Design Optimization of Integrated Anti-Rotation Feature for Power Turbine Nozzles

Abstract

Gas turbine nozzles are static components that are meant to turn and accelerate high temperature, high pressure, and low-velocity flue gas into the downstream turbine row of buckets. During gas turbine operation, nozzles are subjected to high-pressure load due to the expansion of flue gases, in axial and tangential directions. This creates a tendency for nozzle movement in tangential direction which has potential to create flow disturbance and intersegment gap opening. To prevent this movement, it should be held in tangential direction firmly by introducing an anti-rotation feature. A slot is introduced in the nozzle outer sidewall and a pin connected with casing in such a way that the nozzle’s tangential movement is restrained. As the nozzle’ s outer sidewall experiences high thermal gradients in the operating condition, it induces high stress at the nozzle anti-rotation feature. There are many possible design options available to mitigate this challenge. In the present work, anti-rotation feature is integrated with the nozzle’s outer sidewall and a matching slot is provided in the casing. A detailed study is performed to optimize this anti-rotation feature to reduce high thermal-mechanical stress and thereby improve reliability. The low cycle fatigue life is one of the vital requirements in improving reliability. The low cycle fatigue life of the optimized anti-rotation feature is validated using the finite element analysis. This paper describes the process step details in optimizing the anti-rotation feature.