Flow measurements in a first stage nozzle cascade having leakage and assembly features: Effects of endwall steps and leakage on aerodynamic losses

This work supports new gas turbine designs for improved performance by evaluating endwall leakage and assembly features in a cascade that is representative of a first stage stator passage. The present paper documents component misalignment and leakage flow effects on the aerodynamic losses within a passage having one contoured and one straight endwall. Steps on the endwall and leakage flows through the endwall can lead to thicker endwall boundary layers, stronger secondary flows and possibly additional vortex structures in the passage. The paper compares losses with steps of various geometries and leakage of various flow rates to assess their importance on aerodynamic losses in this contoured passage. In particular, features associated with the conibustor-to-turbine transition piece and the slash-face gap, a gap between two vane segments on the vane platform, are addressed.