Patent Publication Number: US-10323653-B2

Title: Centrifugal compressor and centrifugal unit having the same

Description:
TECHNICAL FIELD OF THE INVENTION 
     The invention relates to the field of refrigerating devices, and in particular to a centrifugal compressor and a centrifugal unit having the same. 
     BACKGROUND OF THE INVENTION 
     For a centrifugal unit, when a running load is reduced, inlet guide blades of a centrifugal compressor are closed gradually, and an air suction quantity is decreased. Suppose a passage area of a diffusion cavity remains unchanged, a flow velocity of air is decreased. When the flow velocity of the air cannot overcome a resistance loss of the diffusion cavity, an airflow will stop. Due to the reduction of kinetic energy of the air, converted pressure energy will be reduced accordingly. When an air pressure is smaller than an exhaust pressure, the airflow flows backwards, and surging is caused. For a single-stage centrifugal compressor, in order to prevent a centrifugal compressor from surging, a diffusion cavity adjustment device and an adjustment mechanism are often linked to act on an outlet of an impeller. When the running load is reduced, the flow velocity of the air can be increased by decreasing the passage area of the diffusion cavity, thereby effectively preventing the centrifugal compressor from surging. For a multi-stage centrifugal compressor, in order to improve the efficiency, an economizer generally exists between every two stages, and therefore an air supply opening exists. If a single movable diffusion cavity adjustment device is used for example, when the centrifugal compressor surges, a surging phenomenon will be improved only at a first stage having an adjustment function since only a single-stage impeller outlet diffusion cavity has the adjustment function while other stages do not have this function, and the surging phenomenon cannot be overcome at each of the other stages yet. If any stage of the multi-stage centrifugal compressor surges, normal working of an entire machine will be influenced, the centrifugal compressor is seriously destroyed, the performance of the centrifugal compressor obviously deteriorates, the noise is increased, vibration of the entire unit is greatly aggravated, and the running reliability of the unit is seriously influenced. 
     SUMMARY OF THE INVENTION 
     The invention aims to provide a centrifugal compressor and a centrifugal unit having same, which are intended to reduce the possibility of surging of any one of multiple stages of compression units of the centrifugal compressor. 
     In order to achieve the aim, the invention provides a centrifugal compressor, which comprises multiple stages of compression units communicated in sequence. Each stage of compression unit comprises: a diffusion cavity; and a diffusion cavity adjustment device, the diffusion cavity adjustment device comprising a movable member configured to change a flow area of the diffusion cavity provided in correspondence thereto, and the movable member being movably provided in an axial direction of the centrifugal compressor. 
     Furthermore, each stage of diffusion cavity adjustment device may further comprises: a transmission rod, the transmission rod being in drive connection with the corresponding movable member; and a guide structure, fixedly connected with a cavity wall of the corresponding diffusion cavity, the transmission rod being movably provided in the axial direction of the centrifugal compressor with respect to the guide structure. 
     Furthermore, each stage of diffusion cavity adjustment device further comprises a reset mechanism configured to move the corresponding movable member to make the flow area of the corresponding diffusion cavity in a maximum state. 
     Furthermore, each diffusion cavity is enclosed by a first cavity wall and a second cavity wall, the first cavity wall and the second cavity wall being provided at an interval, and each guide structure comprises a bushing arranged at the periphery of the corresponding transmission rod in a sleeving manner, the bushing being fixed inside an accommodating hole provided at the corresponding first cavity wall. 
     Furthermore, each reset mechanism comprises: a baffle, connected with an end of the corresponding transmission rod; and a spring, arranged at a periphery of the corresponding bushing in a sleeving manner. Each accommodating hole on the corresponding first cavity wall comprises a first segment adapting to the corresponding bushing and a second segment adapting to the corresponding spring, the spring being located between a step surface, connecting the first segment and the second segment, and the corresponding baffle. 
     Furthermore, each movable member comprises a circular ring, an axis of the centrifugal compressor serving as a centre. A groove adapting to each circular ring is provided at the corresponding first cavity wall; and each accommodating hole has an opening which is provided at a bottom of the corresponding groove and allows the penetration of the corresponding transmission rod. 
     Furthermore, an accommodating slot is provided at an inner circumferential surface of each bushing. Each guide structure further comprises a supporting belt provided in the corresponding accommodating slot, the supporting belt being matched with the corresponding transmission rod slidably. 
     Furthermore, each guide structure comprises at least one guide ring coaxial with the corresponding transmission rod. 
     Furthermore, each reset mechanism comprises: a baffle, connected with an end of the corresponding transmission rod; and a spring, arranged outside the corresponding transmission rod in a sleeving manner and provided between the baffle and the guide ring adjacent to the baffle. 
     Furthermore, each diffusion cavity is enclosed by a first cavity wall and a second cavity wall, the first cavity wall and the second cavity wall being provided at an interval. A accommodating hole is provided at the corresponding first cavity wall, and an outer circumferential surface of at least one guide ring is connected with an inner circumferential surface of the corresponding accommodating hole. 
     Furthermore, each movable member is annular. A groove adapting to each movable member is provided at the corresponding first cavity wall. Each accommodating hole has an opening which is provided at a bottom of the corresponding groove. 
     Furthermore, the centrifugal compressor further comprises: an air inlet; a plurality of inlet guide blades, provided at the air inlet; a drive device, the drive device being in drive connection with the inlet guide blades; and a plurality of transmission shafts, each of the transmission shafts being in drive connection with the drive device respectively, and the transmission shafts being in drive connection with the inlet guide blades in a one-to-one correspondence manner. The transmission rod of the compression unit closest to the air inlet being in transmission connection with one of the corresponding transmission shafts, and the transmission rod of each of the remaining stages of compression units being in transmission connection with the movable member of the previous stage of compression unit. 
     Furthermore, the centrifugal compressor further comprises at least one drive wheel, the drive wheel sleeves the corresponding transmission shaft and is provided in correspondence to one transmission rod. 
     Furthermore, the drive wheel is a cam or an eccentric bearing. A first end of the corresponding transmission rod of the drive wheel abuts against an outer circumferential surface of the drive wheel. A second end of the corresponding transmission rod of the drive wheel is connected with the corresponding movable member. 
     According to another aspect of the invention, a centrifugal unit is also provided, which comprises an above-mentioned centrifugal compressor. 
     By means of the technical solutions of the invention, the centrifugal compressor comprises multiple stages of compression units which are communicated in sequence, each stage of compression unit comprises the diffusion cavity and the diffusion cavity adjustment device, the diffusion cavity adjustment device comprises the movable member configured to change the radial flow area of the diffusion cavity arranged in correspondence thereto, and the movable member is movably provided in the axial direction of the centrifugal compressor. By means of the technical solutions of the invention, each stage of compression unit comprises the movable member which is movably provided in the axial direction of the centrifugal compressor. The movable member of each stage of compression unit changes the flow area of the diffusion cavity of this stage of compression unit, thereby effectively reducing the possibility of surging. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The specification drawings forming a part of the invention are intended to provide further understanding of the invention. The schematic embodiments and descriptions of the invention are intended to explain the invention, and do not form improper limits to the invention. In the drawings: 
         FIG. 1  shows a structural diagram of a centrifugal compressor according to an embodiment of the invention; 
         FIG. 2  shows a structural diagram of amplification of a point A in  FIG. 1 ; and 
         FIG. 3  shows a structural diagram of amplification of a point B in  FIG. 1   
     
    
    
     Drawing marks:  1 , diffusion cavity;  21 , movable member;  22 , transmission rod;  23 , bushing;  24 , guide ring;  25 , reset mechanism;  26 , supporting belt;  251 , baffle;  252 , spring;  3 , inlet guide blade;  4 , transmission shaft; and  5 , drive wheel. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     It is important to note that the embodiments of the invention and the characteristics in the embodiments can be combined under the condition of no conflicts. The invention is described below with reference to the drawings and the embodiments in detail. 
     As shown in  FIG. 1 , a centrifugal compressor according to an embodiment of the invention comprises multiple stages of compression units which are communicated in sequence. Each stage of compression unit comprises a diffusion cavity  1  and a diffusion cavity adjustment device, wherein the diffusion cavity adjustment device comprises a movable member  21  configured to change a flow area of the diffusion cavity  1  provided in correspondence thereto, the movable member  21  being movably provided in an axial direction of the centrifugal compressor. 
     In the process that each movable member  21  moves in the axial direction of the centrifugal compressor, the flow area of the corresponding diffusion cavity  1  is changed. When a running load is reduced, a flow velocity of air can be increased by decreasing the flow area of each diffusion cavity  1 , thereby effectively preventing the compressor from surging. 
     Each stage of diffusion cavity adjustment device further comprises a transmission rod  22  and a guide structure. Each transmission rod  22  is in drive connection with the corresponding movable member  21 . 
     In the embodiment, each movable member  21  is fixedly connected with one end of the corresponding transmission rod  22 . Each transmission rod  22  drives the corresponding movable member  21  to move in the axial direction of the centrifugal compressor. 
     Each guide structure is fixedly connected with a cavity wall of the corresponding diffusion cavity  1 . Each transmission rod  22  is movably provided in the axial direction of the centrifugal compressor with respect to the corresponding guide structure. 
     Each guide structure is configured to guarantee that the corresponding transmission rod  22  moves in the axial direction of the centrifugal compressor with respect to the corresponding diffusion cavity  1 . Furthermore, each guide structure reduces a friction force in a movement process of the corresponding transmission rod  22 , improves the practicality of the corresponding diffusion cavity adjustment device, and prolongs the service life of this diffusion cavity adjustment device. Furthermore, the precision of this diffusion cavity adjustment device is effectively improved. 
     Each stage of diffusion cavity adjustment device further comprises a reset mechanism  25  configured to move the corresponding movable member  21  to make the flow area of the corresponding diffusion cavity  1  in a maximum state. 
     Each reset mechanism  25  provides a force F 1  for the corresponding movable member  21  to move to a position where the flow area of the corresponding diffusion cavity  1  is in the maximum state. When the running load is reduced, each transmission rod  22  exerts a force F 2  on the corresponding movable member  21  to make it move to a direction in which the flow area of the corresponding diffusion cavity is reduced. If F 2  is greater than F 1 , each movable member  21  moves to the direction in which the flow area of the corresponding diffusion cavity is reduced. 
     As shown in  FIG. 2 , in the embodiment, each diffusion cavity  1  is enclosed by a first cavity wall and a second cavity wall, the first cavity wall and the second cavity wall being provided at an interval. Each guide structure comprises a bushing  23  arranged at a periphery of the corresponding transmission rod  22  in a sleeving manner. Each bushing  23  is fixed inside an accommodating hole provided at the corresponding first cavity wall. 
     Each reset mechanism  25  comprises a baffle  251  and a spring  252 . Each baffle  251  is connected with the corresponding transmission rod  22  and extends to a direction, away from this transmission rod  22 , in a direction of this transmission rod  22 . Each baffle  251  is connected to an end of the corresponding transmission rod  22 . 
     Each spring  252  is arranged at a periphery of the corresponding bushing  23  in a sleeving manner. The accommodating hole on each first cavity wall comprises a first segment adapting to the corresponding bushing  23  and a second segment adapting to the corresponding spring  252 . Each spring  252  is located between a step surface, connecting the corresponding first segment and the corresponding second segment, and the corresponding baffle  251 . 
     An accommodating slot is provided at an inner circumferential surface of each bushing  23 . Each guide structure further comprises a supporting belt  26  arranged in the corresponding accommodating slot. Each supporting belt  26  is matched with the corresponding transmission rod  22  slidably. 
     Each accommodating slot is an annular slot which is provided at the inner circumferential surface of the corresponding bushing  23  and is coaxial with the corresponding transmission rod  22 . Each supporting belt  26  arranged in the corresponding accommodating slot is in an annular shape adapting to this accommodating slot. An inner surface of each supporting belt  26  is higher than that of the corresponding bushing  23 . Consequently, in the axial movement process of each transmission rod  22 , this transmission rod  22  is only in contact with the inner surface of the corresponding supporting belt. The inner surface of each supporting belt  26  is a smooth surface, thereby effectively reducing a friction force in a movement process of the corresponding transmission rod  22 . 
     When the running load is increased, each spring  252  drives the corresponding movable member  21  to move to a direction in which the flow area of the corresponding diffusion cavity is increased, thereby improving the working efficiency of the centrifugal compressor. 
     Each movable member  21  comprises a circular ring, the axis of the centrifugal compressor serving as a centre. A groove adapting to each circular ring is provided at the corresponding first cavity wall. Each accommodating hole has an opening which is provided at a bottom of the corresponding groove and allows the penetration of the corresponding transmission rod  22 . 
     When each movable member  21  is completely located in the corresponding groove, the flow area of the corresponding diffusion cavity  1  is in the maximum state. In the process that each transmission rod  22  drives the corresponding movable member  21  to move to the corresponding second cavity wall in the axial direction of the centrifugal compressor, the flow area of the corresponding diffusion cavity  1  is gradually decreased. 
     Also preferably, as shown in  FIG. 3 , each guide structure comprises at least one guide ring  24  coaxial with the corresponding transmission rod  22 . Each reset mechanism  25  comprises the baffle  251  and the spring  252 . Each baffle  251  is connected with an end of the corresponding transmission rod  22 . Each spring  252  is arranged outside the corresponding transmission rod  22  in a sleeving manner and is provided between the corresponding baffle  251  and a guide ring adjacent to this baffle  251 . 
     Each diffusion cavity  1  is enclosed by a first cavity wall and a second cavity wall, the first cavity wall and the second cavity wall being provided at an interval. A accommodating hole is provided at the corresponding first cavity wall, and an outer circumferential surface of at least one guide ring  24  is connected with an inner circumferential surface of the accommodating hole. 
     In the embodiment, each reset mechanism comprises a guide ring  24  which is provided at one end, close to the corresponding second cavity wall, of the corresponding accommodating hole. Each spring  252  is arranged on the corresponding transmission rod  22  in a sleeving manner and is located between the corresponding guide ring  24  and the corresponding baffle  251 . 
     Each guide ring  24  reduces the friction force in the movement process of the corresponding transmission rod. A path is provided for the movement of this transmission rod  22 . The movement precision of each movable member  21  is guaranteed. 
     Each movable member  21  is annular. Each groove adapting to the corresponding movable member  21  is provided at the corresponding first cavity wall. Each accommodating hole has an opening which is provided at a bottom of the corresponding groove. 
     When each movable member  21  is completely located in the corresponding groove, the flow area of the corresponding diffusion cavity  1  is in the maximum state. In the process that each transmission rod  22  drives the corresponding movable member  21  to move to the corresponding second cavity wall in the axial direction of the centrifugal compressor, the flow area of the corresponding diffusion cavity  1  is gradually decreased. 
     When the running load is increased, each spring  252  drives the corresponding movable member  21  to move to a direction in which the flow area of the corresponding diffusion cavity is increased, thereby improving the working efficiency of the centrifugal compressor. 
     When the running load is reduced, each transmission rod  22  drives the corresponding movable member  21  to move to a direction in which the flow area of the corresponding diffusion cavity is decreased, so that the flow velocity of the air is increased by decreasing the flow area of each diffusion cavity  1 , thereby effectively preventing the centrifugal compressor from surging. 
     The centrifugal compressor further comprises a drive device, an air inlet, a plurality of inlet guide blades  3  and a plurality of transmission shafts. The inlet guide blades  3  are provided at the air inlet. The drive device is in drive connection with the inlet guide blades  3 . 
     Each of the transmission shafts  4  are in drive connection with the drive device respectively, and the transmission shafts  4  are in drive connection with the inlet guide blades  3  in a one-to-one correspondence manner. The transmission rod  22  of a compression unit closest to the air inlet is in transmission connection with one of the corresponding transmission shafts  4 , and the transmission rod  22  of each of the remaining stages of compression units is in transmission connection with the movable member  21  of the previous stage of compression unit. 
     The inlet guide blades  3  rotate with respect to the air inlet in axial directions of the transmission shafts  4  along with the rotation of the transmission shafts. In the rotation process of the inlet guide blades  3 , the air inflow of the air inlet of the centrifugal compressor is changed, thereby changing the running load of the centrifugal compressor. 
     The centrifugal compressor further comprises at least one drive wheel  5 . The drive wheel  5  sleeves the corresponding transmission shaft  4  and is arranged in correspondence to one certain transmission rod  22 . 
     The drive wheel  5  is a cam or an eccentric bearing. A first end of the corresponding transmission rod  22  of the drive wheel  5  abuts against an outer circumferential surface of the drive wheel  5 . A second end of the corresponding transmission rod  22  of the drive wheel  5  is connected with the corresponding movable member  21 . 
     In the process that each inlet guide blade  3  rotates to a direction in which the air inflow of the centrifugal compressor is decreased, the corresponding drive wheel rotates, a distance from an abutting point between this drive wheel and the corresponding transmission rod  22  to an axis of the corresponding transmission shaft  4  is gradually increased, and this drive wheel drives the corresponding movable member  21  to move to a direction in which the flow area of the corresponding diffusion cavity  1  is decreased via this transmission rod  22 . 
     In the process that each inlet guide blade  3  rotates to a direction in which the air inflow of the centrifugal compressor is increased, the corresponding drive wheel rotates, a distance from an abutting point between this drive wheel and the corresponding transmission rod  22  to an axis of the corresponding transmission shaft  4  is gradually decreased, and this transmission rod  22  drives the corresponding movable member  21  to move to a direction in which the flow area of the corresponding diffusion cavity  1  is increased under the driving of the corresponding spring  252 . 
     According to another aspect of the invention, a centrifugal unit is also provided, which comprises an above-mentioned centrifugal compressor. 
     The above is only the preferred embodiments of the invention, and is not intended to limit the invention. There can be various modifications and variations in the invention for those skilled in the art. Any modifications, equivalent replacements, improvements and the like within the spirit and principle of the invention shall fall within the protection scope of the invention.