Secondary Flow Measurements in a Turbine Cascade With High Inlet Turbulence

Abstract

Measurements of the mean and turbulent flow field have been made in a cascade of high turning turbine rotor blades. The inlet turbulence was raised to 5% by a grid placed upstream of the cascade, and the secondary flow region was traversed within and downstream of the blades using a 5 hole probe and crossed hot-wires. Flow very close to the end wall was measured using a single wire placed at several orientations. Some frequency spectra of the turbulence were also obtained. The results shows that the mean flow field is not affected greatly by the high inlet turbulence. The Reynolds stresses were found to be very high, particularly in the loss core. Assessment of the contributions to production of turbulence by the Reynolds stresses show that the normal stresses have significant affects as well as the shear stresses. The calculation of eddy viscosity from two independent shear stresses show it to be fairly isotropic in the loss core. Within the blade passage, the flow close to the end wall is highly skewed and exhibits generally high turbulence. The frequency spectra show no significant resonant peaks, except for one at very low frequency, attributable to an acoustic resonance.

Computational analysis of pitch-width effects on the secondary flows of turbine blades

“…Previous CFD studies [4][5][6][7] on turbomachines were mainly based on a linear cascade of high turning turbine blades where the secondary flow was very strong. In this study, an annular turbine blade was focused, which is similar to actual turbine stator vanes.…”

“…The ability to accurately simulate complex flow phenomena inside turbine blade passages can provide reliable guidance for new turbine designs. During the last decade, a large number of experimental studies on the secondary flows in turbine cascades for different pitchwidth ratios have been carried out [4][5][6]. Some of the experiments [4,5] provided important data about the secondary flow due to the solidity changes.…”

“…The loss mechanisms within turbine blade passages as well as the influence of pitch-width ratio on the secondary flow have long been recognized. Many investigations [4][5][6] have been undertaken into better understand these phenomena. The main parameters which influence the growth of the secondary flow are now known.…”

Turbulence Measurements and Analysis in a Multistage Axial Turbine

“…Therefore, particularly in low aspect ratio blading, common isotropic turbulence models validated in simple geometry may not be suitable. Several investigations were performed on turbine blading focusing on the effect of turbulence intensity on the heat transfer [1,2], secondary flows development and transition [3][4][5][6]. Ristic et al [7] and Xiao and Lakshminarayana [8] performed detailed measurements using LDA inside a turbine rotor where a high level of anisotropy has been reported in the wake and secondary flow region.…”

Heat transfer and film-cooling for the endwall of a first stage turbine vane

“…In general, there are some slight disagreements in the different flow models that have been proposed but, for the most part, these flow models, which are primarily based on uniform inlet profiles except for the turbulent endwall boundary layers, agree on the existence of the leading edge and passage vortices. Experimental flowfield data presented by Bailey [6], Moore et al [7], Gregory-Smith and Cleak [8], and Kang et al [9] have all quantified some aspects of the secondary flows. All of these studies, however, have had an inlet boundary condition of a uniform flow except for a turbulent endwall boundary layer such as that shown in Fig.…”