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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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A comparison of low-pressure premixed laminar flames of 1,3-butadiene and 1,3-butadiene/acetylene with synchrotron radiation 7

A comparison of low-pressure premixed laminar flames of 1,3-...

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7th Asia-Pacific Conference on Combustion, ASPACC 2009

作者： Wei, L.X. Wu, X.S. Chen, Z.Y. Huang, Z.H. Yuan, T. Li, Y.Y. Tian, Z.Y. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China

Low-pressure premixed laminar flames of 1,3-butadiene/oxygen /argon and 1,3-butadiene+acetylene/oxygen/argon have been investigated with tunable synchrotron photoionization and molecular beam mass spectrometry. Flame species, including not only isomeric intermediates, but also those with same molecular weight while different formulae, are identified by measuring the ionization energies. Mole fraction profiles of the main species are derived from the measured signal intensities at different flame positions. Comparison between the two flames reveals that the existence of excessive acetylene in 1,3-butadiene flame can not lead to an obvious increase of aromatics formation under the condition investigated. © 2009 Combustion Institute. All rights reserved.

关键词： Acetylene

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Research on the hydraulic characteristics of a 600MW supercritical pressure CFB boiler

Research on the hydraulic characteristics of a 600MW supercr...

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20th International Conference on Fluidized Bed Combustion

作者： Yang, D. Pan, J. Bi, Q.C. Zhang, Y.J. Jiang, X.G. Yu, L. State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Harbin Boiler Co. Ltd. Harbin 150046 China

Water wall design is a key technology of supercritical pressure CFB boiler. On account of the low heat flux and its homogeneous distribution in furnace, internally ribbed tubes with low mass flux and smooth tubes with moderate mass flux can be applied in the water wall of supercritical CFB boilers. An experimental research on the flow and heat transfer characteristics of internally ribbed tubes and smooth tubes with different inner diameters was conducted in the range of sub-critical and supercritical pressure. The departure from nucleate boiling (DNB) and dry-out boundary and the empirical correlations of heat transfer are obtained from the experiments. The mathematical model for predicting the circuit mass flux and grid pressure of a flow network system is based on the mass and momentum conservation equations and an iterative method is used to solve the nonlinear equations. Harbin Boiler Works has developed a 600MW supercritical CFB boiler with external heat exchangers and 6 separators. The mass flux and metal temperature distribution of water wall in the CFB boiler are calculated and the results show that the water wall can operate safely at BMCR and 75%BMCR load.

关键词： Nonlinear equations

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Effects of hydrogen addition on spherically expanding n-butane flames

Effects of hydrogen addition on spherically expanding n-buta...

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Fall Meeting of the Eastern states Section of the Combustion Institute 2009

作者： Tang, Chenglong Li, Yuyang Huang, Zuohua Law, C.K. State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China Department of Mechanical and Aerospace Engineering Princeton University PrincetonNJ08544 United States

ISBN: (纸本)9781615676682

Laminar flame speeds of hydrogen blended n-butane flames at atmospheric pressure and room temperature was measured in a combustion vessel with Schlieren photography, and determined using nonlinear regression analysis. According to the hydrogen addition parameter (RH) and effective equivalence ratio (φF) defined by Yu et al (1986), laminar flame speeds (Suo) for φF between 0.6 and 1.4 were found to increase linearly with RH from 0 to 0.5, with the slope of the variation assuming a minimum around stoichiometry. These experimental results correlate well with computed laminar flame speeds using the detailed reaction mechanism, USC Mech II. Furthermore, the adiabatic flame temperature was found to also increase monotonously with RH at specific φF, with the extent of the increase being the smallest around stoichiometry. It is therefore suggested that the effect of hydrogen addition on the laminar flame speeds of n-butane flames can be satisfactorily correlated with the response of the corresponding adiabatic flame temperature.

关键词： Stoichiometry

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Possible consumption pathways of 2,5-dimethylfuran in low-pressure premixed laminar flames 7

Possible consumption pathways of 2,5-dimethylfuran in low-pr...

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7th Asia-Pacific Conference on Combustion, ASPACC 2009

作者： Wu, X.S. Wei, L.X. Huang, Z.H. Yuan, T. Zhang, K.W. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China

Low-pressure (4.0 kPa) premixed laminar 2,5-dimethylfuran (DMF)/oxygen/argon flame with an equivalence ratio (ø) of 2.0 was studied with tunable vacuum ultraviolet synchrotron radiation photoionization and molecular-beam mass spectrometry. Photoionization mass spectrum of DMF/O2/Ar flame was recorded and the photoionization efficiency curves (PIEs) of the combustion intermediates were measured. Flame species, including isomeric intermediates, are identified by comparing the measured ionization energies with those reported in literatures or those calculated with Gaussian-03W procedure. More than 70 species have been detected, including furan and its derivatives, aromatics, free radicals, and so on. Possible reaction pathways of DMF are proposed based on the intermediates identified. DMF can be consumed by H-abstraction and pyrolysis reactions. © 2009 Combustion Institute. All rights reserved.

关键词： Free radicals

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Low pressure premixed laminar n-heptane+propane/oxygen flames studied with tunable synchrotron photoionization 7

Low pressure premixed laminar n-heptane+propane/oxygen flame...

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7th Asia-Pacific Conference on Combustion, ASPACC 2009

作者： Yu, W. Wei, L.X. Ma, Z.H. Huang, Z.H. Yuan, T. Tian, Z.Y. Li, Y.Y. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei230029 China

Low pressure premixed laminar n-heptane/propane/O2/N2 flames were investigated with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Three flames with different mass percentage of propane in the fuel blends of 0%, 10%, and 20% were studied. The combustion intermediates were identified by comparing the measured IEs with those values in literatures. Mole fraction profiles of the main species were compared among the three flames. The experimental results provide detailed experimental data in understanding the combustion of n-heptane and n-heptane/propane blends in engine. They are also helpful in establishing and verifying the kinetic model. © 2009 Combustion Institute. All rights reserved.

关键词： Combustion

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Two-phase flow instability in parallel nine-channel system under rolling condition

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Yuanzineng Kexue Jishu/Atomic Energy Science and Technology 2009年第10期43卷 886-892页

作者： Zhang, You-Jia Su, Guang-Hui Qiu, Sui-Zheng Guo, Yu-Jun State Key Laboratory of Multiphase Flow in Power Engineering Department of Nuclear Science and Technology Xi'an Jiaotong University Xi'an 710049 China

Two-phase flow instability in parallel multi-channel system was studied under rolling motion condition. A parallel nine-channel model was established by using the control volume integrating method based on the homogeneous flow model with considering the rolling motion condition. The gear method was used to solve the control equations. The influences of the entrance, upward sections and the heating power on the flow instability under rolling motion condition were analyzed. The marginal stability boundary (MSB) under rolling motion condition was obtained. The unstable regions occur in both low and high equilibrium quality regions. The region with low inlet sub-cooling is also unstable. In high equilibrium quality region, the multiplied period phenomenon is found and the chaotic phenomenon appears at the MSB.

关键词： Stability

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Numerical simulation of predicting and reducing solid particle erosion of solid-liquid two-phase flow in a choke

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Petroleum Science 2009年第1期6卷 91-97页

作者： Li Guomei Wang Yueshe He Renyang Cao Xuewen Lin Changzhi Meng Tao State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an Shaanxi 710049 China China Special Equipment Inspection and Research Institute Beijing 100013 China School of Transport ＆ Storage and Civil Engineering China University of Petroleum Qingdao Shandong 266555 China Petroleum Exploration and Production Research Institute Sinopec Beijing 100083 China

Chokes are one of the most important components of downhole flow-control equipment. The particle erosion mathematical model, which considers particle-particle interaction, was established and used to simulate solid particle movement as well as particle erosion characteristics of the solid-liquid two-phase flow in a choke. The corresponding erosion reduction approach by setting ribs on the inner wall of the choke was advanced. This mathematical model includes three parts： the flow field simulation of the continuous carrier fluid by an Eulerian approach, the particle interaction simulation using the discrete particle hard sphere model by a Lagrangian approach and calculation of erosion rate using semiempirical correlations. The results show that particles accumulated in a narrow region from inlet to outlet of the choke and the dominating factor affecting particle motion is the fluid drag force. As a result, the optimization of rib geometrical parameters indicates that good anti-erosion performance can be achieved by four ribs, each of them with a height （H） of 3 mm and a width （B） of 5 mm equaling the interval between ribs （L）.

关键词： Solid-liquid two-phase flow discrete particle hard sphere model choke erosion rate antierosion numerical simulation

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Numerical studies on natural circulation precooling loop of cryogenic liquid rocket engine

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Hangkong Dongli Xuebao/Journal of Aerospace power 2009年第3期24卷 698-704页

作者： Chen, Er-Feng Li, Yan-Zhong Cheng, Xiang-Hua School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

One set of one-dimensional unsteady homogenous mathematic models for flow and heat process of natural circulation precooling loop of cryogenic liquid rocket engine was established, whilst both inverted annular model and dispersed model were introduced for the prediction of filming boiling region. The results indicate the unstable characteristics of circulation flow rate in precooling process is caused by the unstable characteristics of natural circulation driving force, that is, the heat flux transferred to the cryogenic liquid from the natural circulation precooling loop. Moreover, about 80% of wall temperature drop takes place in filming boiling region, and the inverted temperature distribution law of the return pipe is well interpreted by introducing the two filming boiling models mentioned above.

关键词： Rockets

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