Patent Grant
10550761
The present disclosure relates to centrifugal compressors, such as used in turbochargers, and more particularly relates to centrifugal compressors in which the effective inlet area or diameter can be adjusted for different operating conditions.
An exhaust gas-driven turbocharger is a device used in conjunction with an internal combustion engine for increasing the power output of the engine by compressing the air that is delivered to the air intake of the engine to be mixed with fuel and burned in the engine. A turbocharger comprises 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 yet another center housing connected between the turbine and compressor housings for containing bearings for the shaft. The turbine housing defines a generally annular chamber that surrounds the turbine wheel and that receives exhaust gas from an engine. The turbine assembly includes a nozzle that leads from the chamber into the turbine wheel. The exhaust gas flows from the chamber through the nozzle to the turbine wheel and the turbine wheel is driven by the exhaust gas. The turbine thus extracts power from the exhaust gas and drives the compressor. The compressor receives ambient air through an inlet of the compressor housing and the air is compressed by the compressor wheel and is then discharged from the housing to the engine air intake.
Turbochargers typically employ a compressor wheel of the centrifugal (also known as “radial”) type 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 inducer portion of the centrifugal compressor wheel and is discharged in a generally radial direction at an exducer portion of the wheel. The compressed air from the wheel is delivered to a volute, and from the volute the air is supplied to the intake of an internal combustion engine.
The operating range of the compressor is an important aspect of the overall performance of the turbocharger. The operating range is generally delimited by a surge line and a choke line on an operating map for the compressor. The compressor map is typically presented as pressure ratio (discharge pressure Pout divided by inlet pressure Pin) on the vertical axis, versus corrected mass flow rate on the horizontal axis. The choke line on the compressor map is located at high flow rates and represents 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 occurs in the compressor.
The surge line is located at low flow rates and represents 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, reducing the flow rate without changing the pressure ratio, or increasing the pressure ratio without changing the flow rate, would lead to surge occurring. Surge is a flow instability that typically occurs when the compressor blade incidence angles become so large that substantial flow separation arises on the compressor blades. Pressure fluctuation and flow reversal can happen during surge.
In a turbocharger for an internal combustion engine, compressor surge may occur when the engine is operating at high load or torque and low engine speed, or when the engine is operating at a low speed and there is a high level of exhaust gas recirculation (EGR). Surge can also arise when an engine is suddenly decelerated from a high-speed condition. Expanding the surge-free operation range of a compressor to lower flow rates is a goal often sought in compressor design.
Applicant's U.S. patent application Ser. No. 15/446,054 filed on Mar. 1, 2017, which claims the benefit of the filing date of Provisional Application No. 62/324,488 filed on Apr. 20, 2016, the entire disclosures of said applications being hereby incorporated herein by reference, describes mechanisms and methods for a centrifugal compressor that can enable the surge line for the compressor to selectively be shifted to the left (i.e., surge is delayed to a lower flow rate at a given pressure ratio). One embodiment described in said applications comprises a turbocharger having the following features:
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 comprising 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 inducer portion, the compressor housing having an air inlet wall defining an air inlet for leading air generally axially into the compressor wheel, the compressor housing further defining a volute for receiving compressed air discharged generally radially outwardly from the compressor wheel; and
a compressor inlet-adjustment mechanism disposed in the air inlet of the compressor housing and pivotable radially inwardly and radially outwardly between an open position and a closed position, the inlet-adjustment mechanism comprising a plurality of blades disposed about the air inlet and each pivotable about one end of the blade, the blades pivoting radially inwardly through a slot in the air inlet wall when the blades are in the closed position so as to form an orifice of reduced diameter relative to a nominal diameter of the inlet.
Applicant is also the owner of additional applications directed to other inlet-adjustment mechanisms employing moving blades, including U.S. application Ser. No. 15/446,090 filed on Mar. 1, 2017, the entire disclosure of which is hereby incorporated herein by reference.
The present disclosure concerns inlet-adjustment mechanisms generally of the type described in the aforementioned '054, '488, and '090 applications, and particularly concerns modifications or redesigns of such mechanisms that aim to improve upon certain aspects of said mechanisms.
One such aspect of the aforementioned inlet-adjustment mechanisms for which improvement is sought concerns the actuation force required for moving the blades of the inlet-adjustment mechanism between the open and closed positions. The inlet-adjustment mechanism is subject to significant aerodynamic load, particularly at low-flow and high compression ratio conditions, which correspond to operating conditions for which the blades typically are closed. Thus, the blades experience a significant pressure differential between their upstream and downstream faces, which urges the blades in the downstream direction against the compressor housing structure immediately adjacent thereto. These aerodynamic loads, combined with internal friction within the inlet-adjustment mechanism, operate to resist the actuator that moves the mechanism between the open and closed positions. This results in the need for a significant amount of actuation force from the actuator, meaning that a larger and more-expensive actuator is required in order to attain the speed of actuation that is needed for proper compressor operation.
Accordingly, Applicant has sought to mitigate this issue.
In accordance with one embodiment disclosed herein, there is described a turbocharger having a combination of features that cooperate to reduce the required actuator force for the inlet-adjustment mechanism. Thus, one turbocharger in accordance with the embodiment of the invention includes:
In one embodiment, the support portion of each blade includes a raised dimple that makes contact with the downstream face of the unison ring and spaces a remainder of the support portion from said downstream face. The dimples reduce the amount of surface area contact between the unison ring and the blades, thereby reducing frictional resistance to unison ring rotation.
In one embodiment of the invention, each blade includes a ring-centering surface disposed on the mounting portion of the blade, the ring-centering surfaces of the blades contacting the radially inner periphery of the unison ring and collectively serving to radially position the unison ring such that the rotational axis of the unison ring is substantially coaxial with the rotation axis of the turbocharger.
In accordance with one embodiment, each blade and the pivot pin therefor comprise an integral one-piece structure.
According to one embodiment, a majority of the radially outer periphery of the unison ring lies on a circle of radius RO from the rotational axis but localized regions of the radially outer periphery in the vicinity of the notches are bulged radially outwardly to a radius RO+ΔR so that the notches lie at a radius greater than RO.
The turbocharger can also include a linear actuator operable to rotate the unison ring, the actuator including an actuator rod, and the compressor housing defining a rod bore extending along a direction tangential to the radially outer periphery of the unison ring. The actuator rod is disposed in the rod bore and is linearly movable therein. The compressor housing defines an opening that proceeds radially outwardly into the rod bore at a distal end of the actuator rod, and the unison ring defines a protrusion extending radially outward from the radially outer periphery of the unison ring. The protrusion passes through said opening into the rod bore and engages the distal end of the actuator rod such that linear movement of the actuator rod is transmitted by the protrusion to the unison ring so as to rotate the unison ring.
In accordance with one embodiment of the invention, frictional resistance to movement of the unison ring, blades, and actuator rod of the inlet-adjustment mechanism is reduced by constructing the blades and their pivot pins of plastic (for example, made by injection molding). Additionally, the actuator rod can comprise a metal rod but the distal end of the actuator rod can include a plastic cover (for example, formed by overmolding around the metal rod). Accordingly, the unison ring engages plastic surfaces of the blades and the actuator rod. The unison ring advantageously is made of metal, and so providing plastic (low-friction) engagement surfaces for the unison ring leads to a reduction in overall frictional resistance to mechanism movement.
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 wherein:
The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some but not all embodiments of the inventions 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 numbers refer to like elements throughout.
In the present disclosure, the term “orifice” means “opening” without regard to the shape of the opening. Thus, an “orifice” can be circular or non-circular. Additionally, when the blades of the inlet-adjustment mechanism are described as pivoting “radially” inwardly or outwardly, the term “radially” does not preclude some non-radial component of movement of the blades (for example, the blades may occupy a plane that is angled slightly with respect to the rotational axis of the compressor, such that when the blades pivot radially inwardly and outwardly, they also move with a small axial component of motion; alternatively, the blades may pivot and translate, such as in a helical type motion).
A turbocharger 10 in accordance with one embodiment of the invention is illustrated in axial end view in
The turbine wheel 22 is disposed within a turbine housing 24 that defines an annular chamber 26 for receiving exhaust gases from an internal combustion engine (not shown). The turbine housing also defines a nozzle 28 for directing exhaust gases from the chamber 26 generally radially inwardly to the turbine wheel 22. The exhaust gases are expanded as they pass through the turbine wheel, and rotatably drive the turbine wheel, which in turn rotatably drives the compressor wheel 14 as already noted.
With reference to
The compressor housing 16 defines a shroud surface 16s that is closely adjacent to the radially outer tips of the compressor blades. The shroud surface defines a curved contour that is generally parallel to the contour of the compressor wheel.
In accordance with the invention, the compressor of the turbocharger includes an inlet-adjustment mechanism 100 disposed in the air inlet 17 of the compressor housing. The inlet-adjustment mechanism comprises a ring-shaped assembly and is disposed in an annular space defined between the compressor housing 16 and the separate inlet duct member 16d. The annular space is bounded between an upstream wall surface 105 and a downstream wall surface 107 (
With reference now to
The inlet-adjustment mechanism further comprises a unison ring 106 for imparting pivotal movement to the blades. The unison ring surrounds the assembly of the blades 102 and is substantially coplanar with the blades, and is rotatable about an axis that coincides with the rotation axis of the compressor wheel. The unison ring includes a plurality of recesses 108 and each blade includes an end portion that is engaged in a respective one of the recesses 108, as described in further detail below in connection with
The radially inner edges of the blades 102 include portions that preferably are generally circular arc-shaped and these edges collectively surround and bound a generally circular opening or orifice (although the degree of roundness varies depending on the positions of the blades, as further described below).
The range of pivotal movement of the blades is sufficient that the blades can be pivoted radially outwardly by rotation of the unison ring in one direction (clockwise in
The blades can also be pivoted radially inwardly (by rotation of the unison ring in the opposite direction, counterclockwise in
It should be noted, however, that it is not essential that the orifice defined by the inlet-adjustment mechanism be circular in the closed position. Alternatively, the orifice can be non-circular. The invention is not limited to any particular shape of the orifice.
As previously described, the blades 102 are actuated to pivot between their open and closed (and, optionally, super-closed) positions by the unison ring 106 that is rotatable about the center axis of the air inlet. Referring now to
As noted, the inlet-adjustment mechanism 100 enables adjustment of the effective size or diameter of the inlet into the compressor wheel 14. As illustrated in
At low flow rates (e.g., low engine speeds), the inlet-adjustment mechanism 100 can be placed in the closed position of
At intermediate and high flow rates, the inlet-adjustment mechanism 100 can be partially opened or fully opened as in
In accordance with one aspect of the invention disclosed herein, the inlet-adjustment mechanism 100 includes features for reducing the frictional resistance of the inlet-adjustment mechanism to movement. As previously noted, the inlet-adjustment mechanism is subject to significant aerodynamic load, particularly at low-flow and high compression ratio conditions, which correspond to operating conditions for which the blades 102 typically are closed. Thus, the blades experience a significant pressure differential between their upstream and downstream faces, which urges the blades in the downstream direction against the compressor housing structure immediately adjacent thereto. These aerodynamic loads, combined with internal friction within the inlet-adjustment mechanism, operate to resist the actuator 116 that moves the mechanism between the open and closed positions. This results in the need for a significant amount of actuation force from the actuator, meaning that a larger and more-expensive actuator is required in order to attain the speed of actuation that is needed for proper compressor operation.
Features of the present invention can reduce the frictional resistance of the mechanism, as well as provide mechanical advantage to the linkage between the actuator, the unison ring, and the blades, the result being that the desired speed and reliability of actuation of the mechanism can be achieved without needing a large and expensive actuator. In accordance with a first aspect of the invention, the actuator-to-blade linkage is designed for improved mechanical advantage, as now explained. As best seen in
With reference now to
The support portion 102s of each blade includes a raised dimple 102r that makes contact with the downstream face of the unison ring 106 (
These features are advantageous for minimizing the actuation force that is required from the actuator 116 for actuating the blades 102. Because the hook portions 102h of the blades engage the notches 108 in the outer periphery of the unison ring 106, the lever arms of the blades can be made longer than they would be if the blades engaged the inner periphery of the unison ring. This means that the actuation force needed to pivot the blades against a given resistance (caused by friction and exacerbated by high aerodynamic loads) is reduced.
Additionally, in accordance with a second aspect of the invention, the frictional resistance to rotation of the unison ring is reduced by features of the present invention. More particularly, the surface area of the downstream face of the unison ring (the face that is urged by high aerodynamic loads against the adjacent structure) that is subject to friction is reduced by the provision of the support portions 102s of the blades having the raised dimples 102r, which space most of the surface of the support portions away from the downstream face of the unison ring. Thus, the downstream face of the unison ring makes contact only with the dimples 102r, which have a small collective surface area in contact with the unison ring.
Furthermore, because the unison ring makes rolling contact with the ring-centering surfaces 102c on the mounting portions of the blades 102, relative sliding and hence friction are reduced at these locations. It is also noteworthy that the provision of the ring-centering surfaces eliminates the need for separate ring-centering guides such as pins or rollers in the inlet-adjustment mechanism.
To further reduce friction and the actuation force required for pivoting the blades, low-friction materials are employed in strategic locations. Thus, in accordance with some embodiments of the invention, the blades 102 are constructed of plastic, which has a lower coefficient of friction than the metal typically used for the blades. Advantageously, each blade 102 and its associated pivot pin 102p constitute a one-piece integral part, which can be formed, for example, by injection molding or the like. The pivot pins thus have low-friction surfaces in contact with the inner surfaces of the bores in the compressor housing in which they rotate. The points of contact between the blades and adjacent parts (such as the unison ring 106 and the upstream wall 105 of the cavity for the inlet-adjustment mechanism) are likewise formed by low-friction plastic.
In this regard, the upstream wall 105 (
With reference to
A further aspect of the invention concerns the method for assembling the inlet-adjustment mechanism. With reference to
Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. For example, although the illustrated embodiment employs three blades 102, the invention is not limited to any particular number of blades. The invention can be practiced with as few as two blades, or as many as 12 blades or more. The number of blades can be selected as desired. Moreover, while blades with circular-arc edges have been illustrated and described, the blades do not have to have circular-arc edges. Blades with edges of different shapes (linear, elliptical, etc.) are also included within the scope of the invention. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that 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 in a generic and descriptive sense only and not for purposes of limitation.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20040096316 | Simon | May 2004 | A1 |
| 20140308110 | Houst | Oct 2014 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20190264604 A1 | Aug 2019 | US |
