Method of controlling wastegate flow using port side wall contour

Abstract

An exhaust gas turbocharger with a wastegate port configured to permit some exhaust gas flow to exit a turbine volute upstream of the turbine wheel and enter a bypass channel thereby bypassing the turbine wheel, a valve with a valve head dimensioned to seat on a valve seat and to move between a seated position and an open position, the bypass channel having a sidewall contoured to surround the valve head as the valve head moves between the seated position and the open position, he bypass channel sidewall shaped so that a throat area (A.sub.t) area between the bypass channel sidewall and valve head gradually increases as the valve head moves between the seated and the open position, such the bypass flow is controlled by the throat area (A.sub.t) and not the area between the valve head and the valve seat.

Claims

1. An exhaust gas turbocharger including: a turbine housing (10) including a turbine volute (18) adapted to guide that uses exhaust gas flow to a turbine wheel housed in the turbine housing (10); a bypass channel formed in the turbine housing (10); a wastegate port (14) communicating between the turbine volute (18) upstream of the turbine wheel and the bypass channel; a valve seat (26) immediately around the wastegate port (14); a valve (16) having an arm (20) connected to a valve head (22), the valve head (22) dimensioned to seat on said valve seat (26), the valve (16) operable to move the valve head (22) between a seated position and an open position relative to the wastegate port (14) for selectively blocking and unblocking the wastegate port (14); and a side wall (30) including an extending wall portion (31) formed by the bypass channel of the turbine housing (10) so as to surround the valve head (22) as the valve head (22) moves between the seated position and the open position; wherein the extending wall portion (31) of the sidewall (30) is formed a throat area (At) between the extending wall portion (31) of the sidewall (30) and valve head (22) gradually increases as the valve head (22) moves between the seated position and the open position; and wherein the exhaust gas flow through the bypass channel is controlled by the throat area (At) between the extending wall portion (31) of the sidewall (30) and valve head (22).

2. The turbocharger of claim 1 wherein the extending wall portion (31) of the side wall (30) extends from the valve seat (26).

3. The turbocharger of claim 1 wherein the side wall (30) has an area progression in a concave portion (40) that is configured to fit a mass flow versus actuator angle profile, and is smaller than an effective curtain area between the valve head (22) and a valve seat (26) surrounding the wastegate port (14).

4. The turbocharger of claim 1 wherein the side wall (30) includes a concave portion (40) adjacent to an outer end (27) of the valve head (22) that corresponds to a desired flow area at a given valve opening angle.

5. The turbocharger of claim 4, wherein the concave portion (40) of the side wall (30) is closer to the valve head (22) at smaller valve opening angles, and correspondingly wherein the concave portion (40) of the contoured side wall (30) is farther from the valve head (22) at increased valve opening angles.

6. The turbocharger of claim 1 wherein the side wall (30) incorporates hole wells (50).

7. The turbocharger of claim 6 wherein the hole wells (50) are channels that extend from the wastegate port (14).

8. The turbocharger of claim 1 wherein the valve (16) is configured to pivot relative to the wastegate port (14).

9. An exhaust gas turbocharger including: a turbine housing (10) including a turbine volute (18) adapted to guide that uses exhaust gas flow to a turbine wheel housed in the turbine housing (10); a bypass channel formed in the turbine housing (10); a wastegate port (14) communicating between the turbine volute (18) upstream of the turbine wheel and the bypass channel; a valve seat (26) immediately around the wastegate port (14); a valve (16) having a pivotable arm (20) connected to a valve head (22), the valve head (22) dimensioned to seat on said valve seat (26), the valve (16) operable to move the valve head (22) between a seated position and an open position relative to the wastegate port (14) for selectively blocking and unblocking the wastegate port (14); and a side wall (30) including an extending wall portion (31) formed by the bypass channel of the turbine housing (10) so as to surround the valve head (22) as the valve head (22) moves between the seated position and the open position; wherein the side wall (30) includes a concave portion (40) that is adjacent to an outer end (27) of the valve head (22) and that corresponds to a desired flow area at a given valve opening angle; wherein the extending wall portion (31) of the sidewall (30) is formed a throat area (At) between the extending wall portion (31) of the sidewall (30) and valve head (22) gradually increases as the valve head (22) moves between the seated and the open position; and wherein the exhaust gas flow through the bypass channel is controlled by the throat area (At) between the extending wall portion (31) of the sidewall (30) and valve head (22).

10. The turbocharger of claim 9 wherein the concave portion (40) of the side wall (30) is closer to the valve head (22) at smaller valve opening angles, and correspondingly wherein the concave portion (40) of the side wall (30) is farther from the valve head (22) at increased valve opening angles.

11. The turbocharger of claim 9 wherein the side wall (30) incorporates hole wells (50).

12. The turbocharger of claim 11 wherein the hole wells (50) are channels that extend from the wastegate port (14).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Advantages of the present disclosure will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

(2) FIG. 1 is a side cross-sectional view of a prior art wastegate assembly in which flow is choked in a valve curtain area;

(3) FIG. 2 is a side cross-sectional view of a wastegate assembly with a contoured side wall in which flow is choked in a valve throat between the valve side and a side wall area;

(4) FIG. 3 illustrate a side wall shape relative to a valve head in various positions;

(5) FIG. 4 is a graph of valve opening angle (degrees) versus area (mm.sup.2) illustrating design effective area;

(6) FIG. 5 is a graph of valve opening area (degrees) versus mass flow rate (kg/sec) illustrating a conventional wastegate valve as a baseline as compared with contoured sidewall assemblies;

(7) FIG. 6A illustrates Mach number contours at an actuator angle of 12.6 degrees for a conventional wastegate valve configuration showing choke in the valve curtain area.

(8) FIG. 6B illustrates Mach number contours at an actuator angle of 12.6 degrees for contoured side wall valves as CSW_1 showing choke against the side wall.

(9) FIG. 6C illustrates Mach number contours at an actuator angle of 12.6 degrees for contoured side wall valves as CSW_2 showing choke against the side wall.

(10) FIG. 7 shows a top cross-sectional view of a side wall incorporating hole wells;

(11) FIG. 8 is a depiction of a prior art wastegate assembly with a poppet valve with a curtain area between the valve and the housing; and

(12) FIG. 9 is a partial cross-sectional view of wastegate assembly having a poppet valve with a contoured side wall with choking the flow in a valve to side wall area.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(13) A turbocharger is generally known and includes a turbine and a compressor, wherein a compressor wheel is rotatably driven via a shaft by a turbine wheel. The rotatable shaft passes through a bearing housing disposed between a turbine housing 10 and a compressor housing. The turbine converts exhaust gas pressure into energy to drive the turbine wheel, which via the shaft drives the compressor wheel. While exhaust gas flow is used to drive the turbine wheel, often some exhaust gas flow may be allowed to bypass the turbine wheel to control turbine work.

(14) Referring to FIG. 2, the turbine housing 10 has a wastegate port 14 formed in a sidewall thereof and communicating with a turbine volute 18. The wastegate port 14 is configured to permit exhaust gas flow to exit the turbine volute 18 which is upstream of the turbine wheel, thereby bypassing the turbine wheel to a bypass channel of the turbine housinq 10. A wastegate assembly 12 is provided on the turbine housing and is used to control exhaust gas flow through the wastegate port 14. The wastegate assembly 12 includes a wastegate valve 16 that is controlled by an actuator (not shown) to selectively block the wastegate port 14 to control exhaust gas flow out of the volute 18 through the wastegate port 14. The valve 16 is moveable with respect to the wastegate port 14 for blocking and unblocking the wastegate port 14, thereby controlling the exhaust gas flow, wherein some exhaust gas flow can bypass the turbine wheel to control turbine work in that the turbine wheel rotates at controlled speeds. The wastegate port 14 allows bypass gas flow in order to control the maximum boost pressure via the actuator 18.

(15) The wastegate valve 16 includes an arm 20 connected to a valve head 22. The valve head 22 may have a peripheral edge (e.g., margin) 25 having a shape that corresponds to the shape of the wastegate port 14, and includes a seat face 23 corresponding to the planar valve surface that faces the wastegate port 14 and cooperates with a planar valve seat 26 surrounding the wastegate port 14 to form a seal. The valve 16 is connected to the actuator via the arm 20. The arm 20 is constructed and arranged to move the valve head 22 with respect to the wastegate port 14 to control the exhaust gas flow through the wastegate port 14. In the illustrated embodiment, the valve 16 is a pivot valve, and the actuator causes the arm 20 to pivot about a pivot point 24 at an end of the arm 20 opposed to the vale head 22 in order to open and close the valve 16, and thereby selectively allow exhaust gas flow to bypass the turbine wheel.

(16) As shown, the arm 20 is relatively short to reduce hinge movement and to fit into a more compact space. The valve head 22 is moveable to at least a first position and a second position so that in the first position the seat face 23 is spaced apart from the valve seat 26, and the wastegate port 14 is fully open, and in the second position, the seat face 23 contacts the valve seat 26 and the wastegate port 14 is closed to preclude exhaust gas flow from flowing through the wastegate port 14. In the closed position, the valve head 22 is secured against the valve seat 26. The valve 16 is pivotable to intermediate positions between fully open and fully closed allow for precise control of exhaust gas through the wastegate port 14. The angle of the lever arm 20 relative to the valve seat 26 forms the actuator angle as the valve head 22 is pivoted relative to the wastegate port 14.

(17) The wastegate assembly 12 includes the turbine housing having a contoured side wall 30 that surrounds the valve head margin 25 when the valve 16 is in the first position (e.g., an open position) to permit choking the flow from the wastegate port 14 between the valve head margin 25 and the side wall 30, e.g., in the throat area A.sub.t. The sidewall 30 includes a longer wall portion 31 at a location corresponding to an outer end 27 (e.g., furthest from the pivot point 24) of the valve head 22, and a shorter wall portion 32 at a location corresponding to an inner end 29 (e.g., closest to the pivot point 24) of the valve head 22. The longer wall portion 31 and shorter wall portion 32 are sized and shaped to cooperate with the valve head 22 in various valve positions to form a desired throat area A.sub.t, and thereby control the flow around the inner end of the valve head 22. The contoured side wall 30 is constructed by a radial offset R.sub.o from the valve head margin 25 and substantially forms a rim that is offset from and surrounds the wastegate port 14. A lip resulting from the offset forms the valve seat 26 around the wastegate port 14 that operably seals when in contact with the valve head 22. The longer wall portion 31 of the contoured side wall 30 is shown at the valve head outer end 27 with a substantially concave portion 40 adjacent to the valve head outer end 27.

(18) Referring to FIG. 3, the valve head 22 is moveable relative to the contoured sidewall 30 between various positions. The specific contour of the side wall 30 may correspond to the desired flow area at a specific valve opening angle. The area progression can take various shapes to fit the specific mass flow versus actuator angle profile, but it has to be smaller than the curtain area A.sub.vc between the valve 16 and the valve seat 26. As shown, an exemplary radial offset R.sub.0=sqrt(Ae/+Rv.sup.2) for side wall construction, where Ae refers an effective area and Rv refers to a radius of the valve head 22. The angle of the concave portion 40 may allow the contoured side wall 30 to be closer to the margin 25 of the valve head 22 at a smaller valve opening angles, and correspondingly the contoured side wall 30 may be farther from the margin 25 of the valve head 22 at increased valve opening angles to help control flow.

(19) Referring to FIG. 4, two different exemplary contoured sidewall profiles were analyzed using computational fluid mechanics. The first profile CSW_01 corresponded to a simple linear flow rate versus actuator angle schedule, while the second profile CSW_02 was linear up to an opening angle of 12.6 degrees, and then exponential up to the maximum opening angle. FIG. 4 is a chart design flow area profile with design effective area at varying valve opening angles.

(20) Referring to FIG. 5, the mass flow rates were calculated for various opening angles in order to compare the mass flow rates of the conventional wastegate valve 112 having no sidewall contouring as the base line with the two exemplary sidewall profiles CSW_01 and CSW_02.

(21) Referring to the baseline flow rate for a conventional wastegate valve for a valve that is actuated by a pivoting lever arm, an undesirable correlation can result between the actuation angle and the resulting flow rate, i.e. flow rate increases rapidly with actuator angle at small valve opening angles, but becomes increasingly insensitive to actuator angle the more the valve is opened. A substantially flat line is shown as the insensitivity to the angle at the top right of the baseline conventional wastegate valve at a valve opening angle beginning at about 23 degrees.

(22) The mass flow rate of the wastegate assemblies 12 with the contoured side walls 30 shows a more consistent (linear) mass flow rate increase as the valve opening angle increases. As shown as CSW_01 and CSW_02, this allows for more consistent and precise control of the bypass of exhaust gas. In a wastegate valve assembly 12 including contoured side walls 30, the flow increase corresponds more steadily and proportionately to the increased valve opening angle.

(23) Referring to FIGS. 6A-6C, Mach contours were calculated for an actuator angle of 12.6 degrees for each of the test configurations in order to illustrate the location of choke for each configuration. As seen in FIG. 6A, for the conventional wastegate valve assembly 112 having no sidewall contouring, choke exists in the valve curtain area A.sub.vc between the valve seat face 23 and the valve seat 26. In contrast, as seen in FIGS. 6B and 6C, when the wastegate valve assembly 12 includes a contoured sidewall 30 such as defined by CSW_01 and CSW_02, choke exists in the throat area A.sub.t between the valve head margin 25 and the sidewall 30.

(24) The contoured side wall 30 surrounding the valve head 22 controls wastegate flow with the port side wall contour of the wastegate assembly 12. More gradual changes in curtain area and more precise control can be accomplished by shaping the side wall 30 near the valve head 22 such that the throat area A.sub.t controlling the flow is between the valve head 22, particularly the valve head margin 25, and side wall 30, instead of the valve head 22, particularly the valve seat face 23, and the valve seat 26. Choking the flow between the valve head margin 25 and a specially contoured side wall 30 is ideal as long as the area between the side wall 30 and the valve head margin 25 is smaller than the valve curtain area A.sub.vc, so the flow will choke against the side wall 30 instead of within the valve curtain area A.sub.vc.

(25) As shown in FIG. 7, the contoured side wall 30 can also incorporate hole wells 50, i.e. channels, that allow fine tuning of mass flow versus actuator angle curve to suit specific requirements. Specific shapes of the hole wells 50, such as lobes into the turbine housing 10, can extend from or otherwise radiate from the wastegate port 14 to direct wastegate flow. By including hole wells 50 in the side wall 30, the wastegate assembly 12 can (1) provide increased precision in flow control and (2) reduce interference with the main turbine exhaust flow. The precise control with hole wells 50 can be generally of the outlet area or in certain embodiments, balance between ports of a twin volute design or correspond with additional channels for exhaust gas flow per specific designs.

(26) Referring to FIGS. 8 and 9, although the wastegate assembly 12 has been described herein as including a pivot-type valve 16 that rotates about a pivot point 24 between open and closed positions, the wastegate assembly 12 is not limited to employing a pivot-type valve. It is understood that the wastegate assembly 12 may include other types of valves such as, for example, a poppet-type valve. In this example, a wastegate assembly 212 includes the poppet valve 216 having a valve head 222 supported on a valve stem 220. The valve head 222 is moved linearly toward and away from the wastegate port 14 by the actuator via the valve stem 220. In some embodiments, the valve 216 could be cam-operated or spring-loaded to linearly reciprocate at substantial right angles from the valve seat 226. When the valve 216 is in an open position (shown in broken lines in FIG. 8), the valve seat face 223 of the valve head 222 is spaced apart from the valve seat 226, and the valve seat face 223 remains parallel to the valve seat 226. When the valve 216 is in a closed position (shown in solid lines in FIG. 8), the valve seat face 223 of the valve head 222 is secured against the valve seat 226. The wastegate assembly 212 also includes a turbine housing having a contoured side wall 230 surrounding the wastegate port 214. In the turbine housing configuration shown in FIG. 8, the valve 216 the contoured side wall 230 defines a recess 236 that is elongated in the direction of valve movement. For example, the recess 236 has a depth that is at least twice the depth of the valve head margin 225, and preferably much greater than the depth of the valve head margin 225. In addition, the contoured side wall 230 shown as substantially linear while widening away from the valve seat 26, but the contoured side wall 230 would still be defined by the formula above where the side wall shape depends on the curtain area desired at a specific valve opening. The construction of the sidewall 230 would not substantially change relative to side wall 30 of the pivoting valve 16, except the reference point would move along a more linear path, instead of a widening arc of the concave portion 40. By providing the contoured side walls 230, the minimum flow area through the wastegate port 214 is controlled such that the flow is choked via the side walls 230 rather than the valve curtain area A.sub.vc. The contoured side wall 230 can be recessed into the housing 210 as shown, or extend from the housing 210.

(27) A wastegate assembly 212 including a contoured sidewall 230 can be compared to a conventional wastegate assembly 312 including poppet valve configuration in which a poppet valve 316 cooperates with a valve seat 326 that includes a lip defined by a shallow cylindrical recess 336 that surrounds the valve head 322 (FIG. 9). The shallow cylindrical recess 336 has a depth that generally corresponds to a depth of the valve head margin 325. In the case of a conventional poppet-valve wastegate assembly 312, when the valve 316 is in the closed position (shown in solid lines), the valve head 322 is secured against the valve seat 326, blocking flow through the wastegate port 314. Due to the shape and shallow depth of the recess 326, the ability to control the flow through the wastegate port 314 is limited once the valve 316 is moved to the open position (shown in broken lines).

(28) The invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of words of description rather than limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically enumerated within the description.