Numerical Simulation of Different Splitter Angles of a Pelton Bucket to Increase the Power Generated by The Pelton Wheel

The efficiency of a Pelton turbine depends mostly on its geometry. A design with suitable dimensions, offers higher generation of energy. However, some of these dimensions are underappreciated because of their low influence. Therefore, this study presents through a recompilation of data, the simulation was developed in ANSYS 19®. The importance of taking in count each parameter of the geometry of a Pelton bucket, analysing in this work the influence of the splitter angle in the force generated by a bucket. Nine geometries of a Pelton bucket are developed with splitter angles between 17 and 25°. The most suitable angle is determined, finding through the simulations that the geometry of 23° generates more force than other geometries. Simplifying the geometry and the mesh can generate faster results, however, exaggerating in the meshing process will affect the reliability of the obtained results

Numerical Simulation of Different Splitter Angles of a Pelton Bucket to Increase the Power Generated by The Pelton Wheel

The efficiency of a Pelton turbine depends mostly on its geometry. A design with suitable dimensions, offers higher generation of energy. However, some of these dimensions are underappreciated because of their low influence. Therefore, this study presents through a recompilation of data, the simulation was developed in ANSYS 19®. The importance of taking in count each parameter of the geometry of a Pelton bucket, analysing in this work the influence of the splitter angle in the force generated by a bucket. Nine geometries of a Pelton bucket are developed with splitter angles between 17 and 25°. The most suitable angle is determined, finding through the simulations that the geometry of 23° generates more force than other geometries. Simplifying the geometry and the mesh can generate faster results, however, exaggerating in the meshing process will affect the reliability of the obtained results

Influence of the solidity and the number of blades in a vertical axis turbine type h-darrieus

El siguiente estudio propone el análisis de una turbina hidrocinética de eje vertical tipo H-Darrieus que puede ser implementada en las regiones no interconectas al sistema eléctrico colombiano en especial las zonas costeras.  El objetivo del estudio es analizar el número de álabes en la eficiencia de la turbina hidrocinética, para esto se proponen 27 tipos de rotores, en los cuales, se varia el número de álabes desde 2 hasta 10 para 3 valores de solidez diferentes. Concluyendo que a partir de 3 álabes se reducen los torques negativos producidos, incrementando la capacidad de autoarranque, sin embargo, cuando el número de álabes aumenta el torque total generado por la turbina disminuye lo que conlleva a una disminución en la eficiencia.The following study proposes the analysis of a Darrieus H-type vertical axis hydrokinetic turbine that can be implemented in regions not interconnected to the Colombian electricity system, especially coastal areas. The objective of the study is to analyze the number of blades in the efficiency of the hydrokinetic turbine, for this, 27 types of rotors are proposed, in which, the number of blades is varied from 2 to 10 for 3 different solidity values. Concluding that from 3 blades the negative torques produced are reduced, increasing the capacity of auto-start, however, when the number of blades increases the total torque generated by the turbine decreases which leads to a decrease in efficiency.The following study proposes the analysis of a Darrieus H-type vertical axis hydrokinetic turbine that can be implemented in regions not interconnected to the Colombian electricity system, especially coastal areas. The objective of the study is to analyze the number of blades in the efficiency of the hydrokinetic turbine, for this, 27 types of rotors are proposed, in which, the number of blades is varied from 2 to 10 for 3 different solidity values. Concluding that from 3 blades the negative torques produced are reduced, increasing the capacity of auto-start, however, when the number of blades increases the total torque generated by the turbine decreases which leads to a decrease in efficiency.El siguiente estudio propone el análisis de una turbina hidrocinética de eje vertical tipo H-Darrieus que puede ser implementada en las regiones no interconectas al sistema eléctrico colombiano en especial las zonas costeras.  El objetivo del estudio es analizar el número de álabes en la eficiencia de la turbina hidrocinética, para esto se proponen 27 tipos de rotores, en los cuales, se varía el número de álabes desde 2 hasta 10 para 3 valores de solidez diferentes. Concluyendo que a partir de 3 álabes se reducen los torques negativos producidos, incrementando la capacidad de autoarranque, sin embargo, cuando el número de álabes aumenta el torque total generado por la turbina disminuye lo que conlleva a una disminución en la eficiencia

Simulation Analysis of a Coanda-Effect Ejector Using CFD

 This work presents the optimization of a Coandă-effect air ejector used widely in industry through computational fluid dynamics. This optimization was developed in ANSYS FLUENT® software V16.2. Two 3D models of the commercial ejector (ZH30-X185 by SMC®) were carried out for the simulation procedure, varying the size of the separation of 0.3 and 0.8 mm in the walls of the nozzle, which communicates the high-pressure region and the mixture zone. In the experiment designed, the feed pressure applied to the ejector take values of 0.20, 0.25, and 0.30 MPa and the dynamic fluid behavior was analyzed for the two geometries mentioned. For the numerical and fluid behavior analysis, a mesh study was conducted to guarantee the independence of the results with the number of discretization cells. The k-ε RNG turbulence model was implemented with treatment of walls, solving in stationary manner [C1] the [C2] phenomenon occurring within it, given that the temporal evolution is quite rapid. Increased secondary mass flow (extracted) relations with respect to the primary mass flow (injected) were found when the separation communicating the high-pressure zone and the mixture zone diminished. With increased feed pressure of the primary flow, a decrease was found in the secondary mass flow relation with respect to the primary mass flow. [C1]Estacionaria [C2]o

Construction methods comparison of stress concentrators curves for different geometries of machine elements.

The aim of this study is to verify that the analysis of the phenomenon of stress concentration with simulation methods provides results that are consistent with the experimental, corroborating the ANSYS ® software is a powerful tool that minimizes costs and time in building graphics stress concentrators. This’s accomplished by showing that the concentration factor curves of experimental efforts available in the scientific literature can be made through simulations achieving results with very low error. For this reason, geometries were select for the study with different aspect ratios. Which were develop in the DesingModeler® ANSYS Workbench® module. Then the meshing of geometries was performing in Mechanical®, and underwent three load’s types: axial force, bending moment and torsional moment, which were set in the StaticStructural® module. Then it was get the maximum effort and it was calculated the nominal effort, relate calculating the numerical concentration factor to build concentration factor charts against the geometrical parameter that was being modified during the virtual experimentation; at the end, they were compared with the experimental curves consulted. With the results obtained it was concluded that it is possible to construct curves of stress concentration factor through simulations with the same confidence that are obtained with conventional experimental methods, but at a lower cost

Effects of pre-operative isolation on postoperative pulmonary complications after elective surgery: an international prospective cohort study an international prospective cohort study

We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care. We aimed to determine the impact of pre-operative isolation on postoperative pulmonary complications after elective surgery during the global SARS-CoV-2 pandemic. We performed an international prospective cohort study including patients undergoing elective surgery in October 2020. Isolation was defined as the period before surgery during which patients did not leave their house or receive visitors from outside their household. The primary outcome was postoperative pulmonary complications, adjusted in multivariable models for measured confounders. Pre-defined sub-group analyses were performed for the primary outcome. A total of 96,454 patients from 114 countries were included and overall, 26,948 (27.9%) patients isolated before surgery. Postoperative pulmonary complications were recorded in 1947 (2.0%) patients of which 227 (11.7%) were associated with SARS-CoV-2 infection. Patients who isolated pre-operatively were older, had more respiratory comorbidities and were more commonly from areas of high SARS-CoV-2 incidence and high-income countries. Although the overall rates of postoperative pulmonary complications were similar in those that isolated and those that did not (2.1% vs 2.0%, respectively), isolation was associated with higher rates of postoperative pulmonary complications after adjustment (adjusted OR 1.20, 95%CI 1.05–1.36, p = 0.005). Sensitivity analyses revealed no further differences when patients were categorised by: pre-operative testing; use of COVID-19-free pathways; or community SARS-CoV-2 prevalence. The rate of postoperative pulmonary complications increased with periods of isolation longer than 3 days, with an OR (95%CI) at 4–7 days or ≥ 8 days of 1.25 (1.04–1.48), p = 0.015 and 1.31 (1.11–1.55), p = 0.001, respectively. Isolation before elective surgery might be associated with a small but clinically important increased risk of postoperative pulmonary complications. Longer periods of isolation showed no reduction in the risk of postoperative pulmonary complications. These findings have significant implications for global provision of elective surgical care

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)