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Effects of load variation on a Kaplan turbine runner
K. Amiri,B. Mulu,M.J. Cervantes,M. Raisee 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.2
Introduction of intermittent electricity production systems like wind and solar power to electricity market together with the deregulation of electricity markets resulted in numerous start/stops, load variations and off-design operation of water turbines. Hydraulic turbines suffer from the varying loads exerted on their stationary and rotating parts during load variations since they are not designed for such operating conditions. Investigations on part load operation of single regulated turbines, i.e., Francis and propeller, proved the formation of a rotating vortex rope (RVR) in the draft tube. The RVR induces pressure pulsations in the axial and rotating directions called plunging and rotating modes, respectively. This results in oscillating forces with two different frequencies on the runner blades, bearings and other rotating parts of the turbine. This study investigates the effect of transient operations on the pressure fluctuations exerted on the runner and mechanism of the RVR formation/mitigation. Draft tube and runner blades of the Porjus U9 model, a Kaplan turbine, were equipped with pressure sensors for this purpose. The model was run in off-cam mode during different load variations. The results showed that the transients between the best efficiency point and the high load occurs in a smooth way. However, during transitions to the part load a RVR forms in the draft tube which induces high level of fluctuations with two frequencies on the runner; plunging and rotating mode. Formation of the RVR during the load rejections coincides with sudden pressure change on the runner while its mitigation occurs in a smooth way.
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최선규,정명호,안영근,조정관,강정채,채성철,허승호,홍택종,김영조,성인환,채제건,류재영,채인호,조명찬,배장호,나승운,김종진,최동훈,장양수,윤정한,정욱성,승기배,박승정,Other Other KAMIRI Investigators 대한심장학회 2010 Korean Circulation Journal Vol.40 No.11
coronary syndrome has been demonstrated in many studies. However, NT-proBNP levels are influenced by various factors such as sex, age, renal function, heart failure severity, and obesity. NT-proBNP concentrations tend to decrease with higher body mass index (BMI). The aim of this study was to examine the influence of obesity on NT-proBNP as a predictive prognostic factor in acute myocardial infarction (AMI) patients. Subjects and Methods: Using data from the Korea Acute Myocardial Infarction Registry (January 2005 to September 2008), 2,736 AMI patients were included in this study. These patients were divided into men (n=1,972, 70%) and women (n=764, 30%), and were grouped according to their BMIs. Major adverse cardiac events (MACE) during 1 year clinical follow-up were evaluated. Results: NT-proBNP was significantly higher in lower BMI (p<0.001). Mean NT-proBNP levels of each obesity group were 2,393±4,022 pg/mL in the lean group (n=875), 1,506±3,074 pg/mL in the overweight group (n=724) and 1,100±1,137 pg/mL in the obese group (n=1,137) (p<0.01). NT-proBNP was an independent prognostic factor of AMI in obese patients by multivariative analysis of independent risk factors of MACE (p=0.01). Conclusion: NT-proBNP is lower in obese AMI patients than in non-obese AMI patients, but NT-proBNP is still of independent prognostic value in obese AMI patients.
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