Computational studies on the effect of speed ratio and stagger angle in a counter rotating turbine with respect to flow field and performance

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. Studies show that speed ratio and stagger angle are the two important parameters that affect the performance of a turbomachine. Present work involves computationally studying the performance and flow field of CRT for different speed ratios and stagger angles. Turbine components nozzle, rotor 1 and rotor 2 are modeled for the cases of CRT with and without staggering. Total pressure and entropy distributions across the blade rows are used to describe the flow through CRT. Enthalpy losses and TKE are estimated at the exit of the blade rows and performance curves are plotted for all the configurations. Results show that the flow composition in rotors varied with speed ratio and improved at the inlet of the second rotor in staggering cases. Due to this the performance of rotor 2 and CRT improved with speed ratio and staggering. Results confirm the beneficial aspect of varying speeds and staggering of second rotor in CRT.