Blade-to-Blade Flow Distribution in a Counter-Rotating Turbine with Flow Rate

It is projected that just 1% improvement in the efficiency of gas turbine would save millions of dollars depending on the application and usage. Thus, it has been the prime interest of the researchers to investigate their performance by analysing the nature of the complex flow in a turbine. In counter-rotating turbine (CRT), nozzle is followed by two rotors that rotate in the reverse direction of each other. Flow interaction between the stationary nozzle and rotor 1 as well as rotor 1 and rotor 2 further adds to the complexity of the flow. None of the earlier works could clearly describe the flow pattern through CRT stage. In this context, present work finds significance with the modelling and simulation of CRT blade rows with respect to the identification of blade-to-blade flow for various flow rates. Equivalent mass flow rates of 0.091–0.137 are considered. Flow rate has significant effect on the pattern of the flow. In rotor 1, the loss region is less compared to rotor 2 for all the flow rates suggesting better performance. Loss regions get initiated at the exit of the nozzle that get expanded from the mid-chord section of the rotor 1 on the suction side. These losses further get propagated till the exit of the turbine stage. The transmission of losses from the mid-chord region of rotor 1 to rotor 2 is more due to rotational effects. As the flow rate is increased, more flow and turbulence losses in rotors are observed with varied magnitude.