59252 - Thermal Characterization of a Steam Turbine Casing Including Measuring of Adiabatic Wall Temperatures Using Proprietary Sensors 

Modern steam turbines must reinforced be designed for flexible operation. However an increasing amount of cold starts and load changes have a massive impact on fatigue resistance of the material. So the monitoring of thermodynamic parameters of the casing is significant for checking thermally induced stresses and furthermore lifetime calculation. Additionally an extra benefit is the future usage of the measurement results as initial CFD data.

This paper presented a new inhouse developed sensor setup and a part of its measurement results. The sensors are flush mounted into a steam turbine at different radial and longitudinal locations in the recirculation area between the intermediate and the lower pressure turbine. Hence it is possible to detect temperatures, temperature gradients and heat fluxes in the part of the wall near the fluid. Moreover the field of temperature within the sensor can be modulated by powering an installed heater. So the adiabatic wall temperature can be identified. For measuring the temperature gradient seven equidistant spaced thermocouples were used in difference circuit. Therefor two different types of thermocouples were applied. Both types have a higher resolution compared to a type K thermocouple. High amplification enables monitoring of small differences in temperature. The absolute temperature measures an integrated resistor thermometer.

The sensors are applied on a real 12 MW industrial steam turbine with maximal live steam parameters of 400 °C and 30 bar. The measurements show various operation points and load changes.