Numerical investigation of dual stage counter-rotating compressor for on-design or off-design conditions

To our knowledge, even in the rare papers in the open literature concerning counter-rotating compressor, we have not found detailed technical information about its flow structure. Our aim is to present the results of our effort to develop such information for a certain dual stage counter-rotating compressor to redesign and optimize the counter-rotating compressor blade. We have investigated by numerical simulation the detailed flow structure of a dual stage counter-rotating compressor near the surge conditions for each of several different rotating speeds. Both the characteristics of each flow pattern on each rotor surface and the interaction between the two counter-rotating rotors for on-design or off-design conditions have been analyzed in depth to optimize the design of counter-rotating compressor blades. The numerical results, given in Figs. 1 through 4, show preliminarily that the inflow incidence and the deviation angle of the counter-rotating rotors are relatively large, implying that there exist separation flows on the blade to blade surface for both the hub and the tip. Taking into consideration both the numerical results given in Figs. 1 through 4 and the discussion of the results shown in Figs. 5 through 8, we are of the opinion that: (1) the radial velocity at the upstream of the separation line of the first row of rotor blades is relatively big; (2) the reversed sweep of the wake effect of the downstream rotor on the upstream rotor induces the separation near the trailing edge of the upstream rotor on the one hand and increases the inflow incidence of the downstream rotor on the other.