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Numerical investigation on thermoacoustic onset

Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第8期30卷 1279-1282页

作者： Wang, Yong He, Ya-Ling Li, Qing Tao, Wen-Quan State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Thermoacoustic phenomena are almost nonlinear, which features self-excited onset. In this paper, a closed-open Rijke tube with the heat source placed at the middle of the tube is modeled. Based on parallel computation, onset of the Rijke tube is carried out numerically. Onset phenomena with various initial fields are observed. Oscillating frequency of the gas within limit cycle is obtained. The gas flow and heat transfer characteristics are studied. These numerical results agree well with those from previous numerical simulations. Such work is helpful for better understanding on the thermoacoustic phenomena, and offers a reference for the study of the thermoacoustic problems with mesoscopic methods such as the lattice Boltzmann method.

关键词： Thermoacoustics

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Premixed combustion of diluted hydrogen-air mixtures in a constant volume bomb

Premixed combustion of diluted hydrogen-air mixtures in a co...

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作者： Miao, Haiyan Huang, Qian Hu, Erjiang Huang, Zuohua Jiang, Deming State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China School of Energy and Powar Engineering Xi an Jiaotong University Xi an 710049 China

Combustion characteristics of diluted hydrogen-air premixed combustion were studied in a constant volume bomb over wide ranges of diluent ratios and equivalence ratios using two kinds of diluent gases. A two-zone model was applied to calculate the heat release rate and combustion duration based on the pressure data. The study showed that, by adding diluent gas into the hydrogen-air mixture, both the combustion development duration and the combustion duration are lengthened. Increasing the diluent ratio reduces the value of the peak pressure, and the reduction is larger on the rich mixture than on the lean one. CO2 diluent gas has greater effects on the normalized mass burning rate, the combustion development duration, and the combustion duration than nitrogen. Within the experimental range of this study, the minimum value of both the combustion development duration and the combustion duration lies within the range of ø = 1.4-1.6. © 2009 American Chemical Society.

关键词： Combustion

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Design and performance simulation of solar powered thermoacoustic engine

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Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2009年第7期30卷 1098-1100页

作者： Shen, Chao He, Ya-Ling Li, Yu-Guang Liu, Ying-Wen State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an 710049 China

The thermoacoustic engine driven by concentrating solar collector is a novel power system with wide application prospect. We designed and built a solar powered thermoacoustic engine. In this study, the thermodynamic performance of the solar focusing collector was numerically studied by using the two-axis solar collector performance simulation program with Simulink. The thermodynamic performance of the solar powered thermoacoustic engine was numerically investigated by coupling the results of the solar collector simulation program with the results of Deltae which is a program to simulate the performance of a thermoacoustic engine. The simulation results provide reference data for experimental study.

关键词： Simulink

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

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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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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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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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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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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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