U.S. patent application number 10/187165 was filed with the patent office on 2004-01-01 for diffuser guide vanes for high-speed screw compressor.
Invention is credited to Khalifa, H. Ezzat, Sahm, Michael K..
Application Number | 20040001770 10/187165 |
Document ID | / |
Family ID | 29735252 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040001770 |
Kind Code |
A1 |
Khalifa, H. Ezzat ; et
al. |
January 1, 2004 |
DIFFUSER GUIDE VANES FOR HIGH-SPEED SCREW COMPRESSOR
Abstract
A screw compressor includes a housing containing at least one
rotor for generating a discharge flow in a discharge flow
direction; a diffuser communicated with the housing and having a
collecting portion for receiving the discharge flow, a diffuser
throat and a diffuser portion, said diffuser extending from the
housing in a diffuser direction; and at least one turning vane
positioned in the collecting portion and adapted to guide flow from
the discharge flow direction to the diffuser direction.
Inventors: |
Khalifa, H. Ezzat; (Manlius,
NY) ; Sahm, Michael K.; (Avon, CT) |
Correspondence
Address: |
GEORGE A. COURY
BACHMAN & LaPOINTE, P.C.
Suite 1201
900 Chapel Street
New Haven
CT
06510-2802
US
|
Family ID: |
29735252 |
Appl. No.: |
10/187165 |
Filed: |
June 28, 2002 |
Current U.S.
Class: |
418/201.1 |
Current CPC
Class: |
F04C 18/16 20130101;
F04C 2240/10 20130101; F04C 2250/102 20130101; F04C 29/12
20130101 |
Class at
Publication: |
418/201.1 |
International
Class: |
F04C 018/16 |
Claims
What is claimed is:
1. A screw compressor, comprising: a housing containing at least
one rotor for generating a discharge flow in a discharge flow
direction; a diffuser communicated with said housing and having a
collecting portion for receiving said discharge flow, a diffuser
throat and a diffuser portion, said diffuser extending from said
housing in a diffuser direction; and at least one turning vane
positioned in said collecting portion and adapted to guide flow
from said discharge flow direction to said diffuser direction.
2. The apparatus of claim 1, wherein said discharge flow has an
average leaving velocity vector and wherein said turning vane is an
arcuate member having a leading edge, a tangent to said leading
edge being substantially parallel to said average leaving velocity
vector.
3. The apparatus of claim 2, wherein said turning vane has a
trailing edge, wherein a tangent to said trailing edge is
substantially parallel to an axis of said diffuser.
4. The apparatus of claim 1, wherein said diffuser direction is
substantially radially oriented relative to said compressor.
5. The apparatus of claim 1, wherein said diffuser direction is
substantially axially oriented relative to said compressor.
6. The apparatus of claim 1, wherein said discharge flow direction
is non-parallel to said diffuser direction.
7. The apparatus of claim 1, wherein said discharge flow direction
is a substantially radial direction.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to screw compressors and, more
particularly, to a screw compressor and diffuser structure wherein
kinetic losses are reduced.
[0002] The compression process in a screw compressor occurs within
rotating pockets. Kinetic energy is imparted to compressed gases.
To reduce dissipative effects of leakage in these machines, and to
reduce their size and cost, it is desirable to run them at high tip
speeds. The optimum tip speed of these machines depends among other
factors, upon the relative balance between leakage losses, which
decrease at high speeds, and viscous and kinetic losses, which
increase at high speed. In an oil-less or near oil-less machine,
the viscous losses are of minor concern, and tip speed is limited
by kinetic losses which increase with the square of speed. Higher
tip speeds could be obtained in screw compressors if part of the
leaving kinetic energy could be efficiently recovered in an exit
diffuser. This is done, for example, with turbo-compressors wherein
the discharge flow is much better directed by the blades and flow
distortion is tolerable.
[0003] Screw compressors, on the other hand, have a much more
complex flow at their discharge port(s), with unfavorable flow
directions and, possibly, high circulatory structure. The complex
geometry of the discharge port relative to the rotors and housing
makes it much more difficult to guide the flow efficiently to a
diffuser throat. This is in part due to the highly tangential
components of flow discharged in opposite tangential or radial
directions from the two or more meshed rotors of the
compressor.
[0004] It is clear that the need remains for an improved structure
for guiding discharge flows from the compressor so as to improve
compressor efficiency.
[0005] It is therefore the primary object of the present invention
to provide such a structure.
[0006] Other objects and advantages of the present invention will
appear hereinbelow.
SUMMARY OF THE INVENTION
[0007] In accordance with the present invention, the foregoing
objects and advantages have been readily attained.
[0008] According to the invention, a screw compressor is provided
which comprises a housing containing at least one rotor for
generating a discharge flow in a discharge flow direction; a
diffuser communicated with said housing and having a collecting
portion for receiving said discharge flow, a diffuser throat and a
diffuser portion, said diffuser extending from said housing in a
diffuser direction; and at least one turning vane positioned in
said collecting portion and adapted to guide flow from said
discharge flow direction to said diffuser direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A detailed description of preferred embodiments of the
present invention follows, with reference to the attached drawings,
wherein:
[0010] FIG. 1 schematically illustrates a radial diffuser with
guide vanes in accordance with the present invention;
[0011] FIG. 2 schematically illustrates an axial diffuser with
guide vanes in accordance with the present invention; and
[0012] FIG. 3 further illustrates the guide vane structure in
accordance with a preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)
[0013] The present invention relates to a screw compressor with a
diffuser structure for recovering kinetic energy within a discharge
flow from the compressor so as to provide more efficient operation
of same. The invention further relates to diffuser guide vanes for
guiding of the flow from the compressor to the diffuser, thus
reducing losses in kinetic energy in the flow.
[0014] FIG. 1 shows a diffuser 10 radially oriented relative to two
schematically illustrated rotors 12, 14 of a compressor, in this
case a high-speed screw compressor. Diffuser 10 is provided as a
housing or wall defining a flow passage having a collecting portion
16, a diffuser throat 18 and a diffusing portion 20. Rotors 12, 14
generate substantially tangential and radially directed pressurized
discharge flows which are collected by diffuser 10 in collecting
portion 16 and which flow through diffuser throat 18 to diffusing
portion 20 wherein a portion of the kinetic energy is recovered as
desired.
[0015] In accordance with the present invention, guide vanes 22 are
advantageously provided and positioned within collecting portion 16
and leading to diffuser throat 18 so as to more smoothly guide the
discharge flows from rotors 12, 14 into diffuser 10 as desired.
Guide vanes 22 serve to reduce dissipative mixing and other kinetic
energy losses which occur within collecting portion 16 as the
substantially tangential and radially directed flows from rotors
12, 14 enter collecting portion 16.
[0016] FIG. 1 illustrates an embodiment wherein diffuser 10 is
mounted extending in a radial position. It should readily be
appreciated that diffuser 10 can be positioned in an axial
orientation or any orientation between radial and axial as well,
and that guide vanes are equally desirable in such a configuration.
The axial embodiment of the present invention is schematically
illustrated in FIG. 2, and shows an axially oriented diffuser 10
extending axially relative to rotors 12, 14 and having guide vanes
22 positioned to smoothly guide flow from rotors 12, 14 into
diffuser 10 as desired.
[0017] Turning also to FIG. 3, a preferred configuration of guide
vanes 22 in accordance with the present invention is
illustrated.
[0018] Guide vanes 22 are preferably provided as substantially thin
curved or arcuate members or vanes having a leading edge 24, a
trailing edge 26 and a body portion 28 therebetween. In accordance
with the present invention, it has been found that particularly
advantageous positioning of leading edge 24 and trailing edge 26
can result in a further smoothing of flow from rotors 12, 14 into
diffuser 10, thereby further reducing kinetic energy losses as
desired.
[0019] Discharge flow from a rotor will have a velocity of gas
relative to the rotor which can be represented by a vector W, and
the rotor will have a peripheral velocity which can be represented
by a vector U. These vectors provide for an absolute velocity of
gas leaving the rotor which can be represented by the resultant
vector C. It has been found to be particularly advantageous to
provide guide vanes 22 having leading portion 24 arranged
substantially tangential to the average leaving absolute velocity
vector C, which advantageously provides for guiding of flow onto
guide vanes 22 without any sudden turning.
[0020] It has also been found to be particularly advantageous to
position trailing edges 26 of guide vanes 22 in an orientation
which is substantially tangential to an axis 30 (FIG. 3) of
diffuser 10. It should readily be appreciated, therefore, that body
portion 28 as illustrated in FIGS. 1-3 is preferably a gradually
curved member which curves or transitions from the desired
positioning of leading edge 24 to the desired positioning of
trailing edge 26.
[0021] It should be appreciated that the average vector as
illustrated in FIG. 3 can change depending upon the tip speed of
the compressor. Compressors do, however, have ratings and expected
operating speeds, and the guide vanes 22 in accordance with the
present invention are preferably positioned to have the desired
tangential surfaces of leading and trailing edges 24, 26 based upon
expected or rated operating speed of the compressor.
[0022] In accordance with the present invention, guide vanes 22
advantageously serve to smooth discharge flow from rotors 12, 14
into diffuser 10, thereby reducing kinetic energy losses and
enhancing efficiency of compressor operation. This advantageously
allows for higher tip speed operation of the compressor, which in
turn allows for smaller compressors in general and thereby reduced
cost and size of the equipment.
[0023] It is to be understood that the invention is not limited to
the illustrations described and shown herein, which are deemed to
be merely illustrative of the best modes of carrying out the
invention, and which are susceptible of modification of form, size,
arrangement of parts and details of operation. The invention rather
is intended to encompass all such modifications which are within
its spirit and scope as defined by the claims.
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