressure sensor and EGR control valve (not shown). The EGR conduit 124 is connected at the opposing end to the air conduit 120. In one aspect, the EGR conduit 124 is connected at an elbow 126 of the air conduit 120 to define an ejector or injector for the EGR gases into the air conduit to define a mixing device.
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The mixing chamber 28 includes an inlet 30 for receiving charge air from a charge air source, including the turbocharger 16 and charge air cooler 18. The mixing chamber 28 also includes an outlet 32 to discharge charge air and exhaust gas. The mixing chamber 28 also includes a port 34 formed therein between the inlet 30 and the outlet 32 to siphon exhaust gas from the EGR conduit 24 into the mixing chamber 28.
A mixer tube 36 which is an end of the EGR conduit 24 passes through the port to extend into the bend 26 and mixing chamber 28.
The mixer tube 36 defines a venturi or ejector device. A venturi device reduces the pressure of a flowing gas by forcing the flow through a constriction. Within the constriction, the neck region of the venturi, the reduced pressure draws exhaust gases from the EGR conduit 24 into the air conduit 20. The air mixes with the exhaust increasing the exhaust oxygen content and reducing the exhaust temperature.
The pressure reduction of a Venturi follows from Bernoulli's principle. Bernoulli's principle states the pressure of a flow will decrease in relation to the flow speed. The decrease is roughly proportional to the density of the fluid multiplied by the flow speed squared. Typically, the venturi will be sized to provide a volume flow of EGR gases from the EGR conduit from 0 to 50%. With zero representing no EGR flow as controlled by a control valve. In one aspect, the EGR flow may be from 20 to 30% by volume based on the volume of the intake air.
In one aspect, as described above, the mixer tube 36 is integrated into the bend 26. A bend 26 is a portion of a conduit over which the direction of the channeled flow, averaged through complete cross-sections of the flow, changes. Within the bend 26, the momentum of the flow concentrates the intake air on the outer portion of the bend. By restricting the airflow to narrow toward the outer portion of the bend 26, the back pressure created by the bend 26 can be utilized as the back pressure for the venturi.
The turbulent flow on the outer portion of a pipe bend imparts flow acceleration. By Bernoulli's principle, the pressure in the outer portion of the bend will be reduced. Positioning the mixing tube 36 within the region of reduced pressure can provide a venturi even without a physical constriction of the flow. In one aspect, a constriction may be utilized to maintain the accelerated flow condition beyond the pipe bend.
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For example, the T5 in temperature sensor may be a sensor at the exit of an EGR cooler and representative of the temperature of the EGR gas entering the ejector. The P1 sensor may be a sensor from a charge air cooler or the outlet pressure of a compressor representative of the pressure of fresh air introduced into the intake charge. The P3 sensor may be a sensor at an intake manifold of an engine and representative of the pressure of the combined EGR gas and fresh air in the intake charge. The P5 in sensor may be a pressure sensor at the exit of an EGR cooler and representative of the pressure of the EGR gas entering the ejector.
The P5 exit sensor may be positioned in the bend of the ejector to calculate an EGR mass flowrate. The P5 exit sensor may have various structures as shown in
The EGR mass flow rate may be calculated according to the following equations:
The calculation of the EGR mass flow rate allows for on board diagnostics or a control unit to control the EGR flow into an engine. The ejector provides a reduced pressure drop for the EGR circuit in comparison to prior art designs.
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In use, a portion of the exhaust gases are routed from the exhaust manifold 14 by the EGR conduit 24. The direction of flow is indicated by the arrows in
The EGR system including the ejector or injector is a passive system without moving parts and is soot and temperature resistant. The system provides a compact packaging integrated into the elbow. The system will work with conventional turbochargers or VGT turbochargers. The injector design will provide the maximum EGR flow and an EGR control valve may be utilized to lessen the flow of EGR gases. Additionally, an EGR pump may be utilized to regulate a flow of EGR gases to the ejector, as described above.
In another aspect, the ejector may be used with an EGR pump 50 as denoted in
Computational Fluid dynamic calculations were performed to analyze various parameters of the ejector including the size of the diameter and radius of the EGR conduit and air conduit, the angle A defined by an angle between the outlet flow path and the inlet flow path, the angle B of the angled face at various engine operating conditions. The parameters shown in the Figures and as displayed in various tables which follow include: P1, the inlet pressure of the air charge, P3, the outlet pressure of the air charge, P5 in, the inlet pressure of the EGR gas, and P5ext, the outlet pressure of the EGR gas.
Table 1 includes the pressure parameters of ejectors of various size at the positions shown in
As can be seen from the data in the table, the size and position of the ejector has an effect on the generation of a negative pressure or suction to move EGR gas into the charge air stream. The ejector at position C having a 16 mm radius produced the greatest negative pressure −0.4 KPa while maintaining a difference between the inlet and outlet pressures of the air charge less than 2.4 KPa.
Table 2 includes the pressure parameters of ejectors of various size at position C and having various angles A at a C100 operating condition. The angle A is shown in
As can be seen from the data in the table 2, the size and angle A of the ejector has an effect on the generation of a negative pressure or suction to move EGR gas into the charge air stream. The ejector at position C having a 16 mm radius at 10 degrees angle and an 18 mm radius at 20 degrees angle produced the greatest negative pressure −550 Pa while maintaining a difference between the inlet and outlet pressures of the air charge less than 2.4 KPa.
Table 3 includes the pressure parameters of ejectors having a 16 mm radius size at position C having various angles B. The angle B is shown in
As can be seen from the data in the table 3, the angle B of the ejector has an effect on the generation of a negative pressure or suction to move EGR gas into the charge air stream. The ejector having a 45 degree angle produced the greatest negative pressure −0.8 KPa while maintaining a difference between the inlet and outlet pressures of the air charge less than 2.4 KPa.
Table 4 includes the pressure parameters of an ejector at position C having a 16 mm radius Angle A of 5 degrees and angle B of 45 degrees at various engine operating conditions.
As can be seen from the data in the table 4, the ejector at position C, having a 16 mm radius, Angle A of 5 degrees and angle B of 45 degrees produced a negative pressure (P5in-P3) over all of the engine conditions while maintaining a difference between the inlet and outlet pressures of the air charge less than 2.4 KPa.
In use, a portion of the exhaust gases are routed from the exhaust manifold 14 by the EGR conduit 24. The direction of flow is indicated by the arrows in
The EGR system including the ejector is a passive system without moving parts and is soot and temperature resistant. The system provides a compact packaging integrated into the bend. The system will work with conventional turbochargers (FGT) or VGT turbochargers. The ejector design will provide the maximum EGR flow and an EGR control valve may be utilized to lessen the flow of EGR gases.
Number | Date | Country | Kind |
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PCT/EP2019/069527 | Jul 2019 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/077943 | 10/15/2019 | WO |
Number | Date | Country | |
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62872729 | Jul 2019 | US |