Unsteady Force on Multi-Stage and Multi-Passage Turbine Long Blade Rows Induced by Wet-Steam Flows

Abstract

At the 2015 ASME Turbo Expo in Montreal, we presented a paper on unsteady three-dimensional wet-steam flow simulations for the last three stages of a low-pressure real steam turbine. We then focused on the investigation of unsteady wetness in the three-stage blade passages, which was conducted by assuming the same number of blades in the previous study and the real blade number. The obtained results showed that wetness is definitively influenced by the blade number difference between the stator and the rotor. This paper presents a numerical investigation of unsteady pressure forces on the multi-stage blade rows caused by stator-rotor interactions, which include unsteady wakes, vortices, shocks, and wetness. In particular, we investigate the effect of blade number variation on the pressure forces. Our results indicate that unsteady pressure forces are significantly influenced by shocks from the upstream stator trailing edges transferred to the adjacent rotor blade noses. We finally found that the unsteady pressure forces on the rotor blades are strongly influenced by shocks from upstream stator trailing edges near the hub region and the forces result in a time-dependent torque difference between neighboring two rotor blades.

Numerical analysis of condensation effects on final-stage rotor-blade rows in low-pressure steam turbine

“…The condensation coefficient and the empirical parameter α in the Young's modification were specified to 1.0 and 5.0 in this study. The wetness values that we obtained varied slightly from those obtained in our previous study (Miyazawa et al, 2016). stage).…”

“…We generated 91 × 91 × 181 grid points for each blade passage, 61 × 91 × 181 grid points for each inlet and outlet region, and 31 × 91 × 181 grid points for each intermediate region in the axial, tangential, and radial directions. The grid topology was the same as that used in our previous studies (Miyake et al, 2015) (Miyazawa et al, 2016) and the grid points employed in this study was the same with those in the study (Miyazawa et al, 2016) . Table 2 shows the computational flow conditions.…”

“…The actual three-stage low-pressure steam turbine developed by Mitsubishi Heavy Industries (MHI) (Watanabe et al, 2003) is modeled for this study as in our previous studies (Miyake et al, 2015) (Miyazawa et al, 2016). The final long-rotor blade is 36-in long and rotates at 3,600 rpm.…”

“…In previous work (Miyake et al, 2015) (Miyazawa et al, 2016), we investigated the effects of unsteady pressure forces due to a wet-steam flow on multi-stage long-blade rows by assuming an actual number of blades. Our study indicated that strong shocks are generated by the trailing edges of the final-stage stator blades near the hub, and that those shockwaves come into contact with the adjacent rotor blades.…”

Mathematical modeling and computation of high-pressure steam condensation in a transonic flow

“…Following such early studies, numerical studies for wet-steam flows have been further reported and 2-D and 3-D wet-steam flow simulations have become possible due to recent improvements in computing power. Our group simulated unsteady wet-steam flows through multi-stage stator and rotor blade rows accounting for nonequilibrium condensation (Miyazawa et al, 2016). As part of the trend of wet-steam flow studies, a Cambridge University group promoted a workshop for wet-steam nozzle flow simulation named the International Wet Steam Modeling Project (IWSMP) to revalidate the condensation models currently used in wet-steam flow simulations.…”