Patent ID: 7641439

Claim:
A flow passage structure disposed in a multi-stage centrifugal refrigerant compressor having a deswirl vane and a return channel bend, the flow passage structure comprising: a two-way flow passage having a first outlet and a second outlet, for diverging externally injected refrigerant; a first side discharge flow passage connected to the first outlet of the two-way flow passage, the first side discharge flow passage having a first side outlet disposed below the deswirl vane such that the refrigerant diverged from the two-way flow passage is allowed to be discharged into the return channel bend and uniformly mixed with the refrigerant in the return channel bend; and a second side discharge flow passage connected to the second outlet of the two-way flow passage, the second side discharge flow passage having a second side outlet disposed below the deswirl vane such that the refrigerant diverged from the two-way flow passage is allowed to be injected into the return channel bend and uniformly mixed with the refrigerant in the return channel bend.