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- 저자 : Jiaxing Lu (검색결과 2 건)
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The characteristics investigation under the unsteady cavitation condition in a centrifugal pump
Jiaxing Lu,Shouqi Yuan,Parameswaran Siva,Jian-Ping Yuan,Xudong Ren,Banglun Zhou 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3
Numerical simulation and experimental method are combined to investigate the pump inlet and outlet pressure fluctuations, the vibration characteristics and the internal flow instabilities under the unsteady cavitation condition in a centrifugal pump. It is found that the unsteady cavitation starts to generate as the NPSHa is lower than 5.93 m. Apparent asymmetric and uneven cavity volume distribution on each blade and in the impeller can be observed as the NPSHa decreases from 4.39 m to 1.44 m, which includes the cavitation develops from cavitation surge, rotating cavitation to asymmetric cavitation. The flow vortexes in each blade channel are produced in the cavity trailing edges by the shedding and collapse of cavitation, which interfere with each other and aggravate the flow instabilities. The dominant frequencies of the pump inlet and outlet pressure fluctuations are the shaft frequency and blade passing frequency under the unsteady cavitation conditions, respectively. Broadband pulses are obtained from both the pump inlet and outlet pressure pulsations, which results from the random shedding and collapse of unsteady cavitation bubbles. Obvious corresponding relationship between the root mean squares of the vibration measured in different positions and the suction performance curve is found under both the non-cavitation and unsteady cavitation conditions.
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Yetao Jiang,Xiaoyu Wang,Zhen Wu,Jiaxing Xu,Lei Hu,Lu Lin 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.4
Cooking with active oxygen and solid alkali (CAOSA) is a mild and environmentally friendly method for separation of lignin components. The degradation mechanism of hemicellulose associated with this method has been investigated. It was found that the hemicellulose-derived polysaccharides were directly oxidized rather than hydrolyzed to monosaccharides for degradation. To avoid the undesirable degradation of hemicellulose components by CAOSA, the idea of separating hemicellulose first in the form of xylan to produce xylooligosaccharide was presented by this study. Although hydrothermal autocatalysis has been commonly used in hemicellulose separation, the effects of acidenhanced hydrothermal method and alkali-suppressed hydrothermal method on hydrothermal autocatalysis were systematically compared for the first time, and it was found that the acid-enhanced method was beneficial for highly selective extraction of xylan. Then, the hemicellulose-removed bamboo was treated with CAOSA process to separate lignin from cellulose. It was found that solid alkali dosage of CAOSA could be evidently decreased for hemicelluloseremoved bamboo, which was helpful to reduce the cost of CAOSA. Coupling hemicellulose pre-extraction and CAOSA lignin fractionation strategy, a comprehensive biorefinery case for bamboo biomass could be anticipated.
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