The Influence of Combustor Hot Streaks on the Aerodynamic Performance of a Turbine Center Frame

This paper investigates the influence of combustor temperature non-uniformities on modern engine turbine center frames (TCFs). Due to their position in an engine, coupled with the trends of more aggressive designs, increased turbine inlet temperatures (TIT), and utilization of lean-burn combustors, turbine center frames are exposed to even higher temperatures and non-uniform temperature flow fields. These temperature non-uniformities, or hot streaks, were previously studied at the combustor - high-pressure turbine (HPT) interface, but there is no available research in the open literature that clarifies their influence on the TCF performance. A new test bench, designed specifically for fundamental research on hot streaks, was set up at the Institute for Thermal Turbomachinery and Machine Dynamics at the Graz University of Technology. The test bench features a 90° sector-cascade of an engine representative TCF geometry, equipped with a hot streak generator and a flow conditioning grid. Experimental data was gathered by means of five-hole-probe area traverses at the TCF inlet and outlet planes. Two individual clocking positions of hot streaks in respect to the leading edges of the struts were investigated, as well as three different radial positions for each of the clocking scenarios. Hot streaks were injected upstream of the flow conditioning grid, generating a representative temperature ratio at the TCF inlet plane. Results show that the hot streaks have migrated radially outwards and are characterized by different temperature distributions, depending on the injection position. An increase in pressure loss and thermal loading of the strut and of the shroud is observed.