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International Conference on Materials for Renewable Energy and Environment

作者： Xu, Z.G. Qu, Z.G. Zhao, C.Y. State Key Laboratory of Multiphase Flow School of Energy and Power Engineering Xi'An Jiaotong University China

ISBN: (纸本)9781612847504

Experimental study of air natural convection in horizontally-positioned copper metallic foams with open cells was conducted. Temperature distributions on the heating surface were tested under different heating power for foam samples having different porosities and pore densities. The effects of porosity and pore density on the total thermal resistance of the foam sample were quantified. It is found that the porous surface can enhance the natural convection and reduce the thermal resistance by about 20% in comparison with a smooth surface. The surface area density and mass flow rate in natural convection are affected by porosity and pore density simultaneously. When the porosity is relative small (Ε = 90%), there exits a critical value of the Gr number (turning point) for two pore densities (10ppi and 40ppi). When the Gr number is less than this critical value, the foam with a higher pore density has the lower total thermal resistance, whereas when the Gr number exceeds the turning point value, the opposite holds. If the porosity is increased to Ε = 95%, the foam with a higher pore density has the lower thermal resistance in the whole experimental range. When the porosity and pore density is the same, the foam with smaller size has the higher thermal resistance in the whole experimental range. If the size is relatively small (10010050mm), for the two pore densities studied (20ppi and 80ppi), there exits a critical value of the Gr number (turning point). The foam with a lower porosity(Ε = 90%) has the lower thermal resistance and the decrease is more obvious for the case of *** the size is relatively big(10010080mm),there exists a critical value of the Gr number (turning point) only for the case of 10ppi. When the Gr number is less than this critical value, the foam with a higher porosity (Ε = 95%) has the higher total thermal resistance, the opposite holds. While for the other two pore densities (20ppi and 40ppi), there is no turning point. The foam with a highe

关键词： Natural convection

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Experimental and modeling study on ignition delay times of dimethyl ether/ n -butane blends at a pressure of 2.0 MPa

Experimental and modeling study on ignition delay times of d...

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作者： Jiang, Xue Zhang, Yingjia Man, Xingjia Pan, Lun Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

In this study, the ignition delay times of dimethyl ether (DME)/n-C 4H10 fuel blends, neat DME, and neat n-C4H 10 diluted with argon were measured behind reflected shock waves. The experiments were performed in the temperature range of 1100-1600 K, at a pressure of 2.0 MPa, and equivalence ratios from 0.5 to 2.0. A latest kinetic mechanism NUIG Aramco Mech 1.3 was validated against the measured ignition data and used to conduct the chemical kinetic analysis. Results showed that different equivalence ratio-dependent behaviors were exhibited at different temperature regimes for DME, n-C4H10, and their blend. The ignition delay time of neat n-C4H10 was increased with an increase in the equivalence ratio. A strong inhibiting trend was exhibited at high temperatures. For the neat DME, however, an opposite influencing tendency from the equivalence ratio was presented in comparison to that on n-C 4H10. Ignition promotion becomes significant at relatively low temperatures. A 50% DME/50% n-C4H10 blend show a combined behavior of both n-butane and DME. Fuel reaction flux analysis, sensitive analysis, and mole fraction analysis were conducted for the understanding of the interaction between the ignition chemistries of DME and n-C4H10 at a pressure of 2.0 MPa. © 2014 American Chemical Society.

关键词： Ethers

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Experimental study of auto-ignition of dimethyl ether at low-temperatures and low-pressures 12

Experimental study of auto-ignition of dimethyl ether at low...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Huang, Wenlin Sun, Wuchuan Wu, Honghuan Qin, Xiaokang Jiang, Xue Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Dimethyl ether (DME) is a property of alternative fuels to attract due to the special molecular structure in terms of either scientific study or engine application. However, the lack of fundamental data at low pressures and low temperatures impedes to understand thoroughly the chemistry of DME. Ignition delay times of DME/"air" mixtures with various equivalence ratios of 0.5 - 5.0 were measured in a shock tube at pressure of 3.0 atm over temperatures of 625 - 1200 K. Aramco Mech 2.0 was selected to reproduce the experimental observation. In general, the kinetic model remains an uncertainty in predicting the reactivity of DME at equivalence ratios below 2.0 but it tends much better at equivalence ratios over 3.0. Unlike the model predictions, the experimental data did not show obvious NTC behavior for the mixtures with equivalence ratios of 0.5 and 1.0. The selected model almost fails to capture the four-stage ignition feature for the mixtures with equivalence of 2.0 even considering the hot spot caused by pre-ignition energy release. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethers

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Burning velocity and flamelet structure of turbulent premixed CH4/H2/air flames with CO2 dilution 10

Burning velocity and flamelet structure of turbulent premixe...

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10th Asia-Pacific Conference on Combustion, ASPACC 2015

作者： Wang, Jinhua Yu, Senbin Zhang, Meng Jin, Wu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Turbulent burning velocity and statistical flame front structure parameters of turbulent premixed CH4/H2/air flames diluted with CO2 were measured with OH-PLIF technique. Hydrogen fractions are up to 0.2 and CO2 dilution ratios are up to 0.1. The instantaneous flame front structure was detected using the OH-PLIF technique on a turbulent premixed Bunsen burner. Through image processing and statistic analysis, turbulent burning velocity ST and statistic quantitative parameters, i.e. flame surface density Σ and flame brush thickness δT were obtained. Results show that turbulent burning velocity ST normalized by laminar burning velocity SL decreases with CO2 dilution. Increased Markstein number LM and flame intrinsic instability li with CO2 dilution leads to the passive response of flame to turbulence wrinkling which resulting in less wrinkled flame front, smaller Σ, lower local burning velocity and ST/SL. Convex structure is more frequent than that of concave ones at normal pressure and the bias distribution is much weaker comparing to that of high pressure. The positive structure decreases while the negative structure increases slightly with CO2 dilution. This would be one of the mechanisms leading to the decrease of the effective contact surface between reaction zone and unburned mixture which resulting in the decrease of ST/SL with CO2 dilution.

关键词： Carbon dioxide

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Modelling of flame structure using thickened flame model coupled with multi-step reaction mechanism 11

Modelling of flame structure using thickened flame model cou...

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11th Asia-Pacific Conference on Combustion, ASPACC 2017

作者： Shilong, Guo Meng, Zhang Jinhua, Wang Zuohua, Huang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Thickened flame (TF) model is one of the effective methods to simulate combustion phenomenon. Theoretically, it could be extended to multi-step chemical reaction mechanism. However, the results in the present work shown that TF model coupled with multi-step mechanism will underestimate burnt gas temperature, whether in confined or unconfined space. Meanwhile, some post-flame species (CO, OH) concentration are overestimated, which means the decrease in burnt gas temperature is mainly caused by enhanced species diffusion. Dynamic thickened flame (DTF) model coupled with multi-step mechanism performs well for predicting species concentration and combustion state. So it is not recommended to use TF model coupled with a multi-step chemical reaction mechanism. However, the dynamically thickened flame thickness is obviously thinner than the theoretical expectations for the dynamic thickening factor, which is always used to determine thickening factor for a certain mesh size. The main heat release rate zone couldn’t be thickened as expected. A new DTF model used for multi-step reaction mechanism was proposed. The results show that it can both predict the flame structure accurately and get the flame thickness as expected. © 2018 Combustion Institute. All Rights Reserved.

关键词： Gas temperature

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An Experimental Study Of Gas-Liquid Slug flow In Vertical And Inclined Tubes Using High Speed Motion Analyzer

An Experimental Study Of Gas-Liquid Slug Flow In Vertical An...

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ASME 1996 International Mechanical engineering Congress and Exposition, IMECE 1996

作者： Xia, Guodong Zhou, Fangde Hu, Mingsheng State Key Laboratory of Multiphase Flow In Power Engineering Xi’an Jiaotong University Xi’an710049 China

ISBN: (纸本)9780791815212

Experimental investigation was carried out for gas-liquid slug flow in vertical and inclined tubes. The non- Invasive measurements of the gas-liquid slug flow were taken by using the EKTAPRO 1000 High Speed Motion Analyzer. The present paper has obtained the information on the velocity of the Taylor bubble, the size distribution of the dispersed bubbles in the liquid slugs and some characteritics of the liquid film around the Taylor bubble. The experimental results are in good agreement with the available data. © 1996 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Liquid films

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Simulation of ultrasonic attenuation in theelastic mixing particle system

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Chinese Journal of Acoustics 2018年第1期37卷 99-109页

作者： LI Yunsi SU Mingxu YANG Huinan FAN Fengxian CAI Xiaoshu Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering University of Shanghai for Science and Technology

For the study of predicting ultrasonic attenuation of elastic, spherical mixing par- ticles in the liquid-solid two-phase system, the Monte Carlo method （MCM） is introduced, serving as a probability and statistics technique to evaluate the inside ultrasonic events during the ultrasound propagation. On the basis of ultrasonic scattering and aborption, the continuous ultrasonic waves are represented as discrete and independent phonons. By recording the scat- tering events, tracing the trajectory of a moving phonon and calculating the number of phonons that finally reach the receiving transducer, the ultrasonic attenuation coefficient is obtained to be a frequence-dependent spectrum. Numerical investigations have been carried out to predict and compare the ultrasonic attenuation for a solid-liquid two-phase system with a single type particle. After verifing its feasibility, such a method is then appalied into mixing particle sys- tern, where the mixing iron particles and glass beads with various ratios are set as examples for the purpose of predicting ultrasonic attenuation for the monodisperse and polydisperse mixing particle systems. The results of MCM, the ECAH model, the Lloyd ~z Berry （LB） model and the Waterman model match well when the particle volume concentration is lower than 10%, corresponding to iron particles and glass beads respectively. In the case of two-phase system with mixing particles, it is shown that as the particle volume concentration increases to 10%, the variation of the ultrasonic attenuation coefficient with mixing ratio yields a nonlinear tendency. The physical properties of particles can also influence ultrasonic attenuation significantly.

关键词： Simulation of ultrasonic attenuation in theelastic mixing particle system

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Corrigendum to “Numerical simulation of an externally heated fixed bed reactor for coal pyrolysis based on porous media” [Chem. Eng. Res. Des. 211 (2024) 137–151]

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Chemical engineering Research and Design 2025年 218卷 454-454页

作者： Haoyue Li Yuanpei Luo Fei Dai Jun Sui Hongguang Jin Laboratory of Distributed Energy Systems and Renewable Energy Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

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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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Interfacial stability in vertical swirling annular two-phase flow 16

Interfacial stability in vertical swirling annular two-phase...

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16th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2015

作者： Liu, Li Bai, Bofeng State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

ISBN: (纸本)9781510811843

The linear stability of liquid film flowing upward the inner surface of vertical cylinder under the action of the swirling gas core flow is investigated taking exactly the centrifugal force and curvature of the cylinder into account. Swirl has been considered by superposing a circular movement on the annular flow. The theoretical model of the stability of interface to small perturbation is established by analyzing the normal force balance condition at the wavy interface. The characteristic equation is solved and the stability criterion is obtained. The stability characteristics of neutral, growing and damped modes are presented showing the influences of swirl intensity, relative motion of gas-liquid flow, and the surface tension force. The modeling results indicate that the swirling of the gas phase stabilizes the film flow while the curvature of the cylinder destabilizes it. For strong swirling annular flow, it is found that there is a small influence of surface tension on the stability of interface because the stabilizing centrifugal force is dominant on this condition. The neutral wavelength is found to be very sensitive to the values of swirl intensity and cylinder radius when gas-liquid relative movement is small. However, when gas flow rate is large enough, there is no significant difference in its value.

关键词： Stability criteria

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