Centrifugal compressor for turbocharger with coordinated ported cover and inlet adjustment mechanism

Abstract

A centrifugal compressor for a turbocharger includes an inlet adjustment mechanism in the air inlet of the compressor, which is operable to move between a closed position, an open position, and an over-open position. The compressor also includes a cover system with ports. The inlet adjustment mechanism includes a plurality of blades arranged around the air inlet and movable radially inward and outward for defining various positions. In the closed position, the effective diameter of the air inlet is reduced, and the blades block the flow through the cover system with ports. In the open position, the blades still block the cover with ports, but the effective inlet diameter increases relative to the closed position. In the over-open position, the blades unblock the cover with ports so that an additional amount of flow can pass through the cover with ports, thereby shifting the blocked streamline of the compressor to a higher flow rate.

Description

Technical Field

[0001] The present disclosure relates to centrifugal compressors, such as those used in turbochargers, and more particularly to centrifugal compressors having an adjustable effective inlet area or diameter for different operating conditions. Background Art

[0002] An exhaust-driven turbocharger is a device used in conjunction with an internal combustion engine to increase the power output of the engine by compressing air, which is delivered to the air intake of the engine to be mixed with fuel and burned in the engine. A turbocharger includes a compressor wheel mounted on one end of a shaft in a compressor housing and a turbine wheel mounted on the other end of the shaft in a turbine housing. Typically, the turbine housing is formed separately from the compressor housing, and there is still another center housing connected between the turbine housing and the compressor housing for accommodating bearings for the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and receives exhaust gas from the engine. The turbine assembly includes a nozzle that is directed from the chamber into the turbine wheel. Exhaust gas flows from the chamber through the nozzle to the turbine wheel, and the turbine wheel is driven by the exhaust gas. Thus, the turbine draws power from the exhaust gas and drives the compressor. The compressor receives ambient air through the inlet of the compressor housing, and the air is compressed by the compressor wheel and then discharged from the housing to the engine air intake.

[0003] Turbochargers typically employ a centrifugal (also called "radial") type compressor wheel because centrifugal compressors can achieve relatively high pressure ratios in a compact arrangement. Intake air for the compressor is received in a generally axial direction at an inlet section portion of the centrifugal compressor wheel and is discharged in a generally radial direction at an outlet section portion of the wheel. Compressed air from the wheel is transmitted to a volute, and the air is supplied from the volute to the intake of an internal combustion engine.

[0004] The operating range of the compressor is an important aspect of the overall performance of the turbocharger. The operating range is usually defined by the surge line and the choke line on the compressor operating map. The compressor performance map (compressor map) is usually presented as the pressure ratio (discharge pressure) on the vertical axis. Pout Divide by the inlet pressure Pin ) versus the corrected mass flow rate on the horizontal axis. The choke line on the compressor performance map is located at high flow rates and characterizes the locus of maximum mass flow rate points over a range of pressure ratios; that is, for a given point on the choke line, it is not possible to increase the flow rate while maintaining the same pressure ratio because a choked flow condition has occurred in the compressor.

[0005] The surge line is located at low flow rates and characterizes the locus of minimum mass flow rate points without surge over a range of pressure ratios; that is, for a given point on the surge line, decreasing the flow rate without changing the pressure ratio, or increasing the pressure ratio without changing the flow rate, will cause surge to occur. Surge is a flow instability that typically occurs when the compressor blade incidence angle becomes so large that significant flow separation occurs over the compressor blades. During surge, pressure fluctuations and flow reversals may occur.

[0006] In a turbocharger for an internal combustion engine, compressor surge can occur when the engine is operated at high load or high torque with low engine speed, or when the engine is operated at low speed and there is a high level of exhaust gas recirculation (EGR). Surge can also occur when the engine is suddenly decelerated from a high speed state. Extending the compressor's surge-free operating range to lower flow rates is a goal that is often sought in compressor design.

[0007] At high flow rates, choked flow may also occur in the compressor.It would be desirable to have a means for shifting the choke line to a higher flow rate when operating conditions require it. Summary of the invention

[0008] The present disclosure describes a mechanism and method for a centrifugal compressor that can allow the surge line of the compressor to be selectively shifted to the left (i.e., surge is delayed to a lower flow rate at a given pressure ratio) and the choke flow line to be shifted to the right (i.e., choke flow is increased to a higher flow rate at a given pressure ratio). One embodiment described herein includes a turbocharger having the following features:

[0009] a turbine housing and a turbine wheel mounted in the turbine housing and connected to the rotatable shaft for rotation therewith, the turbine housing receiving the exhaust gas and supplying the exhaust gas to the turbine wheel;

[0010] a centrifugal compressor assembly including a compressor housing and a compressor wheel mounted in the compressor housing and connected to a rotatable shaft for rotation therewith, the compressor wheel having blades and defining an inlet section portion, the compressor housing having an air inlet wall defining an air inlet for directing air generally axially into the compressor wheel, the compressor housing further defining a shroud surface adjacent to and extending along a radially outer contour of the compressor wheel;

[0011] a compressor inlet adjustment mechanism disposed in the air inlet of the compressor housing and movable between a closed position and a super-open position, the inlet adjustment mechanism comprising a plurality of vanes distributed around the circumference of the air inlet and collectively forming a ring defining an orifice, the vanes being movable generally radially inwardly to define the closed position and generally radially outwardly to define the super-open position; and

[0012] wherein the compressor housing defines a ported shroud system, the ported shroud system comprising: an inner wall forming an upstream extension of the shroud surface; and an outer wall spaced radially outward of the inner wall such that an annular space is defined between the inner wall and the outer wall; and a bleed port formed by the inner wall and positioned adjacent to an inlet section portion of the compressor wheel for allowing air to pass between the annular space and the inlet section portion, the inner wall extending upstream from the compressor wheel and terminating at an upstream edge, an opening into the annular space being defined between the outer wall and an upstream edge of the inner wall,

[0013] wherein the vanes of the inlet regulating mechanism are arranged such that: in a closed position, the vanes block the opening into the annular space and prevent air flow from entering the annular space, wherein the orifice has a diameter smaller than the diameter defined by the inner wall; and in an over-open position, the vanes unblock the opening and allow air to flow into the annular space and into the compressor wheel through the bleed air port.

[0014] In one embodiment, the inlet adjustment mechanism can be adjusted to an open position between the closed position and the over-open position, and in the open position, the vane still blocks the opening into the annular space. In the open position, the orifice can have a diameter approximately equal to the diameter defined by the inner wall.

[0015] At low to medium engine speeds (and correspondingly low compressor speeds), the inlet adjustment mechanism may be placed in a closed position in which the ported cover is closed and the effective inlet diameter is reduced, thereby shifting the compressor surge line to the left on the compressor performance map and improving low flow efficiency.

[0016] At higher engine speeds (and correspondingly high compressor speeds), the inlet adjustment mechanism may be moved to an over-open position in which the ported cover is opened and causes the choked flow line to shift to the right on the compressor performance map.

[0017] Under moderate operating conditions where neither choked flow nor surge has an effect, the inlet adjustment mechanism can be placed in the open position. In the open position, the compressor is configured as if it were a normal compressor without an inlet adjustment mechanism or a ported hood system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and in which:

[0019] Figure 1 is an end view of a turbocharger according to one embodiment of the present invention, looking axially from the compressor end of the turbocharger toward the turbine end, with the inlet adjustment mechanism in a fully closed position;

[0020] Figure 2 It is along Figure 1 A cross-sectional view of the turbocharger taken along line 2-2;

[0021] Figure 2A yes Figure 2 The enlarged part of

[0022] Figure 3 is with Figure 1 a similar view with the inlet adjustment mechanism in the open position;

[0023] Figure 3A is with Figure 2A a similar view with the inlet adjustment mechanism in the open position;

[0024] Figure 4 is with Figure 1 a similar view with the inlet adjustment mechanism in the over-open position;

[0025] Figure 4A is with Figure 2A a similar view with the inlet adjustment mechanism in an over-open position;

[0026] Figure 5 is used for Figure 1 An exploded view of a compressor housing assembly of a turbocharger;

[0027] Figure 6 is an exploded view of the inlet adjustment mechanism;

[0028] Figure 7 is an isometric view of the inlet adjustment mechanism in an over-open position;

[0029] Figure 8 is an isometric view of the inlet adjustment mechanism in an open position;

[0030] Fig. 9is an isometric view of the inlet adjustment mechanism in a closed position;

[0031] Fig.10 is with Figure 2A Similar views showing an alternative embodiment of the present invention; and

[0032] Fig.11 is with Figure 2A Similar views show still another embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the invention are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like reference numerals refer to like elements throughout.

[0034] In this disclosure, the term "orifice" means "opening" without regard to the shape of the opening. Thus, an "orifice" may be circular or non-circular. In addition, when the vanes of the inlet adjustment mechanism are described as moving "radially" inward or outward, the term "radial" does not exclude some non-radial component of the vane movement (e.g., the vanes may occupy a plane that is slightly angled relative to the axis of rotation of the compressor, so that when the vanes move radially inward and outward, they also move with a small axial component of motion). In addition to the radial component, the movement of the vanes may also include some circumferential motion component.

[0035] A turbocharger 10 according to one embodiment of the present invention is illustrated in an axial end view. Figure 1 and an axial cross-sectional view of the turbocharger is shown in Figure 2 . A turbocharger includes a compressor and a turbine. The compressor includes a compressor wheel or impeller 14 mounted in a compressor housing 16 on one end of a rotatable shaft 18. The compressor housing includes a wall defining an air inlet 17 for directing air generally axially into the compressor wheel 14. The shaft is supported in bearings mounted in a center housing 20 of the turbocharger. The shaft is rotated by a turbine wheel 22 mounted on the other end of the shaft separately from the compressor wheel, thereby rotatably driving the compressor wheel, which causes air drawn in through the compressor inlet to be compressed and causes the compressed air to be discharged generally radially outwardly from the compressor wheel into a volute 21 for receiving the compressed air. From the volute 21, the air is routed to the intake of an internal combustion engine (not shown) for improving the performance of the engine.

[0036] The turbine wheel 22 is arranged within a turbine housing 24 which defines an annular chamber 26 for receiving exhaust gas from an internal combustion engine (not shown). The turbine housing further defines a nozzle 28 for directing the exhaust gas from the chamber 26 generally radially inwardly to the turbine wheel 22. As the exhaust gas passes through the turbine wheel, the exhaust gas expands and rotatably drives the turbine wheel, which in turn rotatably drives the compressor wheel 14, as already mentioned.

[0037] refer to Figure 1-3 In the illustrated embodiment, the wall defining the air inlet 17 is formed in part by the compressor housing 16 and in part by a separate inlet duct member 16d which is received in a cylindrical container defined by the compressor housing.

[0038] The compressor housing 16 defines a shroud surface 16s that is immediately adjacent the radially outer tips of the compressor blades. The shroud surface defines a curved profile that is generally parallel to the profile of the compressor wheel.

[0039] According to the present invention, the compressor of the turbocharger comprises an inlet adjustment mechanism 100 arranged in the air inlet 17 of the compressor housing. The inlet adjustment mechanism comprises an annular assembly, and the inlet adjustment mechanism is arranged in the annular space defined between the compressor housing 16 and the separate inlet pipe member 16d. The inlet adjustment mechanism is operable to adjust the effective diameter of the air inlet into the compressor wheel. Thus, the inlet adjustment mechanism can be moved between an open position and a closed position, and can be arranged to be adjusted to various intermediate positions between the open position and the closed position.

[0040] The present invention may be practiced with various types of inlet adjustment mechanisms having blades or vanes or ring segments distributed around the circumference of the air inlet and collectively forming a ring defining an orifice (the orifice may be circular or non-circular), the diameter of the orifice being adjustable to various sizes in order to adjust the flow into the compressor. Thus, the blades or vanes or ring segments (any of which will be collectively referred to as "blades" hereinafter) may be moved generally radially inwardly and outwardly for adjusting the orifice size. As a non-limiting example, the present invention may be practiced with the inlet adjustment mechanisms described in any of the following commonly owned U.S. patent applications of the present applicant: Serial No. 14 / 642,825 filed on March 10, 2015; Serial No. 14 / 551,218 filed on September 9, 2015; Serial No. 15 / 446,054 filed on March 1, 2017; Serial No. 15,446,090 filed on March 1, 2017; and Serial No. 15,456,403 filed on March 10, 2017. The entire disclosures of the above applications are hereby incorporated herein by reference.

[0041] Reference now Figures 6 to 9 The inlet adjustment mechanism includes a plurality of first blades 102A and a plurality of second blades 102B, the plurality of first blades 102A being arranged about a central axis of the air inlet and each being pivotable about a first pivot pin 104A positioned at or near one end of the blade, and the plurality of second blades 102B being arranged about a central axis and each being pivotable about a second pin (not visible in the drawings) positioned at or near one end of the blade. The first blades 102A are located in a first plane, and the second blades 102B are located in a second plane, the second plane being parallel to and axially adjacent to the first plane. Each first blade 102A includes a protrusion 105A positioned radially outward of the first pivot pin 104A, and similarly, each second blade includes a protrusion 105B positioned radially outward of the second pivot pin. The first synchronizing ring 106A defines a plurality of circumferentially spaced grooves or recesses 107A that receive the projections 105A of the first vanes, and similarly, the second synchronizing ring 106B includes recesses 107B that receive the projections 105B of the second vanes. The inlet adjustment mechanism may include a cartridge including a pair of axially spaced annular end plates 101, 109 ( Figure 2A ), wherein the synchronizing ring and the first and second vanes are arranged in the axial space between the end plates. The first pivot pin 104A can be received in a recess defined in the adjacent end plate 101, and correspondingly, the second pivot pin can be received in a recess defined in the other end plate 109. In an alternative non-cartridge form mechanism, the recess for the vane pivot pin can be defined in a portion of the compressor housing assembly. In any case, the vane pivot pins are fixed in place so that when the synchronizing rings 106A, 106B rotate about the axis of the inlet adjustment mechanism, the vanes 102A, 102B pivot about their pivot pins due to the engagement of the protrusions 105A, 105B in the recesses 107A, 107B of the synchronizing rings.

[0042] Although the illustrated embodiment employs two sets of blades 102A and 102B, a single set of blades or more than two sets of blades may be employed in a similar manner.

[0043] like Figure 2 As shown in FIG. 1 , the entire assembly of the inlet adjustment mechanism 100 is disposed in the annular space defined between the compressor housing 16 and the inlet duct member 16d. The vanes 102A, 102B are disposed through slots in the inlet wall, which are actually provided thereby.

[0044] Although the illustrated embodiment includes two synchronizing rings for two sets of blades, alternatively a single synchronizing ring may be employed (whether the mechanism includes a single set of blades or multiple sets of blades).

[0045] The inlet adjustment mechanism is composed of an actuator 116 ( Figure 5 ) is actuated, the actuator 116 has an actuating rod 117 that extends through a passage defined in the compressor housing 16 and is connected to a fork 108A on the first synchronizing ring 106A and a fork 108B on the second synchronizing ring 106B ( Figure 6 ). Extension of the actuating rod rotates the synchronizer ring in one direction, and retraction of the rod rotates the synchronizer ring in the other direction.

[0046] The compressor housing 16 also defines a ported hood system that is effective for increasing the mass flow rate of the compressor under choked conditions (i.e., for shifting the choked flow line to a higher flow rate on a performance diagram of the compressor pressure versus flow). More specifically, referring to Figure 2 , the ported shroud is defined by an inner wall 19 of the compressor housing 16, which is actually an upstream extension of the shroud surface 16s at the same radius from the compressor axis. The inner wall 19 is radially inwardly spaced from the outer wall 16e, which is actually a downstream extension of the inner surface of the air inlet 17 defined by the inlet duct member 16d, so that there is an annular space or passage 16r defined between the inner wall 19 and the outer wall 16e of the air inlet. The inner wall 19 may be formed by a plurality of circumferentially spaced struts 23 or the like (see Figure 4 ) is connected to the outer wall 16e. The inner wall 19 defines one or more bleed ports 16b located in the inlet section area of ​​the compressor wheel 14. The bleed port can be a single circumferentially continuous slot extending 360 degrees around the circumference of the wall, or can be a series of ports circumferentially spaced around the circumference. The bleed port 16b connects the inlet section area of ​​the compressor wheel with the annular space 16r.

[0047] The inner wall 19 extends from the inlet section of the wheel in an upstream direction and terminates at an upstream edge. Figure 2 In the embodiment shown in , the upstream edge of the inner wall 19 is spaced apart by a very small gap from the inlet adjustment mechanism 100. However, alternatively, the gap may be larger than shown.

[0048] The inlet adjustment mechanism 100 and the ported hood system work in conjunction with each other, as now referred to Figure 2A , Figure 3A and Figure 4A Explained. Figure 2A The inlet adjustment mechanism is shown in the closed position (see also Figure 1 The corresponding axial end view in Fig. 9). In the closed position, the vanes of the inlet regulating mechanism are moved radially inward to their maximum extent and they close the annular space 16r of the hood system with ports. Accordingly, when the inlet regulating mechanism is completely closed, the effective diameter D of the air inlet is 关闭 The orifice is defined by a reduced diameter orifice determined by the closed vanes 102A, 102B of the inlet regulating mechanism. Figure 2A As indicated by arrow A, the air flow is restricted to a reduced diameter D 关闭 Defined area.

[0049] Figure 3A Depicted is the inlet adjustment mechanism in the open position (see also Figure 3 The corresponding axial end view in Figure 8 19). In the open position, the vanes 102A, 102B move radially outward until the orifice defined by the vanes is at least as large as the inner diameter of the inner wall 19, but at the same time the vanes 102A, 102B still close the annular space 16r of the ported hood system. Thus, air flow through the annular space 16r is prevented. In this open position, the air flow (see arrow A) is restricted to the annular space 16r defined by the diameter D 打开 The area defined by the diameter D 打开 It preferably corresponds to the inner diameter of the inner wall 19 .

[0050] Figure 4A Illustration of the inlet adjustment mechanism in the "over-open" position (see also Figure 4 The corresponding axial end view in Figure 7 16b of the compressor wheel). In the over-open position, the vanes 102A, 102B move further radially outward until they no longer block the opening into the annular space 16r of the ported shroud system. Thus, the available flow area is further increased because air can flow both through the main flow path defined by the inner wall 19 and through the annular space 16r of the ported shroud system and then inwardly through the bleed air port 16b to the compressor wheel.

[0051] Fig.10 An alternative embodiment of the invention is illustrated which is substantially similar to the embodiment described above in most respects. The main differences are: Fig.10In the embodiment of the invention, the inner wall 19 is shortened in the axial direction, so that when the mechanism is in the closed position as shown, there is an axial gap G between the upstream edge of the inner wall and the vane 102B of the inlet regulating mechanism. This is effective in allowing part of the air that is led out into the annular space 16r through the bleed port 16b to be recirculated back into the air inlet through the axial gap G. Such air recirculation helps to further reduce the possibility of surge under low flow operating conditions.

[0052] Still another embodiment having a similar purpose is Fig.11 102A, 102B. In this embodiment, instead of an axial gap, there is a hole H defined through the blades 102A, 102B. Air from the annular space 16r can pass through the hole and be recirculated back into the air inlet. The hole is positioned so that: when the inlet adjustment mechanism is in the open position or the over-open position, the hole is retracted radially outward into the space defined between the inlet pipe member 16d and the compressor housing 16.

[0053] At low to medium flow rates (eg, low to medium engine speeds), the inlet adjustment mechanism 100 may be placed in the closed position (see Figure 1 , Figure 2A , Fig. 9 , Fig.10 and Fig.11 ). This can have the effect of reducing the effective inlet diameter and therefore increasing the flow rate into the compressor wheel. The result will be: reducing the compressor blade incidence angle, effectively stabilizing the flow (i.e., making blade stall and compressor surge less likely). In other words, the surge line of the compressor will be moved to lower flow rates (to the left on a performance graph of the compressor's pressure ratio versus flow rate).

[0054] At higher flow rates, the inlet adjustment mechanism 100 may be placed Figure 3 , Figure 3A and Figure 8 This may have the effect of increasing the effective inlet diameter so that the compressor regains its high flow performance essentially as if the inlet adjustment mechanism did not exist and as if the compressor had a conventional inlet matched to the wheel diameter at the inlet section portion of the wheel.

[0055] At high flow rates where choked flow may occur, the inlet adjustment mechanism can be placed Figure 4 , Figure 4A and Figure 7 The ported hood system is opened to an over-open position so that the choke flow line is shifted to a higher flow rate.

[0056] The present invention is not limited to an inlet adjustment mechanism having three positions (i.e., closed, open, and over-open). The mechanism may be adjusted to other positions as desired (e.g., one or more positions between the closed position and the open position, and / or one or more positions between the open position and the over-open position).

[0057] With the benefit of the teachings given in the above description and the associated drawings, those skilled in the art to which these inventions pertain will think of many modifications and other embodiments of the inventions set forth herein. For example, although the illustrated embodiment employs two sets of pivoting blades for the inlet adjustment mechanism, the invention is not limited to any specific inlet adjustment mechanism configuration. In the practice of the invention, any type of inlet adjustment mechanism having blades or vanes or segments that can block flow into a ported hood system in certain positions and unblock convection in other positions may be employed. Instead of pivoting, the blades may translate radially inward and outward, or may move both radially and circumferentially (i.e., spirally). Therefore, it will be understood that the invention is not limited to the specific embodiments disclosed, and modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used only in a general and descriptive sense and not for limiting purposes.

Claims

1. A turbocharger, comprising: a turbine housing and a turbine wheel mounted in the turbine housing and connected to a rotatable shaft for rotation therewith, the turbine housing receiving exhaust gas and supplying the exhaust gas to the turbine wheel; a centrifugal compressor assembly including a compressor housing and a compressor wheel mounted in the compressor housing and connected to the rotatable shaft for rotation therewith, the compressor wheel having blades and defining an inlet section portion, the compressor housing having an air inlet wall defining an air inlet for directing air generally axially into the compressor wheel, the compressor housing further defining a shroud surface adjacent to and extending along a radially outer contour of the compressor wheel; a compressor inlet adjustment mechanism disposed in the air inlet of the compressor housing and movable between a closed position and an over-open position, the inlet adjustment mechanism comprising a plurality of vanes distributed around a circumference of the air inlet and collectively forming a ring defining an orifice, the vanes being movable generally radially inwardly to define the closed position and generally radially outwardly to define the over-open position; and wherein the compressor housing defines a cover system with a port, the cover system with a port comprising: an inner wall, the inner wall forming an upstream extension of the cover surface; and an outer wall, the outer wall being spaced radially outward from the inner wall so that an annular space is defined between the inner wall and the outer wall; and a bleed port, the bleed port being formed by the inner wall and positioned adjacent to the inlet section portion of the compressor wheel for allowing air to pass between the annular space and the inlet section portion, the inner wall extending upstream from the compressor wheel and terminating at an upstream edge, an opening into the annular space being defined between the outer wall and the upstream edge of the inner wall, wherein the vanes of the inlet regulating mechanism are arranged such that: in a closed position, the vanes block the opening into the annular space and prevent air flow from entering the annular space, in which the orifice has a diameter smaller than the diameter defined by the inner wall; and in an over-open position, the vanes unblock the opening and allow air to flow into the annular space and into the compressor wheel through the bleed air port.

2. The turbocharger according to claim 1, wherein: The inlet adjustment mechanism is adjustable to an open position between a closed position and an over-open position, and in the open position, the vane still blocks the opening into the annular space, and in the open position, the orifice has a diameter approximately equal to the diameter defined by the inner wall.

3. The turbocharger according to claim 2, wherein: The vane is arranged to pivot between the closed position, the open position and the over-open position.

4. The turbocharger according to claim 1, wherein: In the closed position of the inlet regulating mechanism, an axial gap is defined between the vane and the upstream edge of the inner wall such that a portion of the air from the annular space recirculates through the axial gap back into the air inlet.

5. The turbocharger according to claim 1, wherein: The vane defines an aperture therethrough, the aperture being positioned such that, in a closed position of the inlet regulating mechanism, a portion of the air is recirculated from the annular space through the aperture back into the air inlet.

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