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Large-eddy simulation of boundary layer separation and reattachment in low-pressure turbine cascade

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical engineering 2009年第29期29卷 77-83页

作者： Zhang, Di Shu, Jing Lan, Ji-Bing Xie, Yong-Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 Shaanxi Province China

Large fraction of the low-pressure turbine cascade boundary layer is laminar flow due to low Reynolds number. High-lift low-pressure turbine blade leads to increase the adverse pressure gradient at rear of the turbine cascade. Boundary layer separation is easy to happen as the layer has low level of momentum and energy under large adverse pressure gradient, and then transition and reattachment occurs in the boundary layer. Large-eddy simulation (LES) was used to study boundary layer separation and reattachment in the low-pressure turbine (LPT) cascade without considering upstream wakes and at Reynolds numbers (based on chord length and throat exit velocity) of 5105. The numerical results agree with experimental measurements in terms of the time averaged static pressure distribution around the blade and the suction side boundary layer separated and reattached points. In addition, Separation and reattachment locations of suction side boundary layer were investigated with different inlet flow angle and different Reynolds numbers. The effect of the previous two parameters on boundary layer separation of cascade is obtained. © 2009 Chin. Soc. for Elec. Eng.

关键词： Large eddy simulation

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Numerical optimizing analyses of pulse tube regenerators

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第3期30卷 370-374页

作者： He, Ya-Ling Gao, Fan Tao, Yu-Bing Zhang, Dong-Wei State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Based on the 1-D & 2-D combined computational model, numerical optimizing analyses on the performance of the orifice type pulse tube refrigerator (OPTR) and double-inlet type pulse tube refrigerator (DPTR) were carried out. The evolvements process of the flow field in the OPTR and DPTR were examined. The results show that in the compressor expansion process the gas separation phenomenon occurs in the pulse tube, and in the compression process, there exists the gas aggregation phenomenon. The gas velocities in the separation and aggregation interfaces are zero, so the interface is called zero interface. In a period, the zero interface will move from one end of the pulse tube to the other end, which is called zero interface effect. The zero interface effect is an important factor for the performance enhancement of the PTR. The longer the time of the zero interface effect existing in a period, the better the PTR performance. Then based on the simulation results, the mechanism analysis for the existing of zero interface effect was performed. The results show that the introduction of the orifice valve leads to the formation of zero interface effect and the introduction of the double-inlet valve could augment the zero interface effect. For the OPTR, the time of the zero interface existing is about 1/6 period and for the DPTR the existing time of the zero interface is about 1/2 period.

关键词： Numerical analysis

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Effect of equivalence ratio on the ignition delay times of propane/hydrogen in argon diluted oxygen

Effect of equivalence ratio on the ignition delay times of p...

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9th Asia-Pacific Conference on Combustion, ASPACC 2013

作者： Tang, Chenglong Man, Xingjia Pan, Lun Huang, Zuohua State Key Laboratory of Multiphase Flows in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

By using the shock tube facility, measurements on ignition delay times of propane/hydrogen mixtures (hydrogen fraction from 0 to 100%) were conducted for the equivalence ratio of 0.5, 1.0 and 2.0. Results show that for XH2 less than 70%, ignition delay time shows a strong Arrhenius temperature dependence, and the ignition delay time increases with the increase of the equivalence ratio. When XH2 is increased to more than 95%, the ignition delay times do not retain the Arrhenius temperature dependence any more, and the effect of the equivalence ratio is very weak. Numerical studies were made using the selected kinetic mechanisms and results show that the predicted ignition delay time gives a reasonable agreement with the measurements at all test conditions. Both measurements and predictions show that for X H2 less than 70%, the ignition delay time is only moderately decreased with the increase of XH2, indicating that hydrogen addition has weak effect on ignition enhancement. Sensitivity analysis reveals the key reactions that control the simulation of ignition delay time. Kinetic study is made to interpret the ignition delay time dependence on equivalence ratio and XH2.

关键词： Hydrogen

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Sand particle lift-off velocity measurements and numerical simulation of mass flux distributions in a wind tunnel

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Journal of Arid Land 2017年第3期9卷 331-344页

作者： XIAO Fengjun DONG Zhibao GUO Liejin WANG Yueshe LI Debiao National Demonstration Center for Experimental Geography Education College of Tourism and Environment Shaanxi Normal University Xi'an 710119 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Xi'an Special Equipment Inspection Institute Xi'an 710065 China

Lift-off velocity of saltating sand particles in wind-blown sand located at 1.0 mm above the sand bed surface was measured using a phase Doppler particle analyzer in a wind tunnel. The results show that the probability distribution of lift-off velocity can be expressed as a lognormal function, while that of lift-off angle follows an exponential function. The probability distribution of lift-off angle conditioned for each lift-off velocity also follows an exponential function, with a slope that becomes steeper with increasing lift-off velocity. This implies that the probability distribution of lift-off velocity is strongly dependent on the lift-off angle. However, these lift-off parameters are generally treated as an independent joint probability distribution in the literature. Numerical simulations were carried out to investigate the effects of conditional versus independent joint probability distributions on the vertical sand mass flux distribution. The simulation results derived from the conditional joint probability distribution agree much better with experimental data than those from the independent ones. Thus, it is better to describe the lift-off velocity of saltating sand particles using the conditional joint probability distribution. These results improve our understanding of saltation processes in wind-blown sand.

关键词： lift-off velocity lift-off angle joint probability distribution sand mass flux saltation

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Experimental study on dryout point in vertical narrow annulus under low flow conditions

Experimental study on dryout point in vertical narrow annulu...

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12th International Conference on Nuclear engineering (ICONE12) - 2004

作者： Tian, Wenxi Myint, Aye Li, Zhihui Qiu, Suizheng Su, G.H. Jia, Dounan State Key Lab. Multiphase Flow P.E. 710049 Xi'an China State Key Lab. Multiphase Flow P.E. Sch. of Energy and Power Engineering Xi'An Jiaotong University 710049 Xi'an China

Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux from 26.6 to 68.8 kg/m2 s and wall heat flux from 5.0 to 50.0 kW/m2. The location of dryout is obtained by observing a sudden rise in surface temperature, Kutateladze correlations is cited, however proved to be not a proper one for annuli gap and modified to predict the location of dryout. Considering in detail the effects of the geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition which has a good agreement with experimental data.

关键词： Two phase flow

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Shock tube and kinetic study of C2H6/H 2/O2/Ar mixtures at elevated pressures

Shock tube and kinetic study of C2H6/H 2/O2/Ar mixtures at e...

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作者： Pan, Lun Zhang, Yingjia Zhang, Jiaxiang Tian, Zemin Huang, Zuohua State Key Laboratory of Multiphase Flows in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Using a high-pressure shock tube facility, the ignition delay times of stoichiometric C2H6/H2/O2 diluted in argon were obtained behind reflected shock wave at elevated pressures (p = 1.2, 4.0 and 16.0 atm) with ethane blending ratios from 0 to 100%. The measured ignition delay times were compared to the previous correlations, and the results show that the ignition delay times of ethane from different studies exhibit an obvious difference. Meanwhile, numerical studies were conducted with three generally accepted kinetic mechanisms and the results show that only NUIG Aramco Mech 1.3 agrees well with the measurements under all test conditions. Sensitivity analysis was made to interpret the poor prediction of the other two mechanisms. Furthermore, the effect of ethane blending ratio on the ignition delay times of the mixtures was analyzed and the results show that ethane blending ratio gives a non-linear effect on the auto-ignition of hydrogen. Finally, chemical interpretations on this non-linear effect were made from the reaction pathway analysis and normalized H radical consumption analysis. © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Shock tubes

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Research on the Preparation of (CuAg)xIn2xZn2(1−2x)S2 Solid Solution Photocatalysts

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AIP Conference Proceedings 2010年第1期1207卷 1066-1069页

作者： K. Zhang D. W. Jing C. J. Xing L. J. Guo State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University China

ZnS‐CuInS2‐AgInS2 solid solution photocatalysts were successfully prepared by co‐precipitation method with heat treatment under different atmosphere ( N2 and H2S). XRD, XRF, UV‐vis, and SEM were used to characterize the prepared photocatalysts, indicated that the composition of result photocatalysts were different from each other and also the rate of charge, though they possessed a wurtzite‐type phase structure. The photocatalysts all showed photocatalytic activities for H2 evolution from aqueous solutions containing SO32− and S2− as sacrificial reagents under visible light irradiation with Ru loading, but sample treated under H2S atmosphere performed better, the possible reason was proposed.

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Turbulent heat transfer in a horizontal helically coiled tube

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Heat Transfer - Asian Research 1999年第5期28卷 395-403页

作者： Bai, Bofeng Guo, Liejin Feng, Ziping Chen, Xuejun State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University China

An experiment has been conducted in detail to study the turbulent heat transfer in horizontal helically coiled tubes over a wide range of experimental parameters. We found that the enhancement of heat transfer in the coils results from the effects of turbulent and secondary flows. With Reynolds number increasing to a high level, the contribution of the secondary flow becomes less to enhance heat transfer, and the average heat transfer coefficient of the coil is closer to that in straight tubes under the same conditions. The local heat transfer coefficients are not evenly distributed along both the tube axis and the periphery on the cross section. The local heat transfer coefficients on the outside are three or four times those on the inside, which is half of the average heat transfer. A correlation is proposed to describe the distribution of the heat transfer coefficients at a cross section. The average cross-section heat transfer coefficients are distributed along the tube axis. The average value at the outlet section should not be taken as the average heat transfer coefficient.

关键词： Heat transfer

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Solid-state anaerobic co-digestion of highland barley straw, food waste, and yak manure:Co-digestion performances and microbial characteristics analysis

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Renewable Energy 2025年 252卷

作者： Rui Bao Jiaqi Feng Wenli Feng Xiujin Li Xuebin Lu Xiaoyu Zuo Rufei Liu Hairong Yuan State Key Laboratory of Chemical Resource Engineering Department of Environmental Science and Engineering Beijing University of Chemical Technology Beijing 100029 PR China Key Laboratory of Thermo-Fluid Science and Engineering of MOE School of Energy and Power Engineering Xi'an Jiaotong University 28 Xianning West Road Xi'an Shanxi Province 710049 PR China State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University 28 Xianning West Road Xi'an Shaanxi Province 710049 PR China School of Environmental·Science and Engineering Tianjin University Tianjin 300350 PR China Key Laboratory of Environmental Engineering and Pollution Control on the Plateau of Tibet Autonomous Region School of Ecology and Environment Tibet University Lhasa Tibet 850000 PR China CUCDE Environmental Technology CO. LTD. Beijing 100120 PR China

Co-digestion performances and microbial characteristics were investigated at solid-state anaerobic co-digestion system for highland barley straw (HBS), food waste (FW) and yak manure (YM). The different mixing ratios of HBS, FW, and YM were set according to the total solid content of different substrates. The results showed that the highest methane was 465.9 mL/g VS when the ratio of HBS:FW:YM was 0:5:1(HFY051), which was 4.5 %–102.6 % higher than those of co-digestion groups, HBS, and YM. The synergistic effect of co-digestion for different substrates contributed 6.3 %–123.1 % to improving methane yields in the first 25 days. Clostridium_sensu_stricto 1 and Fastidiosipila were the key bacterials and Methanosarcina and Methanobacterium were dominant methanogens at genus levels for different experimental groups. LEfSe indicated that 26 species have a great impact on co-digestion experimental groups. Therefore, solid-state anaerobic co-digestion of HBS, FW, and YM could improve the co-digestion performances and achieve higher methane yield.

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Experimental and kinetic study on ignition delay times of iso -butanol

Experimental and kinetic study on ignition delay times of is...

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作者： Pan, Lun Zhang, Yingjia Tian, Zemin Yang, Feiyu Huang, Zuohua State Key Laboratory of Multiphase Flows in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Ignition delay times of iso-butanol with fuel concentration of 0.5-1.0% were measured behind reflected shock waves. The experiments were conducted in the temperature range of 900-1700 K, at pressures of 1.2-10.0 atm and equivalence ratios of 0.5-2.0. The measured ignition delay times were compared with previous data under the same conditions and were correlated through multiple linear regression. Using the correlation, the ignition delay times of iso-butanol were compared to those of n-butanol. It was found that iso-butanol presented longer ignition delay time than that of n-butanol. Three available models were used to simulate the ignition delay times. Results showed that Sarathy model exhibited the best predictions at high temperature, but none of these models could well reproduce the measured ignition delay times at intermediate-low temperature. Reaction pathway analysis was performed to chemically interpret the observed difference in ignition delay times of n-butanol and iso-butanol. In addition, sensitivity analysis was made to ascertain the key reactions that control the intermediate-low temperature ignition in the Sarathy model. © 2014 American Chemical Society.

关键词： Temperature

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