Analysis of conjugate heat transfer of a gas turbine first stage nozzle

Steady-state analysis of heat transfer in a base-load power generation gas turbine was conducted by thermal conjugation inside and outside of the first stage nozzle, which consists of thermal convection and conduction by coupling of fluid flow and solid body. A computer CFD code, Star CD V 3.150A, was used to solve the problem. The principal issues of the work were concerned with the three-dimensional behavior of the temperature distribution of the nozzle vane, which is influenced by the inlet gas flow conditions, internal cooling conditions and film cooling conditions. The numerical results of the effects of cooling flow rate and temperature on heat transfer rates in the nozzle are also presented. The paper focuses on the estimation of the temperature distribution on the nozzle vane by prediction of the thermal environment around the nozzle vane and heat conduction in the nozzle which is necessary to carry out the nozzle thermal load analysis and finally life assessment. Also, the evaluation of service induced degradation of cobalt base alloy FSX-414 of the nozzle, after 24,000 h of operation at high temperature is presented. The assessment includes the precipitation of the nozzle carbides and grain type and size characterization. The predictions were used to estimate stress and creep strain, which are demanded to evaluate the damage of the nozzle during steady-state operation conditions.