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2016年大连国际微流控和芯片实验室大会

作者： Liang-Liang Fan Hong Zhao Qing Yan Jing Guo Liang Zhao Jiang Zhe Fuli School of Food Equipment Engineering and Science(FEES) Xi'an Jiaotong University State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Department of Mechanical Engineering University of Akron

Particles subjected to the inertial lift force will be focused in several equilibrium positions in *** to now,most research on inertial focusing of particles have been focused on the microchannel with a constant cross-section,such as the straight *** study the influence of variable cross-section on the inertial focusing of particles in microchannel,three kinds of microchannels with different cross-sections including the gradually constricted,the constant,and the gradually expanded were designed and fabricated,where inertial focusing behavior of particles was investigated by *** result shows,in comparison with the microchannels with the constant and the gradually constricted cross-sections,7.32 um particles are focused in two symmetric streams with narrower bandwidth in the microchannel with the gradually expanded cross-section,indicating the gradually expanded geometrical structure is more efficient for the inertial focusing of ***,smaller secondary flow was generated at outlet of the microchannel with the gradually expanded cross-section,which is helpful for keeping the focused particle streams in a narrow *** further investigate the influence of the arrangement of the gradually expanded cross-section on the inertial focusing of particles,a series of gradually expanded geometrical structures arranged on one side,symmetrically arranged on two sides,and asymmetrically arranged on two sides of the microchannel were designed,*** on inertial focusing of particles were conducted using7.32 um and 9.9um particles,showing particles are focused in one or two streams in the microchannels with gradually expanded geometrical structures arranged on one side or symmetrically arranged on two sides while particles are focused in two or three streams in the microchannel with gradually expanded geometrical structures asymmetrically arranged on two *** it can be obtained that to achieve one-stream inert

关键词： Influence of Geometrical Structure on Inertial Focusing of Particle in the Microchannel

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Temporal and spatial non-uniformity of surface heat transfer during r404a spray cooling in laser surgery 13

Temporal and spatial non-uniformity of surface heat transfer...

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13th International Conference on Liquid Atomization and Spray Systems, ICLASS 2015

作者： Wang, R. Zhou, Z.F. Chen, B. Bai, F.L. Wang, G.X. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China

Cryogen spray cooling has been applied to protect epidermis from thermal damage in laser dermatology. However, present cryogen R134a shows insufficient cooling capacity on minimizing the laser energy absorption by the melanin in darkly pigmented human skins. With lower boiling point, R404A has potential to improve the cooling capacity. This paper presents an experimental study on the temporal and spatial variation in surface temperature and heat flux during spray cooling using R404A by a straight tube nozzle with expansion chamber, which significantly improves the atomization effect. The experimental results indicate that the temporal and spatial conditions strongly influence the uniformity of surface heat transfer. There exists a sub-region of uniform cooling with radius of 2 mm around spray center with high transient heat flux above 400 kW/m2, which is conducive for physicians to control the therapy area precisely with enhanced laser energy. © 2015 International Conference on Liquid Atomization and Spray Systems. All rights reserved.

关键词： Laser surgery

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Energy efficiency evaluation method for plate heat exchanger

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Kexue Tongbao/Chinese Science Bulletin 2016年第8期61卷 802-808页

作者： Zhang, Yanfeng Jiang, Chen Shou, Binan Zhou, Wenxue Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Technology Service Center CO. LTD Beijing100011 China LanZhou Guanyu Heat Transfer and Energy Saving Engineering and Technology Research CO. LTD Lanzhou730050 China

In heat exchangers, heat transfer between the cold and the hot fluid consumes pumping power. Evaluating the energy efficiency of this process scientifically and quantitatively is an urgent issue for both academic research and industrial applications, and has important significance to energy saving and emission reduction. We comprehensively analyzed the flow and heat transfer characteristics of water-water heat transfer process without phase-change in a heat exchanger, and proposed the energy efficiency index (=k/pn, k is overall heat transfer coefficient and p is flow pressure gradient). EEI reflects the inherent energy efficiency properties of a heat exchanger, which represents the overall heat transfer coefficient per equivalent flow pressure drop consumption. At a given temperature difference and fluid flow rate, for the heat exchangers with the same heat transfer area and fluid flow length, bigger EEI means a lager heat transfer rate per equivalent pumping power consumption. EEI is independent on the heat transfer area;no dependence or weak dependence on the flow velocity can be achieved by choosing the index n reasonably, indicating a good stability of EEI. Evaluation result based on national standard of heat exchanger performance test measured could represent the energy efficiency of the heat exchanger. Combined with the water-water heat transfer process without phase-change flow and heat transfer performance database of the plate heat exchangers, the value of index n and the overall EEI distribution of plate heat exchangers in industry are obtained, providing a basis for the classification of the energy efficiency of plate heat exchangers. © 2016, Science Press. All right reserved.

关键词： Heat exchangers

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Numerical simukation of nitrogen condensation flow in acryogeni nozzle 24

Numerical simukation of nitrogen condensation flow in acryog...

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24th IIR International Congress of Refrigeration, ICR 2015

作者： Wan, Sun Guoqing, Liu Lu, Niu Shuangtao, Chen Yu, Hou State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 China

ISBN: (纸本)9782362150128

2-D numerical simulations on the nitrogen expansion flow with spontaneous condensation in a nozzle were conducted based on the equilibrium model and the non-equilibrium model respectively. In the equilibrium model, the mass transfer between the liquid and vapor is determined by the saturation enthalpies of the liquid and vapor phases. The pressure distribution of the nozzle could be influenced slightly by the condensation process. In the non-equilibrium model, the classical nucleation model is used for the droplets formation. The flow is heated by the latent heat and consequently the decrease of pressure and the increase of Mach number are delayed. Meanwhile, due to the requirement of a certain supercooling level, the condensation onset point is pushed away from the nozzle inlet, and the nozzle outlet wetness fraction becomes smaller. Then, the influence of the nozzle inlet temperature and inlet pressure on gas supercooling, nucleation rate and wetness are analyzed.

关键词： Nucleation

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Dynamics of Internal Jets in the Merging of Two Droplets of Unequal Sizes

Dynamics of Internal Jets in the Merging of Two Droplets of ...

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第八届海峡两岸激波与复杂流动学术会

作者： Chenglong Tang Jiaquan Zhao Peng Zhang Chung K.Law Zuohua Huang Department of Mechanical and Aerospace Engineering Princeton University State Key Laboratory of Multiphase Flow and Power Engineering Xi'an Jiaotong University Department of Mechanical Engineering Hong Kong Polytechnic University Center for Combustion Energy Tsinghua University

*** Collision of two droplets in a gaseous environment plays an essential role in many natural and industrial processes,such as raindrop and cloud formation,insecticide spraying,spray painting,and spray combustion in various liquid-fueled *** the most symmetrical event,namely the head-on collision between two identical droplets,it has been experimentally and theoretically-demonstrated that,

关键词： simulation Dynamics of Internal Jets in the Merging of Two Droplets of Unequal Sizes

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Investigation on the matching performance of a small cryogenic air turboexpander 24

Investigation on the matching performance of a small cryogen...

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24th IIR International Congress of Refrigeration, ICR 2015

作者： Yang, Shanju Li, Bowen Liu, Guoqing Hou, Yu Chen, Shuangtao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9782362150128

The matching performance of a turboexpander is essential for a small reverse Brayton air refrigerator, especially when it works under varied operation parameters. Generally, an appropriate brake pressure is required when the turboexpander works under different operation parameters. In this paper, the matching performance of a turboexpander supported by a bump journal foil bearing and a pressurized thrust gas bearing is studied. A centrifugal blower is used as a brake. The performance curve is analyzed through a numerical simulation using CFX. The matching calculations were carried out with different brake blowers under both room temperature and low temperature. A brake pressure feedback control is applied in the experimental study. A thermal performance of the refrigerator is tested. The results indicated that the appropriate brake blower and brake pressure facilitate the system thermal performance under both room and low temperature. The simulation agrees well with the experimental results.

关键词： Temperature

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Shock Tube Experimental and Modeling Study of MTHF Ignition Characteristics at High Temperatures

Shock Tube Experimental and Modeling Study of MTHF Ignition ...

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JSAE/SAE 2015 International powertrains, Fuels and Lubricants Meeting, FFL 2015

作者： Wang, Jingshan Wang, Xibin Fan, Xiangshan Yang, Kangkang State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China

High temperature ignition delays of 2-methyltetrahydrofuran(MTHF) were measured behind a reflected shock tube under conditions of pressures from 1.2 to 10 atm, temperatures from 1050 to 1800 K, equivalence ratios from 0.5 to 2.0, and fuel concentrations of 0.25%, 0.5% and 1.0% diluted in argon. Results showed that the ignition delay of MTHF decreases with the increase of pressure, temperature, fuel concentration and increases with equivalence ratio. The trend is less notable at higher fuel concentrations and equivalence ratios. Based on sensitivity and pathway analysis at pressure of 10 atm, fuel concentration of 1.0%, equivalence ratio of 1.0 and temperature of 1550K, it was found that the most sensitive reaction of MTHF at high temperature is H+O2=O+OH, and the main consumption way is fuel decomposition instead of H-abstraction. Finally, ignition delays of MTHF were compared with THF both on experimental and kinetic analyses, and MTHF has lower ignition delays than THF. To our knowledge, it is the first time to present the ignition delays of MTHF under these conditions. © 2015 SAE Japan.

关键词： Shock tubes

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Modelling of control system and efficiency analysis for a 600MW supercritical lignite-fired boiler

Modelling of control system and efficiency analysis for a 60...

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International Conference on power engineering, ICOPE 2015

作者： Wang, Bingqi Han, Xiaoqu Mu, Qiwei Zhou, Yan Chen, Weixiong Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In this paper, the control system of a 600MW supercritical lignite-fired boiler was modeled and coupled with boiler thermal system through GSE simulation software. Simulation experiments were conducted under load decrease condition and load rise condition in order to test control effect and analyze efficiency change in the dynamic mode. Simulation results show that the applied control strategies and established control model are reliable and effective. From BMCR condition to THA condition, boiler efficiency falls from 92.08% to 91.71%, then slowly increases to 92.02%. From THA condition to 75%THA condition, boiler efficiency drops from 92.02% to 91.42%, then slowly rises to 91.90%. From 75%THA condition to 45%BMCR condition, boiler efficiency slumps from 91.90% to 91.37%, then gradually ascends to 91.76%. From THA condition to BMCR condition, boiler efficiency rises from 92.02% to 92.30%, then slowly decreases to 92.08%. From 75%THA condition to THA condition, boiler efficiency soars from 91.87% to 92.41%, then slowly falls to 92.02%. From 45%BMCR condition to 75%THA condition, boiler efficiency ascends from 91.76% to 92.24%, then gradually drops to 91.87%. Load rise condition undertakes lower energy losses than load decrease condition. © 2015 The Japan Society of Mechanical Engineers.

关键词： Drops

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Cellular instability of syngas/air mixtures with H2O dilution 10

Cellular instability of syngas/air mixtures with H2O dilutio...

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10th Asia-Pacific Conference on Combustion, ASPACC 2015

作者： Xie, Yongliang Wang, Jinhua Cai, Xiao Nie, Yaohui Peng, Cheng Yu, Qianqian Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

A study on effects of CO/H2 ratio, H2O dilution and pressures on the cellular structure of moist syngas flame was conducted using spherically expanding flames. Experimental conditions for the CO/H2/H2O/air mixtures are the pressures from 0.1 to 0.3 MPa, initial temperature of 373K and H2O dilution ratios are from 0 to 0.15. Results show cellular instability is promoted at atmospheric pressure and suppressed at elevated pressure when H2O is added into the mixture. In addition, critical radius increases with the increase of H2O dilution ratio for the mixture with CO/H2 ratio of 50/50 and changes little when CO/H2 ratio is 20/80. Critical Peclet number decreases with the addition of H2O and increases with the decrease of CO/H2 ratio.

关键词： Dilution

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Shock tube and kinetic study of 1-pentene and N-pentane 10

Shock tube and kinetic study of 1-pentene and N-pentane

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10th Asia-Pacific Conference on Combustion, ASPACC 2015

作者： Cheng, Yu Hu, Erjiang Deng, Fuquan Yang, Feiyu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

Ignition delay times of the 1-pentene/O2/Ar mixtures and n-pentane/O2/Ar mixtures were measured behind the reflected shock wave at 10 atm, stoichiometric equivalence ratio, in the temperature range of 1100 K to 1580 K. Empirical correlations of the ignition delay time for 1-pentene and n-pentane were obtained through regression analysis. The simulations with the updated natural gas model show well agreement with the experimental data. Both the experimental and simulation results show a crossover in the ignition delay time of these two mixtures. Reaction pathways and sensitivity analysis are conducted to understand the oxidation process of 1-pentene and n-pentane. The chain branching reaction R1(H+O2O+OH) shows a strong promoting effect while the resonantly stablized allyl radical may be responsible for the longer ignition delay time of 1-pentene in the high temperature region.

关键词： Mixtures

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