Basis of the computational domain selection in the problems of modeling a viscous flow in lowflow stages of a centrifugal compressor

Abstract

The paper examines the problem of definition of the computational domain of the gasflow part at numerical simulation (RANS-approach) of gas flow in the low-flow stage of a centrifugal compressor at conditional flow rate Ф = 0.008. Several variations of replacing the design assembly of the flow part of the simulation stage with a gasdynamic model are considered: main working path of the stage; main working path of the stage taking into account the inlet area (inlet pipe and cowling); main working path of the stage taking into account the adjacent areas with full and partial connection with the gasflow part; main working path of the stage taking into account the friction surfaces of the stage rotor hub. It is shown that in case of axial suction into the stage the inlet pipe and cowling don’t significantly affect the parameter profile in front of the stage rotor and the gasdynamic characteristics of the stage. Modeling without areas adjacent to the path gives unsatisfactory quantitative and qualitative results. The most relevant option to take into account the losses of disk friction and leaks is a full twoway connection of adjacent areas with the flow part along the stage rotor disks, because when connecting only at the outlet of the stage rotor, the friction and leak losses are simulated, but the effect on the flow in the stage rotor is not taken into account. In some cases, it is important to consider the additional areas involved in friction losses.