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9th Asia-Pacific Conference on Combustion, ASPACC 201.

作者： Wang, Jinhua Zhang, Meng Huang, Zuohua Kudo, Taku Kobayashi, Hideaki State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China Institute of Fluid Science Tohoku University Sendai Miyagi 9808577 Japan

Instantaneous detailed flame front structure of syngas turbulent premixed flames was investigated and compared to that of CH4/air flames. Results show that the flame front of turbulent premixed flames at high pressure is a wrinkled flame front with small scale convex and concave structures superimposed with large scale flame branches. The convex structures are much more frequent than the concave ones on flame front which reflects a general characteristic of the turbulent premixed flames at high pressure. The syngas flames possess much wrinkled flame front with much smaller fine cusps structure compared to that of CH4/air flames and the main difference is on the convex structure. The effect of turbulence on the general wrinkled scale of flame front is much weaker than that of the smallest wrinkled scale. The general wrinkled scale is mainly dominated by the turbulence vortex scale, while, the smallest wrinkled scale is determined by the flame intrinsic instability. The effect of flame intrinsic instability on flame front of turbulent premixed flame is mainly on the formation of a large number of convex cusps structure propagating to the unburned reactants and enlarge the effective contact surface between flame front and unburned reactants.

关键词： Turbulence

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Experimental study on boiling heat transfer and two-phase frictional pressure drop characteristics of glycol-water solution in a vertical porous surface tube

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AIP Conference Proceedings 2013年第1期1547卷 390-399页

作者： Shouxu Qiao Haijun Wang Hongfang Gu Yushan Luo Lei Zhang Wei Xiong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

Although much research has been conducted on investigating the flow boiling heat transfer of low saturation temperature refrigerants, there are few experimental data and theory about the flow boiling heat transfer of high saturation temperature organic mixture which exists widely in the petrochemical industry. To investigate the characteristics of flow boiling heat transfer of high saturation temperature organic mixture, experiments of glycol-water solution flow boiling in a vertical porous surface tube and a vertical smooth tube are conducted. Test tubes are uniformly heated by electrical current with a heated length of 2,000 mm. The mass flux in the experiment ranges from 500 to 1.500t⋅h−1.and the heat flux on test tubes ranges from 1. to 40 kW⋅m−2. The flow boiling heat transfer coefficients and two-phase frictional pressure drops of the two types of tubes are obtained and compared. The results indicate that: the flow boiling heat transfer coefficient in the porous surface tube is 3.8∼5.7 times of that in smooth tube and the pressure drop of the porous surface tube is 0.99∼1.007 times of that in the smooth tube. The physical mechanisms of the enhanced heat transfer characteristics of flow boiling in the porous surface tube are analyzed. By the regression analysis of the experimental data, correlations predicting the flow boiling heat transfer coefficient and pressure drop of glycol-water solution within the error range of ±20% are established. The experimental results can be used to guide the design of heat exchange equipment using the porous surface tube as heat transfer elements under these test conditions.

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Investigation on the impact of the environment wind velocity on the indirect air-cooling tower performance

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AIP Conference Proceedings 2013年第1期1547卷 469-476页

作者： Yongbo Qin Hongfang Gu Haijun Wang Guoyong Chen State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 21.;330MW vertical arrangement indirect air-cooled system was taken as research object, and numerica...

The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerical simulation method was used to analyze the relative influence of the wind speed, ranging from 4m/s to 1.m/s, on the outlet water temperature of cooling tower, the outlet air temperature of radiator, the facing wind speed of the fan segment and on the outlet air speed of the cooling tower. The result shows that the impact of the natural wind speed on the cooling tower efficiency varies greatly and this impact increases as the wind speed increases.

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Study on heat transfer characteristic of ethanol-water mixture condensation on a vertical micro-tube

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AIP Conference Proceedings 2013年第1期1547卷 362-372页

作者： Xiping Chen Jinshi Wang Junchao Qin Daotong Chong Junjie Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

In present experiment, the vapor mixture with different velocities (2m⋅s−1. 4m⋅s−1. and different ethanol mass fraction (0.5%, 1., 2%, 5%, 1.%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tube surface at pressure 31.1.kPa, 47.36kPa. The condensation modes were observed by CCD camera, and the characteristics of the heat transfer coefficients versus the vapor-to-surface temperature differences for different experimental conditions were obtained. The condensation heat transfer coefficients of vapor mixture decrease with the vapor concentration increasing. The maximum peak value of heat transfer coefficients, up to 39 kW⋅m−2⋅K1. which was about 3-4 times greater than that of steam, appeared when the ethanol mass fraction was 2%. A heat transfer coefficient correlation including the effects of all the tested parameters is proposed by using the multiple linear least squares method based on the experimental data. The calculated values agreed well with the experimental data and the deviations between them were from −20% to 20%.

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Optimization research on the structure of horizontally-arranged indirect air-cooling tower under strong wind condition

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AIP Conference Proceedings 2013年第1期1547卷 454-462页

作者： Guoyong Chen Hongfang Gu Haijun Wang Yongbo Qin State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University 710049 Xi'an China

Strong wind has a significant impact on the heat radiation of the air-cooling system. In this research, a numerical calculation model of 21.;1.00MW horizontally arranged air-cooling tower is established to simulate...

Strong wind has a significant impact on the heat radiation of the air-cooling system. In this research, a numerical calculation model of 2×1.00MW horizontally arranged air-cooling tower is established to simulate the flow distribution and heat exchanging capability of three different structures-horizontally-arranged indirect air-cooling tower, tower with guide wall outside, and tower with a cross wall inside-under high-speed wind and extreme-speed wind conditions. The result reveals that the structure with the guide wall outside the tower only works under strong wind condition while the structure with cross wall inside shows the anti-wind capability under both high-speed wind and extreme-speed wind conditions.

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Visualization and flow boiling heat transfer of hydrocarbons in a horizontal tube

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AIP Conference Proceedings 2013年第1期1547卷 432-441页

作者： Zhuqiang Yang Qincheng Bi Yong Guo Zhaohui Liu Jianguo Yan State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

Visualizations of a specific hydrocarbon fuel in a horizontal tube with 2.0 mm inside diameter were investigated. The experiments were conducted at mass velocity of 21..4, 426.5 and 640.2 kg/ (m2⋅s), diabatic lengths of 1.0, 240 and 420 mm under the pressure from 2.0-2.7 MPa. In the sub-pressure conditions, bubbly, intermittent, stratified-wave, churn and annular flow patterns were observed. The frictional pressure drops were also measured to distinguish the patterns. The development of flow patterns and frictional pressure drop were positively related to the mass velocity and the heat flux. However, the diabatic length of the tube takes an important part in the process. The residence time of the fluid does not only affect the transition of the patterns but influence the composition of the fuel manifested by the fuel color and carbon deposit. The special observational phenomenon was obtained for the supercritical pressure fluid. The flow in the tube became fuzzier and pressure drop changed sharply near the pseudocritical point. The flow boiling heat transfer characteristics of the hydrocarbons were also discussed respectively. The curve of critical heat flux about onset of nucleate boiling was plotted with different mass velocities and diabatic tube lengths. And heat transfer characteristics of supercritical fuel were proved to be better than that in subcritical conditions.

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A kinetic modeling study of high temperature chemistry of n-pentanol 8

A kinetic modeling study of high temperature chemistry of n-...

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8th US National Combustion Meeting 201.

作者： Li, Qianqian Merchant, Shamel S. Green, William H. Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'n Jiaotong University Xi'an710049 China Department of Chemical Engineering Massachusetts Institute of Technology CambridgeMA02139 United States

ISBN: (纸本)9781627488426

With increasing environmental deterioration and energy demand, studies on new alternative fuels have been attracting more attention. N-pentanol is a five carbon, straight-chain alcohol, which can be produced through natural microbial fermentation and/or engineered microorganisms. It has many advantages over lower carbon alcohols, including higher energy density, lower vapor pressure and better fuel compatibility. In this study, a detailed reaction mechanism of n-pentanol, on the basis of a previously proposed n-butanol mechanism, is generated using the open-source software Reaction Mechanism Generator (RMG). High temperature chemistry of the mechanism was validated against recently published laminar flame speeds and ignition delays. Encouraging results between simulations and experiments were observed under most conditions. Simulations were also conducted using a recently developed n-pentanol oxidation mechanism (NUI model) by Heufer et al. For lean mixtures, the two mechanisms show similar results, while the RMG model yields better predictions for rich mixtures and at an elevated pressure. Reaction pathways and sensitivity analysis reveal the key differences between the two mechanisms in terms of intermediates formed and fuel consumption.

关键词： Alternative fuels

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Experimental study on performance and emissions of diesel/n-pentanol blends on a DI diesel engine

Experimental study on performance and emissions of diesel/n-...

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9th Asia-Pacific Conference on Combustion, ASPACC 201.

作者： Wei, Liangjie Cheung, C.S. Huang, Zuohua Department of Mechanical Engineering Hong Kong Polytechnic University Hung Hom Kowloon Hong Kong State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an 710049 China

In this work, experiments were conducted on a diesel engine fueled with n-pentanol/diesel blends to examine the effect of n-pentanol addition on the engine performance and emissions. Results show that, the addition of n-pentanol to diesel increases the brake specific fuel consumption and has little effect on the brake thermal efficiency. Additionally, the emissions of HC, CO and NOx are slightly increased with the increase of n-pentanol in the fuel blends, however, the particulate matter emission is significantly reduced.

关键词： Brakes

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Stability analysis of a square rod bundle sub-channel in supercritical water reactor

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AIP Conference Proceedings 2013年第1期1547卷 181-189页

作者： Wang Hai-jun You Ting Zhang Lei Gu Hong-fang Luo Yu-shan Bian Ji-lian State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiao tong University Xi'an 710049 China

Extensive investigations on the flow and heat transfer behavior in SCWR fuel assembly have been undertaken worldwide. However, stability analysis of supercritical water in the sub-channels of tight lattices is still lacking. In this paper, the flow stability of a fuel bundle channel with square pitches has been analyzed using commercial CFD code-ANSYS Fluent. Typical dynamic instability of Density Wave Oscillation (DWO) has occurred in heated channel containing fluids at supercritical pressure. A further discussion about the impacts of various operational parameters (e.g. power input, system pressure, mass velocity, inlet temperature, etc) shows that the system becomes more stable as system pressure and/or mass flow rate increases. An increase in inlet temperature also has a stabilizing effect on the system.

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Boiling and two-phase flow phenomena of refrigerant-based nanofluids: Fundamentals, applications and challenges

Boiling and two-phase flow phenomena of refrigerant-based na...

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作者： Cheng, Lixin Liu, Lei School of Engineering University of Portsmouth Anglesea Building Anglesea Road Portsmouth PO1 3DJ United Kingdom State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

The study of refrigerant-based nanofluid boiling and two-phase flow phenomena is still in its infancy. This field of research provides many opportunities to study new frontiers but also poses great challenges. To summarize the current status of research in this newly developing interdisciplinary field and to identify the future research needs as well, this paper presents a comprehensive review of nucleate pool boiling, flow boiling, condensation and two-phase flow of refrigerant-based nanofluids. The effects of nanolubricants on boiling and two phase flow phenomena are presented as well. Furthermore, studies of applications and challenges of refrigerant-based nanofluids are presented and future research needs are identified. For the limited studies done so far, there are some controversies from one study to another. Conclusions and contradictions on the available refrigerant-based studies of physical properties, boiling and two phase flow are presented. According to this review, it has been realized that the physical properties have significant effects on the refrigerant-based nanofluid boiling and two-phase flow characteristics but the lack of the accurate knowledge of these physical properties has greatly limited the study in this interdisciplinary field. Furthermore, the limited available experiments and quite contradictive results have limited the understanding of the fundamentals of boiling and two phase flow phenomena. flow regimes are very important in understanding the phenomena but less investigated so far. Apparently it is still a long way to go to achieve systematic fundamental knowledge and theory in the relevant subject. Therefore, effort should be made to contribute to the physical property database of nanofluids as a first priority. Secondly, systematic accurate experiments and flow regime observations on boiling and two-phase flow phenomena under a wide range of test conditions and nanofluid types should be emphasized to understand the fundamentals.

关键词： Two phase flow

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