Academic literature on the topic 'Percentage clearance'
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Journal articles on the topic "Percentage clearance"
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Ping-guo, Zou, Zhang Zhen-tao, and Li Gang. "Research on the Influence of Steam Turbine Seal Leakage." E3S Web of Conferences 248 (2021): 01014. http://dx.doi.org/10.1051/e3sconf/202124801014.
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CFD was employed to simulate the steam flow in 1.5-stage cascades with three different seal clearances. When the seal clearance is 0, there is no steam seal leakage, no obvious secondary flow in the cascade, and the stage efficiency reaches 88.27%. When the clearance of diaphragm seal and rotor tip seal is 1mm, the leakage of diaphragm seal strongly interferes with the flow in the cascade, which promotes the formation and development of the end-wall secondary flow near rotor hub, and the rotor tip leakage flow has little effect on next stage, and the stage efficiency drops by about 2 percentage points. When the seal clearance is 4mm, the end-wall secondary flow near rotor hub and next stator casing is strengthened significantly, and the attack angle loss increases, so the stage efficiency decreases by about 13 percentage points.
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Alwan, Salih K., Akbar Arabhosseini, Mohammed H. Kianmeher, and Ali M. Kermani. "The Effect of Clearance on the Performance of Machine Husking Rubber Rolls for Two." JOURNAL OF UNIVERSITY OF BABYLON for Pure and Applied Sciences 26, no. 3 (2018): 207–14. http://dx.doi.org/10.29196/jub.v26i3.595.
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The effect of clearance between cylinders of machine husking rubber rolls (type Yanmar rubber roll – ST 50) on rice husk quality and breakage percentage was evaluated for two cultivars of rice. Tarm Hashemi (TH) and Daillman (DM) and clearance between cylinders of machine husking rubber at three different levels of 0.4, 0.6 and 0.8mm.The experiment was done in factorial experiment under complete randomized design (CRD) with three replications the results indicate that the TH cultivar is significantly better than the D M in all studied traits. There was a negative relationship between increased clearance with head rice percentage and brown rice percentage in addition to the positive relationship between the increased percentage of cracked grain ,broken rice percentage and husking efficiency.
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LOOH, George Ashwehmbom, Fondzenyuy Cedric MANGEH (III), Xunwei WANG, and Xiushan WANG. "Performance Assessment of a Self-propelled Paddy Grain Thresher under Different Threshing Functional Parameters." Applied Engineering in Agriculture 36, no. 2 (2020): 141–49. http://dx.doi.org/10.13031/aea.13585.
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HighlightsThis research was aimed at assessing the performance of a self-propelled paddy grain thresher.Increasing cylinder speed increased the threshing percentage and percentage of broken grains of the machine.More broken grains were obtained at a lower concave clearance.The feed rate did not have much significance on the performance parameters that were evaluated. Abstract.This research was conducted to assess the performance of a self-propelled mini combine harvester, model number 4LZ-0.8 under different threshing functional parameters such as cylinder speed, concave clearance, and feed rate. An indoor experiment was conducted using the mini combine with an axial flow threshing cylinder and tangential feeding of material. These functional parameters were set at 5 levels each. The responses were obtained in terms of threshing percentage, percentage of unthreshed grains and percentage of broken grains. Response values were analyzed using the response surface tool (rstool) in MATLAB. Analysis of variance was done to determine the significant effects of the factor variations on the response values. MATLAB was used to present response surface graphs that were used to describe the variations of the responses as the factors changed from one level to the other. Results showed that with an increase in cylinder speed from 697 to 1202 rpm, the percentage of broken grains increased significantly from 0.0384% to 3.4052%, respectively. At cylinder speeds of 697 and 1202 rpm, the percentage of unthreshed grains increased from 0.1515% to 0.2162%, respectively. Furthermore, an increase in feed rate decreased the threshing percentage. The highest threshing percentage was obtained at an average concave clearance of 27 mm. Furthermore, it was realized that increasing the concave clearance from 18 to 35 mm, equally increased the percentage of unthreshed grains from 0.1478% to 0.3177%. The percentage of grain damage decreased from 3.2758% to 0.0268% with an increase in concave clearance from 18 to 35 mm, respectively. From the results obtained, it was tested and suggested that operating the threshing cylinder at a cylinder speed of 1100 rpm, concave clearance of 27 mm and feed rate of 0.9 kg s-1 offered the best machine performance. At these suggested values of the operating parameters, the threshing percentage was 99.9801%, the percentage of broken grains was 0.0134%, and the percentage of unthreshed grains was 0.0199%. Keywords: Assessment, Axial threshing unit, Cylinder speed, Concave clearance, Feed rate, Functional parameters, Threshing percentage.
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Krawiec, Donald R., Robert R. Badertscher, A. Robert Twardock, Stanley I. Rubin, and Howard B. Gelberg. "Evaluation of 99mTc-diethylenetriaminepentaacetic acid nuclear imaging for quantitative determination of the glomerular filtration rate of dogs." American Journal of Veterinary Research 47, no. 10 (1986): 2175–79. https://doi.org/10.2460/ajvr.1986.47.10.2175.
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SUMMARY Thu suitability of 99mTc-diethylenetriaminepentaacetic acid (99mTc-dtpa) as an agent to assess glomerular filtration rate (gfr) in dogs was evaluated. Glomerular filtration rates of 12 healthy dogs were determined on the basis of creatinine and/or inulin clearance. Glomerular filtration rates also were determined in 7 dogs after induction of acute renal failure by administration of amphotericin B. The healthy dogs and the amphotericin B-treated dogs were given 99mTc-dtpa (1 to 2 mCi) iv. The percentage of the 99mTc-dtpa dose in the kidneys (percentage dose) was determined, with background activity subtracted from total activity at 15-s intervals 0 to 6 minutes after 99mTc-dtpa infusion. Linear regression analyses (lra) were performed to determine whether the percentage dose at various time intervals after injection correlated with gfr calculated on the basis of creatinine and inulin clearance data. One to 3 minutes after 99mTc-dtpa administration appeared to be the best period for analysis of the data. The percentage dose of 99mTc-dtpa (corrected for kidney depth differences) was determined and lra against gfr were performed. The percentage dose correlated better with inulin clearance (r = 0.94) than with endogenous creatinine clearance (r = 0.83). Only inulin clearance correlations improved with kidney depth correction. The lra was used to derive an equation that could be used to calculate gfr on the basis of the percentage dose. The equation derived from inulin regression was: gfr (milliliter/minute/kilogram of body weight) = 0.194 (depth-corrected percentage dose) − 0.37; the equation derived from the creatinine regression was: gfr (milliliter/minute/kilogram) = 0.171 (depth-corrected percentage dose) − 0.15. Therefore, 99mTc-dtpa can be used as an agent for the rapid, noninvasive, and accurate determination of gfr in dogs.
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Adiele, DF. "Serious crime in Nigeria: an empirical analysis using time series data (between 2000-2010)." Global Journal of Mathematical Sciences 12, no. 1 (2015): 25–29. http://dx.doi.org/10.4314/gjmas.v12i1.14.
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This paper empirically examined the effect of the clearance rate, the unemployment rate, the percentage of females in employment and the percentage of the labour force with tertiary education on Serious Crime in Nigeria for the period 2000-2011. Time-series data from (NBS) National Bureau of statistics and Nigeria police annual reports 2011are used and tests for the existence of a long runcointegration relationship among serious crime, clearance rate and various socio economic indicators is carried out. The cointegration analysis provides strong evidence of the existence of a long-run model. With the normalized coefficients showing a negative effect of the clearance rate, percentage of females in the labourforce and the percentage of the labour force with tertiary education on serious crime, with the exception being the unemployment rate which is found to exert a positive effect.KEYWORDS: Crime, Cointegration, Unit Root, Time-Series.
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Baud, Frédéric J., Pascal Houzé, Jean-Herlé Raphalen, Pascal Philippe, and Lionel Lamhaut. "Vancomycin Sequestration in ST Filters: An In Vitro Study." Antibiotics 12, no. 3 (2023): 620. http://dx.doi.org/10.3390/antibiotics12030620.
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Background. Sequestration of vancomycin in ST® filters used in continuous renal therapy is a pending question. Direct vancomycin-ST® interaction was assessed using the in vitro NeckEpur® technology. Method. ST150® filter and Prismaflex dialyzer, Baxter-Gambro, were used. Two modes were assessed in duplicate: (i) continuous diafiltration (CDF): 4 L/h, (ii) continuous dialysis (CD): 2.5 L/h post-filtration. Results. The mean initial vancomycin concentration in the central compartment (CC) was 51.4 +/− 5.0 mg/L. The mean percentage eliminated from the CC over 6 h was 91 +/− 4%. The mean clearances from the CC by CDF and CD were 2.8 and 1.9 L/h, respectively. The mean clearances assessed using cumulative effluents were 4.4 and 2.2 L/h, respectively. The mean percentages of the initial dose eliminated in the effluents from the CC by CDF and CD were 114 and 108% with no detectable sequestration of vancomycin in both modes of elimination. Discussion. Significant sequestration adds a clearance to that provided by CDF and CD. The study provides multiple evidence from the CC, the filter, and the effluents of the lack of an increase in total clearance in comparison with the flow rates without significant sequestration in the ST® filter comparing cumulative effluents to the initial dose in the CC. Conclusions. There is no evidence ST® filters directly sequestrate vancomycin.
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Walsh, Donald, M., and Henry D. Royal. "Evaluation of a single injection of 99mTc-labeled diethylenetriaminepentaacetic acid for measuring glomerular filtration rate in horses." American Journal of Veterinary Research 53, no. 5 (1992): 776–80. http://dx.doi.org/10.2460/ajvr.1992.53.05.776.
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Summary Glomerular filtration rate (gfr) was measured in 12 clinically normal horses, using the standard inulin clearance method, and values were compared with values for 2 methods, using a single rapid iv injection of 99mTc-la-beled diethylenetriaminepentaacetic acid (99mTc-dtpa). The first 99mTc-dtpa method used a 2-compartment model to calculate gfr blood clearance of the tracer. The second method used sequential digital gamma camera images of the kidneys to determine fractional accumulation of the total dose of the tracer in the kidneys (percentage of injected dose, gamma camera) from 0 to 10 minutes after radionuclide administration. Linear correlation among the 3 methods was determined. Mean (± SD) gfr, using the inulin clearance method, was 154.67 ± 42.28 ml/min/100 kg of body weight. Mean gfr, using the 2-compartment blood clearance curve, was 146.92 ± 27.49 ml/min/100 kg. Mean gfr, using percentage of injected dose (gamma camera method) was 154.7 ± 22.00 ml/min/100 kg. The percentage of injected dose (gamma camera method) did not correlate significantly to the inulin clearance results. However, a significant (r = 0.666, P < 0.018) correlation was observed between the inulin method and the 99mTc-dtpa blood clearance method. Significant (P < 0.0001) difference also was observed in the split function of the equine kidneys, with gfr of the right kidney contributing 60.1 ± 9.12% of the total function, as determined by 99mTc-dtpa gamma camera imaging. Because the 99mTc-dtpa blood clearance method does not require urine collection, it may be a more practical procedure to measure gfr in the horse.
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Al-Dola, ayoob. "Evaluation the performance of the locally Developed Corn Thresher Machine from Manual to Mechanical System." Kirkuk University Journal For Agricultural Sciences 14, no. 2 (2023): 54–66. http://dx.doi.org/10.58928/ku23.14205.
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This study was conducted to develop corn thresher located in the College of Agriculture and Forestry, University of Mosul - Iraq in 2022, and this thresher operated by manual system. 1The factors were studied using two varieties of corn (Rayal, ZP), rotation speed 50, 100 rpm, and clearance between threshing wheel and pressing plate 10, 20 mm on some indicators, namely: productivity (kg.h-1), percentage of damaged grains (%), percentage of non-threshed grains (%).Operating costs (dinars. kg-1), the experiment was implemented according to a Complete Randomized Design (CRD), and with three replications .The main objectives of the study were to develop a manual system of thresher machine and to select the most appropriate operating factors that affect its performance. The results of the study showed that the (Rayal) variety was superior to the (ZP) variety in recording the lowest percentage of damaged grains. The rotation speed 100 rpm achieved the highest productivity values and the lowest values for each of (percentage of non-threshed grains, Operating costs), The clearance 20 mm was superior in achieving the highest values for productivity and the lowest values for the percentage of damaged grains, while the clearance 10 mm achieved the lowest values for the percentage of non-threshed grains.
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Genetzky, R. M., F. V. Loparco, and A. E. Ledet. "Clinical pathologic alterations in horses during a water deprivation test." American Journal of Veterinary Research 48, no. 6 (1987): 1007–11. https://doi.org/10.2460/ajvr.1987.48.06.1007.
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SUMMARY A 72-hour water deprivation test was performed in 12 horses to determine clinical pathologic changes. Reference values for electrolyte (X) clearance, expressed as a percentage of creatinine clearance (clCR; %clCRX), were also determined. A comparison was made between urine concentration measurement techniques. Results of %clCRX determination in 12 horses before water deprivation were 0.034 ± 0.095 %clCRNa, 42.4 ± 9.8 %clCRK, 0.352 ± 0.190 %clCRCl, and 0.710 ± 0.250 %clCRP. During water deprivation, there was individual variation for electrolyte clearances, but Na excretion increased significantly (P < 0.01) at 24 and 48 hours. After 48 hours’ water deprivation, %clCRNa decreased significantly, but was still greater than the initial clearance. Plasma protein was a better indicator of water deprivation (dehydration) in the horse than was pcv. Electrolyte concentrations in serum and urine were determined. Little significant (P < 0.01) change in acid-base values was noticed after 72 hours’ water deprivation. Urine osmolality (as determined by osmometry) was compared with sp gr (determined by refractometry) in determining urine concentration. Initially, sp gr correlated well with urine osmolality determinations, but this correlation decreased after 48 hours.
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N K Bansall and Shiv Kumar Lahan. "Design and Development of an Axial Flow Thresher for Seed Crops." Journal of Agricultural Engineering (India) 46, no. 1 (2009): 1–8. http://dx.doi.org/10.52151/jae2009461.1357.
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An axial flow thresher was designed and developed to maintain the seed quality of major oil seed and pulse crops. Major features of the thresher are minimum injury to seed, higher seed recovery and good seed quality, easy feeding and less fatigue to labour. The cylinder speed and aspirator speed are independent and very convenient to vary as per seed size. It has provision of easy adjustment of concave clearance, sieve clearance and slope of sieves. At optimum combination of cylinder sped and concave clearance at different seed moisture contents to thresh oilseeds and pulse crops, the performance parameters were within acceptable ranges of visible seed damage 12% and threshing efficiency 195% with threshed seed germination percentage of green gram (88%), black gram (90%), soybean (90%). chickpea (90%) and sunflower (86%). The germination percentages were above the minimum seed standards suggested by ISTA, (1999).
Book chapters on the topic "Percentage clearance"
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Kremen, Elizabeth, and Sahel Keshavarzi. "Metabolism, Fluid Distribution, and Renal Function." In Advanced Anesthesia Review, edited by Alaa Abd-Elsayed. Oxford University PressNew York, 2023. http://dx.doi.org/10.1093/med/9780197584521.003.0234.
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Abstract Pediatric physiology differs keenly from adult physiology in a number of ways. This chapter looks at differences in metabolism, fluid distribution, and renal function. Neonates and acutely ill children are more vulnerable to depletion of glycogen stores. Metabolism of medications is often prolonged in neonates due to fewer active enzymes; is more rapid in children; and reaches adult values in adolescence. Infants have a higher body water percentage by weight than adults do. Infants also have more fluid in the extracellular compartment, including the intravascular space, compared to adults. Renal filtration function and urine-concentrating ability in neonates are much less developed than in adults, leading to prolonged clearance rates of renally excreted drugs. Similarly, neonates are also more vulnerable to fluid perturbations and electrolyte imbalances until their homeostatic autoregulatory mechanisms more fully develop.
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Dumea, Elena, and Simona Claudia Cambrea. "The Influence of Protease Inhibitors on the Evolution of Hepatitis C in Patients with HIV and HCV Co-Infection." In Advances in Hepatology. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96282.
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Prevalence of hepatitis C in HIV infected patients is much higher than in the general population. There is the possibility of viral clearance HCV, in some patients co-infected HIV and HCV, in the phase of immune reconstruction after antiretroviral treatment (ART). There are patients’ anti-HCV positive who initially did not show HCV viral load detected and after the start of ART becomes HCV viral load detectable. There are studies that described that immune restoration with increase in CD4+ and CD8+ T cells, from ART, was important in control of HCV viremia. Has been proposed hypothesis that direct or indirect effect of ART on HCV replication play a role in spontaneous resolution of HCV infection. We evaluated the co-infected patients with HIV and HCV under combined antiretroviral treatment, containing PI boosted with ritonavir in terms of immunological and virological status (for both infection) and also liver disease. Patients were evaluated for liver damage by non-invasive methods. We have shown that a small percentage of patients have severe liver damage. We demonstrated the negative role of HCV on immunological status and in liver fibrosis in co-infected patients. A high proportion of these HIV and HCV co-infected patients had no detectable viremia, higher than other studies published.
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Pradhan, P. P. "Overview of Treating Skin Diseases and Rejuvenating Skin using Light Sources." In Materials Research Foundations. Materials Research Forum LLC, 2024. http://dx.doi.org/10.21741/9781644903056-3.
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The electromagnetic spectrum of sunlight, which includes infrared (IR, 52–55%), visible (VIS, 42–43%), and ultraviolet radiation (UV, 3-5%), is a naturally occurring source of light. Out of all these radiations, UV radiations with specific wavelengths have been shown to have clinically important biological effects that are both efficient and safe for human skin. UV radiation exposure primarily aids in the formation of vitamin D synthesis and has the potential to suppress immunological response, making it a more acceptable wavelength range for the diagnosis and treatment of various skin dermatoses. While comparing natural sunlight which contains less percentage of UV radiation with broadband range artificial UV therapy is an efficient, reliable, affordable, and, nonsurgical therapeutic option available for skin dermatoses. Recent investigations and literature reviews demonstrate that various types of phototherapies such as UVB narrowband, PUVA, etc. have incompatible efficacy toward the management of dermatoses that often depend upon the action, for instance, and absorption spectra of the biological molecule (chromophores) contained in the human skin. We attempt to categorize human skin conditions by their symptoms, topological facts, and dosimetry prescribed for the cures by the minimal erythemal dosage (MED) of phototherapy recommended by the dermatologist. Descriptive analysis of types of therapies carried out on narrowband (311 ± 2 nm) and broadband (295-315 nm) ultraviolent radiation B (UVB) therapy, light-sensitive organic drug (Psoralen) in combination with UVA (PUVA) therapy and laser therapy. This review article aims at the development in the field of dermatology by reviewing historical data, therapeutic options available, a detailed understanding of skin dermatoses, and the availability of light sources for the clearance of various skin dermatoses.
Conference papers on the topic "Percentage clearance"
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Zheng, Yun, Xiubo Jin, Hui Yang, Qingzhe Gao, and Kang Xu. "Effects of Circumferential Nonuniform Tip Clearance on Flow Field and Performance of a Transonic Turbine." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15295.
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Abstract The numerical study is performed by means of an in-house CFD code to investigate the effect of circumferential nonuniform tip clearance due to the casing ovalization on flow field and performance of a turbine stage. A method called fast-moving mesh is used to synchronize the non-circular computational domain with the rotation of the rotor row. Four different layouts of the circumferential nonuniform clearance are calculated and evaluated in this paper. The results show that, the circumferential nonuniform clearance could reduce the aerodynamic performance of the turbine. When the circumferential nonuniformity δ reaches 0.4, the aerodynamic efficiency decreases by 0.58 percentage points. Through the analysis of the flow field, it is found that the casing ovalization leads to the difference of the size of the tip clearance in the circumferential direction, and the aerodynamic loss of the position of large tip clearance is greater than that of small tip clearance, which is related to the scale of leakage vortex. In addition, the flow field will become nonuniform in the circumferential direction, especially at the rotor exit, which will adversely affect the downstream flow field.
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Liangfeng, Wang, Xiang Kangshen, Mao Luqin, Tong Hang, and Qiao Weiyang. "Numerical Simulation of the Effect of the Tip Clearance Flow on Rotor-Stator Interaction Tone Noise in Axial-Flow Fan." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14179.
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Abstract The present study is focused on the sound generation due to the rotor tip clearance flow interaction with stator in an axial flow fan. A hybrid URANS/Goldstein’s equations method is applied to calculate the unsteady flow and tone noise in a high loaded axial-flow fan with different rotor tip clearance. The numerical simulation results show that the main sound sources of fan tip clearance tone noise are concentrated in the leading edge of downstream stator blades. It is found that when the rotor tip clearance increases from zero to 2.5 mm (0.94% relative blade height), the mass flow of the fan decreases by about 2% and the efficiency of the fan decreases by about 1 percentage, and the sound power level at 1BPF forward tone increases by 1.47dB, and that of backward tone increases by 0.65dB. However, the influence of tip clearance on the tone noise intensity at 2BPF and 3BPF is more complex, and the variation range is less than 1dB. It is found that the wake width and wake strength at the rotor exit increase with the increase of tip clearance. The tip secondary flow caused by rotor clearance seriously affects the circumferential inhomogeneity of stator leading edge inflow conditions.
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Sakai, Haruka, Takahiro Kiwata, Hiroaki Nakata, Takaaki Kono, Hiroko Furumichi, and Akito Nakaguchi. "Performance of a Cross-Flow Wind Turbine Located Above a Windbreak Fence." In ASME/JSME/KSME 2015 Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ajkfluids2015-28628.
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The performance of a cross-flow wind turbine located above a windbreak fence (snowbreak fence) and the associated velocity fields were investigated through wind tunnel tests. The effects of the amount of vertical clearance between the wind turbine and the fence, the percentage of the fence area that is nonporous, and the rotational direction of the turbine were examined. In addition, a two-dimensional numerical flow analysis of the cross-flow wind turbine above the fence was performed using the CFD software ANSYS FLUENT 13.0. The fence and wind turbine models were built to a scale of 1:5; the porous fence model had a height of h = 500 mm, and the diameter of the wind turbine was 80 mm. It was found that the relationship between the inflow velocity into the clearance gap and the rotational direction of the turbine affects the power coefficient of the turbine.
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Xu, Jinming, Matthew S. Ambrosia, and David L. Rhode. "Effect of Tooth Bending Damage on the Leakage of Straight-Through Labyrinth Seals." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77455.
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Unavoidable rotordynamic impacting on labyrinth seal teeth sometimes occurs when centrifugal compressors, for example, undergo transients. Consequently, the labyrinth seal teeth are damaged or disfigured in various ways when the surface opposite to the teeth is non-abradable. Thus far, no quantitative information concerning the effect on seal leakage is available. The present work focuses on the effect of seal leakage due to such permanently bent labyrinth seal teeth. The investigation was done numerically by solving the 2-D, axisymmetric RANS equations with a finite-volume algorithm. The high-Reynolds number k-ε turbulence model was used with standard wall functions. A broad variety of tooth seal bending was studied by varying the bending curvature and the length of bending, as well as the after-bend tooth radial clearance. The results show that the bending damage drastically affects the leakage as well as the flow pattern. This is due largely to the altered clearance caused by the bending. However, other bending factors, such as the bending curvature and the percentage of tooth length that is bent, also contribute to the change of leakage and flow pattern.
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D’souza, Rohann, and Rajnish Sharma. "Numerical Investigation of Flow Through an Ultra-Micro Scale Gas Turbine." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70265.
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The ultra-micro scale gas turbine (UMGT) is an ongoing area of research, as an alternate power source for portable electronic devices. To advance our understanding that will help in its development, this paper focuses on a numerical analysis via computational fluid dynamics (CFD) of flow through a 3 dimensional (3D) blade profiled UMGT turbine. CFD modelling was based off an integrated turbine that consists of a volute, nozzle guide vanes (NGV) and rotor. Firstly, the flow through the integrated system as well as each component was analyzed. Secondly, the turbine was simulated under three different isothermal conditions and compared to the adiabatic situation, in order to understand the loss mechanisms. Lastly, the effect of tip clearance was studied, where it was varied between 0–10% of the blade height. CFD results showed, the flow through the turbine was quite well behaved, however separation of flow at the NGV leading edge, and residual swirl at the rotor trailing edge, were observed. The effects of the isothermal wall boundary condition was very pronounced at the volute and NGV, resulting in a large amount of good heat to be conducted away, at the rotor however conduction was only a percentage of the viscous heat generated. Lastly tip clearance proved to have a linearly detrimental effect on power.
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Nettis, Leonardo, and Luca Lombardi. "Leakage Flow Impact on High Aspect Ratio Steam Turbine Reaction Blades." In ASME 2013 Turbine Blade Tip Symposium. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/tbts2013-2042.
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The steam turbine stage efficiency is significantly affected by clearance losses due to leakage flow re-entering the main flowpath. The impact, in terms of delta of efficiency Δη, is usually assessed by assuming the proportionality Δη = K × (mLeak/mMain), being mLeak/mMain the fraction of the leakage flow relative to the main mass flow rate and K the constant evaluated by experimental and numerical evidence. Several studies are present in the literature concerning low aspect ratio blades, where this constant K is found to be equal to 1, or even higher for very low percentage leakage massflow. The main purpose of the current work consists of assessing this factor in the case of steam turbine reaction blades of the HP sector, characterized by a high aspect ratio. A numerical analysis has been set up where the detailed 3D geometry of two HP stages has been modeled and simulated by a 3D-CFD approach. Then a sensitivity analysis has been carried out by varying the leakage flows coming from stator and rotor labyrinth seals, realized by changing the radial gap of the clearance. This analysis has been repeated for several working points in order to obtain the leakage impact in the whole operating range of the reaction stages. The K factor comes out to be close to 0.8 at design point, whilst it increases up to 1 for highly loaded off-design condition.
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Wei, X., J. R. Mallon, L. F. Correa, M. R. Dorfman, and F. Ghasripoor. "Microstructure and Property Control of CoNiCrAlY Based Abradable Coatings for Optimal Performance." In ITSC 2000, edited by Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p0407.
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Abstract A CoNiCrAlY-hBN/Polyester material has recently been developed for clearance control applications in gas turbine compressors that use titanium alloy blades. While engine tests serve as the final evaluation of the coating performance, quality assurance laboratories and production shops would rely upon the more readily available coating hardness values to predict performance. This paper will focus on the reproducibility of coating macrohardness with a plasma spray process. It is shown that plasma spray parameters affect the hardness of CoNiCrAlY-hBN/Polyester coatings by changing the level of polyesters retained in the coating and the volume percentage of metallic matrix. The correlation between hardness, retained polyester level and microstructure of these coatings is captured in a coating hardness map from which desired microstructure and polyester entrapment are determined. Based on the understanding of the correlation between coating hardness and microstructural features, the use of additional criteria other than hardness such as retained polyester level and non-metallic portion of the coating is recommended in order to assure the quality of the coating more effectively.
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Kimoto, Kenta, Hitoshi Asano, Masafumi Sakurai, Tetsuro Hamada, Makoto Hirotsu, and Sakiko Kimura. "Effect of Surface Roughness and Micro-Grooves on Condensed Water Removal in Latent Heat Recovery Heat Exchanger." In ASME 2011 Power Conference collocated with JSME ICOPE 2011. ASMEDC, 2011. http://dx.doi.org/10.1115/power2011-55389.
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Hot-water supply has high percentage of energy consumption in Japanese civilian sector. Gas water heaters are used in most cases. Therefore, improvement in thermal efficiency of a gas water heater is an important issue for energy saving. In order to improve thermal efficiency of a gas water heater, an additional heat exchanger is required for latent heat recovery from exhaust humid combustion. The purpose of this study is to develop a compact latent heat recovery heat exchanger with a simple configuration. It is necessary for compactness to reduce the gap between the heat transfer tubes. However, the narrow gap will cause stagnation of condensed water. In order to remove the condensed water from horizontal tube bank, three kinds of tubes with different surface treatments, polished tubes, unpolished tube, and smooth tube with circular micro-grooves, were examined. As the result, condensed water was easily removed by the groove with the 0.7mm depth, to avoid the formation of water bridges between tubes. The effect could lead to no deterioration in the heat transfer performance by decreasing the tube clearance to 1.0mm.
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McKenzie, E. A., J. R. Etherton, J. R. Harris, D. M. Cantis, and T. J. Lutz. "NIOSH AutoROPS 3rd Generation Static Testing and Human Interaction Element." In ASME 2003 International Mechanical Engineering Congress and Exposition. ASMEDC, 2003. http://dx.doi.org/10.1115/imece2003-41330.
Full textAbstract:
To address the need for rollover protective structures (ROPS) on farm tractors that are easily adapted to low overhead clearance situations, the Division of Safety Research (DSR), National Institute for Occupational Safety and Health (NIOSH), developed an automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS at the present is in the third generation design and static testing phase, and the first phase of human subject (human operator) testing and manufacturing. The static testing is based on the SAE J2194 standard for testing ROPS for agricultural tractor use. The nature of the NIOSH AutoROPS is to be in a retracted position until an overturn is determined to be imminent. It is during the deployment time period that potential safety hazards exist that are not present in a traditional fixed ROPS and not addressed in the standards. Human interaction is a key ingredient in refining the design to be both functional and desirable while considering possible hazards. Feedback from farmers who have operated a tractor with the NIOSH AutoROPS installed and in the ready state will enhance the design and acceptability. NIOSH’s goal is to reduce the number of fatal agricultural overturns by increasing the percentage of tractors with ROPS and seatbelts which operate in low clearance environments. This design has met laboratory static testing criteria of the SAE J2194 standard for ROPS on agricultural tractors. Field evaluation of the AutoROPS use by poultry farmers (N=32) in eastern West Virginia showed favorable results and a preference for wanting to purchase and use the NIOSH AutoROPS compared with a currently available manually foldable ROPS. This paper discusses the overall performance of the NIOSH AutoROPS as subjected to the SAE J2194 standard and human interaction/feedback of operating an agricultural tractor with this added safety device.
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Mourelatos, Zissimos P., Nickolas Vlahopoulos, Omidreza Ebrat, Jinghong Liang, and Jin Wang. "Probabilistic Main Bearing Performance for an Internal Combustion Engine." In ASME/STLE 2004 International Joint Tribology Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/trib2004-64058.
Full textAbstract:
A probabilistic analysis is presented for studying the variation effects on the main bearing performance of an I.C. engine system, under structural dynamic conditions. For computational efficiency, the probabilistic analysis is based on surrogate models (metamodels), which are developed using the kriging method. An Optimum Symmetric Latin Hypercube (OSLH) algorithm is used for efficient “space-filling” sampling of the design space. The metamodels provide an efficient and accurate substitute to the actual engine bearing simulation models. The bearing performance is based on a comprehensive engine system dynamic analysis which couples the flexible crankshaft and block dynamics with a detailed main bearing elastohydrodynamic analysis. The clearance of all main bearings and the oil viscosity comprise the random variables in the probabilistic analysis. The maximum oil pressure and the percentage of time within each cycle that a bearing operates with oil film thickness below a threshold value of 0.27 μm at each main bearing constitute the system performance measures. Probabilistic analyses are first performed to calculate the mean, standard deviation and probability density function of the bearing performance measures. Subsequently, a probabilistic sensitivity analysis is described for identifying the important random variables. Finally, a Reliability-Based Design Optimization (RBDO) study is conducted for optimizing the main bearing performance under uncertainty. Results from a V6 engine are presented.