Experimental validation of condensing flow theory for a stationary cascade of steam turbine blades

Abstract
The paper describes a detailed experimental and theoretical study of non-equilibrium condensing steam flow in a stationary cascade of turbine blades operating transonically. Instrumentation was installed for obtaining colour schlieren photographs of the shock wave structure, the blade surface static pressure distribution, the pitchwise variation of the mean droplet radius downstream of the cascade and the stagnation pressure loss across the cascade. Only one blade profile was tested but a comprehensive set of measurements was acquired covering a wide range of inlet steam conditions and exit Mach numbers. By careful interpretation of the data, it was possible, for the first time, to infer the thermodynamic loss due to irreversible condensation directly from experimental measurements. An elaborate comparison of the experimental data with condensing flow theory was also undertaken using a two-dimensional inviscid time-marching calculation scheme, simulating both steady and unsteady flows. Excellent agreement was obtained throughout and it can be stated with some confidence that the theory and calculation procedures used reproduce accurately all the main features of steady transonic condensing flow in stationary cascades.