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Study of low-pressure premixed laminar n-heptane+propane/oxygen/nitrogen flames

Chinese Science Bulletin 2009年第9期54卷 1477-1486页

作者： YU Wu WEI LiXia MA ZhiHao HUANG ZuoHua YUAN Tao TIAN ZhenYu LI YuYang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China National Synchrotron Radiation Laboratory University of Science and Technology of China Hefei 230029 China

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

关键词：正庚烷火焰丙烷混层低压氮氧真空紫外

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A two-phase non-isothermal mass transport model for direct methanol fuel cells

A two-phase non-isothermal mass transport model for direct m...

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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Miao, Zheng He, Ya-Ling Li, Xiao-Yue Zou, Jin-Qiang State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

ISBN: (纸本)9780791802908

A two-dimensional two-phase non-isothermal mass transport model for liquid feed direct methanol fuel cells (DMFCs) is presented in this paper. The heat and mass transfer across the membrane electrode assembly (MEA) is formulated based on the classical multiphase flow theory in the porous media. The effects of methanol crossover and non-equilibrium evaporation/condensation of methanol and water at the gas-liquid interface on the cell performance are considered. Results of this model show that the methanol feeding concentration and cell operation temperature have great effects on the cell performance. The distribution of cell temperature is non-uniform and the highest temperature appears in the cathode catalyst layer (CL). The effects of open-ratio of the flow field plate and the thermal conductivity of diffusion layers, catalyst layers and membrane are also investigated in this work. Copyright © 2009 by ASME.

关键词： Methanol

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Numerical study on a novel SOFC with bi-layer interconnector

Numerical study on a novel SOFC with bi-layer interconnector

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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Chen, Qiuyang Zhang, Jian Wang, Qiuwang Zeng, Min State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9780791802908

Solid oxide fuel cells (SOFCs) have received considerable interest nowadays, because they promise greater electrical efficiency than that obtained by a conventional heat engine or other types of low temperature fuel cells. Validated mathematical models provide a very powerful tool for the development of improved SOFC designs and operating conditions. From some literature and numerical simulation results, it could be found that the concentration gradient of fuel and oxidant gas is great on the plane which is normal to the SOFC tri-layer, especially in the porous electrode. But the structures in the previous literature and inventions are always focusing on the disturbance of flow on the plane which is parallel to the SOFC tri-layer. In order to lower the concentration polarization of SOFC, We have invented a novel SOFC with bi-layerer interconnector which can disturb the fuel and air gas on the plane which is normal to the SOFC tri-layer and enhance the mass transfer effectively. In this paper, the primary objective is to compare the concentration overpotentials under the different interconnects modes. A 2D half-cell model has been developed to study on concentration overpotentials of fuel side of the SOFC stack with conventional interconnects and novel bi-layer *** numerical simulation results show that the novel interconnect can disturb the fuel and air gas on the plane which is normal to the SOFC tri-layer and reduce the concentration overpotential of SOFC. It can enhance the mass transfer in porous electrode and improve the performance of SOFC. Copyright © 2009 by ASME.

关键词： Mass transfer

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Performance of a domestic refrigerator using R600a/nano-TiO2 as working fluid

Performance of a domestic refrigerator using R600a/nano-TiO2...

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4th Asian Conference on Refrigeration and Air-Conditioning, ACRA 2009

作者： Bi, Shengshan Guo, Kai Liu, Zhigang Wu, Jiangtao State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9868509610

In this work, an experimental work was investigated on the nano-refrigerant. A domestic R600a refrigerator was selected and instrumented with 19 resistance thermometers and three pressure transducers. R600a/TiO 2 nano-refrigerants were used as working fluid without any system reconstruction. The refrigerator performance was then investigated using energy consumption test and freeze capacity test. The results indicate that R600a/TiO2 nano-refrigerant works normally and safely in the refrigerator. The refrigerator performance was better than the pure R600a system, with 9.6% less energy used with 0.5 g/L nano-refrigerant. Thus, using R600a/ TiO2 nano-refrigerant in domestic refrigerators is feasible.

关键词： Refrigerators

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Equations for the thermophysical properties of dimethyl carbonate

Equations for the thermophysical properties of dimethyl carb...

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2009 AIChE Annual Meeting, 09AIChE

作者： Zhou, Yong Wu, Jiangtao State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

Dimethyl carbonate (DMC) is a nonirritating and nontoxic chemical, further more;it can be used as a fuel additive. In this work, the thermophysical properties formulations for dimethyl carbonate has been developed based upon a selection of available experimental thermophysical property data. In determining the coefficients of the equation of state, multi-property fitting methods were used;including single-phase pressure-volume-temperature (pVT), heat capacity, vapor pressure, and saturated liquid density data. The equation of state has been developed to conform to the Maxwell criterion for two-phase liquid-vapor equilibrium states and is valid for temperatures from 280 K to 400 K and pressure to 60 MPa, and the extrapolation behavior of the equation of state at high temperatures and high pressures is reasonable. The deviation of the density (100x(ρcal-ρexp)/ρexp) is generally less than 0.1% and does not exceed 0.2% except for very few data points in liquid region. The uncertainty of the vapor pressure of the equation of state is generally less than 2.0%. The deviation of viscosity equation developed is generally less than 2.0%, and the absolute average deviation (AAD) between experimental and calculated values is 1.03%. In additional, the extended corresponding states (ECS) model with R134a as the reference fluid was used to represent viscosities and thermal conductivities, and the absolute average deviations are 1.34% and 1.47%, respectively. Detail comparisons between experimental and calculated data have been performed in the work.

关键词： Hydrostatic pressure

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Numerical study of heat transfer characteristics in the solar receiver tube combined with MCRT method

Numerical study of heat transfer characteristics in the sola...

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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Cheng, Z.D. He, Y.L. Xiao, J. Tao, Y.B. Xu, R.J. State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaan xi China

ISBN: (纸本)9780791802908

The solar energy flux distribution on the outer wall of the inner absorber tube of parabolic solar collector receiver is calculated successfully by a homemade code adopting Monte Carlo Ray-Trace Method (MCRT Method). It is revealed that the non-uniformity of the solar energy flux distribution is very large. Three-dimensional numerical simulation of coupled heat transfer characteristics in the receiver tube is calculated and analyzed by combining the MCRT Method and the FLUENT software, in which the heat transfer fluid and physical model are Syltherm 800 liquid oil and LS2 parabolic solar collector from the testing experiment of Dudley et al., respectively. Temperature- dependent properties of the oil and thermal radiation between the inner absorber tube and the outer glass cover tube are also taken into account. Then three typical testing conditions are chosen from the experiment to validate the reliability of the simulation code. Numerical results show that the predicted results agree well with the experimental data, the average relative error is within 2%. And then the mechanism of the coupled heat transfer in the receiver tube is further studied. Copyright © 2009 by ASME.

关键词： Numerical methods

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Numerical study on the coupled heat transfer performance of the parabolic solar absorber tube

Numerical study on the coupled heat transfer performance of ...

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2009 US-EU-China Thermophysics Conference - Renewable Energy, UECTC'09

作者： Tao, Y.B. He, Y.L. State Key Laboratory of Multiphase Flow in Power Engineering School of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

ISBN: (纸本)9780791802908

In present paper, a two-dimensional numerical model for the coupled heat transfer process in the solar collector tube was developed and the unified dimensionless governing equations were derived. The full field computation method was adopted to deal with the fluid-solid conjugated heat transfer problem. The effects of Ra numbers and tube diameter ratio on the heat transfer and fluid flow performance were numerically analyzed under the constant heat flux conditions. The distributions of flow field, temperature field, local Nu and local temperature gradient were examined. The results show that when Ra is larger than 105, the effects of nature convection must be taken into account. Due to the effect of the nature convection, along the θ direction, the temperature in the cross-section decreases and the temperature gradient on the inner tube surface increases at first. When θ is near to π, the temperature and temperature gradients would present a converse variation. The local Nu on the inner tube surface increases along θ direction until it reaches a maximum then it decreases again. Due to the existing of the nature convection vortexes, the temperature distributions in some cross-sections present fluctuations along the r direction. Copyright © 2009 by ASME.

关键词： Heat flux

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Experimental study of nitrogen oxide emissions in a circulating fluidized bed

Experimental study of nitrogen oxide emissions in a circulat...

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20th International Conference on Fluidized Bed Combustion

作者： Liu, R.W. Zhou, Q.L. Hui, S.E. Xu, T.M. State Key Laboratory of Power Engineering Multiphase Flow Department of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaanxi 710049 China

The experimental study was carried out on the emission characteristics of nitrogen oxide in a 0.3MW circulating fluidized bed as well as analysis of the formation and destruction mechanism of nitrogen oxide. Several variables associated with the combustion system were investigated in the experiment, which include bed temperature, excess air, primary-to-secondary air ratio, and coal species. It is found that the NOx emissions decrease along the height of the furnace, while the N2O emissions increase continuously. More NOx emissions and less N2O emissions are generated as the bed temperature increases. It is also illustrated that an increase of air stoichiometry leads to a significant NOx increase and an obvious N2O increase. And air staging is proved to be an effective way to control the nitrogen oxide emissions in the fluid bed. Besides, it is also shown in the experiment that the concentration of NOx and N2O is higher during the combustion of anthracite than that during the combustion of bituminous.

关键词： Nitrogen oxides

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Lattice Boltzmann method and its applications in engineering thermophysics

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Chinese Science Bulletin 2009年第18期54卷 4117-4134页

作者： HE YaLing LI Qing WANG Yong TANG GuiHua School of Energy and Power Engineering State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049 China

The lattice Boltzmann method (LBM), a mesoscopic method between the molecular dynamics method and the conventional numerical methods, has been developed into a very efficient numerical alternative in the past two decades. Unlike conventional numerical methods, the kinetic theory based LBM simulates fluid flows by tracking the evolution of the particle distribution function, and then accumulates the distribution to obtain macroscopic averaged properties. In this article we review some work on LBM applications in engineering thermophysics: (1) brief introduction to the development of the LBM; (2) fundamental theory of LBM including the Boltzmann equation, Maxwell distribution function, Boltzmann-BGK equation, and the lattice Boltzmann-BGK equation; (3) lattice Boltzmann models for compressible flows and non-equilibrium gas flows, bounce back-specular-reflection boundary scheme for microscale gaseous flows, the mass modified outlet boundary scheme for fully developed flows, and an implicit-explicit finite-difference-based LBM; and (4) applications of the LBM to oscillating flow, compressible flow, porous media flow, non-equilibrium flow, and gas resonant oscillating flow.

关键词：格子玻尔兹曼方法工程热物理格子Boltzmann 麦克斯韦分布函数分子动力学方法可压缩流动应用数值方法

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Experimental study on air-staged combustion in a W-shaped boiler furnace 9

Experimental study on air-staged combustion in a W-shaped bo...

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9th International Conference on power engineering, ICOPE 2009

作者： Liu, Ruwei Zhou, Qulan Hui, Shien Zhao, Qinxin Fan, Qingwei Xu, Tongmo Yu, Zhanying State Key Laboratory of Power Engineering Multiphase Flow Department of Energy and Power Engineering Xi'an Jiaotong University Xi'an Shaan xi710049 China

The experimental study was carried out on the air-staged combustion of different coal in a 1 MW W-shaped furnace. The combustion process occurred in two zones: the pre-stage combustion zone and the primary combustion zone. A variable SR was introduced to represent the air stoichiometric ratio in the pre-stage combustion zone. It is found that as SR decreases in the test range, the flame penetration depth is lengthened, and the temperature at the exit of the furnace decreases. Meanwhile, the maximum temperature in the central of the furnace first increases and then decreases, whereas the combustible loss and nitrogen oxides (NOx) emissions first decrease and then increase. The value of SR corresponding to the optimal combustion performance is 0.67 for lean coal and 0.65 for anthracite. Besides, it is also indicated that the effects of air-staging method are more significant on the lean coal than that on the anthracite.

关键词： Furnaces

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