Simulation and analysis of vane-blade interaction in a two-stage high-pressure axial turbine

Abstract

The characterization of aerothermodynamic performance and components interactions are of great importance to improve the design of multi-stage axial turbines. The steady and unsteady flow simulations were carried out to investigate the performance maps and the vane-rotor interaction in a two-stage high-pressure (hp) axial turbine. The obtained results show that the expansion properties are controlled mainly by the first stage nozzle guide vane (NGV). Besides, the aerodynamic characteristics of the second stage vanes and blades are affected by the impingements of wakes from upstream stage, hence lesser isentropic efficiency compared with an isolated stage. Moreover, the secondary flows, tip leakage flow and vortices emanating from the first rotor are convected downstream, thereby inducing considerable flow deviations and losses. The clocking of vane/blade rows has revealed variations in aerodynamic loading and isentropic efficiency. Indeed, the maximum isentropic efficiency clocking position corresponds to upstream wakes close to the leading edge of second stage vanes, while the minimum efficiency clocking position corresponds to wakes passing midway. The unsteady flow computations and FFT analysis revealed different modes of components interaction identified in terms of the passing frequencies (BPF) of the two rotors and their combinations.