Performance deterioration of the governing stage nozzle caused by solid particle erosion in the steam turbine

Abstract

In the steam turbine, solid particle erosion on a nozzle cascade is known to damage the profile and surface smoothness of the cascade, which increases the flow loss of steam. The present study aims to make clear the relations between nozzle loss and surface degradation, aerodynamic parameters, as well as the shape, location, and size of the erosion notch. A series of numerical simulations were conducted to model the aerodynamic performance of various existing eroded nozzles. The results indicate that the nozzle loss caused by the surface degradation shows an approximate linear decrease with an increase in notch depth. The nozzle loss caused by the erosion notch increases with either a decrease in the exit Mach number or an increase of the notch area. For the same erosion-induced weight loss of the nozzle, the asymmetric notch and local notch cause more nozzle loss than the symmetric notch and quasi-global notch. This means that the performance deterioration can be reduced to a minimum value if the erosion is uniform along the span-wise of the nozzle. In addition, a combined experimental and numerical investigation is conducted to explore the erosion damage process of the nozzle. The result suggests that the eroded nozzle should be replaced by a new nozzle before the notch begins to propagate.

Effects of leakage vortex on aerodynamic performance and loss mechanism of steam turbine

“…The result of the SST k –ω turbulence model is the closest to the experimental results. 21 The maximum deviation is less than 2%. Therefore, the SST k –ω model is adopted.…”

Experimental Evaluation of Service-Exposed Nozzle Guide Vane Damage in a Rolls Royce A-250 Gas Turbine

“…Islam [4] observed that for a blade with a scalloped TE, the lack of TE material reduced the TE blockage, leading to a decrease in mixed-out boundary layer losses. For similar TE damage, Wang et al [3] found a com parable trend. Islam [4] hypothesized that this increased the base pressure, reducing the base pressure's contribution to loss, as indi cated by Denton [5], Sjolander et al [6] performed an extended study on two scalloped trailing edge blades.…”

“…overturning towards the PS b. undertuming towards the SS Studies by Wang et al [3], Islam [4], DeCecco [11], and Sjolander et al [6] conducted research concerning the aerody namic impact of material removal from the trailing edge of a tur bine vane or blade. The general consensus of these studies showed that scalloped trailing edges or trailing edges with significant cracking will cause a pitchwise shift in the total pressure deficit towards the suction surface.…”

“…Wang et al [3] numerically simulated the TE damage caused by solid particle erosion on 24 models. They found a linear increase in the enthalpy loss coefficient with an increase in material removal from the trailing edge.…”

A numerical study of flow pattern in a deteriorated gas turbine under real operating condition

“…Although these approaches make possible to understand influences of gas turbine deterioration on plant performance quantitatively, mechanisms of the performance degradation cannot be clarified. On the other hand, computational fluid dynamics (CFD) simulations were used to understand mechanisms of loss increase in deteriorated gas turbines (Bouchard, D. et al, 2014;Edwards, R. et al, 2012;Wang, S.-S. et al, 2009). The authors also carried out CFD simulations for deteriorated gas turbine and steam turbine using real blade geometries measured at a power plant during a maintenance work (Yonezawa, K., et al, 2016(Yonezawa, K., et al, , 2017(Yonezawa, K., et al, , 2018(Yonezawa, K., et al, , 2019.…”