Patent Grant
8313300
The present invention relates to an improved rotor of a centrifugal compressor and a method for manufacturing a rotor.
A centrifugal compressor utilizes rotors, also known as impellers, to impart to a fluid (typically air) the energy necessary to change the pressure of the fluid. The rotor of a common type of centrifugal compressor includes a number of blades, also known as vanes, disposed radially between a doughnut-shaped cap, also known as a shroud, and a circular base, also known as a hub. The blades, cap, and base of such a rotor are arranged to form fluid flow passages within the rotor that converge towards the center of the rotor.
When the above-described rotors are rotated at high speeds, they can generate high pressures and temperatures. These rotors preferably have high rotational and structural stability (e.g., strength, balance), high heat resistance, high efficiency, and also are relatively easy to manufacture. These design constraints are particularly significant as the size of the rotors increases, because the stresses on the rotors increase as the size of the rotors increases.
Attempts have been made to improve the dynamic performance of such rotors by changing the geometry and/or arrangement of the blades within the rotors. For example, U.S. Pat. No. 6,729,845 to Rossi discloses the use of curved blades within the rotor. Attempts have also been made to improve the methods of manufacturing such rotors. For example, U.S. Pat. No. 6,276,899 to Lambert et al. discloses a method of welding together rotor components; U.S. Pat. No. 6,976,828 to Godichon et al. discloses a method of bolting together rotor components; US 2002/0051707 to Takahashi et al. discloses a method of molding a rotor; and U.S. Pat. No. 7,305,762 to Mola and U.S. Pat. No. 6,676,826 to Battistini et al. disclose methods of machining a rotor. Notwithstanding these advances, further improvements in the design, construction, and overall performance of centrifugal compressor rotors are desirable.
An object of the present disclosure is to provide an improved rotor of a centrifugal compressor. The improved rotor includes a blade arrangement and geometry that increase the overall effectiveness of the rotor. The rotor in some embodiments of the invention includes uniquely shaped curved airfoil blades. In other embodiments the rotor includes a unique arrangement of shorter and longer blades. Another object of the present disclosure is to provide an improved method for production of a rotor involving molding a rotor of a synthetic resin.
The principles of the present disclosure are described herein with reference to the figures. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Referring to
Referring to
Referring to
In the depicted embodiment, the main housing structure 40 is shown bolted to the base 42. The base 42 is configured to support a bearing assembly, which in turn supports the drive shaft 46 that mounts to the rotor 10. The drive shaft 46 connects the rotor 10 to the motor output 48. In the depicted embodiment, the drive shaft 46 bolts to the rotor 10 and is supported by a flange bearing 50, a pillow block bearing 52, and a coupler 54. The flange bearing 50 and pillow block bearing 52 are shown directly mounted to the base 42, and the coupler 54 is supported on the base 42 via a bracket 56. It should be appreciated that alternative configurations of the single-stage compressor 22 are possible.
Still referring to
Comparable size centrifugal compressors with prior art rotors generate significantly less pressure when driven by the same size motor at similar speeds. In the typical pneumatic conveyor embodiment the rotor 10 has high tail/tip speeds due to its relatively large size. For example, if the diameter of the rotor is 27 inches at 5000 RPM the tail of the blades have a linear velocity of about 589 ft/sec (27 in*1 foot/12 inches*3.14*1 minute/60 sec*5000 rpm). At 4000 rpm the linear velocity of the tails are about 471 ft/sec.
Finite element analysis (FEA) was used as a tool in the geometric design process of the rotor 10. FEA is a computer simulation technique used in engineering analysis that applies a numerical technique called the finite element method (FEM). The FEA tool was used by the inventors to test the geometry and arrangement of unusual shaped and arranged blades. The geometry of an embodiment of the rotor 10 is described below in further detail.
Referring to
A seal helps to maintain a pressure differential between the input and the output regions of the rotor 10. More particularly, the cap 14 includes a neck 60 which forms a seal with the intake 26 of the body 30. The neck 60 includes an annular groove 62 shown in
In the depicted embodiment, the primary blades 68 are interspersed with secondary blades 70. Both the primary blades 68 and secondary blades 70 generally extend from the periphery edge of the rotor 10 towards the center of the rotor 10. In the depicted embodiment the diameter of the rotor 10 is about 27 inches (R1=13.5 inches) and the diameter of the inlet 18 is about 10 to 11 inches (R2=5 to 5.5 inches). The primary blades 68 extend from the periphery edge to about 5-7 inches from the center of the hub 16, and the secondary blades 70 extend from the periphery edge to about 8-10 inches to the center of the hub 16. More particularly, the twelve secondary blades 70 extend to line DD, which is about 8-9 inches (e.g., 8.5 inches) from the center of the hub 16, and the twelve primary blades 68 extend to line EE, which is about 5-7 inches (e.g., 6 inches) from the center of the hub 16 (i.e., the rotational axis of the rotor 10). In the depicted embodiment the primary and secondary blades 68, 70 are approximately evenly spaced apart on the hub 16. It should be appreciated that alternative embodiments may include more or less blades. For example, one alternative embodiment could include ten blades and another alternative embodiment could include fifteen blades.
In the depicted embodiment, line AA passing through a tip 95 and a tail 82 of a primary blade 68 is disposed at an angle t between about 10-20 degrees from a dashed line shown passing through the tail 82 of the blade 68 and the center of the hub 16. The tip 95 is located on the proximal end of the blade 68 and the tail 82 is located on the distal end of the blade 68. More particularly, the angle α is as shown between about 14-16 degrees. Generally, this configuration may be referred to as an example of a backward inclined configuration. In the depicted embodiment, the line AA passes primarily outside of the primary blade 68 because the primary blade is curved. The angle α describes the orientation of the blade as a whole and not necessarily the orientation of any particular part of the blade 68. Line CC passes through the center of the proximal fourth of the blade and is disposed at an angle β between about 120 degrees to about 140 degrees relative to the line passing through the tip 95 of the blade 68 and the center of the hub 16. More particularly, the angle β is between about 125 degrees to about 135 degrees.
The line BB passing through the tip 84 and tail 86 of a secondary blade 70 is disposed at an angle γ between about 5 degrees to about 10 degrees from a line passing though the center of the hub 16 to the tail 86 of the secondary blade 70. More preferably, the angle γ is between about 6 degrees to 8 degrees. In the depicted embodiment the angle α is greater than the angle γ. In other words, the primary blades 68 are more inclined than the secondary blades 70. Also, angle β+α is less than 180 degrees, in other words, the first portion of the primary blade 68 is more inclined than the blade as a whole. It should be appreciated that in alternative embodiments of the invention the above angles can vary outside of the above example ranges.
In the depicted embodiment the profile of one of the primary blades 68 can be described by a line connecting the following Cartesian coordinates of the referenced points, provided first in inches: 90 (9.36, 0.143); 91 (7.450, 1.058); 92 (6.54, 1.555); 93 (6.093, 1.834); 94 (5.875, 1.990); 95 (5.699, 2.302). The polar coordinates of the referenced points in degrees and inches are as follows: 90 (9.36, 2.55°); 91 (7.525, 8.08°); 92 (6.722, 13.37°); 93 (6.363, 16.75°); 94 (6.203, 18.72°); 95 (6.146, 22.00°). The polar coordinates above expressed in terms of R are as follows: 90 (R9.36/13.5, 2.55°); 91 (R7.525/13.5, 8.08°); 92 (R6.722/13.5, 13.37°); 93 (R6.363/13.5, 16.75°); 94 (R6.203/13.5, 18.72°); 95 (R6.146/13.5, 22.00°). In the depicted embodiment the radius R of the rotor is about 13.5 inches. Though the geometry and layout of a primary and secondary blade 68, 70 are described in particular detail herein, it should be appreciated that many other blade configurations and arrangements are also possible. For example, in an alternative embodiment the R coordinates at the various angles might vary by +/−0.04 or more. More preferably, the R coordinates might vary by +/−0.02 or less. The numerical value for R itself may also vary. For example, in some embodiments the R value is between about 11-15 inches, and in other embodiments the R value is between about 12-14 inches.
Referring to
With the exception of points p and q, all the above points are along the upper and lower curves that define the geometry of the depicted primary blade 68. Points p and q are used to define the lines bisecting the end portions of the primary blade 68. It should be appreciated that the above coordinates describe a particular geometry that can vary in alternative embodiments of the invention. For example, in an alternative embodiment of the invention one or more of the Y coordinates might vary by as much as 30 percent or even more. For example, the Y coordinates at reference b can be between about 0.0546-0.1014 (i.e., 0.078−0.3*0.078 and 0.078+0.3*0.078), more preferably, the Y coordinates vary 10 percent or less. The L value can also vary. For example, in some embodiments the L value is between 6-10 inches. In other example embodiments the L value is between 7-9 inches. It should be appreciated that in alternative embodiments of the invention, the above coordinates and L values can vary even outside of the above example ranges.
In the depicted embodiment the angle δ is the angle defined between the line that bisects the front and rear portions of the primary blade 68. The line that bisects the front of the blade passes through point 80 and point p, and the line that bisects the rear portions of the blade passes through the end of the primary blade between points b and c and through point q. The point q is ¾ the length of the blade and approximately midway between points h and i (vertically). Similarly, point p is ¼ the length of the blade and approximately midway between points f and g (vertically). As included in the chart below, the angle δ in the depicted embodiment is about 155.72°. It should be appreciated that in alternative embodiments the angle δ may be greater than or less than 155.72°. For example, the angle δ may in some embodiments range from 145-165 degrees.
The above chart compares the length of the upper curve (line 80-b) and the lower curve (line 80-c). The upper curve is longer than the lower curve. In the depicted embodiment, the length of the upper curve (line 80-b) is about 102 percent longer than the length of the lower curve (line 80-c). The above chart also describes the relative lengths of the curves in terms of L, which, as discussed above, is the distance between the tip 80 and tail end of the primary blade 68. The chart above also provides data describing how and where blades 68 bend. In the depicted embodiment the inflection point (i.e., the point where the slope changes) of the upper curve is forward (towards the tip) in comparison to the inflection point of the lower curve. The location of the inflection point of the upper curve is about 3.5183/8.3792 (0.42) towards the front end of the upper curve, whereas the location of the inflection point of the lower curve is about midway at about 4.1100/8.1754 (0.50) of the length of the lower curve. It should be appreciated that in alternative embodiments of the invention the data can vary even outside of the above example ranges.
Referring to
With the exception of points P and Q, all the above points are along the upper and lower curves that define the geometry of the secondary blade 70. Points P and Q are to define the lines bisecting the end portions of the secondary blade 70. In the depicted embodiment the angle θ is the angle defined between the line that bisects the front and rear portions of the secondary blade 70. The line that bisects the front of the blade passes through point 84 and point P, and the line that bisects the rear portions of the blade passes through the end of the secondary blade between points B and C and through point Q. The point Q is ¾ the length of the blade and approximately midway between points H and I (vertically). Similarly, point P is ¼ the length of the blade and approximately midway between points F and G (vertically). As included in the chart below, the angle θ in the depicted embodiment is about 174.56°, which indicates that the blade is almost straight (straight would be 180°). It should be appreciated that in alternative embodiments of the invention the angle θ, the angle defined between the line that bisects the front and rear ends of the secondary blade values, can vary. In the depicted embodiment the secondary blades 70 are straighter than the primary blades 68. The secondary blade 70 is about 48% percent ( 3.896/8.081) the length of the primary blade 68. As discussed above, though precise numerical values and ratios have been referenced in the description of the blades, it should be appreciated that the values and ratios are not meant to be absolute and limiting. Alternative embodiments of the invention may include numerous modifications to the above provided blade geometries.
The rotor 10 in one embodiment is molded from a synthetic resin. In one embodiment the resin used is commonly referred to as a Neat Resin. The Neat Resin can be, for example, RTM VE441 OFG which has a tensile strength of 13,000 psi, flexural strength of 24,000 psi, flexural modulus of 510,000 psi, and heat distortion temperature at 264 psi of 245 degrees F. For high temperature environments the Neat Resin can be, for example, RTM EP8606 OFG which has a tensile strength of 9,300 psi, flexural strength of 15,000 psi, flexural modulus of 390,000 psi, and Glass Transition Temperature of 344 degrees F. The rotor 10 can be molded as one piece by using a wax core molding process. The process involves using a first mold to form a wax core in the shape of the empty space inside the rotor 10. Fibers are then placed into a second mold around the wax core, wherein the second mold is in the shape of the outer surfaces of the rotor 10. Subsequently, resin is injected into the second mold to impregnate the fibers therein. After the resin is cured, the wax core is melted out from within the rotor 10.
The above specification, examples, and data provide a complete description of the manufacture and design of a rotor embodying the principles of the present disclosure. Since many alternative embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/934,886, filed Jun. 14, 2007, which application is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2613609 | Büchi | Oct 1952 | A |
| 3069133 | Swearingen | Dec 1962 | A |
| 4566166 | Donelson | Jan 1986 | A |
| 4666373 | Sugiura | May 1987 | A |
| 4875831 | Fetiveau | Oct 1989 | A |
| 5438755 | Giberson | Aug 1995 | A |
| 5605444 | Paton et al. | Feb 1997 | A |
| 6062819 | Zangench et al. | May 2000 | A |
| 6264429 | Koeller et al. | Jul 2001 | B1 |
| 6338610 | Harada et al. | Jan 2002 | B1 |
| 6340291 | Reckert | Jan 2002 | B1 |
| 6494676 | Yokoyama et al. | Dec 2002 | B2 |
| 6712593 | Takahashi et al. | Mar 2004 | B2 |
| 6715991 | Rossi et al. | Apr 2004 | B2 |
| 6729845 | Rossi | May 2004 | B2 |
| 6739835 | Kim | May 2004 | B2 |
| 6814540 | Sishtla et al. | Nov 2004 | B2 |
| 20040093727 | Mola | May 2004 | A1 |
| 20080050228 | Chen et al. | Feb 2008 | A1 |
| Number | Date | Country |
|---|---|---|
| 0 992 310 | Apr 2000 | EP |
| 1 211 009 | Jun 2002 | EP |
| Number | Date | Country | |
|---|---|---|---|
| 20090142196 A1 | Jun 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60934886 | Jun 2007 | US |
