JP4952465B2 - Pipe diffuser centrifugal compressor - Google Patents

Description

  The present invention relates to a pipe diffuser centrifugal compressor, and more particularly to a pipe diffuser centrifugal compressor used as an air supply source for factory air (plant air).

  Some industrial centrifugal compressors are provided with a suction control valve for controlling the suction flow rate on the suction side of the compressor, and the air volume (flow rate) is controlled by the suction control valve (for example, Patent Document 1). In this centrifugal compressor, when the amount of air used is small, the suction side is throttled by the suction control valve to reduce the suction flow rate, so that it is possible to save energy in the compressor operation without causing the excessive flow rate operation. . Especially when the centrifugal compressor is driven at the rated rotational speed by an electric motor and the rotational speed of the drive motor is not controlled, such as a centrifugal compressor used as an air supply source for factory air, the air volume of the centrifugal compressor is It can only be controlled by an intake control valve.

  However, in a centrifugal compressor, if the intake flow rate is too small, stall occurs in the diffuser for decelerating the air flow accelerated by the rotation of the impeller, and surging is caused from stall (stall). The intake flow rate (air volume) at which no stall occurs in the diffuser is called a surge limit, and is determined by the discharge air pressure and the diffuser flow characteristics.

  On the other hand, surge resistance (surge limit), which is the limit of suction flow restriction, is achieved by partially closing the flow path with one side wall of the flow path of the vaned diffuser as a movable wall and restricting the diffuser flow path. There is a centrifugal compressor in which a surge phenomenon is prevented from occurring even with a small air volume by increasing the pressure (for example, Patent Document 2).

Further, as a centrifugal compressor of a fixed diffuser, a pipe diffuser (channel diffuser) type centrifugal compressor having a plurality of diffuser passages formed around the outer side of an impeller is known (for example, Patent Documents 3 and 4). ).
Japanese Patent Laid-Open No. 1-219397 JP-A-60-1332099 Japanese Patent Laid-Open No. 5-19591 JP 10-61586 A

  By restricting the diffuser flow path, it is possible to increase the surge limit and prevent a surge phenomenon from occurring even with a small air flow. However, in the case of restricting the diffuser flow path and quantitatively controlling the flow rate (flow velocity) in the diffuser, The structure becomes complicated. In addition, if the diffuser flow path is restricted, the diffuser action may be adversely affected, the original performance of the diffuser may not be exhibited, and the efficiency may be reduced.

  The problem to be solved by the present invention is that in a centrifugal compressor, particularly in a pipe diffuser type centrifugal compressor, the surge limit (suction flow restriction limit) without complicating the structure and without adversely affecting the diffuser action. The surge phenomenon is prevented from occurring even with a small air volume.

A centrifugal compressor according to the present invention is a pipe diffuser type centrifugal compressor having a plurality of diffuser passages formed around an outer side of an impeller, and has an on-off valve that selectively closes the diffuser passage, The on-off valve is characterized in that the specified diffuser passage located at a position equally dividing the circumferential direction of the impeller among the plurality of diffuser passages is closed on and off.

  In addition, among the plurality of on-off valves that are in a position equally dividing the circumferential direction of the impeller, the on-off valve at a point-symmetrical position about the rotation axis of the impeller opens and closes the diffuser passage on and off Yes.

  According to the pipe diffuser type centrifugal compressor according to the present invention, the on-off valve opens and closes the diffuser passage on and off, and does not squeeze the diffuser flow path to quantitatively control the air flow rate in the diffuser. The surge limit can be increased without complicating the structure and without adversely affecting the diffuser action. The on-off valve opens and closes the specified diffuser passage at a position that equally divides the impeller circumferential direction among the plurality of diffuser passages. Therefore, the rotating body is caused by fluid unbalance by opening and closing the diffuser passage by the on-off valve. It is possible to prevent the occurrence of vibration.

  Further, since the on-off valve at a point-symmetrical position opens and closes around the impeller rotational axis, the opening and closing of the diffuser passage can prevent the vibration of the rotating body due to fluid imbalance.

  One embodiment of a pipe diffuser centrifugal compressor according to the present invention will be described with reference to FIGS.

  The pipe diffuser centrifugal compressor includes a bearing housing 11, an impeller 15 attached to a rotary shaft 13 that is rotatably supported by the bearing housing 11, and a scroll housing 17 that is fixedly fastened to the bearing housing 11. The scroll housing 17 includes a suction port 19, an impeller chamber 21 that houses the impeller 15, a pipe diffuser 23 that is formed around the outside of the impeller 15, a scroll passage 25 that communicates with the outlet side of the pipe diffuser 23, a scroll A discharge port (not shown) is provided at the end of the passage 25. The suction port 19 is provided with a suction control valve 27 that controls the suction flow rate.

  The impeller 15 is rotationally driven by the rotary shaft 13. The flow of air is quantitatively controlled by the suction control valve 27, enters the impeller chamber 21 through the suction port 19, is accelerated by the rotation of the impeller 15, is decelerated by the pipe diffuser 23, and then flows into the scroll passage 25 to be discharged from the discharge port. (Not shown).

  As shown in FIG. 2, the pipe diffuser 23 has a plurality of pipe diffuser passages 33 defined at equal intervals around the outside of the impeller 15. In this embodiment, 16 pipe diffuser passages 33 are provided at rotational positions that divide the entire circumference of the impeller 15 into 16 equal parts, and each extend in the tangential direction of the outer circumference of the impeller. Here, the 16 diffuser passages 33 are numbered # 1 to # 16, # 1 and # 9, # 2 and # 10, # 3 and # 11, # 4 and # 12, # 5 and # 13. , # 6 and 14, # 7 and # 15, and # 8 and # 16 are provided at point-symmetrical positions around the axis center of the rotating shaft 12 of the impeller 15, respectively.

  Each of the 16 diffuser passages 33 (# 1 to # 16) is provided with an opening / closing valve 35. The on-off valve 35 is constituted by a ball valve, a butterfly valve, a flapper valve or the like, and is on / off that takes either a valve open state in which the diffuser passage 33 is fully opened or a closed state in which the diffuser passage 33 is substantially completely shielded. Works. The on-off valve 35 selectively opens and closes the specified diffuser passage 33 at a position that equally divides the circumferential direction of the impeller 15 among the plurality of diffuser passages 33.

For example, in this pipe diffuser 23, as shown in Table 1, the first state in which the on / off valve 35 of the two diffuser passages 33 of # 1 and # 9 is closed, and the opening and closing of # 1, # 9, # 5 and # 13 are opened. A second state in which the valve 35 is closed, a third state in which the on-off valves 35 of # 1, # 9, # 5, # 13, # 3, # 11, # 7, and # 15 are closed, # 1, # 9, # 5, # 13, # 3, # 11, # 7, # 15, # 2, # 10, # 6, # 14, the fourth state in which the on-off valve 35 is closed, 1, # 9, # 5, # 13, In addition to the on / off valves 35 of # 3, # 11, # 7, # 15, # 2, # 10, # 6 and # 14, the fifth on / off valves 35 of # 4, # 12, # 8 and # 16 are closed. Any of the above states, that is, the fully closed state can be selectively taken.

  In this case, in the first state to the fourth state, the open / close valve 35 of the diffuser passage 33 is simultaneously opened and closed with the open / close valve 35 at the symmetrical position about the rotation shaft 13 of the impeller 15. In the case of the state 2, the on-off valve 35 (# 5 and # 13) at a position equally dividing the circumferential direction is opened and closed. In the case of changing from the second state to the third state, the on-off valves 35 (# 3 and # 11, # 7 and # 15) located at positions that equally divide the circumferential direction are opened and closed. That is, the on-off valve 35 at a position equally dividing the circumferential direction is always opened and closed. Thereby, it can prevent generating the vibration of the rotary body by the fluid unbalance.

  Then, when the specified diffuser passage 33 is closed by the on-off valve 35, the flow velocity of the air flowing through the remaining diffuser passage (the diffuser passage not closed by the on-off valve 35) 33 is increased, and the surge limit is reduced. Improved on the flow side. Thereby, the allowable minimum air volume by the suction control valve 27 is reduced, and the operation range of the centrifugal compressor on the low air volume side is expanded.

  FIG. 3 shows surge line characteristics determined by the relationship between the air volume (Q) and the discharge pressure (P). In FIG. 3, the horizontal axis represents the air volume Q, and the vertical axis represents the discharge pressure Pd. Reference symbol A1 is a surge line indicating a surge limit when the open / close state of the on-off valve 35 is in the first state, reference symbol A2 indicates the second state, reference symbol A3 indicates the third state, and reference symbol A4 indicates the fourth state. A state, code | symbol A5 is a surge line which shows each surge limit at the time of a 5th state.

  In FIG. 3, the fact that the specified diffuser passage 33 is blocked by the opening / closing valve 35, for example, indicates that the surge line of the opening / closing valve 35 has been improved and shifted from A 0 to the surge line A 1 in the first state. Show. As a result, at the rated discharge pressure Ps, the surge limit air volume is improved from Qa to Qb, the operation area on the low air volume side of the centrifugal compressor is expanded, and operation at a lower air volume becomes possible.

  Thus, the on-off valve 35 closes the diffuser passage 33 on and off, and does not restrict the diffuser passage 33 to quantitatively control the air flow rate in the diffuser, so the structure becomes complicated. There is nothing.

  The on-off valve 35 operates on and off to take either a valve open state in which the diffuser passage 33 is fully opened or a closed state in which the diffuser passage 33 is substantially completely blocked. In any state, it does not work to deflect the air flow in the diffuser flow path 33. Thereby, the on-off valve 35 does not adversely affect the diffuser action.

  Further, the on-off valve 35 closes the specified diffuser passage 33 at a position that equally divides the impeller circumferential direction among the plurality of diffuser passages 33, so that the high-speed rotating impeller 15 is blocked by closing the diffuser passage by the on-off valve 33. The rotating body is not vibrated due to the non-uniformity of the fluid.

  FIG. 3 shows an embodiment of the control system of the pipe diffuser centrifugal compressor according to this embodiment.

  The suction control valve 27 is controlled by the controller 51. The controller 51 quantitatively controls the opening degree of the intake control valve 27 so that the air pressure on the discharge side detected by the pressure sensor 51 is maintained at a predetermined pressure.

  The on-off valve 35 is controlled by a controller 55. The controller 55 controls the open / close valve 35 so that the number of valves to be closed increases stepwise as the air flow rate decreases according to the air flow rate on the discharge side detected by the flow rate sensor 57.

  With this control, as the air flow rate Q is decreased by the intake control valve 27, the surge line is improved and shifted from A0 to the lower airflow side as A1, and accordingly, the surge limit airflow is lower than Qa to Qb. Will be improved.

  Hereinafter, control of the control system shown in FIG. 4 will be described with reference to FIGS. 5 and 6. FIG. 5A shows a control flow of the controller 51 and the controller 55 when the use flow rate of air decreases.

  FIG. 5A shows the movement of the intake control valve 27 and the on-off valve 35 when the air flow rate decreases. When the flow rate of air decreases, the discharge pressure of the compressor that is operating at a rated value increases, and this is detected by the pressure sensor 53. Based on the detection result of the pressure sensor 53, the controller 51 closes the suction control valve 27. When the intake control valve 27 is closed, the flow rate of air into the compressor is reduced, so that the air flow accelerated by the rotation of the impeller is decelerated. At this time, the flow rate sensor 57 detects a decrease in the air flow rate, and based on the detection result, the controller 55 switches the opening / closing valve 35 of the pipe diffuser 23 stepwise from the first state, that is, the air flow rate. The second state, the third state, and the fourth state are set according to the amount of decrease.

  Next, when the intake control valve 27 is throttled and the on-off valve 35 is in any of the first to fourth states, the intake control valve 27 and the on-off valve when the amount of air used increases. The movement of 35 is shown in FIG.

  When the flow rate of air increases from the rated operation at point A shown in FIG. 6, the discharge pressure of the compressor operating at rated operation decreases, and the operation is performed at point B in FIG. The pressure sensor 53 detects the drop. Based on the detection result of the pressure sensor 53, the controller 51 changes the suction control valve 27 from the closed state to the open state. When the intake control valve 27 is opened, the flow rate of the intake air increases accordingly, and the operation is performed at the point C in FIG. When the flow rate sensor 57 detects an increase in the air flow rate, the controller 55 opens the on-off valve 35 of the pipe diffuser 23. In this case, for example, the on-off valve 35 is opened by changing from the third state to the second state, or from the fourth state to the second and first states.

  In this manner, in addition to the intake control valve 27, the pipe diffuser is provided with the opening / closing valve 35, and the opening / closing valve 35 is opened / closed according to the air flow rate to change the surge limit. Can be prevented.

  In the above-described embodiment, the number of on-off valves 35 is 2, 4, and 8. In addition to this, the number of on-off valves 35 is 3, 6, 9, 2, 3, 2, 6, 8, and 9. In FIG. 2, the open / close valves 35 are provided in all the diffuser passages 33, but the open / close valves 35 are provided only in the diffuser passages 33 for realizing these. That's fine. Further, the position of the opening / closing valve 35 may be provided at any of the inlet portion, the outlet portion, and the passageway of the diffuser passage 33.

It is a sectional view showing one embodiment of a pipe diffuser type centrifugal compressor by this invention. It is explanatory drawing of the pipe diffuser part which shows one Embodiment of the pipe diffuser type centrifugal compressor by this invention. It is a graph which shows the surge line characteristic determined by the relationship between an air volume and discharge pressure. It is a block diagram which shows one Embodiment of the control system of the pipe diffuser type centrifugal compressor by this embodiment. The operation of the on-off valve and the suction control valve is shown. (A) shows the operation of the on-off valve and the suction control valve when the use flow rate is lowered. (B) is the on-off valve and the suction control when the use flow rate is raised. It is a flowchart which shows the effect | action of a valve. It is a graph which shows the relationship between an air volume and discharge pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Bearing housing 13 Rotating shaft 15 Impeller 17 Scroll housing 19 Suction port 21 Impeller chamber 23 Pipe diffuser 25 Scroll passage 27 Suction control valve 31 Channel 33 Diffuser passage 35 On-off valve 51 Controller 53 Pressure sensor 55 Controller 57 Flow rate sensor

Claims (2)

A pipe diffuser type centrifugal compressor having a plurality of diffuser passages formed around the outside of an impeller,
An open / close valve that selectively opens and closes the diffuser passage, and the open / close valve turns the specified diffuser passage on and off at a position that equally divides the circumferential direction of the impeller among the plurality of diffuser passages. Pipe diffuser centrifugal compressor, which opens and closes automatically.   The on-off valve at a point-symmetrical position about the rotation axis of the impeller opens and closes the diffuser passage on and off, among the plurality of on-off valves at positions equally dividing the circumferential direction of the impeller. Item 2. A pipe diffuser centrifugal compressor according to Item 1.

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