CA1051845A - Rotary compressor - Google Patents
Rotary compressorInfo
- Publication number
- CA1051845A CA1051845A CA260,334A CA260334A CA1051845A CA 1051845 A CA1051845 A CA 1051845A CA 260334 A CA260334 A CA 260334A CA 1051845 A CA1051845 A CA 1051845A
- Authority
- CA
- Canada
- Prior art keywords
- elements
- wells
- impeller
- lobes
- impellers
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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- Structures Of Non-Positive Displacement Pumps (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A rotary compressor having a pair of rotatable impellers in mating engagement in working chambers, each impeller having a plurality of constant cross-sectional profiles, each profile having a plurality of lobes and wells, the trailing well region of each profile communicating with the working chambers and an outlet located out of the plane of at least one of the profiles on each impeller.
A rotary compressor having a pair of rotatable impellers in mating engagement in working chambers, each impeller having a plurality of constant cross-sectional profiles, each profile having a plurality of lobes and wells, the trailing well region of each profile communicating with the working chambers and an outlet located out of the plane of at least one of the profiles on each impeller.
Description
- The present application relates to an improvement in the rotary compressor disclosed and claimed in Canadian application 231479 filed July 15, 1975 by the applicant herein.
In our earlier application we have discussed and claimed a rotary compressor which comprises a housing within which mating impellers are mounted for rotation about side by side axes preferably lying in a common plane. Each impeller has a number of constant cross-sectional profiles (three in the disclosed embodiments) arranged one behind the other along their axes of rotation. Each profile is provided with at least one lobe and at least one well, a feature of our prior applica-tion being that the lobes and wells of any one profile are angularly offset in a direction about its axis of rotation relative to the lobes and wells of the profile immediately ad-jacent thereto along the axis of rotation.
By virtue of the noted arrangement, fluid in eachworking chamber undergoes separate precompressions. That is, fluid is precompressed in each working chamber independently of the action in the other working chamber because the inlet fluid
In our earlier application we have discussed and claimed a rotary compressor which comprises a housing within which mating impellers are mounted for rotation about side by side axes preferably lying in a common plane. Each impeller has a number of constant cross-sectional profiles (three in the disclosed embodiments) arranged one behind the other along their axes of rotation. Each profile is provided with at least one lobe and at least one well, a feature of our prior applica-tion being that the lobes and wells of any one profile are angularly offset in a direction about its axis of rotation relative to the lobes and wells of the profile immediately ad-jacent thereto along the axis of rotation.
By virtue of the noted arrangement, fluid in eachworking chamber undergoes separate precompressions. That is, fluid is precompressed in each working chamber independently of the action in the other working chamber because the inlet fluid
2~ sequentially passes through and is progressively trapped in the decreasing total well volume of the profiles occasioned by the interaction of the lobes on one profile of one impeller with the wells of the reversely rotating complementary profile o*
the other impeller and by the co~munication afforded between the trailing regions of the wells of one profile with the leading regions of the wells of adjoining profiles of each of the impellers.
As described in our prior applicationJ the fluid is thus precompressed because it is not exposed to the dis-charge port during the precompression step. In fact, not until after the fluid has been precompressed to a predetermined pressure above the inlet pressure is the precompressed fluid exposed to the discharge port for discharge of pressurized fluid therethrough.
We have now found that higher precompression of fluid in a compressor may be obtained by utilizing the basic structure of our earlier application and by controlling (a) the thickness or extent of each of the i~peller profiles along the axis of rotation of the impeller and/or (b) the angular displacement of each profile relative to adjoining profiles about the rotational a~is of the impeller.
More specifically ~nd in accordance with the invention we provide a rotary compressor co~prising a housing formed with working chambers having mating rotors, or so-called impellers mounted therein for rotation about parallel axes, said housing having an inlet region and an outlet region, each of said impellers having within its working chamber along its axis of rotation at least two elements, each element having a uniform cross-sectional profile, the elements being aligned one behind the other along the axis of rotation of the respective impellers, each of the elements of the mating impellers having lobes and wells, the lobes and wells of any element on the same impeller 105~845 being angularly offset in overlapping rela~ion relative to the lobes and wells of the elements on the same impeller immediately adjacent thereto, the lobes and wells on the elements of one of the impellers being arranged relative to the lobes and wells on the elements of the other impeller so that the lobes and wells of the elements of one of the impellers mate with the wells and lobes, respectively, on the elements of the other impeller, and inlet and outlet passage means communicating respectively with said inlet and outlet regions of said working chambers, the number of elements in each impeller and the degree of overlap of the wells and sizing thereof in the axially aligned element being such that total internal precompression of the gaseous medium is developed from said inlet region to said outlet region in said overlapping wells of the elements of each impeller during rotational movement of each of the impellers a distance slightly larger than the arcuate exte~t of any one of the wells of any of said elements, the element on each impeller that is most remote from the outlet port in the housing having an axial thick-ness that is greater than that of the element immediately adjacent said most remote element.
Advantageous results are obtained when the most remote profile is provided with an axial thickness that is at least 20 percent greater than that of the profile immediately adjacent.
Precompression limits may further be increased if the angular distance between the lobe centerlines of the profile ~ost remote from the outlet port and the prof;le immediately -adjacent the ~ost remote profile is at least substantially 55 degrees and if the angular displacement between the lobe centerlines of the two remotest profiles on each impeller is at least substantially 110 degrees.
Objects and advantages of the invention will be apparent from the following disclosure taken in conjunction with the accompanying drawings, in which:
Figures 1 and 2 illustrate developed views of one set of relationships which are satisfactory for campression ratios below twoj and Figures 3 and 4 illustrate developed views of a second set of relationships ~Jhich are suitable for compression ratios greater than two.
~.ore specifically, Figure 1 is a developed view of one impeller, having three profiles, showing the start of the precompression process and Figure 2 shows the relative profile positions at the con~letion thereof. For ease in explanation -4a-105~845 only one impeller is shown, however the operation is the same for the other impeller as well. The line C represents a line through the pitch points which separates the two impellers and prevents flow therebetween. Bl and ~2 represent the angular displacements defined as the arcuate angular lag be~
tween the lobe centers of adjacent profiles of the impeller whereas dl, d2 and d3 represent the respective axial thickness of each profile. The common gas volume located between the profiles is designated at V. Since Figures 1 and 2 are developed views the space between the leading edge of one lobe to the leading edge of the other on each profile represents 180 arcuate degrees and l and 2 are shown substantially 45 arcuate degrees. The thicknesses dl, d2 and d3 are shown in the embodiment of Figs. 1 and 2 to be substantially equal.
In Figure 1, the trapped well volume V is illustrated at the beginning of the precompression process where port 40 is blocked from communication with the well volume between trailing edge 112 and leading edge 114. Thus, the gas in volume ~ is trapped. This entrappment continues as the impeller rotates in the direction of arrow R causing the volume V to decrease until the position of Figure 2 is reached. In Figure 2 the trailing edge 112 has just passed discharge port 40 whereby further movement establishes communication with the volume V
to end the precompression process. The magnitude of pre-compression is de~elmined by a comparison betweeaLthe trappedvolume V in Figure S and the volume V in Figure ~. It can be seen that the volume V has undergone only about a 15 to 20 percent reduction in volume resulting in only about a 20 to 30 percent build up of pressure before the discharge port is opened. Such a build up while satisfactory to accomodate a pressure ratio of under 2, is less than desirable when higher pressure ratios are to be acco~modated.
Moreover, as can be seen in Figure 2, when the dis-charge port 40 is opened the profiles remote fr~m the discharge port are in a discharge mode. That is say, the gas in volume V
that lies between leading edge 8~ and line C and between leading edge 64 and line C is forced out of discharge port 40 at the very beginning of the discharge process, resulting in a discharge overpressure in the compressor. Such overpressure increases the work required to displace the gas from the compressor.
Greater precompression and lower overpressures can be achieved to accomodate higher compression ratio by modifying the relative dimensional and angular relationships between the profiles in the manner generally suggested in Figures 3 and 4, which are developed views, similar to Figures 1 and 2 showing, respectively, the start of the precompression and the completion thereof.
For illustrative purposes only, Figure 3 shows the profile in the plane of the discharge port (or the one in direct communication with the discharge port) as having a thickness d3 which is about four thirds that of d2, the thickness of the profile immediately adjacent thereto which, in turn, is about three fifths that of dl, the thickness of the profile most remote from the discharge profile, d3. Moreover, the lag angles l and ~2 are much greater than those of Figures 1 and 2, being about 67 degrees, for example.
A comparison of the trapped well volumes V in Figure 3 with the trapped well volume V in Figure 4 indicates a substantial reduction, about 50 percent for the illustrative example given. Such a reduction will permit a precompression pressure buildup of about 170 percent.
Moreover, as can be seen in Figure 4, when the discharge process begins only the relatively thin profile, d2 is in a displacement mode and the overpressures are greatly reduced in comparison to the Figure 2 example where profiles of thickness d2 and dl are in a displacement mode. The dis-placement of profile dl has already been completed in Figure ! 4 because of the greater lag angles than existed in the Figure 2 example.
Although specific dimensional and angular relation-ships have been given, these should be taken as illustrative, and not as limitations, of the beneficial results of optimizing the precompression process and of reducing the overpressures.
In practice it has been found that whenever the profile most remote from the discharge profile (in the illustrated embodi-ment dl) is greater than its adjacent profile (d2) by at least substantially 20~/o~ the above discussed additional benefits will be achieved. This is true regar~less of the total number of profiles. Additionally, or alternatively, the angular dis-placement between the center of the lobe of the profile most remote from the discharge profile and the center of the lobe of the profile immediately adjacent to such remote profile should be at least substantially 55 degrees. Moreover, the angular displacement between the first profile (most remote fr~m discharge profile) and the discharge profile should be at least substantially 110 degrees regardless of the total number of profiles. To summarize, the greater precompressions and lower overpressures to acc~modate compressor pressure ratios in excess of two can be acc plished in one or more of the following ways, taken singly or in combination:
1. The first profile is thicker by at least twenty percent than its immediately adjacent profile;
2. The angular displacement between the centerlines of the lobes of the first and second profile is at least 55 degrees; - -
the other impeller and by the co~munication afforded between the trailing regions of the wells of one profile with the leading regions of the wells of adjoining profiles of each of the impellers.
As described in our prior applicationJ the fluid is thus precompressed because it is not exposed to the dis-charge port during the precompression step. In fact, not until after the fluid has been precompressed to a predetermined pressure above the inlet pressure is the precompressed fluid exposed to the discharge port for discharge of pressurized fluid therethrough.
We have now found that higher precompression of fluid in a compressor may be obtained by utilizing the basic structure of our earlier application and by controlling (a) the thickness or extent of each of the i~peller profiles along the axis of rotation of the impeller and/or (b) the angular displacement of each profile relative to adjoining profiles about the rotational a~is of the impeller.
More specifically ~nd in accordance with the invention we provide a rotary compressor co~prising a housing formed with working chambers having mating rotors, or so-called impellers mounted therein for rotation about parallel axes, said housing having an inlet region and an outlet region, each of said impellers having within its working chamber along its axis of rotation at least two elements, each element having a uniform cross-sectional profile, the elements being aligned one behind the other along the axis of rotation of the respective impellers, each of the elements of the mating impellers having lobes and wells, the lobes and wells of any element on the same impeller 105~845 being angularly offset in overlapping rela~ion relative to the lobes and wells of the elements on the same impeller immediately adjacent thereto, the lobes and wells on the elements of one of the impellers being arranged relative to the lobes and wells on the elements of the other impeller so that the lobes and wells of the elements of one of the impellers mate with the wells and lobes, respectively, on the elements of the other impeller, and inlet and outlet passage means communicating respectively with said inlet and outlet regions of said working chambers, the number of elements in each impeller and the degree of overlap of the wells and sizing thereof in the axially aligned element being such that total internal precompression of the gaseous medium is developed from said inlet region to said outlet region in said overlapping wells of the elements of each impeller during rotational movement of each of the impellers a distance slightly larger than the arcuate exte~t of any one of the wells of any of said elements, the element on each impeller that is most remote from the outlet port in the housing having an axial thick-ness that is greater than that of the element immediately adjacent said most remote element.
Advantageous results are obtained when the most remote profile is provided with an axial thickness that is at least 20 percent greater than that of the profile immediately adjacent.
Precompression limits may further be increased if the angular distance between the lobe centerlines of the profile ~ost remote from the outlet port and the prof;le immediately -adjacent the ~ost remote profile is at least substantially 55 degrees and if the angular displacement between the lobe centerlines of the two remotest profiles on each impeller is at least substantially 110 degrees.
Objects and advantages of the invention will be apparent from the following disclosure taken in conjunction with the accompanying drawings, in which:
Figures 1 and 2 illustrate developed views of one set of relationships which are satisfactory for campression ratios below twoj and Figures 3 and 4 illustrate developed views of a second set of relationships ~Jhich are suitable for compression ratios greater than two.
~.ore specifically, Figure 1 is a developed view of one impeller, having three profiles, showing the start of the precompression process and Figure 2 shows the relative profile positions at the con~letion thereof. For ease in explanation -4a-105~845 only one impeller is shown, however the operation is the same for the other impeller as well. The line C represents a line through the pitch points which separates the two impellers and prevents flow therebetween. Bl and ~2 represent the angular displacements defined as the arcuate angular lag be~
tween the lobe centers of adjacent profiles of the impeller whereas dl, d2 and d3 represent the respective axial thickness of each profile. The common gas volume located between the profiles is designated at V. Since Figures 1 and 2 are developed views the space between the leading edge of one lobe to the leading edge of the other on each profile represents 180 arcuate degrees and l and 2 are shown substantially 45 arcuate degrees. The thicknesses dl, d2 and d3 are shown in the embodiment of Figs. 1 and 2 to be substantially equal.
In Figure 1, the trapped well volume V is illustrated at the beginning of the precompression process where port 40 is blocked from communication with the well volume between trailing edge 112 and leading edge 114. Thus, the gas in volume ~ is trapped. This entrappment continues as the impeller rotates in the direction of arrow R causing the volume V to decrease until the position of Figure 2 is reached. In Figure 2 the trailing edge 112 has just passed discharge port 40 whereby further movement establishes communication with the volume V
to end the precompression process. The magnitude of pre-compression is de~elmined by a comparison betweeaLthe trappedvolume V in Figure S and the volume V in Figure ~. It can be seen that the volume V has undergone only about a 15 to 20 percent reduction in volume resulting in only about a 20 to 30 percent build up of pressure before the discharge port is opened. Such a build up while satisfactory to accomodate a pressure ratio of under 2, is less than desirable when higher pressure ratios are to be acco~modated.
Moreover, as can be seen in Figure 2, when the dis-charge port 40 is opened the profiles remote fr~m the discharge port are in a discharge mode. That is say, the gas in volume V
that lies between leading edge 8~ and line C and between leading edge 64 and line C is forced out of discharge port 40 at the very beginning of the discharge process, resulting in a discharge overpressure in the compressor. Such overpressure increases the work required to displace the gas from the compressor.
Greater precompression and lower overpressures can be achieved to accomodate higher compression ratio by modifying the relative dimensional and angular relationships between the profiles in the manner generally suggested in Figures 3 and 4, which are developed views, similar to Figures 1 and 2 showing, respectively, the start of the precompression and the completion thereof.
For illustrative purposes only, Figure 3 shows the profile in the plane of the discharge port (or the one in direct communication with the discharge port) as having a thickness d3 which is about four thirds that of d2, the thickness of the profile immediately adjacent thereto which, in turn, is about three fifths that of dl, the thickness of the profile most remote from the discharge profile, d3. Moreover, the lag angles l and ~2 are much greater than those of Figures 1 and 2, being about 67 degrees, for example.
A comparison of the trapped well volumes V in Figure 3 with the trapped well volume V in Figure 4 indicates a substantial reduction, about 50 percent for the illustrative example given. Such a reduction will permit a precompression pressure buildup of about 170 percent.
Moreover, as can be seen in Figure 4, when the discharge process begins only the relatively thin profile, d2 is in a displacement mode and the overpressures are greatly reduced in comparison to the Figure 2 example where profiles of thickness d2 and dl are in a displacement mode. The dis-placement of profile dl has already been completed in Figure ! 4 because of the greater lag angles than existed in the Figure 2 example.
Although specific dimensional and angular relation-ships have been given, these should be taken as illustrative, and not as limitations, of the beneficial results of optimizing the precompression process and of reducing the overpressures.
In practice it has been found that whenever the profile most remote from the discharge profile (in the illustrated embodi-ment dl) is greater than its adjacent profile (d2) by at least substantially 20~/o~ the above discussed additional benefits will be achieved. This is true regar~less of the total number of profiles. Additionally, or alternatively, the angular dis-placement between the center of the lobe of the profile most remote from the discharge profile and the center of the lobe of the profile immediately adjacent to such remote profile should be at least substantially 55 degrees. Moreover, the angular displacement between the first profile (most remote fr~m discharge profile) and the discharge profile should be at least substantially 110 degrees regardless of the total number of profiles. To summarize, the greater precompressions and lower overpressures to acc~modate compressor pressure ratios in excess of two can be acc plished in one or more of the following ways, taken singly or in combination:
1. The first profile is thicker by at least twenty percent than its immediately adjacent profile;
2. The angular displacement between the centerlines of the lobes of the first and second profile is at least 55 degrees; - -
3. The total angular displacement between the centerlines of the lobes of the first profile and discharge profile is at least 110 degrees.
Although each profile is depicted in our earlierapplication as having two lobes and two wells, it is to be understood that additional lobes and wells can be provided.
Also, while the axis of discharge port 40 has been illustrated in our earlier application as perpendicular to the axis of rotation of the impellers, it is obvious that the discharge port axis could also be parallel thereto or have parallel and perpendicular components; it only being necessary that the pre-compressed fluid find access to the discharge port when the fluid is pressurized to the desired level.
Although each profile is depicted in our earlierapplication as having two lobes and two wells, it is to be understood that additional lobes and wells can be provided.
Also, while the axis of discharge port 40 has been illustrated in our earlier application as perpendicular to the axis of rotation of the impellers, it is obvious that the discharge port axis could also be parallel thereto or have parallel and perpendicular components; it only being necessary that the pre-compressed fluid find access to the discharge port when the fluid is pressurized to the desired level.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A rotary compressor comprising a housing formed with working chambers having mating rotors, or so-called impellers mounted therein for rotation about parallel axes, said housing having an inlet region and an outlet region, each of said impellers having within its working chamber along its axis of rotation at least two elements, each element having a uniform cross-sectional profile, the elements being aligned one behind the other along the axis of rotation of the respective impellers, each of the elements of the mating impellers having lobes and wells, the lobes and wells of any element on the same impeller being angularly offset in overlapping relation relative to the lobes and wells of the elements on the same impeller immediately adjacent thereto, the lobes and wells on the elements of one of the impellers being arranged relative to the lobes and wells on the elements of the other impeller so that the lobes and wells of the elements of one of the impellers mate with the wells and lobes, respectively, on the elements of the other impeller, and inlet and outlet passage means communicating respectively with said inlet and outlet regions of said working chambers, the number of elements in each impeller and the degree of overlap of the wells and sizing thereof in the axially aligned element being such that total internal precompression of the gaseous medium is developed from said inlet region to said outlet region in said overlapping wells of the elements of each impeller during rotational movement of each of the impellers a distance slightly larger than the arcuate extent of any one of the wells of any of said elements, the element on each impeller that is most remote from the outlet port in the housing having an axial thickness that is greater than that of the element immediately adjacent said most remote element.
2. The improved compressor according to claim 1, wherein said axial thickness of said most remote element is at least 20 percent greater than that of said element immediately adjacent.
3. The compressor according to claim 1, wherein the angular displacement between the lobe centerlines of said element most remote from said outlet port and said element immediately adjacent said most remote profile is at least substantially 55 degrees.
4. The compressor according to any one of claims 1, 2 or 3, wherein the angular displacement between the lobe center-lines of the two remotest elements on each impeller is at least substantially 110 degrees.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA260,334A CA1051845A (en) | 1976-09-01 | 1976-09-01 | Rotary compressor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA260,334A CA1051845A (en) | 1976-09-01 | 1976-09-01 | Rotary compressor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1051845A true CA1051845A (en) | 1979-04-03 |
Family
ID=4106762
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA260,334A Expired CA1051845A (en) | 1976-09-01 | 1976-09-01 | Rotary compressor |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1051845A (en) |
-
1976
- 1976-09-01 CA CA260,334A patent/CA1051845A/en not_active Expired
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