Studies on the Effect of Staggering the Rear Rotor in a Counter Rotating Turbine with Respect to Flow and Performance Parameters

Counter rotating turbine is an axial turbine with nozzle followed by a rotor and another rotor that rotates in the opposite direction of the first one. Absence of the second guide vane makes it more beneficial. Present work involves computationally studying the performance and flow pattern of CRT with different stagger angles ranging from 8 to 13 degrees in case of rotor 2. Equivalent mass flow rates of 0.091 to 0.137 are considered. Turbine components nozzle, rotor 1 and rotor 2 are modeled for the cases of CRT with and without staggering. Total pressure, entropy and TKE distributions across the blade rows are used to describe the flow through CRT. Results show that the flow composition at the inlet of rotor 2 is improved for staggering cases. Due to this, the performance of rotor 2 and CRT increased with staggering. For the intermediate mass flow rate of 0.108, the efficiency of CRT stage is found to be increasing by 1.2, 2.1 and 1% for the staggering cases. The beneficial aspect of staggering the rear rotor is thus confirmed that can provide long-term design solutions in terms of reducing weight, losses and improving the performance.