TURBO MACHINE

To provide a turbo machine capable of suppressing surging or choke while suppressing degradation of efficiency, and having a simple constitution.SOLUTION: A turbo machine has a casing including a cavity portion formed in a radial range including an upstream end of a diffuser vane, a first communication passage for communicating the cavity portion to a first part at an upstream side with respect to an upstream end of the diffuser vane, and a second communication passage for communicating the cavity portion to a second part between the upstream end and a downstream end of the diffuser vane, and a movable portion in the cavity portion. The movable portion is constituted to be movable between a communication blockage position for blocking the communication between the first part and the second part of the flow channel through the first communication passage, the cavity portion, and the second communication passage, and a communication permission position for permitting the communication between the first part and the second part, and includes a valve capable of switching a low-pressure conduit between a chamber capable of receiving a pressure medium for pressing the movable portion and a fluid flow channel at an upstream side of an impeller, and a conduit disposed between the chamber and a fluid flow channel at a downstream side of the diffuser vane.SELECTED DRAWING: Figure 1 【課題】効率の低下を抑制しながらサージング又はチョークを抑制可能であり、簡素な構成を有するターボ機械を提供する。【解決手段】ディフューザベーンの上流端を含む径方向範囲に形成される空洞部と、ディフューザベーンの上流端よりも上流側の第１部分に空洞部を連通させる第１連通路と、ディフューザベーンの上流端と下流端との間の第２部分に前記空洞部を連通させる第２連通路と、を含むケーシングと、空洞部内の可動部とを備え、可動部は、第１連通路、空洞部および第２連通路を介した流路の第１部分と第２部分との間の連通を阻害する連通阻害位置と、第１部分と前記第２部分との間の連通を許容する連通許容位置と、の間で移動可能に構成され、可動部を押圧する圧力媒体を受け入れ可能なチャンバとインペラの上流側の流体流路との間の低圧導管と、チャンバとディフューザベーンの下流側の流体流路との間に設けられる導管を切り替え可能なバルブを備える。【選択図】図１