Comparison of flow and loss aspects in the rotors of a counter-rotating turbine

Abstract

A counter-rotating turbine (CRT) is considered as an alternative way of obtaining more work without the use of another guide vane in a multi-stage turbine. In such a scenario, the present study discusses the flow transmission that takes place in rotors, which are rotating in the reverse direction to each other. The CRT stage with nozzles and rotors is modeled using ICEMCFD 14.5. Total pressure is specified at the inlet of the turbine stage, and flow rate is specified at the second rotor outlet. Contours of total pressure and turbulence kinetic energy provide the flow pattern in terms of steadiness, wake formation, incidence, flow circulation, and flow turbulence. Velocity vectors and streamlines offer clarity about flow separation, vortex formation, and wake detection. The deviation of flow characteristics from inlet to outlet of the CRT stage is also presented. For further understanding of the flow, transverse planes at different locations of the rotors are taken. Entropy and secondary velocity vectors are used to identify the loss aspect at each section of the rotors. From the blade-to-blade contours, the effect of the absence of a second guide vane is clear. Clearly, flow through rotor 1 is advantageous, and flow through rotor 2 is chaotic.