Curtis Stage Nozzle/Rotor Aerodynamic Interaction and the Effect on Stage Performance

Abstract

Curtis, or velocity compounded, stages commonly don’t achieve the same accuracy of performance prediction expected of most other turbine stages. A review of Curtis stage design practices, field wear, and dirt patterns, in conjunction with performance testing and computational fluid dynamics (CFD) modeling, determined that the nozzle/rotor aerodynamic interaction is far more complex than typical design and performance calculations assume. Understanding this nozzle/rotor interaction is key to obtaining both improved performance, and a more accurate performance prediction. This paper discusses the nature of this interaction, and it’s implications to Curtis stage performance prediction.