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Study on the Unsteady Cavitation Flow Characteristics Inside the Mixed Transport Twin Screw Pump
Xuejing Zhang,Li Wang,Guisheng Zhu,Wei Han 한국유체기계학회 2024 International journal of fluid machinery and syste Vol.17 No.1
With the development of screw pumps towards high speed, high pressure, and large flow rate, cavitation in screw pumps has become a phenomenon that cannot be ignored. Based on ANSYS CFX, use SST turbulence model and combine with Rayleigh-Plesset equation to effectively simulate the internal flow of mixed transport twin screw pump, analyze the changes in cavitation morphology and the evolution of cavitation within the entire cycle of the pump, and explore the degree of cavitation on the surface of the screw rotor and the changes in pressure and velocity at the monitoring point with rotation period under different inlet pressures and speeds, and then analyze the changes in cavitation of the twin screw pump under different temperature. The calculation results indicate that cavitation first occurs at the inlet and then gradually penetrates into the interior of the chamber, mainly concentrated in the inlet section and the first chamber. The inlet pressure has a significant impact on cavitation phenomenon. As the inlet pressure decreases, the cavitation intensity continues to strengthen, and the cavitation area also continues to expand. Rotating speed can also affect cavitation, but the effect of speed changes on cavitation is not as significant as that of inlet pressure changes. In addition, increasing the water temperature will also increase the cavitation area. This study reveals the characteristics of cavitation flow in mixed transport twin screw pump, which is of great significance in avoiding cavitation and improving pump performance.
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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.
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Xuejing Zhang,Chong Ma,Li Wang,Xiaolin Huang,Wei Han,Yubing Gong 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.1
The existing methods for studying the dynamics, thermodynamics and deformation characteristics of screw pumps do not consider the coupling effect of multi field interaction, which deviates from the actual working conditions. Based on SolidWorks and ANSYS software, a three-dimensional finite element model of a lead of conventional single screw pump is established in this paper. The influence of different gas(GVF) volume fraction on the temperature, pressure, deformation, leakage and volumetric efficiency of screw pump was studied by using the fluid-thermal-solid coupling method. The numerical simulation results of volumetric efficiency changing with the inlet and outlet pressure difference under pure liquid condition were verified by the published literature experimental data, and the optimal installation interference value was proposed. The results show that the GVF has an important influence on the comprehensive deformation of the rotor and pump bushing and the volumetric efficiency of the pump; the comprehensive deformation value of the rotor increases gradually from the inlet to the outlet, and increases gradually with the increase of the GVF; with the increase of GVF, the comprehensive deformation value of stator first decreases gradually, and then increases sharply; with the increase of GVF, the leakage first decreases slowly, then increases rapidly, and the volumetric efficiency first increases slowly, then decreases rapidly; the numerical simulation results are in good agreement with the experimental values, and the average deviation is less than 7%.
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A Domain-independent Dual-image based Robust Reversible Watermarking
Xuejing Guo,Yixiang Fang,Junxiang Wang,Wenchao Zeng,Yi Zhao,Tianzhu Zhang,Shi Yun-Qing 한국인터넷정보학회 2022 KSII Transactions on Internet and Information Syst Vol.16 No.12
Robust reversible watermarking has attracted widespread attention in the field of information hiding in recent years. It should not only have robustness against attacks in transmission but also meet the reversibility of distortion-free transmission. According to our best knowledge, the most recent robust reversible watermarking methods adopt a single image as the carrier, which might lead to low efficiency in terms of carrier utilization. To address the issue, a novel dual-image robust reversible watermarking framework is proposed in this paper to effectively utilize the correlation between both carriers (namely dual images) and thus improve the efficiency of carrier utilization. In the dual-image robust reversible watermarking framework, a two-layer robust watermarking mechanism is designed to further improve the algorithm performances, i.e., embedding capacity and robustness. In addition, an optimization model is built to determine the parameters. Finally, the proposed framework is applied in different domains (namely domain-independent), i.e., Slantlet Transform and Singular Value Decomposition domain, and Zernike moments, respectively to demonstrate its effectiveness and generality. Experimental results demonstrate the superiority of the proposed dual-image robust reversible watermarking framework.
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Li Wang,Xuejing Zhang,JunHu Yang,Chong Ma,Wei Han,Yubing Gong 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.2
When GVF in the inlet of the oil-gas mixed transmission twin-screw pump is high, the temperature difference between the inlet and outlet of the screw pump will rise significantly, and rotor expansion jam will occur. To prevent the expansion jam caused by the overheating of the screw pump, the cooling water jacket is designed for gas-liquid mixed screw pump with high GVF to continuously cool. Using the theory of fluid-structure interaction heat transfer, the cooling effect of the cooling water jacket of the equal pitch screw pump and the variable pitch screw pump is numerically calculated, and after comparison with the experiment, it finds that the maximum deviation of the outlet temperature of the variable pitch screw pump does not exceed 4K and the average deviation is about 6 %. When GVF is 96%, the calculation of the cooling water cavity shows that the average temperature drop of the liner after the cooling of the equal pitch screw pump and the variable pitch screw pump is about 4K and 3K, respectively. When GVF rises from 90% to 99%, the average temperature drop is about 3.5K. Cooling water jacket has obvious cooling effect on screw pump with high GVF.
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Ming Yuan,Xuejing Jia,ChunBang Ding,Haiqiong Zeng,Lei Du,Shu Yuan,Zhongwei Zhang,Qi Wu,Chao Hu,Jing Liu 한국식품과학회 2015 Food Science and Biotechnology Vol.24 No.5
Effects of light on phenolic compounds and antioxidant activities during germination of soybean seeds were studied. Soybean seeds were germinated in the presence and absence of light. Chlorophylls and morphological characteristics of sprouts were evaluated daily. Antioxidant activities were determined using 2,2-diphenyl-1-picryl-hydrazyl (DPPH) and ferric reducing activity power methods. Morphological characteristics of light-grown sprouts were superior to dark-grown sprouts and the metabolism of phenolic compounds was regulated by light. Light treatment improved accumulation of phenolic compounds in soybean sprouts and increased antioxidant activities. The optimum harvest time of light-grown sprouts was on the seventh day when sprouts achieved the best nutraceutical value. Green sprouts can serve as a good vegetable source for the human diet.
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( Haoliang Zhao ),( Ming Zhang ),( Xuejing Yang ),( Dong Song ) 한국미생물 · 생명공학회 2021 Journal of microbiology and biotechnology Vol.31 No.10
In this study, we evaluated the mechanism of long non-coding RNA MIR22 host gene (LncRNA MIR22HG) in osteosarcoma cells. Forty-eight paired osteosarcoma and adjacent tissues samples were collected and the bioinformatic analyses were performed. Target genes and potential binding sites of MIR22HG, microRNA (miR)-629-5p and tet methylcytosine dioxygenase 3 (TET3) were predicted by Starbase and TargetScan V7.2 and confirmed by dual-luciferase reporter assay. Cell Counting Kit-8, colony formation and flow cytometry assays were utilized to determine the viability, proliferation and apoptosis of transfected osteosarcoma cells. Pearson’s analysis was introduced for the correlation analysis between MIR22HG and miR-629-5p in osteosarcoma tissue. Relative expressions of MIR22HG, miR-629-5p and TET3 were measured by quantitative real-time polymerase chain reaction or Western blot. MiR-629-5p could competitively bind with and was negatively correlated with MIR22HG, the latter of which was evidenced by the high expression of miR-629-5p and low expression of MIR22HG in osteosarcoma tissues. Overexpressed MIR22HG repressed the viability and proliferation but enhanced apoptosis of osteosarcoma cells, which was reversed by miR-629-5p upregulation. TET3 was the target gene of miR-629-5p, and the promotive effects of upregulated miR-629-5p on the viability and proliferation as well as its repressive effect on apoptosis were abrogated via overexpressed TET3. To sum up, overexpressed MIR22HG inhibits the viability and proliferation of osteosarcoma cells, which was achieved via regulation of the miR-629- 5p/TET3 axis.
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Cho, Seungho,Yun, Chao,Kim, Yoon Seo,Wang, Han,Jian, Jie,Zhang, Wenrui,Huang, Jijie,Wang, Xuejing,Wang, Haiyan,MacManus-Driscoll, Judith L. Elsevier 2018 Nano energy Vol.45 No.-
<P><B>Abstract</B></P> <P>Lead-free perovskite oxide thin films prepared by alloying of titanates and materials with lower melting points are shown to have enhanced ferroelectric and dielectric properties. BaTiO<SUB>3</SUB> (or SrTiO<SUB>3</SUB>) with 25% addition of BiFeO<SUB>3</SUB> has much improved crystalline perfection because of the lower melting point of the BiFeO<SUB>3</SUB> giving enhanced growth kinetics. The maximum dielectric peak temperature of BaTiO<SUB>3</SUB> is increased by ~ 200°C and leakage currents are reduced by up to a factor of ~ 100. The loss tangent reduces up to 300°C, with a factor of > 14 reduction at room temperature. The dielectric breakdown strength is higher by a factor of ~ 3 (> 2200kVcm<SUP>−1</SUP>) and from room temperature up to 500°C the dielectric constant is > 1000. Also, a low variation of dielectric constant of ~ 9% from room temperature to 330°C is obtained, compared to ~ 110% for BaTiO<SUB>3</SUB>. The maximum polarization (<I>P</I> <SUB>max</SUB>) is double that of BaTiO<SUB>3</SUB>, at 125.3μCcm<SUP>−2</SUP>. The film has high energy storage densities of > 52Jcm<SUP>−3</SUP> at 2050kVcm<SUP>−1</SUP>, matching Pb-based ferroelectric films. The strongly improved performance is important for applications in energy storage and in high temperature (up to 300°C) capacitors as well as wider application in other electronic and energy technologies.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High crystallinity is achieved by mixing titanate with a lower melting point material. </LI> <LI> The film with enhanced crystallinity has strongly enhanced dielectric properties. </LI> <LI> The film has high energy storage densities of > 52Jcm<SUP>−3</SUP>, matching Pb-based films. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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