Sakae Kawasaki

An Experimental Investigation of Thermal Wetness Loss in the Full Scale Size Low Pressure Turbine

Experimental investigation with a full scale low pressure steam turbine is carried out to reveal the thermal wetness loss. This paper focuses on thermal wetness loss of the last stage in a six-stage low pressure turbine. The temperature of superheating at the inlet of the last stage varies within a range of several tens of degrees under the condition that enthalpy at the stage outlet is below the saturation point. Radial distributions of pressure and temperature at the stage inlet and outlet are measured with rake probes and traverse probes, whereas the stage outlet enthalpy is identified by using the generator output and turbine mass flow rate. Higher stage efficiency is obtained the superheating inlet temperature becomes higher in this experimental condition. A three-dimensional CFD taking into consideration a non-equilibrium/equilibrium condensation model is carried out to understand the experimental results. A non-equilibrium condensation model can take into account the thermal wetness loss associated with supercooling and non-equilibrium condensation. The amount of thermal wetness loss is evaluated by comparing the results of non-equilibrium and equilibrium condensation models. The results show that the degree of superheating at the inlet of the stage affects the supercooling temperature distribution in the last stage flow path, resulting in lower thermal wetness loss at a higher inlet superheat condition.Copyright