Numerical Investigation of Plasma-Based Flow Control for Transitional Highly-Loaded Low-Pressure Turbine

Abstract

Plasma-based active flow control was simulated numerically for the subsonic flow through a highly loaded low-pressure turbine. The configuration corresponded to previous experiments and computations which considered flow at a Reynolds number of 25,000 based upon axial chord and inlet conditions. In this situation, massive separation occurs on the suction surface of each blade due to uncovered turning. The present exploratory numerical study was performed to investigate the use of asymmetric dielectric-barrier-discharge actuators for mitigating separation, thereby decreasing turbine wake losses and increasing efficiency. Solutions were obtained for the Navier-Stokes equations, which were augmented by a phenomenological model that was used to represent plasma-induced body forces imparted by the actuator on the fluid. The numerical method used a high-fidelity time-implicit scheme, employing domain decomposition to carry out calculations on a parallel computing platform. A high-order overset grid approach preserved spatial accuracy in a locally refined embedded region. The magnitude of the plasma-induced body force required for control is examined, and both continuous and pulse-modulated actuations are considered. Novel use of counterflow actuation is also investigated, and the effects of pulsing frequency and duty cycle are considered. Features of the flowfields are described, and resultant solutions are compared with each other, with previous mass-injection control cases, and with the baseline situation where no control was enforced.