Effect of Inlet Conditions on Endwall Secondary Flows

Abstract

Exit combustor ow and thermal elds entering downstream stator vane passages in a gas turbine engine are highly nonuniform. These ow and thermal elds can signi cantly affect the development of the secondary ows in the turbine passages attributing to high platform heat transfer and large aerodynamic losses. An analysis is presented of the effects of both the temperature and velocity pro les on the secondary ows in the endwall region of a rst-stage stator vane geometry. These effects were assessed using the predicted ow eld results from computational uid dynamics (CFD) simulations. Prior to using the predictions, these CFD simulations were benchmarked against ow eld data measured in a large-scale, linear, turbine vane cascade. Good agreement occurred between the computational predictions and experimentally measured secondary ows. Analyses of the results for several different cases indicate the stagnation pressure gradient is a key parameter in determining the character of the secondary ows. Nomenclature= mass ow through passage n = coordinate normal to inviscid streamline P = pitch P 0 = total pressure p = static pressure q = velocity vector R = radius of curvature of an inviscid streamline R g = gas constant Re ex = Reynolds number, CU ex / m Re in = Reynolds number, CU in / m S = span of stator vane s = coordinate aligned with inviscid streamline T S = static temperature U = freestream velocity U, V , W = absolute velocity components u, v, w = secondary ow plane, transformed velocity components V n = normal velocity, ¡ u sin w ms + v cos w ms V S = streamwise velocity, u cos w ms + v sin w ms V z = spanwise velocity, w X, Y, Z = absolute, stationary coordinate system x = distance normal to the secondary ow plane Y S = pressure loss coef cient,Çm y = distance tangent to the secondary ow plane z = radial or spanwise distance z + = inner coordinates spanwise distance, z p (s w / q )/ m c = speci c heat ratio= boundary-layer thickness d th = thermal boundary-layer thickness e = dissipation m = viscosity q = density s w = wall shear stress w ms = midspan turning angle, tan ¡ 1 (v ms / u ms ) X s = streamwise vorticity, X x cos(w ms ) + X y sin(w ms ) X x = x vorticity, (@W / @Y ) ¡ (@V / @Z ) X y = y vorticity, (@U / @Z ) ¡ (@W / @X ) Subscripts av = mass averaged value ex = value at vane exit in = value at 0.7C upstream of vane mid = value at vane midspan wall = value at vane endwall

A hot-streak (combustor) simulator suited to aerodynamic performance measurements

“…An area-survey of inlet total pressure was also conducted with the uniform inlet temperature condition and with EOTDF to determine the uniformity of the pressure distribution in both cases. It has been shown by, for example, Hermanson and Thole [12] that the total pressure profile is a key driving parameter for secondary flow development in the NGV passage. For direct comparative studies of heat transfer with different temperature profiles, it is therefore important to have similar pressure profiles.…”

Study on Aerodynamic Performance and Optimization Design of a Turbine in Liquid Rocket Engine

“…As shown in Figure 4, there are high and low total pressure zone distributing locally at the admission chamber outlet. As mentioned in related reports (Hermanson and Thole, 2002), when the inlet total pressure presents a pattern with low value in end walls, it will strengthen the development of passage vortex; when the inlet total pressure presents a pattern with low value in mid-span, it will induce counter rotating vortex. The streamlines on pressure side of vane in Figure 5 show radial expansion (enhanced passage vortex) or compression (counter rotating vortex) at different circumferential positions.…”

Evaluating a Three-Dimensional Slot Design for the Combustor-Turbine Interface

“…The RNG k − ε turbulence model exhibits improved performance in comparison to the standard k − ε model for complex shear flows and flows with high strain rates, swirl, and separation. Hermanson and Thole [22] showed good prediction of secondary flows with the RNG k − ε turbulence model. The enhanced wall function option in Fluent employs a two-layer zonal model in the near-wall region where the laminar sublayer is resolved directly if grid resolution is fine enough (y + ≈ 1) and a blending function is applied in the buffer layer [23].…”

“…The domain was extended 0.1C beyond the trailing edge in the flow exit direction followed by an axial length of 0.25C to an outflow boundary. These locations were determined by Hermanson and Thole [22] to be free of pressure effects from the vane. Periodic boundary conditions were specified in the stagnation plane and beyond the trailing edge.…”