Rotary kinetic fluid motors or pumps – With means for re-entry of working fluid to blade set – Re-entry working fluid joins inlet working fluid upstream of...
Reexamination Certificate
1998-11-02
2001-03-06
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
With means for re-entry of working fluid to blade set
Re-entry working fluid joins inlet working fluid upstream of...
C415S119000, C415S914000
Reexamination Certificate
active
06196789
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a compressor and in particular to a compressor having an inlet structure the characteristics of which are such that noise levels external to the structure are reduced as compared with conventional inlet structures.
BACKGROUND OF THE INVENTION
Turbochargers have been designed which incorporate a compressor inlet structure that has become known as a “map width enhanced” (MWE) structure. Such an MWE structure is described in for example U.S. Pat. No. 4,930,979. In such arrangements, the compressor inlet comprises two coaxial tubular inlet sections, the inner inlet section being shorter than the outer section and having an inner surface which is an extension of a surface of an inner wall of the compressor housing which faces vanes defined by an impeller wheel mounted within the housing. An annular flow path is defined between the two tubular inlet sections, the annular flow path being open at the upstream end and opening at the downstream end through apertures communicating with the inner surface of the housing which faces the impeller wheel.
With an MWE inlet structure, when the flow rate through the compressor is high, air passes axially along the flow path defined between the two tubular sections towards the compressor wheel. When the flow through the compressor is low, the direction of air flow through the flow path is reversed so that air passes from the apertures adjacent the impeller wheel to the upstream end of the inner tubular section of the inlet structure. As is well known, the provision of such a flow path stabilises the performance of the compressor.
It is well known that compressors incorporating MWE inlet structures tend to exhibit higher levels of noise than conventional structures in which an inlet is defined by a single tubular member. This problem is addressed in British patent number 2256460 which disloses an MWE inlet which incorporates a noise-reduction baffle located upstream of the inner tubular section of the structure and retained within the upstream end of the outer tubular section of the structure. The baffle thus closes off the otherwise open axial end of the annular flow path defined between the inner and outer tubular sections of the inlet structure, the flow path communicating with the inlet through slots defined between the baffle and the upstream end of the inner tubular section of the inlet structure. The baffle may incorporate a conical section expanding outwards from the slots adjacent the upstream end of the inner tubular section of the structure.
The provision of a cone shaped baffle of the form illustrated in British patent 2256460 does reduce the noise emitted from the annular flow path defined between the two tubular sections of the structure and generally results in a reduction in the overall noise level. In some operational circumstances however the noise level within the main inlet flow passage is increased.
It is an object of the present invention to provide an improved MWE structure which addresses the noise problems referred to above.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a compressor comprising a housing defining an inlet and an outlet, and an impeller wheel rotatably mounted in the housing such that on rotation of the wheel gas within the inlet is moved to the outlet, the housing having an inner wall defining a surface located in close proximity to radially outer edges of vanes supported by the wheel, wherein the inlet is defined by a first tubular portion an inner surface of which is an extension of the said surface of the inner wall of the housing, a second tubular portion located radially outside the first portion to define an annular passage between the first and second portions, and a wall extending across the annular passage between the first and second tubular portions, the wall being located between upstream and downstream ends of the first tubular portion, sections of the passage on opposite sides of the wall communicating through at least one aperture, and at least one aperture being defined adjacent the wheel in the said surface of the inner wall of the housing to communicate with the annular passage.
The wall which extends across the annular passage suppresses the propagation of noise along the annular passage. Preferably the wall is located at or adjacent the position of an anti-node of a noise wave which may be expected to propagate along the annular passage during normal use of the compressor. The wall may be in the form of a simple radially extending flange, or alternatively may extend in a direction inclined to the radial direction, and may be shaped to define a helix or other configuration with an axial component.
The inlet may comprise a wall defining an annular surface facing the annular passage and extending outwards from adjacent the upstream end of the first tubular portion to the upstream end of the second tubular portion, an aperture being defined between the upstream end of the first tubular portion and the radially inner edge of the annular surface. The annular surface may be frusto-conical, and may extend in the radially outwards and upstream direction from adjacent the upstream end of the first tubular portion.
Preferably the inlet comprises a wall defining a tubular surface extending in the upstream direction from adjacent the upstream end of the first tubular portion. Such a structure ensures that noise propagating in the upstream direction along the inlet is subjected to a rapid expansion at the upstream end of the tubular surface. This further reduces the noise output.
The wall extending across the annular passage may be in the form of a flange extending radially outwards from the first tubular portion, at least one aperture being defined in radially outer portions of the flange adjacent the second tubular portion.
At least the first tubular portion and the wall extending across the annular passage may be defined by a sub-assembly which is received within the second tubular portion. The sub-assembly may be retained in position within the second tubular portion by engagement between radially outer sections of the wall defining an annular surface and indentations defined within the second tubular portion.
The invention also provides a compressor comprising a housing defining an inlet and outlet, and an impeller wheel rotatably mounted in the housing such that on rotation of the wheel gas within the inlet is moved to the outlet, the housing having an inner wall defining a surface located in close proximity to radially outer edges of vanes supported by the wheel, wherein the inlet is defined by a first tubular portion an inner surface of which is an extension of the said surface of the inner wall of the housing, a second tubular portion located radially outside the first portion to define an annular passage between the first and second portions, a wall defining a surface facing the annular passage and extending from adjacent the upstream end of the first tubular portion to the upstream end of the second tubular portion, and a wall defining a tubular surface extending axially in the upstream direction from the upstream end of the first tubular portion, at least one first aperture being defined between the downstream end of the wall defining the tubular surface and the upstream end of the first tubular portion to communicate with the annular passage, at least one second aperture being defined adjacent the wheel in the said surface of the inner wall of the housing to communicate with the annular passage, and the surface facing the annular passage being inclined to the radial direction.
REFERENCES:
patent: 4930979 (1990-06-01), Fisher et al.
patent: 1368497 (1988-01-01), None
Brierley Paul
Bruffell W. Kenneth
Gee David J.
McEwen Jim A.
Gron Gary M.
Holset Engineering Company
Look Edward K.
McDowell Liam
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