Effects of location, shape and width of a suction slot on the water removal performance of a hollow stator blade

Abstract

Experimental tests were implemented on a wet steam test rig to investigate the effects of location, shape and width of a suction slot on the water removal performance of a hollow stator blade. A straight cascade with varying outlet Mach numbers and suction pressure differences was used for the tests. The inlet flow conditions were consistent with the real running condition before the last stage stator of a 1000-MW nuclear steam turbine. Results show that the flow Mach number and suction pressure difference affect the amount of water removed. A moderate increase in the suction pressure difference triggers water film vaporisation, which decreases water removal performance. The amount of water removed continuously increases, as the slot location moves from 0.24 to 0.42 times the axial chord in the suction surface. Compared with the straight slot, the step-shaped slot cannot improve the water removal performance. On the contrary, the result is poor when the Mach number is above 0.7 because additional sharp corner leads to more serious water vaporisation. A suction slot with an arc-shaped inlet significantly improves the water removal performance by eliminating water film vaporisation under the test conditions. A 0.35-mm-width suction slot is apt to allow water film across, and a 2-mm-width suction slot cannot form an effective suction pressure difference along the slot height, both leading to poor water removal performance. Meanwhile, 0.7-and 1-mm-width suction slots promote good water removal performance, but the latter is less affected by water vaporisation.

Numerical and Experimental Study of Droplet-Film-Interaction for Low Pressure Steam Turbine Erosion Protection Applications

“…Air is modelled as ideal gas in this analysis. As the REFPROP data for surface tension is based on the assumption of a planar interface between liquid and gaseous phase, the calculated surface tension values are multiplied by a factor of 0.85 in case of the spherical liquid particles as suggested by Li et al (2010). Volume source smoothing and shell source smoothing are activated for the two-way coupling of continuous air phase and liquid particulate phase within the Lagrangian Multiphase solver.…”

“…Particularly the application of extraction / suction slots has been in focus of numerical and experimental investigations in the last decades. (Wang et al, 2009;Gribin et al, 2015;Li et al, 2018;Hoznedl et al, 2019) Passive measures however aim at increasing the erosion resistance of the blading by either applying better materials with increased hardness (Lee et al, 2003), flame/laser hardening of leading edges (Schuerhoff et al, 2015;Yao et al, 2010) or by shielding the affected areas with materials such as stellite. Also the application of coatings either for protection or for fog rejection purposes is investigated (Walsh et al, 1993;Buehlmann et al, 2018).…”

Numerical and experimental study of droplet-film-interaction for low pressure steam turbine erosion protection applications

“…Particularly the application of extraction / suction slots has been in focus of numerical and experimental investigations in the last decades. (Wang et al, 2009;Gribin et al, 2015;Li et al, 2018;Hoznedl et al, 2019).…”