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Yumeng Yang,Jianzhong Liu,Xiang He,Zhihua Wang,Junhu Zhou,Kefa Cen 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.4
Same amounts of moisture were removed from Ximeng lignite (XL) with different particle size ranges pretreated at different drying temperatures. The effect of conventional drying on the grindability of the XLs was investigated. Increasing the drying temperature improved the grindability of all the samples. The results of scanning electron microscopy and mercury intrusion porosimetry revealed that the dominant mechanism enhancing the grindability of XL with high moisture was the pore structure destruction induced by the steam jet flow generated with the removal of moisture. Especially, the development of large fractures had a strong connection with the change in the grindability. According to the pore size distribution, the internal structure of the 2.5-4.0mm coal samples did not develop well under high drying temperature because of the exceedingly short heating time. Therefore, coal particle size, drying temperature, and heating time must be coordinated well to achieve the enhanced drying effect. The grindability of XL had a negative linear correlation with the pore volume fractal dimension, revealing the possibility of fractal dimension for the analysis of lignite grindability.
Effect of Different Guide Vane Numbers on Transient Radial Force of Pump as Turbine
Shi, FengXia,Yang, JunHu,Wang, XiaoHui Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1
Guide vane was added to pump as turbine (PAT), the transient flow characteristics of PAT were calculated and experimented under different guide vane numbers. The results show that after the PAT was added guide vane, the distribution of speed streamline and blade load is more uniform than before, and the unsteady radial force on impeller decreased greatly, which is good for the stability of PAT's operation. When the guide vane number is equal to 9, both the maximum radial force difference and dominant frequency amplitude of radial force are the minimum. So there is an optimal guide vane number, for the given geometric parameters of PAT.
Luo, Dingyuan,Yang, Fengxia,Yang, Xiaojun,Yao, Junhu,Shi, Baojun,Zhou, Zhenfeng Asian Australasian Association of Animal Productio 2009 Animal Bioscience Vol.22 No.9
The study was conducted to investigate the effects of different levels of xylanase on performance, blood parameters, intestinal morphology, microflora and digestive enzyme activities of broilers. The wheat-based diets were supplemented with 0, 500, 1,000, 5,000 U/kg xylanase. Xylanase supplementation significantly (p<0.05) improved the feed:gain ratio of broilers from 1 to 21 d and 1 to 42 d. Supplementing 500 U/kg and 1,000 U/kg xylanase improved (p<0.05) the villus height and the ratio of villus height to crypt depth in the small intestine. Excess supplementation of xylanase (5,000 U/kg) increased the villus height in the ileum (p<0.01) and the ratio of villus height to crypt depth in the duodenum and ileum (p<0.05). The microflora in the ileum and caecum, digestive enzyme activities in the small intestine and the concentrations of serum glucose, uric acid, insulin and IGF-I were not affected by the supplementation of xylanase. Excess level of xylanase (5,000 U/kg) had a tendency to induce the multiplication of E. coli and total aerobes. The results suggested that supplementing 500 U/kg and 1,000 U/kg xylanase was beneficial for broilers and excess xylanase supplementation resulted in no further improvement or negative effects.
Xuejing Zhang,Junhu Yang,Wenkai Bei,Wei Han,Canyang Chen,Le Yang 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.2
The efficiency of multiphase twin-screw pump decreases sharply under wet gas conditions (GVF>95%) with severe vibration and thermal problems. Based on the design characteristics of twin-screw pump and screw compressor, a design method of multigradient variable pitch decompression screw pump is to address these problems in this paper. This method keeps the cross section profiles of screw pump unchanged,only changes the pitch of screw. According to the design concept of decompression of screw compressor, the screw rotor is divided into three regions from the inlet to the outlet. The pitch of screw and thread width in these regions are designed separately to increase the volumetric efficiency of the screw pump and reduce the vibration. The effective clearance leakage model of twin-screw pump is simplified and modified. Considering two-phase back flow and combining mechanical model with thermodynamic model, the flow capacity, volumetric efficiency, pressure, and temperature distribution of new and conventional screw pumps are predicted by non-isothermal compression model. The calculations show that the design scheme of multi-gradient variable-pitch decompression screw pump can solve the volumetric efficiency and vibration problems under wet gas conditions fundamentally and can significantly reduce the power consumption of screw pump. However, the problem of temperature rise of screw pump still exists. Cooling system for the screw pump should be designed to continuously cool the screw pump.
Study on the Effect of Gas-Liquid Two-Phase Medium on PAT Performance
Shi Fengxia,Yang Junhu,Wang Xiaohui,Miao Senchun,Guo Rui 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.3
A pump as turbine is optimized firstly, then the distribution of gas, the vortex structure evolution, the force characteristic and energy conversion characteristic are analyzed under pure liquid and gas-liquid two-phase conditions. The result manifests that because of the existence of gas, the pressure gradient decreased and the normal flow of high-pressure fluid in the turbine is inhibited by gas. The radial force vector, the time domain value and the main frequency amplitude are all smaller than that of pure liquid condition, and hydraulic vibration is more likely to be caused by the flow uncertainty of gas. The energy conversion performance of the unit is worse.
Analysis on Characteristic of Pressure Fluctuation in Hydraulic Turbine with Guide Vane
Shi, FengXia,Yang, JunHu,Wang, XiaoHui Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.3
An unsteady three-dimensional simulation based on Reynolds time-averaged governing equation and RNG $k-{\varepsilon}$ turbulence model, was presented for pump-as-turbine, the pressure fluctuation characteristic of hydraulic turbine with guide vane was obtained. The results show that the time domains of pressure fluctuation in volute change periodically and have identical cycles. In volute tongue and inlet pressure fluctuations are light, while in dynamic and static coupling interface pressure fluctuations are serious; In impeller blade region the pressure fluctuation of pressure surface are lighter than that of suction surface. The dominant frequencies of pressure fluctuation concentrate in low frequency region, and concentrate within 2 times of the blade passing frequency.
Effect of Different Guide Vane Numbers on Transient Radial Force of Pump as Turbine
FengXia Shi,JunHu Yang,XiaoHui Wang 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1
Guide vane was added to pump as turbine (PAT), the transient flow characteristics of PAT were calculated and experimented under different guide vane numbers. The results show that after the PAT was added guide vane, the distribution of speed streamline and blade load is more uniform than before, and the unsteady radial force on impeller decreased greatly, which is good for the stability of PAT’s operation. When the guide vane number is equal to 9, both the maximum radial force difference and dominant frequency amplitude of radial force are the minimum. So there is an optimal guide vane number, for the given geometric parameters of PAT.
Analysis on Characteristic of Pressure Fluctuation in Hydraulic Turbine with Guide Vane
FengXia Shi,JunHu Yang,XiaoHui Wang 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.3
An unsteady three-dimensional simulation based on Reynolds time-averaged governing equation and RNG k-ε turbulence model, was presented for pump-as-turbine, the pressure fluctuation characteristic of hydraulic turbine with guide vane was obtained. The results show that the time domains of pressure fluctuation in volute change periodically and have identical cycles. In volute tongue and inlet pressure fluctuations are light, while in dynamic and static coupling interface pressure fluctuations are serious; In impeller blade region the pressure fluctuation of pressure surface are lighter than that of suction surface. The dominant frequencies of pressure fluctuation concentrate in low frequency region, and concentrate within 2 times of the blade passing frequency.
Yuan, Jiu,Yao, Junhu,Yang, Fengxia,Yang, Xiaodan,Wan, Xinjie,Han, Jincheng,Wang, Yaojie,Chen, Xinke,Liu, Yurui,Zhou, Zhenfeng,Zhou, Ningbo,Feng, Xinyu Asian Australasian Association of Animal Productio 2008 Animal Bioscience Vol.21 No.5
A trial was conducted to study the influence of different levels of a commercial enzyme complex on performance, nutrient availability, blood parameters, digestive tract measurements, amylase and trypsin activity of the digestive tract and gut morphology in broilers fed the typical diets in north China. There were four treatments: the control diet and the other three enzyme complex supplemented diets which were 180 mg/kg, 360 mg/kg and 720 mg/kg enzyme complex supplemented to the control diet, respectively. The birds fed the diets supplemented with 180 mg/kg and 360 mg/kg enzyme complex had better performance and nutrient availability, the activities of amylase and trypsin in the digestive tract in the two treatments were improved, the villus height and surface area of villus in the small intestine increased and the crypt depth and epithelial thickness of small intestine decreased. Relative weights of pancreas and relative weights and lengths of small intestine decreased. However, the addition of 720 mg/kg enzyme complex had no effects on these parameters and increased crypt depth and epithelial thickness of the small intestine. The data suggested that suitable supplementation of enzyme complex was beneficial for the birds, while excess enzyme complex inhibited secretion of endogenous enzyme and destroyed the structure of the small intestine.