Abstract: Apparatus for compressing fluid flow and for controlling said flow, comprising in combination, a casing having an interior, an impeller rotating within said interior between a fluid supply zone and pressurized fluid discharge zone, fluid flow control members at least one of which is shiftable in the casing interior relative to the other to control fluid back-flow from said discharge zone to said supply zone via through ports in each of said members, and an actuator operatively connected to said one member to shift said one member relative to the other to control the degree of registration of said flow ports in said members, in response to changes in the supply of fluid to said supply zone.

Abstract: Apparatus for compressing fluid flow and for controlling said flow, comprising in combination, a casing having an interior, an impeller rotating within said interior between a fluid supply zone and pressurized fluid discharge zone, fluid flow control members at least one of which is shiftable in the casing interior relative to the other to control fluid back-flow from said discharge zone to said supply zone via through ports in each of said members, and an actuator operatively connected to said one member to shift said one member relative to the other to control the degree of registration of said flow ports in said members, in response to changes in the supply of fluid to said supply zone.