Session: 21-02: Wet Steam

Paper Number: 151602

Wet-Steam Flow Simulation With Coarse Water Droplets Through a Turbine Cascade Based on Eulerian-Eulerian Method 

Wetness loss is the primary loss in low-pressure steam turbines. The loss comprises thermodynamic and mechanical losses in wet-steam flows through the stator and rotor blade rows of steam turbines. Thermodynamic losses are associated with supercooling and the release of latent heat via water droplet formation. Mechanical losses are associated with velocity slip between the vapor and coarse water droplets. An empirical correlation model known as Baumann’s rule is often used to predict steam turbine efficiency with respect to wetness loss. Accurate prediction of wetness loss is crucial in the development of efficient and reliable steam turbines. Over the past few decades, thermodynamic losses in nozzles, cascades, and steam turbines have been numerically and experimentally investigated in wet-steam flows, considering nonequilibrium condensation and the release of latent heat. Wet-steam flows containing coarse water droplets larger than 1 µm cannot be assumed to be a uniform fluid flow owing to the velocity slip of vapor flow and the motion of water droplets. Few studies exist on numerical methods for determining mechanical losses in steam turbine flows. We proposed an Eulerian-Eulerian model to simulate the motion of coarse water droplets in compressible two-phase flows to simulate moist air flows (GT2022- 81246). However, the classification of the thermodynamic and mechanical losses remains unclear.

In this study, we simulated a wet-steam flow through a turbine cascade considering the velocity slip between the vapor and coarse water droplets using the Eulerian-Eulerian model developed by our research group. The conservation equations of mass, momentum, and number density of coarse water droplets were coupled with the compressible Navier–Stokes equations for vapor flows. The drag force caused by velocity slip resulted in a biased distribution of coarse water droplets in the cascade. The capture loss by water droplet impingement depended on the inlet droplet size owing to the interaction of vapor flow and the motion of water droplets. The distribution of the inlet water droplets was approximated using the Nukiyama–Tanazawa function, and the thermodynamic loss due to the condensation resulting in the droplet growth was investigated in the cascade flow. The acceleration loss due to droplet detachment from the trailing edge of the cascade affects the efficiency of the turbine cascade flow. Furthermore, the classification of condensation, capturing, and acceleration losses is discussed in this paper.

Presenting Author: Takashi Furusawa Tohoku University

Presenting Author Biography: Takashi FURUSAWA is an Associate professor in Dept. of Computer and Mathematical Sciences, Tohoku University, Japan. He received his Ph.D. from Tohoku University in 2012. His research interests are in the numerical method and numerical modeling for condensation models and supercritical fluid flows.

Authors:

Takashi Furusawa Tohoku University
Kazushi Morikita Tohoku University
Hironori Miyazawa Tohoku University
Satoru Yamamoto Tohoku University
Yasuhiro Sasao Mitsubishi Heavy Industries, Ltd.
Satoshi Miyake Mitsubishi Heavy Industries, Ltd.
Soichiro Tabata Mitsubishi Heavy Industries, Ltd.