Experimental Investigation of Unsteady Flow Field Within a Two-Stage Axial Turbomachine Using Particle Image Velocimetry

Abstract

Detailed measurements of the flow field within the entire 2nd stage of a two-stage axial turbomachine are performed using particle image velocimetry. The experiments are performed in a facility that allows unobstructed view on the entire flow field, facilitated using transparent rotor and stator and a fluid that has the same optical index of refraction as the blades. The entire flow field is composed of a “lattice of wakes,” and the resulting wake-wake and wake-blade interactions cause major flow and turbulence nonuniformities. The paper presents data on the phase averaged velocity and turbulent kinetic energy distributions, as well as the average-passage velocity and deterministic stresses. The phase-dependent turbulence parameters are determined from the difference between instantaneous and the phase-averaged data. The distributions of average passage flow field over the entire stage in both the stator and rotor frames of reference are calculated by averaging the phase-averaged data. The deterministic stresses are calculated from the difference between the phase-averaged and average-passage velocity distributions. Clearly, wake-wake and wake-blade interactions are the dominant contributors to generation of high deterministic stresses and tangential nonuniformities, in the rotor-stator gap, near the blades and in the wakes behind them. The turbulent kinetic energy levels are generally higher than the deterministic kinetic energy levels, whereas the shear stress levels are comparable, both in the rotor and stator frames of references. At certain locations the deterministic shear stresses are substantially higher than the turbulent shear stresses, such as close to the stator blade in the rotor frame of reference. The nonuniformities in the lateral velocity component due to the interaction of the rotor blade with the 1st-stage rotor-stator wakes, result in 13 percent variations in the specific work input of the rotor. Thus, in spite of the relatively large blade row spacings in the present turbomachine, the nonuniformities in flow structure have significant effects on the overall performance of the system.

Experimental Investigation of the Effects of Winglets on the Tip Vortex Behavior of a Model Horizontal Axis Wind Turbine Using Particle Image Velocimetry

“…For each measurement window and each phase, 1000 image pairs are recorded to obtain converged statistics [22,23].…”

Decomposition of the spatially filtered and ensemble averaged kinetic energy, the associated fluxes and scaling trends in a rotor wake

“…[8][9][10][11][12][13] However, most of the data have been constrained by optical obstructions due to the complex geometry of turbomachines. Uzol et al [14][15][16] and Chow et al [17][18][19] have recently introduced a two-stage axial-turbomachine facility with transparent acrylic blades whose optical refractive index matches that of the working fluid, enabling unobstructed PIV measurements. Resulting complete two-dimensional ͑2-D͒ data sets, which cover an entire stage, have been used for examining the turbulent flow structures generated by bladewake and wake-wake interactions.…”

“…Resulting complete two-dimensional ͑2-D͒ data sets, which cover an entire stage, have been used for examining the turbulent flow structures generated by bladewake and wake-wake interactions. [15][16][17][18][19] Some of these data are analyzed in this paper.…”

Study of modeling unsteady blade row interaction in a transonic compressor stage part 1: code development and deterministic correlation analysis

“…Hence, recently some researchers have studied these experimentally and numerically [14][15][16][17]. This paper also attempts to address these deficiencies to contribute to the modeling development.…”