The application relates generally to centrifugal compressors of gas turbine engines and, more particularly, to an impeller of such centrifugal compressors.
Centrifugal compressors generally consist of at least two main components: an impeller and a diffuser. The impeller includes a hub which it is mounted to a drive shaft so as to be rotated therewith. Vanes (i.e., blades) of the impeller extend from the hub and are arranged to redirect an axially-directed inbound gas flow radially outwardly, toward the diffuser located downstream of the impeller. Stresses may however be imparted on the impeller, often in or near the hub. Such stress concentrations may adversely affect the life of the impeller. At the same time, vane bulk is generally regarded as being detrimental to aerodynamic properties of the flow passed from the impeller to the diffuser, thus rendering oversizing approaches undesirable in solving the issue of stress concentration. As such, there continues to be a need for improvement.
In one aspect, there is provided an impeller for a centrifugal compressor, the impeller comprising: a hub defining a rotation axis about which the impeller is rotatable; and a vane extending from the hub, the vane having a leading edge, a trailing edge, and a chord defined therebetween, a pressure side of the vane and a suction side of the vane opposite the pressure side, a vane thickness defined transversely between the pressure side and the suction side, the vane thickness reducing over at least a downstream 40% of the chord, the vane thickness having a trailing edge thickness value at the trailing edge of between 40% and 80% of a maximum thickness value of the vane thickness.
In another aspect, there is provided a centrifugal compressor for a turbine engine, the centrifugal compressor comprising: a diffuser configured to be disposed downstream of an inlet case of the turbine engine; and an impeller upstream of the diffuser, the impeller including a hub and a vane extending from the hub, the vane having a leading edge, a trailing edge and a chord defined therebetween, a pressure side of the vane and a suction side of the vane opposite the pressure side, a vane thickness defined transversely between the pressure side and the suction side, the vane thickness reducing over at least a downstream 40% of the chord, the vane thickness having a trailing edge thickness value at the trailing edge of between 40% and 80% of a maximum thickness value of the vane thickness.
In a further aspect, there is provided a turbine engine for an aircraft, the turbine engine comprising: an inlet; and a centrifugal compressor disposed downstream of the inlet, the centrifugal compressor including an impeller and a diffuser downstream of the impeller, the impeller including a hub and a vane extending from the hub, the vane having a leading edge, a trailing edge and a chord defined therebetween, a pressure side of the vane and a suction side of the vane opposite the pressure side, a vane thickness defined transversely between the pressure side and the suction side, the vane thickness reducing over at least a downstream 40% of the chord, the vane thickness having a trailing edge thickness value at the trailing edge of between 40% and 80% of a maximum thickness value of the vane thickness.
Reference is now made to the accompanying figures in which:
Referring to
Still referring to
Turning now to
The true chord 60 of the vane 32a is defined as the chord line that extends between the leading and trailing edges 56, 58, following the pressure and/or suction sides 52, 54 of the vane airfoil, and measured at the hub 30 (i.e. at the junction between the pressure or suction side of the vane and the outer surface 38 of the hub 30. In
As best seen in
Turning now to
In the graph, vane thicknesses of the vanes 32b are respectively depicted by curves 70, 72 and 74. In some embodiments, at the 0% chord position 66, the vane thickness has vane thickness value being a minimum thickness value 76 of the vane 32a. In some such embodiments, at the 0% chord position 66, the vane thickness has vane thickness value corresponding to less than 10% (and in one particular embodiment about 5%) of the maximum thickness value (shown at 78).
From the graph, it can be appreciated that the vane thickness reduces over at least a downstream 40% of the chord, i.e., downstream from a 60% chord position 80 to the 100% chord position at the trailing edge 58.
At the 60% chord position 80, the vane thickness has a thickness value of between about 90% and 100% of the maximum thickness value 78, and more particularly between about 90% and about 97% of the maximum thickness value 78. For instance, in the embodiments depicted by the curves 70, 72 and 74, the vanes have thickness values of approximately 92%, 96% and 96% at the 60% chord position, respectively.
At a 70% chord position 82, the vane thickness has a thickness value of between about 80% and about 95% of the maximum thickness value 78. For instance, in the embodiments depicted by the curves 70, 72 and 74 indicate thickness values of approximately 83%, 93% and 93%, respectively.
At a 90% chord position 84, the vane thickness has a thickness value of between about 50% and 95% of the maximum thickness value 78, and more particularly between about 55% and 90%. For instance, the curves 70, 72 and 74 indicate thickness values of approximately 60%, 77% and 90%, respectively.
At the 100% chord position 68, i.e. at the trailing edge of the vane, the vane thickness has a thickness value of between 40% and 80% of the maximum thickness value 78, and more particularly between 45% and 75% of the maximum thickness value 78. For instance, the curves 70, 72 and 74 indicate trailing edge thickness values of approximately 50%, 66% and 73%, respectively.
In some embodiments, the maximum thickness value 78 may be at a position upstream of a 50% chord position 86, or in other words within the upstream half of the vanes. For instance, the curves 70, 72 and 74 are indicative of their respective maximum thickness values 78 being generally between a 15% chord position and a 40% chord position.
In light of the preceding, it can be appreciated that a chordwise reduction in thickness of the vanes 32, 32a, 32b as disclosed herein can result in an impeller 22 having a greater life when compared to some conventional impellers. The reduction in thickness of the vanes 32, 32a, 32b over at least the downstream 40% of the chord 60 is arranged so as to impart the impeller 22 with a desired resistance to stress at the bore 31 under certain operating conditions. For instance, the reduction in thickness results in a distribution of a mass of the vanes 32, 32a, 32b as they extend away from their root, yielding a desired inertial load at the root. Upstream of the reduction, a bulging 88 of the vanes 32, 32a, 32b inclusive of the portion thereof having the maximum vane thickness value 78 yields a desired resistance to stress concentration typically borne by conventional impellers. It should also be understood that the vanes 32, 32a, 32b are also arranged so as to impart the impeller 22 with certain desired aerodynamic properties. For instance, in some embodiments, the reduction in thickness of the vanes 32, 32a, 32b over at least the downstream 40% of the chord 60 is arranged such that, under certain operating conditions, the flow 34 is imparted with a desired maximum amount of disturbance upon moving downstream from the trailing edge 58. In some embodiments, a geometry of the vanes 32, 32a, 32b over at least the downstream 40% of the chord 60 may be configured with respect to a shape of the corresponding diffuser 40.
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For example, the impellers can be provided in centrifugal compressors of other types of turbine engines than that described herein. Fluids passed downstream of the impellers can be collected by other types of structures than the diffusers described. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.