58887 - A Key Flow Parameter to the Profile Loss of Low-Pressure Turbine Blades
For an optimum performance design of low-pressure turbine (LPT) blades, it is crucial to understand the generation mechanism of profile loss properly. As the profile loss is usually taken to be the loss generated inside the blade boundary layer due to viscous effects, most of the efforts for the performance optimization have concentrated on the reduction in the boundary layer loss using the flow parameters that represent the loss generation in the boundary layers. Kodama and Funazaki [1] investigated the generation mechanism of profile loss from a view point of blade drag forces, friction drag force and pressure drag force, and suggested that the loss due to pressure drag is dominant in the profile loss of a typical LPT blade. The loss due to pressure drag is not a boundary layer loss, because it is not generated in the boundary layers, but generated downstream of the trailing edge as a mixing loss. It is necessary to clarify a key flow parameter to the loss due to pressure drag for an effective performance optimization.
In this paper, we attempt to break down the profile loss into the loss sources expressed by the boundary layer integral parameters at the trailing edge and categorize them into the loss due to friction drag or the loss due to pressure drag. The magnitude of each loss source is evaluated to investigate the contribution to the total profile loss by using the results of steady Reynolds Averaged Navier-Stokes simulations. The evaluations are conducted for two kinds of blade profiles used in the low speed linear cascade tests at three different Reynolds numbers, 57,000, 100,000 and 147,000. It is found that the largest contributor to the loss due to pressure drag is the loss associated with a mixing loss of accelerated free stream flow by the flow blockage at the trailing edge plane. The magnitude of the loss is simply determined by the flow blockage. This suggest that the flow blockage at the trailing edge is the most important flow parameter for an optimum performance design of LPT blades.
[1] Kodama, H. and Funazaki, K., 2020 “Interpretation of Low-Pressure Turbine Profile Loss Generation Mechanisms from a Viewpoint of Blade Drag Forces,” ASME paper GT2020-14519.
A Key Flow Parameter to the Profile Loss of Low-Pressure Turbine Blades
Paper Type
Technical Paper Publication
Description
Session: 35-01 Loss Generation & High Fidelity CFD
Paper Number: 58887
Start Time: June 10th, 2021, 09:45 AM
Presenting Author: Hidekazu Kodama
Authors: Ken-Ichi Funazaki Iwate University
Hidekazu Kodama Iwate University