Development and initial application of a blade design methodology for overspeed power-regulated tidal turbines

The range and variability of flow velocities in which horizontal axis tidal stream turbines operate introduces the requirement for a power regulation method in the system. Overspeed power regulation (OSPR) has the potential to improve the structural robustness and decrease the complexity associated with active pitch power regulation methods, while removing the difficulties of operating in stalled flow. This paper presents the development of a methodology for the design of blades to be used in such systems. The method requires a site depth, maximum flow velocity and rated power or flow speed as input parameters. The pitch setting, twist and chord distribution were set as input parameters, variable through the use of alteration functions. Rotor performance has been broken down into OSPR performance metrics which consider coefficients of power and thrust, and cavitation inception. Three visual-numerical tools have been developed: the OSPR performance metrics were used in conjunction with a one-at-a-time sensitivity analysis approach to develop a design space; cavitation inception analyses gave plots of converging cavitation and pressure terms for each blade section; the local angle of attack and torque distribution across the blade designs were plotted at key turbine operation states. Alterations to pitch setting and twist distribution are shown to have most impact upon the design requirement of increased gradient in the rotor speed-efficiency relationship in the overspeed region; coupled with such alterations, targeted changes to the chord distribution have been shown to increase the maximum efficiency. The prevention of cavitation has been highlighted as a driver for speed-limiting design alterations. While facilitating blade design, the methodology also produces experiential knowledge which can be stored, and shared in graphical format

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

A blade design methodology for overspeed power regulation of horizontal axis tidal turbines

Employed in tidal turbines, overspeed power regulation (OSPR) can improve the structural robustness and decrease the complexity associated with active pitch methods, while removing the diffculties of operating in stalled flow. This may be a method by which the cost of tidal energy can be brought down. The aim of this research was to investigate the OSPR method, increase understanding of associated benefits and constraints, and develop a methodology for the design of suitable blades. It is identified that: the challenges to OSPR are higher rotational velocities, leading to increased voltage levels, an increased chance of cavitation on the rotor, and potentially detrimental thrust forces; these challenges may be best overcome with blade design alterations limiting the maximum rotational velocity.;The blade design methodology uses a design platform to set boundary conditions, an existing blade design as the base case, and a blade element momentum theory (BEMT) tool as the modelling method. Blade root pitch setting, twist and chord length distribution are the variable parameters investigated. A set of ospr performance metrics and a design space sensitivity analysis, with whole-blade cavitation analyses and diagnostic plots of torque and angle of attack, are used to ascertain how function-based and then precise blade design alterations affect rotor performance.;Tow tank tests defined base case rotor performance and verified the BEMT tool.Tests on the new blades allowed comparison to the base case test performance and to the BEMT prediction. Simulations showed that the new blade design regulated power without cavitation inception, without an increase in the thrust forces and with only a 3.6% drop in efficiency - as per the set boundary conditions and design requirements.The blade design methodology can be used to overcome challenges associated with overspeed and produce blades which give significant performance improvements for use in OSPR.Employed in tidal turbines, overspeed power regulation (OSPR) can improve the structural robustness and decrease the complexity associated with active pitch methods, while removing the diffculties of operating in stalled flow. This may be a method by which the cost of tidal energy can be brought down. The aim of this research was to investigate the OSPR method, increase understanding of associated benefits and constraints, and develop a methodology for the design of suitable blades. It is identified that: the challenges to OSPR are higher rotational velocities, leading to increased voltage levels, an increased chance of cavitation on the rotor, and potentially detrimental thrust forces; these challenges may be best overcome with blade design alterations limiting the maximum rotational velocity.;The blade design methodology uses a design platform to set boundary conditions, an existing blade design as the base case, and a blade element momentum theory (BEMT) tool as the modelling method. Blade root pitch setting, twist and chord length distribution are the variable parameters investigated. A set of ospr performance metrics and a design space sensitivity analysis, with whole-blade cavitation analyses and diagnostic plots of torque and angle of attack, are used to ascertain how function-based and then precise blade design alterations affect rotor performance.;Tow tank tests defined base case rotor performance and verified the BEMT tool.Tests on the new blades allowed comparison to the base case test performance and to the BEMT prediction. Simulations showed that the new blade design regulated power without cavitation inception, without an increase in the thrust forces and with only a 3.6% drop in efficiency - as per the set boundary conditions and design requirements.The blade design methodology can be used to overcome challenges associated with overspeed and produce blades which give significant performance improvements for use in OSPR

Effect of Antiplatelet Therapy on Survival and Organ Support–Free Days in Critically Ill Patients With COVID-19

International audienc