Heat Transfer and Thermal Stress Analysis of Gas Turbine Blade Considering Off-Design Condition

Nowadays, Gas turbine’s hot components need to be applied adequate cooling technique because increasing Turbine Inlet Temperature exceeds material’s melting temperature limit. And gas turbine is designed to operate at full load condition, But it is often operated at various off-design conditions, like DSS(Daily Start and Stop) operating condition, since the generated electricity should be matched with the market demand. Because of the off-design operating condition, gas turbine’s hot components suffer undesirable and unpredictable thermal load. It can cause unexpected damages which haven’t been considered while it is designed and makes hard to expect the lifespan of gas turbine. So, heat transfer and thermal stress characteristics at off-design condition should be analyzed to handle the unexpected damages properly. And the way to reduce thermal damage at off-design condition should be found if it is possible. In this study, temperature distribution and thermal stress at off-design condition with various coolant mass flow rate are especially considered to reduce the thermal damages. Using operating data from power generation company for boundary conditions, CFD simulation has been accomplished by ANSYS 19.2 CFX. As a result, Increasing coolant mass flow rate makes film cooling effect weaker and internal cooling effect greater. So, the temperature distribution after film cooling hole is getting more uneven when coolant mass flow rate increases, but the maximum temperature is getting lower because it is much more affected by internal cooling effect than film cooling effect. And the trend of thermal stress increases since temperature distribution after film cooling hole is getting more uneven, but maximum thermal stress has an optimum point because it is similarly affected by both internal cooling and film cooling effect. Thus, proper coolant mass flow rate can be found by considering temperature distribution and thermal stress with various off-design operating conditions in further study.

(Acknowledgement: This work was supported by the Human Resources Development program (No.20174030201720) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Trade, Industry and Energy.)