Influence of Purge Flow on Performance of an End Wall Profiled Turbine

The goal of this study is the investigation of the promising secondary flow control technique of non-axisymmetric end wall profiling in a more engine representative environment. In this work end wall profiling is applied to the first stage of a high work, 1.5 stage, unshrouded turbine. Without purge flow non-axisymmetric end wall profiling has demonstrated a considerable increase of total-to-total efficiency. The two designs increased the total-to-total efficiency by 1% and 0.3% respectively relative to a baseline efficiency of already 91%. The first end wall design having the highest efficiency without purge flow shows the highest efficiency drop of 1.2% per injected massflow percent if purge flow is applied. The second end wall design and the baseline case show comparable sensitivities with -0.7%/% and -0.6%/% to purge flow. The reason for the increased sensitivity of the first design is an increased circumferential pressure gradient at the first vane rim compared to the baseline case and the second end wall design. Resulting in the strongest injection jets and therefore in more induced vorticity.