Patent Application
20110305554
The present invention relates to systems for containing a burst impeller or impeller fragments and, more particularly, to containment systems that include a vaneless diffuser.
Vaneless compressor containment design is usually heavier than the same design with diffuser vanes. The reason is due to the worst tri-hub burst fragments are not reduced much from the tri-hub pieces, if the original wheel is not designed as a frangible wheel with fuses to shed all bladings from the hub that remains with the shaft, by the diffuser vanes and related fasteners. The relatively large fragments reach the last containment wall may have sufficient kinetic energy to break out radially or tangentially, if the wall is not sized for piercing by the large pieces.
A prior art compressor 30, as depicted in
Another prior art compressor 40, as depicted in
U.S. Pat. No. 6,695,574 discloses an energy absorber and deflection device for deflecting engine debris fragments from a core of a gas turbine engine. The device includes a deflection plate radially spaced from and adapted to cover any rotating component of the engine. The disclosed device may be used to contain fan blade fragments, rotor fragments, broken shaft fragments, compressor fragments, turbine blade fragments or turbine rotor fragments. Unfortunately, the deflection plate adds weight to and increases the space envelope of the engine.
Other fragment containment methods have included increasing the material strength of the shroud and/or increasing the thickness of the housing walls. Unfortunately, both approaches increase system weight also.
For some compressors, the inclusion of vaned diffusers can provide sufficient fragment containment. Unfortunately, vaned diffusers may not be suitable for all compressor designs.
As can be seen, there is a need for improved vaneless diffuser compressor containment systems. Additionally, containment systems are needed that do not adversely affect the weight and space envelope of the engine/machine.
In one aspect of the present invention, a system for an impeller comprises a housing surrounding the impeller; a diffuser passage defined by the housing; and first and second sets of fasteners or passage obstructers having obstructing portions, the obstructing portions extending through the diffuser passage, wherein the first set of fasteners or passage obstructers is disposed circumferentially about a first radius; the second set of fasteners or passage obstructers is disposed circumferentially about a second radius; and the first radius is smaller than the second radius.
In another aspect of the present invention, a containment system for a compressor having a vaneless diffuser comprises first and second sets of fasteners or passage obstructers having obstructing portions, the obstructing portions extending through a diffuser passage, wherein the first set of fasteners or passage obstructers is disposed circumferentially about a first radius; the second set of fasteners or passage obstructers is disposed circumferentially about a second radius; and the first radius is smaller than the second radius.
In a further aspect of the present invention, a method of containing a burst impeller fragment comprises obstructing a path of the burst impeller fragment with first and second sets of fasteners or passage obstructers having obstructing portions, the first set of passage obstructers being disposed circumferentially about a first radius, the second set of fasteners or passage obstructers being disposed circumferentially about a second radius, and the first radius being smaller than the second radius; and absorbing at least a portion of the energy of the burst impeller fragments.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
Various inventive features are described below that can each be used independently of one another or in combination with other features.
Broadly, embodiments of the present invention may provide a vaneless compressor containment design having an inner bolt circle with fasteners situated in the vaneless space to cut up tri-hub pieces to smaller pieces prior to reaching an outer bolt circle and its associated flange. The containment design of the present invention may allow a thinner radial wall thickness for the outermost flange as compared with conventional designs. The thinner radial wall thickness may reduce the weight of the compressor. This weight reduction may be achieved with little or no increase in the compressor space envelope.
Referring to
The passage obstructers 114, 116, as depicted in
If one has in mind of multi-stage compressors, the increased obstructer length through more in-between housings can be used to provide more efficient obstructers by more plastic deformed in-between obstructers.
The obstructing portion of the fastener (i.e., the shoulder) may be designed to bend plastically by the impact of an impeller fragment and reduce its velocity or stop the outward movement. It might break up to smaller fragments if it were not stopped totally. The obstructing portion diameter may be large enough that impeller fragments may be contained and small enough that compressor performance may not be degraded.
Still referring to
The first set of passage obstructers 114 may include from about 5 to about 11 individual passage obstructers arranged circumferentially about the radius 118. In one embodiment, the first set of passage obstructers 114 may include seven (7) passage obstructers spaced equidistantly about a circumference defined by the radius 118. The angle between adjacent passage obstructers may be about 52 degrees.
The second set of passage obstructers 116 may include from about 5 to about 11 individual passage obstructers arranged circumferentially about the radius 120. In one embodiment, the second set of passage obstructers 116 may include seven (7) passage obstructers spaced equidistantly about a circumference defined by the radius 120. The angle between adjacent passage obstructers may be about 52 degrees. The second set of passage obstructers 116 may be disposed with offset from the first set of passage obstructers 114. In one embodiment the second set of seven passage obstructers 116 may be disposed about 26 degrees offset from the first set of seven passage obstructers 114. In this embodiment the second set of passage obstructers 116 is disposed centrally between adjacent ones of the first set of passage obstructers 114.
The use of two sets of passage obstructers (for example, first and second sets of passage obstructers 114, 116) may result in a significant weight reduction of the compressor with the built-in much larger than 3 number of fragments. In one exemplary embodiment, a weight reduction of about 2.7 pounds may be achieved. In another exemplary embodiment, a weight reduction of about 4.2 pounds may be achieved. These weight reductions may be due to the ability to use a decreased thickness in the scroll and/or the outer flange housing of the compressor. Further weight reductions may be achieved by increasing the number of bolts in the first set of passage obstructers 114.
The above containment systems 112 may move a first set of passage obstructers 114 into close proximity to the impeller 122. A computational fluid dynamics (CFD) model of exemplary embodiment designs has verified that this close proximity will not degrade the performance of the vaneless diffuser. Additional tests of the compressor design of
A method 200 of containing a burst impeller fragment that is traveling along a path in a radially outward direction is depicted in
The step 210 of obstructing the path of the burst impeller fragment may comprise obstructing the path of the burst impeller fragment such that the direction of the burst impeller fragment is altered by contact with the passage obstructers. The step 210 of obstructing the path of the burst impeller fragment may comprise obstructing the path of the burst impeller fragment such that the radial movement of the burst impeller fragment is halted by contact with the passage obstructers.
The step 220 of absorbing at least a portion of the energy of the burst impeller fragment may comprise absorbing at least a portion of the energy of the burst impeller fragment with the passage obstructers. The step 220 of absorbing at least a portion of the energy of the burst impeller fragment may comprise absorbing the energy of the burst impeller fragment such that the velocity of burst impeller fragment is reduced by contact with the passage obstructers. The step 220 of absorbing at least a portion of the energy of the burst impeller fragment may include bending an obstructing portion of the passage obstructer by impacting the obstructing portion with the burst impeller fragment.
It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.
