EP2422061A1

EP2422061A1 - Fluid mixing system

Info

Publication number: EP2422061A1
Application number: EP10767642A
Authority: EP
Inventors: Scott A. Falconer; Glenn M. Wethington; Oswald Baasch
Original assignee: International Engine Intellectual Property Co LLC
Current assignee: International Engine Intellectual Property Co LLC
Priority date: 2009-04-20
Filing date: 2010-04-20
Publication date: 2012-02-29
Also published as: JP2012524213A; WO2010123905A1; EP2422061A4; CN102439271A; BRPI1016239A2

Abstract

A fluid mixing system has first fluid conduit and second fluid conduit in fluid communication with the first fluid conduit. The second fluid conduit includes a first tube and a second tube, wherein at least one of the first and second tubes causes a swirling or tumbling fluid flow. The fluid mixing system may be an exhaust gas recirculation system having an air intake conduit and an exhaust gas recirculation conduit, wherein the exhaust gas recirculation conduit causes a swirling or tumbling fluid flow. A method of introducing multiple fluids includes providing a first fluid flow in a conduit, providing a second fluid flow in a first tube, and providing a third fluid flow in a second tube. The second fluid flow is introduced to the first fluid flow at a first entry angle relative to the conduit.

Description

FLUID MIXING SYSTEM

BACKGROUND

[0001] Fluid mixing systems have been used in exhaust gas recirculation (EGR) systems since the 1970's to reduce emissions in many gas and diesel engines. In conventional EGR fluid mixing systems, exhaust gases from an engine are recirculated and combined with gas in an air intake manifold. The exhaust gases usually lower the combustion temperature of the fuel below the temperature of formation of nitrogen oxides (NOx) during the combustion process in the cylinders.

SUMMARY

[0002] A fluid mixing system is described. In one embodiment, a fluid mixing system has a first fluid conduit and second fluid conduit in fluid communication with the first fluid conduit. The second fluid conduit has a first tube and a second tube, wherein at least one of the first and second tubes causes a swirling or tumbling fluid flow.

[0003] At least one embodiment provides an exhaust gas recirculation system having an air intake conduit and an exhaust gas recirculation conduit that is in fluid communication with the air intake conduit. The exhaust gas recirculation conduit causes a swirling or tumbling fluid flow.

[0004] At least one embodiment provides a method of introducing multiple fluids. The method includes providing a first fluid flow in a conduit, providing a second fluid flow in a first tube, and providing a third fluid flow in a second tube. According to the method, the second fluid flow is introduced to the first fluid flow at a first entry angle relative to the conduit, and the third fluid flow is introduced to the first fluid flow at a second entry angle relative to the conduit. At least one of the first tube and the second tube causes the respective second or third fluid flow to swirl or tumble.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] In order to facilitate a fuller understanding of the exemplary embodiments, reference is now made to the appended drawings. These drawings should not be construed as limiting but are intended to be exemplary only.

[0006] FIG. 1 is a side perspective view of a prior art exhaust gas recycling system.

[0007] FIG. 2 is a top perspective view of a prior art exhaust gas recycling system.

[0008] FIG. 3 is a side perspective view of a fluid mixing system, in accordance with an exemplary embodiment described herein.

[0009] FIG. 4 is a top perspective view of a fluid mixing system, in accordance with an exemplary embodiment described herein.

[0010] FIG. 5 is a sectional view of a fluid mixing system, in accordance with an exemplary embodiment described herein.

[0011] FIG. 6 is a chart showing pressure pulse charging for an exhaust gas recirculation system in which three recirculation ports have been merged into one port.

[0012] FIG. 7 is a chart showing pressure pulse charging for an exhaust gas recirculation system in which six recirculation ports have been merged into one port.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0013] The following description is intended to convey a thorough understanding of the embodiments by providing a number of specific embodiments and details involving a fluid mixing system such as an exhaust gas recirculation system. It is understood, however, that the invention is not limited to these specific embodiments and details, which are exemplary only. It is further understood that one possessing ordinary skill in the art, in light of known devices, systems, and methods, will appreciate the use of the invention for its intended purposes and benefits in any number of alternative embodiments.

[0014] In conventional EGR systems, the mixing of the recirculated exhaust gas and the air intake gas has been accomplished in one of several ways. For example, in a simple design the recirculated exhaust gas conduit and the air intake conduit may form a "tee" or similar connection. However, in such systems, the mixing of exhaust gases and combustion gases is poor.

[0015] While various improvements have been proposed to improve upon the mixing of the recirculated exhaust gas and the air intake gas, these improvements do not adequately blend the gases. Referring to FIGS. 1 and 2, in one EGR mixing design, generally referred to as 100, recirculated exhaust gas is split into two air streams — first air stream 110 and second air stream

120, each of which is injected into opposite sides of the air intake conduit 130. In this design, the recirculated exhaust gas may be injected into the air intake conduit 130 at two ports, spaced approximately 180 degrees apart. In addition to providing inadequate mixing between the gas systems, this design is very difficult to manufacture.

[0016] In the various conventional mixing systems, the resultant fluid mixture is not uniform, including pockets, zones, regions or strata of higher or lower concentrations of exhaust gases. The dispersion of exhaust gas within the air intake gas may be more uneven when the exhaust gases enter on one side of the air intake stream.

[0017] In comparison to the conventional mixing systems, the systems of the exemplary embodiments provide improved fluid mixing. Generally speaking, the systems of the embodiments have a plurality of tubes that carry fluid to a larger conduit. At least one of the tubes swirls and/or tumbles the fluid flow, providing better mixing of the fluids when in the larger conduit. In some exemplary embodiments, the fluid mixing system may be used to optimize the homogeneity of the fluid mixture. While the exemplary embodiments are described herein with reference to an exhaust gas recirculation system, it will be understood that the systems can be used in other fluid mixing systems.

[0018] Referring to FIGS. 3-5, in an exemplary embodiment, an exhaust gas recirculation system 200 includes a plurality of parallel tubes 300 that carry recirculated exhaust gas to an air intake conduit 210. Air conduit 210 has air inlet 212 and air outlet 214, with a passageway therebetween. Parallel tubes 300 intersect with air conduit between the inlet 212 and outlet 214. The conduit 210 may have any suitable shape or cross section, as necessary or desired. The conduit 210 may be made of any suitable material such as, for example, aluminum, cast iron, stainless steel, plastic, etc.

[0019] In an exemplary embodiment, at least one of the tubes 300 provides a swirling or twisting fluid flow. While the embodiments are described herein with reference to two tubes 300, it is understood that more parallel tubes may be provided within the scope of the embodiments. A singular tube 300 is described in more detail below. Where a plurality of parallel tubes (such as 300A, 300B) are described or shown in combination, like reference numerals are used to describe like features.

[0020] In various embodiments, the parallel tubes 300 may carry a fluid, such as recycled exhaust gas to the air intake conduit 210. In some embodiments, one or more of the parallel tubes 300 may carry other fluids instead of or in addition to the recycled exhaust gas. In some embodiments, each of the tubes 300 may carry the same fluid. In other embodiments, the tubes 300 may carry different fluids to the conduit 210. For example, in an exemplary embodiment, one tube 300A may carry recycled exhaust gas, and a second tube 300B may carry cold air. One or more of the tubes 300 may carry other fluids, such as a power enhancer, or an oxidation- reduction compound, as necessary or desired.

[0021] In exemplary embodiments, each parallel tube 300 may have an air inlet 302 and an air outlet 304, and a body 306 extending therebetween. The air outlet 304 of the parallel tube 300 leads to the air intake conduit 210, so that the tube 300 is in fluid communication with the conduit 210. The tubes 300 may be made of any suitable material such as, for example, aluminum, cast iron, stainless steel, plastic, etc. In various embodiments the tubes 300 may be formed so that they are unitary with the conduit 210. In other embodiments, the tubes 300 may be separately formed, and otherwise joined with the conduit 210. For example, the tubes 300 may be welded to the conduit 210, the tubes 300 and the conduit 210 may have a corresponding notch/groove or flange assembly that is fastened together, the tubes 300 and the conduit 210 may be press fit together, or adhesively attached together. Multiple tubes 300 may be formed together or separately, and joined together or separately with conduit 210. Other methods of joining the tubes 300 and conduit 210 may be used, as necessary or desired, based upon several variables including method of manufacture and packaging.

[0022] In the various embodiments, each tube 300 may have any suitable length. For example, in an exemplary embodiment, tube 300 may have a length of about 2 inches to about 10 inches measured from the air inlet 302 to the air outlet 304. It will be understood that the length of the tube 300 may be determined as necessary or desired, based upon several variables, including casting size, requirements for engine assembly, etc. In the various embodiments, each tube 300 may have any suitable diameter and cross-sectional shape. For example, the diameter and cross-section may be configured to reduce losses, to induce swirling or tumbling, or reduce or increase turbulance. Exemplary cross-sections include, for example, circular, oblong, hourglass, J-shape, U-shape, etc., and may include a combination of cross-sectional shapes. In some embodiments, the cross-section may increase or decrease along the length, as desired or necessary, to reduce or expand the fluids flowing therethrough.

[0023] In exemplary embodiments, at least one of the tubes 300 is configured to create a swirling fluid flow. For example, in various embodiments, at least one of the tubes 300 is twisted to cause a swirling fluid flow. In other various embodiments, at least one of the tubes 300 has internal contours, or structures, baffles, vanes, protrusions, fins, rifling, etc. that cause swirling fluid flow. In exemplary embodiments, at least one of the tubes 300 is configured to create a tumbling fluid flow. For example, in various embodiments, at least one of the tubes 300 has internal contours, or structures, baffles, vanes, protrusions, fins, rifling, etc. that cause a tumbling fluid flow. In various embodiments, the tubes 300 may create swirling or tumbling fluid flow within the tubes 300, and/or may create a swirling tumbling fluid flow after the fluid exits the air outlet 304. In exemplary embodiments, at least one of the tubes 300 is configured to create a swirling and tumbling fluid flow. In one embodiment the tubes 300 are configured to provide a swirling and/or tumbling fluid flow to optimize the homogeneity of the downstream fluid mixture.

[0024] Referring to FIGS. 3 and 4, in one exemplary embodiment, the tube 300 has a twist along its length between the air inlet 302 to the air outlet 304 that causes a swirling fluid flow. Tube 300 may have any suitable degree of twisting to provide a swirling fluid flow. The degree of twisting of the tubes 300 may affect the mixing efficiency of the EGR system 200. In various embodiments, the twist in a twisted tube 300 may be from about 15 degrees per inch to about 90 degrees per inch, or from about 30 degrees to about 45 degrees per inch. In some embodiments, a plurality of tubes 300A, 300B, has the same degree of twisting. In some embodiments, a plurality of tubes 300A, 300B, may be twisted about each other. In some embodiments, one tube 300A may have a higher degree of twisting than the other tube 300B. In some embodiments, one tube 300A may be straight, and the second tube 300B may be twisted. In some embodiments, one or more of the tubes 300A, 300B, may have one or more geometries that affect the mixing of the fluids by changing the swirl, tumble or recirculation of gases, such as, for example, a bend or fold in the tube 300.

[0025] In various exemplary embodiments, the conduit 210 may be configured to have one or more structures or geometries that affect the mixing of the fluids by changing the swirl, tumble, and/or recirculation of fluids within the conduit 210. The conduit 210 may have any of the swirling and/or tumbling means and devices described herein with reference to the tubes 300. [0026] In the various exemplary embodiments, each tube 300 terminates at the larger conduit 210, such as, for example, with the air outlet 304 providing a passageway between the tube 300 and the conduit 210. In some embodiments, one or more of the tubes 300 may terminate at the inner surface of the larger conduit 210. Referring to FIG. 5, in some embodiments, the tubes 300 may terminate beyond the inner surface of the larger conduit 210, so that the air outlet 304 extends into the conduit 210, thereby injecting the recirculated exhaust gas more toward the centerline of the conduit 210.

[0027] In various embodiments, each tube 300 may intersect the larger conduit 210 in such a manner as to inject the contents of the smaller tubes 300 into the larger conduit 210 at a predetermined entry angle. The "entry angle" is the angle measured between the centerline of the tube 300 and centerline of the larger conduit 210 at the point of intersection, or tangent of the conduit 210 if the conduit 210 is curved at the point of intersection. In the exemplary embodiments, the entry angle of a tube 300 may be suitable angle. In one embodiment, the entry angle of each twisted tube 300 may be from about 90 degrees to about 45 degrees. In some embodiments, the entry angle may be oriented in a direction that is perpendicular with, toward the same direction, or toward the opposite direction of the fluid flow direction in the conduit 210. In some embodiments, the tube 300 may have a bend at or near the outlet 304, to change the direction of flow in the tube 300 just prior to its introduction to the conduit 210. In various embodiments, each tube 300A, 300B may inject air in a different direction. In some embodiments, the entry angle of each of the tubes 300A, 300B may be offset from the other to cause a swirling effect, which may further increase the mixing of all fluids. For example, in one embodiment, the entry angle of tube 300A may be offset from the entry angle of tube 300B by about 30 degrees.

[0028] In exemplary embodiments, the tubes 300 may intersect the conduit at any suitable point along the conduit 210. In some embodiments, two or more tubes 300A, 300B, may intersect the conduit 210 at adjacent points. In other embodiments, two or more tubes 300A, 300B may intersect the conduit 210 on opposite sides of the conduit. The respective intersection points of tubes 300A, 300B, and conduit 210 may be configured to provide a predetermined mixing profile. In one exemplary embodiment, a stream of compressed air or other fluid may be introduced at or near the intersection of one or more of the tubes 300, to affect the fluid mixing at that point.

[0029] In some embodiments, two or more tubes 300A, 300B may merge into a singular intermediate tube that feeds into the conduit 210. Merging the tubes into an intermediate tube may have an effect on the pressure pulse charging. For example, FIG. 6 shows an exemplary pressure pulse charge for a system having three merged streams. In this embodiment, there is a difference between the average pressure (the horizontal line on the chart) and the pressure peaks, which enables the air stream to open and charge the downstream reed valve. In comparison, FIG. 7 shows an exemplary pressure pulse charge for a system having six merged streams. In this embodiment, the difference between the average pressure and the peak pressure is much less, and may be insufficient to open and charge the downstream reed valve. In an exemplary embodiment, the merger of the tubes, and the length of the tubes will be configured as necessary or desired to provide a predetermined pressure pulse charging.

[0030] In exemplary embodiments, the tube 300 and/or the air intake conduit 210 may have one or more additional devices, such as nozzles, baffles, fins, and the like, to mix or improve the mixing of the fluids, as necessary or desired.

[0031] In the preceding specification, various embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments implemented, without departing from the broader scope of the exemplary embodiments as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.

Claims

What is claimed is:

1. A fluid mixing system comprising: a first fluid conduit; and a second fluid conduit in fluid communication with the first fluid conduit, comprising a first tube and a second tube; wherein at least one of the first and second tubes causes a swirling or tumbling fluid flow.

2. The fluid mixing system of claim 1, wherein at least one of the first and second tubes cause a swirling and tumbling fluid flow.

3. The fluid mixing system of claim 1, wherein the first tube has a first entry angle relative to a centerline of the first conduit, and the second tube has a second entry angle relative to the centerline of the first conduit

4. The fluid mixing system of claim 3, wherein the first entry angle is different from the second entry angle.

5. The fluid mixing system of claim 3, wherein the first entry angle is substantially the same as the second entry angle.

6. The fluid mixing system of claim 3, wherein the first entry angle or the second entry angle ranges from about 45 degrees to about 90 degrees.

7. The fluid mixing system of claim 1 wherein one of the first tube and the second tube has a twist that causes a swirling fluid flow.

8. The fluid mixing system of claim 7, wherein the twist ranges from about 30 degrees per inch to about 45 degrees per inch.

9. The fluid mixing system of claim 7 wherein both first tube and second tube have a twist that causes swirling fluid flow.

10. The fluid mixing system of claim 9 wherein the first tube has a different twist than the second tube.

11. The fluid mixing system of claim 1 wherein one of the first and second tubes does not cause a swirling or a tumbling fluid flow.

12. The fluid mixing system of claim 1 wherein at least one of the first and second tubes has an air outlet that extends beyond an inner surface of the air intake conduit.

13. The fluid mixing system of claim 1 wherein the first tube and second tube communicate the same fluid.

14. The fluid mixing system of claim 1 wherein the first tube and the second tube communicate different fluids.

15. The fluid mixing system of claim 1 wherein the first tube or the second tube communicate a plurality of fluids.

16. The fluid mixing system of claim 1 wherein at least one of the first tube and second tube has a bend.

17. The fluid mixing system of claim 1 wherein the first tube and the second tube merge into a single combined tube prior to their introduction to the first conduit.

18. The fluid mixing system of claim 1 further comprising a third tube.

19. The fluid mixing system of claim 18 wherein the third tube has a twist.

20. The fluid mixing system of claim 18, wherein the first tube, the second tube, and the third tube communicate the same fluid.

21. The fluid mixing system of claim 1 wherein the first fluid conduit is an air intake conduit, and the second fluid conduit is a recirculated exhaust gas conduit.

22. An exhaust gas recirculation system comprising: an air intake conduit; and an exhaust gas recirculation conduit; wherein the exhaust gas recirculation conduit is in fluid communication with the air intake conduit, and wherein the exhaust gas recirculation conduit causes a swirling or tumbling fluid flow.

23. The exhaust gas recirculation system of claim 22, wherein the exhaust gas recirculation conduit comprises a plurality of parallel tubes, wherein at least one of the parallel tubes causes a swirling or tumbling fluid flow.

24. The exhaust gas recirculation system of claim 22, wherein exhaust gas recirculation conduit has a twist that ranges from about 30 degrees per inch to about 45 degrees per inch.

25. The exhaust gas recirculation system of claim 22, wherein the exhaust gas recirculation conduit has an entry angle relative to a centerline of the air intake conduit that ranges from about 45 degrees to about 90 degrees.

26. The exhaust gas recirculation system of claim 23, wherein the exhaust gas recirculation conduit comprises a first tube having a first entry angle relative to a centerline of the air intake conduit, and a second tube having a second entry angle relative to a centerline of the air intake conduit.

27. The exhaust gas recirculation system of claim 26, wherein the first entry angle is different from the second entry angle.

28. The exhaust gas recirculation system of claim 26, wherein the first entry angle is substantially the same as the second entry angle.

29. The exhaust gas recirculation system of claim 26, wherein the first entry angle or the second entry angle ranges from about 45 degrees to about 90 degrees.

30. The exhaust gas recirculation system of claim 22, wherein the exhaust gas recirculation conduit communicates a plurality of fluids.

31. The exhaust gas recirculation system of claim 22, wherein the exhaust gas recirculation conduit causes a swirling and tumbling fluid flow.

32. A method of introducing multiple fluids comprising: providing a first fluid flow in a conduit; providing a second fluid flow in a first tube; providing a third fluid flow in a second tube; introducing the second fluid flow to the first fluid flow at a first entry angle relative to the conduit; and introducing the third fluid flow to the first fluid flow at a second entry angle relative to the conduit; wherein at least one of the first tube or the second tube causes the respective second fluid flow or third fluid flow to swirl or tumble.

33. The method of claim 32, wherein the first fluid flow comprises air.

34. The method of claim 32, wherein at least one of the second fluid flow and third fluid flow comprise recirculated exhaust gas.

35. The method of claim 34, wherein both the second fluid flow and third fluid flow comprise recirculated exhaust gas.

36. The method of claim 34, wherein one of the second fluid flow and third fluid flow comprises a fluid other than recirculated exhaust gas.

37. The method of claim 34, wherein one of the second fluid flow and third fluid flow comprises a mixture of recirculated exhaust gas with another fluid.

38. The method of claim 32, further comprising introducing a fourth fluid flow in a third tube.

39. The method of claim 32, comprising merging the second fluid flow and third fluid flow into a merged fluid flow prior to their introduction to the first fluid flow.

40. The method of claim 32, wherein one of the first entry angle and second entry angle ranges from about 45 degrees to about 90 degrees.

41. The method of claim 32, wherein the first entry angle is different from the second entry angle.

42. The method of claim 32, wherein at least one of the first tube or the second tube causes the respective second fluid flow or third fluid flow to swirl and tumble.