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.
The vapour–liquid two-phase flow in the low-pressure cylinder of a 1000 MW nuclear steam turbine has been investigated. Firstly, a comparative study of the flows with equilibrium and non-equilibrium condensation is described. The vapour extraction and moisture removal processes are included in the calculations to simulate the actual operating conditions in the low-pressure cylinder. Differences in the thermodynamic expansion lines, and in the distributions of wetness and degree of reaction, for equilibrium and non-equilibrium flow calculations are discussed. Secondly, the deposition of the fog and coarse water droplets in the last stage stator is investigated computationally. An empirical approach, together with the predictions of the non-equilibrium flow calculation, is used to redistribute the spanwise profile of the wetness at inlet to the last stage of the turbine. The movement and deposition of the water droplets are tracked in a Lagrangian frame. The variations of the fog and coarse water deposition rates are obtained in both the spanwise and axial-chordwise directions.
The article "Omega-3 polyunsaturated fatty acids alleviate adenine-induced chronic renal failure via regulating ROS production and TGF-β/SMAD pathway", by J. Xu, Z.-P. Feng, H.-Y. Peng, P. Fu, published in Eur Rev Med Pharmacol Sci 2018; 22 (15): 5024-5032-DOI: 10.26355/eurrev_201808_15645-PMID: 30070341, has been retracted by the authors due to input errors which occurred in the experimental data. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/15645.
The present study aimed to probe into the mechanism of p38MAPK in the failure of autogenous arteriovenous fistula (AVF) caused by stenosis. A total of 24 patients with maintenance hemodialysis and the autologous AVF as the hemodialysis route were enrolled in the present study. In the experimental group, the internal fistula operation mode was the end-to-side anastomosis, and patients were those who needed autogenous AVF repair due to the venous hyperplasia and stenosis of the internal fistula anastomosis (n = 12). The control group was composed of patients who underwent autogenous AVF surgery for the first time (n = 12). The discarded venous tissues in each group were used for immunohistochemistry and Western blot detection of ASK1, P38, and ATF-2. SPSS 17.0 and GraphPad Prism 5 software were adopted for data analysis. The measurement data were expressed as means ± standard deviations ( x ± s), and P < 0.05 was considered statistically significant. The results of immunohistochemistry staining: the expressions of ASK1, P38, and ATF-2 in the experimental group were significantly higher than those in the control group, and the differences were statistically significant (P < 0.01). The results of Western blot: the expression of P38 in the experimental group was significantly higher than that in the control group, and the difference was statistically significant (P < 0.05). There was no significant difference in the expression of ASK1 and ATF-2 between the experimental group and the control group (P > 0.05). In stenotic AVF, the expressions of ASK1, P38, and ATF-2 all significantly increased, indicating that the p38MAPK signaling pathway might be involved in the formation of venous stenosis in AVF, and the p38MAPK signaling pathway might become a therapeutic target in preventing and treating the vascular stenosis in the fistula.
The iron oxide scales exfoliated from the inner wall of a boiler tube and a main steam pipe is known to cause solid-particle erosion on the control-stage nozzle. A combined experimental and numerical investigation was conducted to explore the optimization method of end-wall contouring for reducing the nozzle's erosion damage most effectively. The results indicate that increasing the end-wall contraction ratio and (or) decreasing the distance between the starting point of end-wall contouring and the trailing edge can significantly reduce the erosion-induced weight-loss of the nozzle, and can slightly improve the nozzle efficiency, irrespective of the variation in the particles size distribution and the aerodynamic parameters of a steam turbine. A main reason of erosion reduction is that the movement of loading towards the rear of the nozzle cascade caused by these contoured end walls has reduced the incident velocity of particles. In this study, the weight-loss of the nozzle was reduced by 40—50 per cent, and the nozzle efficiency was improved by 0.4—0.5 per cent by improving the end-wall contouring of the nozzle according to the methods mentioned above.
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