Search

The performance and stability of turbine are easily affected by the complex turbulence such as clearance vortex and leakage flow. For the purpose of analyzing the influence of seal clearance on the energy features and interior flow characteristics of Francis turbine, with referencing N-S equation and SST turbulence model, the three-dimensional steady flow in the full flow passage of the Francis turbine model under five schemes of clearance were calculated. Four flow rates were chosen as: 0.6 Qd, 0.8 Qd, Qd and 1.2 Qd. Five schemes of clearance size were selected of 0.4, 0.6, 0.8, 1.0 and 1.3 mm. By comparing the effects of different clearance schemes on the efficiency and volume loss of Francis turbine, the relationship between clearance and turbine performance was analyzed based on the characteristics of internal fluid field, and the calculation results showed that by increasing the size of clearance, the turbine efficiency could be reduced, and the leakage of the turbine indicated an upward trend. When the turbine operated at a small flow rate of 0.6 Qd, the clearance appeared the most obvious influence on the energy features of the turbine. With the increase of clearance, the leakage ratio increased from 0.18% to 0.54%, and the efficiency decreased by 4.1 percentage points. At the flow rate of 1.2 Qd, the clearance presented the least influence on the energy features of the turbine. The leakage ratio increased from 0.07% to 0.27%, and the efficiency decreased by 1.38 percentage points when the clearance was increased. If the turbine was operated at small flow rates of 0.6 Qd and 0.8 Qd, the clearance increased, and the internal fluid fields inside both the clearance and the draft tube deteriorated slightly. The average velocity in the clearance increased gradually, and the eddy current intensity in the inlet and outlet pressure chambers of the clearance increased little by little, the volume of vortex rope in the center of draft tube inlet was increased simultaneously. If the unit was operated at a large flow rate of 1.2 Qd, with the clearance increased from 0.4 mm to 1.3 mm, the characteristics of fluid field inside clearance and the pressure distribution on the suction surface of the runner blades, also the fluid field inside the draft tube were all improved. The area of negative pressure zone on suction surface of runner blades decreased, and the volume of the cavity vortex rope at the inlet center of the draft tube decreased, the streamline inside the draft tube also tended to be smooth. This study could provide an effective reference for the design of seal clearance of Francis turbine. [ABSTRACT FROM AUTHOR]

BACKGROUND: The vascular endothelial growth factor (VEGF) plays an important role in the development and formation of blood vessels. Up to now, there are few reports about the treatment of postoperative complications of vascular anastomosis surgery by mcrosutures with VEGF in China. OBJECTIVE: To synthesiize microsutures with VEGF and to evaluate its effect in revascularization following small vessel anastomosis. METHODS: The method of emulsification-diffusion was use to produce biodegradable polymer polylactic acid/glycolic acid (PLGA) copolymer microparticles containing VEGF, and then, the microparticles were added into microsutures to prepare microsutures with VEGF. Ninety Sprague-Dawley rats were enrolled to make animal models of caudal artery anastomosis using microsutures with VEGF in experimental group and microsutures alone in control group. Complications and VEGF level in the peripheral blood were detected and hematoxylin-eosin staining at the anastomotic site was performed at 2, 12 hours, 1, 3, 7 days after anastomosis. RESULTS AND CONCLUSION: (1) Postoperative complications: The postoperative incidence of skin necrosis was significantly lower in the experimental group than the control group (P < 0.05). (2) VEGF level: Compared with the control group, the peripheral blood VEGF level was significantly higher in the experimental group at each time point after operation (P < 0.05). (3) Hematoxylin-eosin staining: In the experimental group, proliferated endothelial cells were seen near the anastomotic site at 1 day after anastomosis; there were a large number of proliferated endothelial cells and subcutaneous tissues covering the sutures completely at 3 days after anastomosis; and endothelial cells and internal elastic lamina were completely repaired, smooth muscle cells proliferated further, and the outer membrane returned to normal at 1 week after anastomosis. In the control group, cell degeneration and necrosis were seen near the anastomotic suture, and only adventitial cells infiltrated and exhibited a traumatic proliferative response at 1 day after anastomosis; neonatal endothelial cells appeared in the exfoliated area of the endothelial cells, grew and migrated, and there was a few endothelial cells covering the anastomotic site at 3 days after anastomosis; and newborn endothelial cells got over the anastomotic crack and covered the suture. To conclude, microsutures with sustained-release VEGF microparticles can promote endothelial cell regeneration in rats at the anastomotic site. [ABSTRACT FROM AUTHOR]

Objective To explore the clinical effect of fluticasone propionate nasal spray combined with subcutaneous immunotherapy and the effect on inflammatory cytokines in allergic rhinitis patients. Methods 120 patients diagnosed with allergic rhinitis in April 2018 in October 2019 were selected as the research subjects. They were randomly divided into an experimental group (n = 60) and control group (n = 60). The control group was given subcutaneous specific immune therapy, and the experimental group was given the fluticasone propionate nasal spray with subcutaneous immunization therapy. We observed the clinical effects and compared the clinical symptom scores, serum interleukin 4 (IL-4), interleukin 12 (IL-12), immunoglobulin E (IgE), adverse reactions occurrence, scores by nose conjunctivitis quality of life questionnaire (RQLQ) between the 2 groups of patients. Results The total effective rate was 96.67% in the experimental group and 85.00% in the control group (P < 0.05). Before treatment, the differences in clinical symptom scores between the two groups were not statistically significant (P > 0.05). After treatment, the clinical symptom scores of the two groups were improved,with significant difference (P < 0.05). Among them, the clinical symptom score of the experimental group was significantly lower than that of the control group (P < 0.05). Before treatment, there were no significant differences in il-4,il-12 and IgE levels between the two groups (P > 0.05). After treatment, the levels of il-4,il-12 and IgE in the two groups were significantly improved (P < 0.05). The levels of il-4 and IgE in the experimental group were significantly lower than those in the control group, while the levels of il-12 in the experimental group were significantly higher than those in the control group (P < 0.05). The incidence of adverse reactions was 6.67% in the experimental group and 16.67% in the control group (P < 0.05). Before treatment, there was no significant difference in RQLQ scores between the two groups (P > 0.05). After treatment, RQLQ scores in the two groups were significantly higher than those in the control group (P < 0.05), and those in the experimental group were significantly higher than those in the control group (P < 0.05). Conclusion Fluticasone propionate nasal spray combined with subcutaneous immunotherapy has a significant clinical effect in the treatment of allergic rhinitis. It can effectively alleviate the clinical symptoms of patients,reduce the levels of il-4 and IgE, improve the level of il-12, control the degree of inflammation, shorten the course of disease of patients, improve the quality of life of patients, and is worthy of promotion [ABSTRACT FROM AUTHOR]