JP2005240696A - Compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compressor suppressing the decrease of compression efficiency in an operating region. <P>SOLUTION: The compressor comprises a moving blade group 5 arranged in a centrifugal compression flow path 3 formed inside a casing 1, a main flow path 2 formed inside the casing 1 as an upstream side of the moving blade group 5, and a detouring flow path 14 formed upstream of the moving blade group 5 in an outer region of the main flow path 2. A downstream side port 15 of the detouring flow path 14 is located upstream of the upstream side end of the moving blade group 5. Such a positional relationship can expand operating range by addition of flow to the end of the moving blade, and suppress the decrease of compression efficiency. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a compressor, and more particularly, to a compressor that suppresses surging and expands an operating range.

  Compressors used in turbochargers, gas turbines, and industrial machines are required to have high efficiency and an extended operating range.

  It is known that a rotating blade group having a specified number of rotations causes a surge phenomenon as the amount of gas decreases. If the amount of gas flowing toward the annular space in which the rotating blade group rotates becomes less than the specified amount, self-excited vibration is generated in the gas in the basin. Such a self-excited phenomenon is called a surge phenomenon. The surge phenomenon is quantitatively represented by a surge curve indicating the relationship between the flow rate and the pressure ratio. The point on the surge curve indicates the minimum flow rate that is allowed to operate. A wide range is required by reducing such a minimum flow rate.

  Wide range is an important issue recently. Technologies for solving such problems are known in Patent Documents 1 and 2 listed below. In the known technology, a wide range is realized by providing a circulation passage through which a gas flow circulates between a gas introduction passage and a compression passage on the upstream side. In the known technique in which the starting end of the circulation channel is arranged downstream from the blade leading edge (upstream blade upstream end), the flow rate of the gas flow introduced from the inlet of the reflux channel and returned to the upstream side is increased. In addition, in order to increase the pressure at the inlet of the reflux channel, an attempt has been made to arrange the inlet downstream of the blade leading edge. There is a problem of compression efficiency in such a known technology that gives priority to wide range. The return of the gas flow compressed in the vicinity of the inlet of the reflux flow path to the upstream side contributes to a wide range, but causes a reduction in compression efficiency. As described above, the known compressor can expand the operating range, but the problem that the compression efficiency is lowered remains.

  It is desirable not to reduce the compression efficiency in the operating region. There is a further need for positive improvements in the operating characteristics of the annular flow path.

JP 2003-106293 A JP 2003-106299 A

  The subject of this invention is providing the compressor which does not reduce compression efficiency in an operation | movement area | region.

  The compressor according to the present invention includes a casing (1), a moving blade group (6) arranged in a centrifugal compression flow path (3) formed inside the casing (1), and an upstream of the moving blade group (6). A main flow path (2) formed inside the casing (1) as a side, and a bypass flow path (14) formed on the upstream side of the blade group (6) in the outer region of the main flow path (2) Has been. The bypass channel (14) communicates with the downstream port (15) communicating with the main channel (2) on the downstream side of the main channel (2) and with the main channel (2) on the upstream side of the main channel (2). And an upstream side port (16). The downstream port (15) is located upstream from the upstream end of the blade group (6).

  If the downstream side port (15) is polymerized in the flow direction to the centrifugal compression channel (3), the high-pressure flow escapes to the bypass channel and the compression efficiency decreases. Since the downstream side port (15) is appropriately positioned upstream from the centrifugal compression flow path (3), a reduction in compression efficiency is suppressed. The effect that the presence of the bypass channel (14) suppresses the surge and expands the operation area follows the effect of the known compressor almost as it is.

  The distance in the rotational axis direction between the downstream end of the downstream port (15) and the upstream end (7) of the blade group (6) is represented by D, and is positioned at the upstream end (7). The diameter of the corresponding compression flow path (3) is represented by 2R, and the rotational axis direction distance D and the diameter 2R are defined by the following relationship: 0 <D <0.3 × 2R. If D is greater than 0.3 × 2R, the expansion of the operating range is not practically meaningful. The range in which the separation distance D is practically appropriate is experimentally confirmed. It is more practically preferable that 0 <D <0.1 × 2R. The diameter of the inner peripheral surface of the flow path (14) is represented by 2R1, and it is significant as in a known compressor that R <R1.

  The bypass channel (14) is openable and closable, and the bypass channel (14) is closed when the flow rate of the main channel (2) is equal to or greater than a specified amount. The distance in the rotational axis direction between the downstream end of the downstream port (15) and the upstream end (7) of the blade group (6) is represented by D, and the following relationship: 0 <D <0.3 The point defined by × 2R is the same as the invention described above.

  The compressor according to the present invention does not reduce the compression efficiency in the operating region.

  The implementation of the compressor according to the invention is described in detail in correspondence with the figures. As shown in FIG. 1, the compressor 10 includes a main flow path 2 on the introduction side, a centrifugal compression flow path 3, and a substantially annular compression chamber 4 communicating with a discharge port (not shown) in the casing 1. Forming. A moving blade group 6 formed of a plurality of moving blades arranged in an annular shape is arranged in an annular space corresponding to the centrifugal compression flow path 3. The moving blade group 6 rotates around the rotation axis L. The main flow 2 is introduced into the casing 1 in the direction of the rotation axis to form an almost axial flow. The gas flow forming the main flow 2 is changed in the flow direction in the centrifugal direction by the moving blade group 6 and is fed into the substantially annular compression chamber 4. Thus, the gas flow is compressed by the moving blade group 6 and sent to the substantially annular compression chamber 4.

  The inner peripheral surface of the casing 1 includes a front edge vicinity region surface 8 located upstream from a front end edge (upstream end edge) 7 of the moving blade group 6, a bypass flow path formation region surface 9, and a main flow formation region surface 11. Are formed as a plurality of flow path forming inner peripheral surfaces. The bypass flow path forming region surface 9 is located upstream of the front edge vicinity region surface 8. The main flow forming region surface 11 is disposed on the upstream side of the detour channel forming region surface 9. An annular detour channel forming ring 12 is fixedly arranged inside the detour channel forming region surface 9. The annular detour channel forming ring 12 is supported by a plurality of supports (not shown) fixed to the detour channel forming region surface 9. Such a plurality of supports are arranged around the rotation axis L, and are fixedly interposed between the inner peripheral surface of the casing 1 and the annular bypass passage forming surface 13 of the annular bypass passage forming ring 12. It is installed. An annular space between the detour channel forming region surface 9 and the annular detour channel forming surface 13 is formed as an annular detour channel 14.

The effective diameter of the front edge vicinity region surface 8 is designed to be 2R1. The front edge vicinity region surface 8 is preferably a substantially cylindrical surface. The effective diameter of the bypass flow path forming region surface 9 is designed to be 2R2. The bypass flow path forming region surface 9 is preferably a substantially cylindrical surface. The effective diameter of the annular detour channel forming surface 13 is designed to be 2R3. The annular bypass flow path forming surface 13 is preferably a generally cylindrical surface. The effective diameter of the main flow forming region surface 11 is designed to be 2R4. The main flow forming region surface 11 is preferably substantially a cylindrical surface. The relationship between the four radii R1, R2, R3, R4 is set as follows.
R1 <R2, R3 <R2
It is preferable that it is the following.
R1 = <R4
In this realization state, the diameter of the inner peripheral surface of the annular bypass flow path forming ring 12 is designed to be approximately equal to the diameter R1 of the front edge vicinity region surface 8. The downstream port 15 of the annular detour channel 14 is positioned on the inner side (rotation axis side) of the annular detour channel forming surface 13 corresponding to the inner peripheral side of the annular detour channel 14, and the annular detour channel The upstream side opening 16 is positioned on the inner side of the annular bypass flow path forming surface 13.

A rotational axis direction distance D between the rear end edge (downstream end edge) of the downstream port 15 and the front end edge 7 of the blade group 6 is defined by the following conditions.
0 <D <0.3 ・ 2R1
Thus, as shown in FIG. 2, the downstream edge position of the downstream port 15 is located upstream from the front edge 7 of the blade group 6, and the maximum diameter of the front edge 7 of the blade group 6. Is separated from the front edge 7 of the blade group 6 upstream by a distance smaller than 30% of the diameter 2R1 of the front edge vicinity region surface 8 that is substantially equal to.

  As shown in FIG. 3, a part of the gas flow of the main flow 2 rapidly increases in pressure at the compression start point P <b> 1 on the downstream side of the front end edge 7 of the moving blade group 6. The pressure at the compression start point P <b> 1 increases slightly with respect to the pressure at the point P <b> 2 immediately before the compression start slightly upstream from the front end edge 7 of the blade group 6. The pressure at the vicinity point P3 of the downstream side port 15 is lower than the pressure at the point P2 immediately before the start of compression, but is affected by the start of compression near the front end of the moving blade group 6, and the effective main stream point on the main stream 2 side. Higher than P4 pressure. The pressure at the effective main stream point P4 is approximately close to the pressure in the vicinity of the upstream side port 16. Since the downstream vicinity position of the point P3 is not separated from the point P2 by a distance larger than 30% of the diameter 2R1 of the front edge vicinity region surface 8 when the flow rate of the main flow 2 decreases to the extent that it approaches the surging occurrence region, The pressure at point P3 is maintained appropriately higher than the pressure at point P4. Since such an appropriate pressure is maintained at the point P3, a portion 18 of the gas flow at the point P3 is sucked into the annular bypass channel 14 from the downstream port 15 as shown in FIG. 2, the refrigerant flows back to the main flow path 2 from the upstream port 16, and further forwards (downstream) toward the centrifugal compression flow path 3 to be replenished to the compression flow of the centrifugal compression flow path 3. The By such replenishment, the surging phenomenon is effectively avoided.

  FIG. 4 shows a performance comparison test. The vertical axis represents the pressure ratio (compression ratio), and the horizontal axis represents the flow rate. A surge line (surge generation boundary line) C2 indicates a known surge line in which no return bypass flow path is provided. The surge line C3 indicates the surge line of the present invention in which the return bypass flow path 14 is provided. The surge line C3 is generally the same shape as a known surge line provided with a return bypass flow path, but the pressure ratio indicated by B1 is known as seen in the pressure ratio curve K (example: K1) of the present invention. Compared to B1 ′ of the compressor with the reflux bypass flow path, the efficiency reduction is suppressed.

  FIG. 5 shows another implementation of the compressor according to the invention. In this realization state, the annular bypass passage 14 formed by the casing 1 and the annular bypass passage forming ring 12 can be opened and closed by the opening / closing operation control lever 21. The downstream port 15 can be freely opened and closed by an opening / closing operation control lever 21. When the decreasing flow rate approaches the surge limit, the closed circular bypass passage forming ring 12 moves backward (moves in the reverse axial flow direction), and the downstream port 15 opens. Control that opens only the downstream port 15 on the small flow rate side where surging is likely to occur is effective.

  FIG. 4 shows the performance test results. By opening the return bypass flow path on the smaller flow rate side from the line indicated by C1 and closing the bypass flow path 14 on the larger flow rate side than C1, the surge flow rate is reduced and the operating range is expanded, Highly efficient operation is realized on the large flow rate side.

FIG. 1 is a cross-sectional view showing an implementation of a compressor according to the present invention. FIG. 2 is a cross-sectional view showing a part of FIG. FIG. 3 is a cross-sectional view showing a part of FIG. FIG. 4 is a graph showing a performance comparison test. FIG. 5 is a sectional view showing still another embodiment of the compressor according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Casing 2 ... Main flow path 3 ... Centrifugal compression flow path 6 ... Moving blade group 7 ... Upstream end 14 ... Detour flow path 15 ... Downstream side port 16 ... Upstream side port 19 ... Swirling blade

Claims (5)

A casing,
A group of blades arranged in a centrifugal compression flow path formed inside the casing;
A main channel formed inside the casing as the upstream side of the blade group;
A detour channel formed on the upstream side of the blade group in the outer region of the main channel,
The bypass channel is
A downstream port communicating with the main channel downstream of the main channel;
An upstream side port communicating with the main channel on the upstream side of the main channel;
The downstream port is located upstream from an upstream end of the blade group. The distance in the rotational axis direction between the downstream end of the downstream port and the upstream end of the blade group is represented by D, and the diameter of the compression flow path corresponding to the upstream end is 2R. The rotational axis center line direction distance D and the diameter 2R are represented by the following relationship:
0 <D <0.3 × 2R
The compressor according to claim 1. 0 <D <0.1 × 2R
The compressor according to claim 2. The compressor according to claim 2, wherein a diameter of an inner peripheral surface of the bypass channel is represented by 2R1 and R <R1. The compressor according to claim 1, wherein the bypass circuit is freely openable and closable, and the bypass channel is closed when a flow rate of the main channel is equal to or greater than a predetermined amount.

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