The Influence of Inlet Contraction on Vane Aerodynamic Losses and Secondary Flows With Variable Turbulence and Reynolds Number

Abstract

Exit survey measurements comparing exit losses for a constant inlet height cascade and a contracting inlet cascade have been acquired in a low speed wind tunnel facility. The measurements were taken for both a low and a high turbulence level across a four to one range in chord Reynolds number (500,000, 1,000,000, and 2,000,000). The high intensity turbulence has been generated using a simulated aero-combustor for both cascades. Exit survey measurements have been acquired for the two cascades using a five-hole cone probe at stations representing an exit location of 1/4 axial chord downstream from the trailing edge plane. Measurements detail total pressure loss, turning angle, and secondary velocities. At the low turbulence condition, the contracting inlet cascade shows a significant reduction in losses compared with the constant height inlet cascade. The contracting inlet cascade also features an aft loaded vane profile which may have some impact on the development of secondary flows. The constant cross-section cascade uses a fully loaded vane profile. The difference in losses between the two cascades is also significant at the high turbulence condition. However, at the high turbulence condition, the losses for the contracting inlet cascade are greater than the constant cross-section cascade. These increased losses are believed to be due to the more aggressive turbulence of the contracting inlet case. The contracting inlet effectively moves the vane leading edge plane forward into the exit of the combustor where the vane passage is subjected to more aggressive turbulence levels.

The Impact of Combustor Turbulence on Turbine Loss Mechanisms

“…This rise in loss was measured at a Reynolds number of 800,000. This is similar to the 50% rise in loss measured on a very different design of vane at a Reynolds number of 1,000,000 by Chowdhury et al [11]. This implies this large rise in loss is not specific to the blade studied.…”

“…The development of a combustor-style turbulence generator for cascade testing was first reported by Ames and Moffat [5]. A number of studies have since investigated the impact of combustor turbulence on downstream components [6][7][8][9][10][11][12][13]. These studies have mainly focused on the effect of combustor turbulence on wall shear stress and heat transfer on a flat plate.…”

“…These papers show that combustor turbulence has the ability to penetrate deep into the boundary layer. Several studies have looked at the effect of combustor turbulence on turbine cascades [7,8,11]. A 16% to 27% increase in skin friction was measured on the blade surface in [7,8].…”

“…A 16% to 27% increase in skin friction was measured on the blade surface in [7,8]. Chowdhury et al [11] is the only study to investigate the effect of combustor turbulence on the loss coefficient of a turbine cascade. They showed that the loss coefficient of the cascade rose by between 38% and 50% depending on Reynolds number.…”

The Impact of Combustor Turbulence on Turbine Loss Mechanisms

“…The development of a combustor-style turbulence generator for cascade testing was first reported by Ames and Moffat [5]. A number of studies have since investigated the impact of combustor turbulence on downstream components [6][7][8][9][10][11][12][13]. These studies have mainly focused on the effect of combustor turbulence on wall shear stress and heat transfer on a flat plate.…”