Numerical Predictions of Turbine Cascade Secondary Flows and Heat Transfer With Inflow Turbulence

Abstract

Turbine passage secondary flows are studied for a large rounded leading edge airfoil geometry considered in the experimental investigation of Varty et al. (J. Turbomach. 140(2):021010) using high resolution Large Eddy Simulation. The complex nature of secondary flow formation and evolution are affected by the approach boundary layer characteristics, components of pressure gradients tangent and normal to the passage flow, surface curvature, and inflow turbulence. This paper presents a detailed description of the secondary flows and heat transfer in a linear vane cascade at exit chord Reynolds number of 500,000 at low and high inflow turbulence. Initial flow turning at the leading edge of the inlet boundary layer leads to a pair of counter-rotating flow circulation in each half of the cross-plane that drive the evolution of the pressure-side and suction side of the near-wall vortices such as the horseshoe and leading edge corner vortex. The passage vortex for the current large leading-edge vane is formed by the amplification of the initially formed circulation closer to the pressure side which strengthens and merges with other vortex systems while moving toward the suction side. The predicted suction surface heat transfer shows good agreement with the measurements and properly captures the augmented heat transfer due to the formation and lateral spreading of the secondary flows towards the vane midspan downstream of the vane passage. Effects of various components of the secondary flows on the endwall and vane heat transfer are discussed in detail.

Active Flow Control for Passage Vortex Reduction in a Linear Turbine Cascade with Various Tip Clearance Sizes Using a Dielectric Barrier Discharge Plasma Actuator

“…Cui et al [11] conducted a numerical analysis to examine the turbine's secondary flow structure by changing the inlet conditions to three types: (1) laminar boundary layer, (2) turbulent boundary layer, and (3) wakes and secondary flow from upstream blades. Kanani et al [12] examined the effects of inlet turbulence and heat transfer on the secondary flow in turbine blades via numerical analysis. Sun et al [13] investigated the leading-edge vortex effect on an unsteady secondary flow generated near the endwall.…”

Entropy Generation of Secondary Flow in a Turning Passage with Different Boundary Layer Characteristics

“…Pichler et al [22] compared the solution by RANS and LES, and it was found that the a high-loss area is related to the counter-rotating vortex. Kanani et al [23] studied turbine passage secondary flow using LES and captured the augmented heat transfer brought by the secondary flow.…”