The present invention relates generally to rotary apparatuses such as turbines and compressors that circulate a gas in a turbocharger and, more particularly, to an apparatus with a rotor having blades that define a nonlinear profile along at least one edge.
Radial turbines and compressors, such as those used in turbochargers, typically include a rotor, or wheel, that is rotatably mounted in a housing and that defines blades extending radially outward in proximity to an inner surface of the housing. The housing defines an inlet for receiving air or other gas, and an outlet through which the gas is circulated. In the case of a turbine, the rotor is a turbine wheel that is rotatably mounted in a turbine wheel housing. Gas, such as exhaust gas from an internal combustion engine, flows into the housing through the inlet, which extends circumferentially around the wheel, and exits in a generally axial direction. As the gas passes through the housing, the turbine wheel is rotated. In a typical turbocharger, the turbine wheel is connected by a shaft to a compressor wheel, i.e., a rotor, that is rotatably mounted in a compressor wheel housing. The compressor wheel housing also defines an inlet and outlet, and the compressor wheel includes radial blades that deliver air through the compressor wheel housing. In particular, the compressor wheel draws air axially inward through the inlet and delivers the air radially outward through a diffuser that extends circumferentially around the compressor wheel.
The blades of the rotors of turbines and compressors typically have edges that are positioned in close proximity to the housing and other relatively stationary components. For example, the turbines and compressors of modern turbochargers can include stators at the inlet and/or outlet to control the flow of gas through the device. In a turbine, the stators can be vanes arranged circumferentially at the inlet to define a stationary or an adjustable nozzle. The nozzle can be selectively opened and closed to control the flow of the gas through the turbine. In a compressor, the stators can be vanes that are arranged circumferentially at the outlet to define a variable diffuser that controls the flow of the air through the compressor. Due to the close proximity of the rotors and stators, the high rotational speeds of the rotors, and the high operating pressures, the blades of the rotors are subject to unsteady aerodynamic excitation forces that induce alternating strains and stresses in the blades. Such unsteady, or cyclic, excitation forces can similarly result from other stationary or adjustable components such as inlet guide vanes or a curved inlet manifold that supplies the gas to the inlet at pressures that vary across the area of the inlet. For example, inlet guide vanes are often provided in the inlet of a compressor to direct the flow of air therethrough. Thus, the blades are cyclically stressed at frequencies associated with the rotational speed of the rotor and the number and location of the vanes or other stationary components. Such cyclic stress can result in fatigue and failure of the rotors.
A forced response analysis can be conducted during the design of a rotary device such as a turbine or compressor to determine the cyclic stresses and strains on the rotor due to any unsteady aerodynamic excitation forces that occur at the rotor's resonant frequencies. The unsteady aerodynamic mechanical response of the rotor can be first analyzed, e.g., by conducting a computational fluid dynamics (CFD) analysis to determine the unsteady aerodynamic excitation forces, and conducting a 3-dimensional finite element method (FEM) analysis to determine the natural resonant frequencies of the rotor. Typically, the geometric configuration of the rotor or other components of the device is adjusted or modified as is practical to reduce the stresses and strains of the rotor that result from the unsteady aerodynamic excitation forces, e.g., by adjusting the configuration of the rotor or other devices such that the resonant frequencies occur outside the operating range of the rotor. The normal operating range of the device may be such that the rotor is not significantly stressed when subjected to cyclic aerodynamic forces that correspond to the lowest of the resonant frequencies of the rotor due to the low speed and pressure associated with that speed of operation. However, it is often impossible or impractical to adjust the higher resonant frequencies out of the operating speed range of the turbocharger. Thus, for example, the rotor may be subjected during some times of operation to a cyclic aerodynamic excitation force having a frequency that is equal to the second mode or higher modes of the resonant vibratory frequency of the rotor. Accordingly, the design analysis can include determining the strains and stresses that occur in the rotor at such frequencies and verifying that the expected life of the rotor meets a minimum design criteria. In some cases, however, the rotor may be subjected to alternating strains that reduce the expected life of the rotor below a minimum design criteria.
Thus, there exists a need for improved rotors for rotary devices such as turbines and compressors that are used in turbochargers, and for a method of manufacturing such devices. Preferably, the devices should be subjected to reduced strains and stresses, thereby extending the operating lives of the devices, despite cyclic aerodynamic excitation forces, which can occur throughout the operating range of the device, including at one or more of the vibratory modes of the rotor of the device.
The present invention provides a rotor, such as turbine wheel or compressor wheel, as well as a rotary apparatus and an associated method. According to one embodiment of the present invention, a turbine wheel is connected to a shaft and configured to be rotated with the flow of gas through a housing to thereby rotate the shaft. The wheel includes a body portion and a plurality of blades. The body portion is configured to rotate about an axis, and the blades extends radially outward from the body portion. Each blade defines first and second edges, with the first edge extending generally radially and the second edge extending generally axially, and the second edge being a leading edge of the blade that defines a nonlinear, concavely curved profile in radial-axial projection. In one embodiment, the profile of the second edge extends smoothly and continuously from a first end to a second end in a generally axial direction, with the first and second ends extending radially to a greater extent than a mid-point of the profile between the first and second ends. A rotary apparatus according to one embodiment of the present invention is configured to circulate a gas. The apparatus includes a housing defining an inlet and an outlet, a rotor with a body portion and radially extending blades disposed in the housing and configured to rotate with a flow of gas through the housing, and a plurality of vanes disposed at circumferentially incremental locations in the housing radially outward from the second edge of the blades. Each blade defines a first edge extending generally radially and a second edge extending generally axially, with the second edge being a leading or trailing edge of the blade that defines a nonlinear profile in radial-axial projection. The blades are subjected to cyclically varying aerodynamic forces as the blades pass in proximity to the vanes during rotation of the rotor, thereby cyclically stressing the blades, the vanes being adjustable to thereby control the flow of the gas through the housing.
According to another embodiment of the present invention, there is provided a method of manufacturing a rotor structured to rotate with a flow of gas through a housing. The method includes providing first parameters defining a geometric configuration of a blade extending radially from the rotor and defining an edge, providing second parameters defining an expected cyclic pressure distribution on the blade during rotation of the rotor in the housing, determining a high displacement portion of the blade being subjected to a relatively higher displacement than adjacent portions of the blade resulting from the expected cyclic pressure distribution, adjusting the first parameters to remove at least part of the high displacement portion from the blade such that the edge of the blade is nonlinear in radial-axial projection, and thereafter forming the blade according to the first parameters.
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 invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, this invention 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.
Referring to
The rotary apparatus 10 includes a housing 12 that defines an inlet 14 and an outlet 16. A rotor 30, which in this case is a turbine wheel, is rotatably mounted in the housing 12 and configured to rotate with the passage of gas through the housing 12. Thus, gas enters the inlet 14 flowing in a direction 15 generally perpendicular to the longitudinal axis of the rotor 30 and a shaft 50, flows circumferentially in a volute 18 extending circumferentially around the rotor 30, and then flows generally radially inward through a nozzle 20 to the rotor 30. The gas exerts pressure on a plurality of radially extending blades 32 on the rotor 30, thereby turning the rotor 30. The gas then flows in a generally axial direction 17 out of the outlet 16 of the housing 12. The rotor 30 is connected to the shaft 50 such that the shaft 50 turns as the rotor 30 is rotated. As used in a turbocharger, the shaft 50 typically extends through a center housing (not shown), where bearings can support the shaft 50 and oil can be provided for lubrication and cooling. Opposite the center housing from the turbine 10, the shaft 50 can be connected to a compressor wheel (not shown) in a compressor such that the compressor is rot atably operated as the turbine 10 rotates the shaft 50.
Stators such as vanes 22 or other flow control devices can be provided in the nozzle 20 to control or adjust the flow of the gas therethrough. For example, the vanes 22 can be arranged at circumferential intervals in the nozzle 20 and configured to be rotatably adjusted, thereby varying the geometry of the nozzle 20 and affecting the flow of gas. Such variable nozzles 20 are further described in U.S. Pat. No. 6,419,464 to Arnold, the entire content of which is incorporated herein by reference. Alternatively, the vanes 22 can be fixed and an axially sliding piston (not shown) can be used for varying the turbine nozzle flow area. It is appreciated that the adjustment of the nozzle 20 can result in an increase in efficiency of the turbine 10 throughout its range of operation.
The rotor 30 includes a body portion 34, which is connected to the shaft 50, and a plurality of the blades 32, which extend generally radially outward from the body portion 34. By the term “generally radially” it is meant that the blades 32 do extend radially but may also extend in the axial direction of the rotor 30. As illustrated in
The second edge 38 of each blade 32 is either a leading or trailing edge of the blade 32. For example, in the case of a turbine, the second edge 38 of each blade 32 is the leading edge, and the first edge 36 is a trailing edge. That is, as the rotor 30 rotates, the second edge 38 contacts gas flowing into the housing 12, and the gas thereafter flows toward the first edge 36. Also, as the rotor 30 rotates, each of the blades 32 passes through a flow field coming off the trailing edge of each of the vanes 22 or other features defined around the circumference of the nozzle 20. The flow field is nonuniform and unsteady relative to the moving blades 32. As a result, the pressure on opposite faces 42, 44 of each blade 32 increases and decreases cyclically. Further, the strain throughout the blades 32 also increases and decreases cyclically at a frequency corresponding to the rotational speed of the rotor 30 and the number and placement of the vanes 22 or other features. Generally, the temporal variation of pressure and strain are not uniform throughout the faces 42, 44 of the blades 32.
Variation in the pressure and strain on the blades 32 can also result from other geometric nonuniformities in the housing 12 or from features outside the housing 12 that affect the flow of gas therethrough. For example, gas flowing into the inlet 14 of the apparatus 10 can be supplied through an intake manifold. Bends in the intake manifold can disrupt the flow of the gas therethrough, such that the gas enters the apparatus 10 with a nonuniform pressure over the cross section of the inlet 14.
Preferably, the second edge 38 of each blade 32 defines a nonlinear profile as projected in the meridional (radial-axial or R-Z) plane. That is, the profile of the second edge 38, as projected in the R-Z plane, is not straight. The nonlinear second edge 38 can include one or more linear portions, but at least part of the edge 38 is nonlinear in the R-Z plane, e.g., including a nonlinearity such as a curved portion or an angle or other discontinuity as projected in the R-Z plane. For example,
According to one embodiment of the present invention, the configuration of the blade 32 is determined by first determining the unsteady pressure on the blade 32 associated with operation and the resulting displacement and strain of the blade 32. The term “displacement” refers generally to the displacement of the blade 32 that occurs in the direction of the unsteady pressure forces on the blade 32. The profile of the blade 32 is then modified to reduce a portion of the blade 32 that is exposed to unsteady high pressure and a high displacement occurring in the direction of the unsteady pressure. For example, the configuration of the blade 32 illustrated in
The displacement and strain contours for each face 42a, 44a of the conventional blade 32a are graphically illustrated in
According to one embodiment of the present invention, the configuration of the blade 32 is modified by adjusting the first parameters that geometrically define the conventional blade 32a. More particularly, the first parameters are adjusted to define a nonlinear edge and at least partially remove the portion 46a that is subjected to relatively higher displacement than adjacent portions. Thus, the blade 32 illustrated in
While the present invention is not limited to any particular theory of operation, it is believed that the change in the profile of the blade 32 can result in a change in the mode shape of the rotor 30 to reduce the displacements or strains that result from exciting a particular mode of the rotor 30 with the excitation forces that occur. That is, it is believed that the change of the shape of the blade 32 results in a corresponding change in the mode shape, thereby making the rotor 30 less affected by the excitation forces.
While
The adjustment of the profile of the second edge 38 need not conform precisely to the portion 46a of the blade 32a that is subjected to relatively high displacements. Instead, the adjustment of the profile can also be determined in consideration of the strength of the blade 32, the ease of casting or otherwise forming the blade 32, the aerodynamic performance of the blade 32 and, hence, the rotor 30, and additional considerations. For example, as shown in
In addition, the adjustment or modification of the profile of the blades 32 can be performed iteratively, e.g., by repeatedly determining the displacement and/or strain profile of the blades 32 and modifying the blades 32 to exclude one or more portions subjected to the highest displacements.
While the foregoing discussion has described the rotor 30 in the context of a turbine wheel for a turbine, it is also appreciated that the rotor 30 can instead be used for other applications. For example, as shown in
In some embodiments of the present invention, the first edge 36 of the blades 32 can also define a nonlinear contour to minimize strains at and proximate to the first edge 36. For example, contouring of the first edges 36 of the blades 32 can be advantageous where the rotor 30 is subjected to cyclic pressure variations at the first edge 36. Such variations at the first edge 36 can be caused, e.g., by inlet guide vanes (not shown), by geometric nonuniformities in the housing proximate to the first edges 36, or by features outside the housing that result in nonuniform flow through the housing 12.
Many modifications and other embodiments of the invention set forth herein will come to mind to one skilled in the art to which this invention pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is 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.
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Number | Date | Country | |
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20050106013 A1 | May 2005 | US |