Experimental and Computational Investigation for Accelerated Testing and Characterization of NextGeneration Steam Turbine Rotors

Abstract

A unique set of test protocols is developed to evaluate new materials for hightemperature and pressure applications (>700 °C and 310 bar) in nextgeneration thermal power plants. These protocols employ accelerated testing processes to provide a realistic estimate of a component’s life under actual field operating conditions. A stateoftheart experimental facility to characterize turbine rotors for advanced ultrasupercritical conditions was commissioned at Bharat Heavy Electricals Limited, India. An alloy rotor mounted inside the test chamber is subjected to cyclic thermal and mechanical stresses at elevated temperatures for a predetermined number of thermal cycles to estimate its creep and fatigue life. Cyclic thermal and mechanical loads are applied by sequentially exposing rotors rotating at high speed to transient heating, steadystate soaking, and transient cooling. These transient heating and cooling processes are carefully designed to achieve specific temperature gradients inside the rotor bulk. The rotor is heated in a vacuum by thermal radiation from heater coils. In contrast, rotor cooling is accomplished by circulating relatively cold nitrogen gas through the chamber. Preliminary findings from accelerated tests are reported here. Two computational fluid dynamics (CFD) models were developed to support the transient heating and cooling experiments. Good agreement is observed between CFD simulations and measurements, validating the approach presented. This facility, established under a clean energy research initiative, plays a vital role in reducing the time and cost involved in finding suitable alloy materials, thus advancing the development of ultraefficient thermal power plants.