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7th Asia-Pacific Conference on Combustion, ASPACC 2009

作者： Wang, J.H. Huang, Z.H. Tang, C.L. Zheng, J.J. State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

Effect of hydrogen addition on early flame growth of lean burn natural gas-air mixtures was investigated experimentally and numerically. The flame propagating photos and pressure derived initial combustion duration of premixed combustion and direct injection combustion was obtained by using a constant volume vessel. The laminar premixed methane-hydrogen-air flames were calculated with PREMIX code of CHEMKIN II program with GRI 3.0 mechanism. The results showed that the early flame growth of lean burn natural gas-air mixtures was enhanced as hydrogen is added to natural gas in the case of both premixed combustion and direct injection combustion. The mole fraction of OH and O are increased with the increase of hydrogen fraction and the position of maximum OH and O mole fraction move closing to the unburned mixture side. A monotonic correlation between initial combustion duration with the reciprocal maximum OH mole fraction in the flames is observed. The enhancement of the spark ignition of natural gas with hydrogen addition can be ascribed to the increase of OH and O mole fraction in the flames. © 2009 Combustion Institute. All rights reserved.

关键词： Natural gas

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Time-resolved investigation of droplet size and velocity inside diesel fuel sprays 11

Time-resolved investigation of droplet size and velocity ins...

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11th Asia-Pacific Conference on Combustion, ASPACC 2017

作者： Feng, Zehao Zhang, Mingzhi Yang, Jiapei Tang, Chenglong Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

To better understand the microscopic spray characteristics, measurements of temporal changes in the size and velocity of droplets inside diesel fuel sprays were conducted at a fixed measurement position of 40mm downstream from the injector tip. Particle/droplet image analysis (PDIA) system was applied to obtain the microscopic droplet images in a long time scale (0-10 ms) which consists of continuous injection stage (0-2.1 ms) and the spray free development stage (2.1-10 ms). The results show that the droplet size distribution has a significant variation at the beginning, but basically independent of time after 1.6 ms. The Sauter mean diameter (SMD) increases significantly at the continuous injection stage, but slightly decreases at the free development stage. In addition, it is observed that most droplets’ velocity are 2-3 m/s while the maximum value is 25 m/s. An interesting similar bimodal shape of velocity distribution probability curves was found at different time after start of injection. What’s more, the scalar velocities gradually decrease as time goes on, but the direction of the velocities is messy due to the air entrainment. © 2018 Combustion Institute. All Rights Reserved.

关键词： Velocity

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Shock tube and kinetic study of 1-pentene and N-pentane 10

Shock tube and kinetic study of 1-pentene and N-pentane

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10th Asia-Pacific Conference on Combustion, ASPACC 2015

作者： Cheng, Yu Hu, Erjiang Deng, Fuquan Yang, Feiyu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

Ignition delay times of the 1-pentene/O2/Ar mixtures and n-pentane/O2/Ar mixtures were measured behind the reflected shock wave at 10 atm, stoichiometric equivalence ratio, in the temperature range of 1100 K to 1580 K. Empirical correlations of the ignition delay time for 1-pentene and n-pentane were obtained through regression analysis. The simulations with the updated natural gas model show well agreement with the experimental data. Both the experimental and simulation results show a crossover in the ignition delay time of these two mixtures. Reaction pathways and sensitivity analysis are conducted to understand the oxidation process of 1-pentene and n-pentane. The chain branching reaction R1(H+O2O+OH) shows a strong promoting effect while the resonantly stablized allyl radical may be responsible for the longer ignition delay time of 1-pentene in the high temperature region.

关键词： Mixtures

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Onset of slugging fluidization in supercritical water fluidized bed

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Particuology 2020年第5期18卷 47-56页

作者： Hao Wang Jikai Huang Youjun Lu State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong UniversityXi'an 710049ShaanxiChina Energy Research Insatute Qilu University of Technology(Shandong Academy of Sciences)Jinan 250014ShandongChina

The supercritical-water fluidized bed(SCWFB)is a reactor for coal and biomass gasification without pollutant *** carried out a series of experiments in a SCWFB,and a dual-capacitance probe measurement system was applied to measure the hydrodynamics of slugs,such as the slug frequency,chord length,and rising *** groups of Geldart-B particles with different mean diameters were fluidized by supercritical water with a system pressure of 20-27MPa and at 410-570℃.The minimum slugging Reynolds number increases logarithmically with Archimedes number and a predicting correlation of the minimum slugging fluidization velocity in the SCWFB is presented:Rems=32908.84 ln(Ar^0.55+260376.65)-*** relative error of the above correlation was within ±15% and the averaged relative error was 7.5%.The effect of operating conditions on the minimum slugging fluidization velocity is *** research provides useful guidance for scaling-up design and for determining the optimum range of operating conditions in the SCWFB.

关键词： Supercritical water fluidized bed Slugging fluidization Dual-capacitance probe method

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Time-domain study on the density wave oscillation of supercritical water in multiple parallel channel system 17

Time-domain study on the density wave oscillation of supercr...

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17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017

作者： Liu, Jialun Zhang, Qian Li, Huixiong Kong, Xiangfei Lei, Xianliang State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi'anShaanxi China

A time-domain model suitable for the study on the density wave instability of supercritical water in multiple parallel channel system (the number of channels is more than 2) was established. The present model developed an iterative solution to solve the coupling among parallel channels. Then the program was verified by the experimental data obtained in open literature. After that, the model was used to study the effect of system pressure (23-28 MPa), inlet fluid temperature (240-350 °C), and adding perturbation in different channels on the density wave instability of supercritical water in multiple parallel channel system. It was found that when the same perturbation was added on some of channels at the initial time (the other working conditions were kept unchanged), the number of perturbation channels had almost no effect on the oscillation period and the system stability. The stability of the multiple channel system increased with the increasing in system pressure. It was also found that a critical value about the inlet fluid temperature, denoted by Tin-cr, existed, and when the inlet fluid temperature was lower than the critical value Tin-cr, the stability of the multiple channel system dropped with the increase of inlet fluid temperature, and that was improved when inlet fluid temperature was higher than Tin-cr. The critical value Tin-cr increased gradually with the increasing in the amount of parallel channels. Moreover, Tin-cr was lower than and near the pseudo-critical temperature of supercritical water, and almost had no changes with varying system pressure. © 2016 Association for Computing Machinery Inc. All Rights Reserved.

关键词： System stability

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Shock-tube measurements and kinetic study of propanal ignition 10

Shock-tube measurements and kinetic study of propanal igniti...

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10th Asia-Pacific Conference on Combustion, ASPACC 2015

作者： Yang, Ke Tang, Chenglong Man, Xingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an Shaanxi China

Ignition delay times of propanal were measured in a shock tube over the temperature range of 1050-1800 K, pressures of 1.2-16 atm, fuel concentrations of 0.5-2.0%, and equivalence ratios of 0.5-2.0. Through multiple linear regression, a correlation for the tested ignition delay times was obtained, and the measured data were also compared to the previous data. Two available models (Veloo mech and NUIG mech), were used to simulate the experimental data. Results suggest that both mechanisms has its own advantages and the Veloo mech exhibits a better prediction on the measured data than NUIG mech except for the fuel-rich condition. Reaction pathway analysis indicates that propanal molecule mainly breaks down through the H-abstraction reactions (accounting for around 80% propanal consumption), while reactions of unimolecular decomposition contribute a little part of the whole consumption.

关键词： Shock tubes

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Measurement on Turbulent Premixed Flame Structure of CH4/H2/Air Mixtures with CO2 Dilution

Measurement on Turbulent Premixed Flame Structure of CH4/H2/...

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JSAE/SAE 2015 International powertrains, Fuels and Lubricants Meeting, FFL 2015

作者： Wang, Jinhua Yu, Senbin Nie, Yaohui Jin, Wu Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an710049 China

Measurement on turbulent premixed CH4/H2/air flames was studied experimentally. Hydrogen blending ratio is defined as the ratio of hydrogen to fuel, while CO2 dilution ratio is defined as the mole fraction of CO2 to those of mixture. Hydrogen blending ratios up to 0.2 and CO2 dilution ratios up to 0.1 were studied. OH profile of the instantaneous flame front was detected using the OH-PLIF visualizations on a turbulent Bunsen burner. 500 OH-PLIF images were used to obtain the turbulent burning velocity and calculate flame surface density, and 280 images was used to calculate the local curvature radius. © 2015 SAE Japan.

关键词： Carbon dioxide

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Boiling coal in water: Hydrogen production and power generation system with zero net CO2 emission based on coal and supercritical water gasification

Boiling coal in water: Hydrogen production and power generat...

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作者： Guo, Liejin Jin, Hui State Key Laboratory of Multiphase Flow in Power Engineering Xi'An Jiaotong University Xi'an 710049 China

Coal is the single most important fuel for power generation today. Nowadays, most coal is consumed by means of "burning coal in air" and pollutants such as NOx, SOx, CO2, PM2.5 etc. are inevitably formed and mixed with excessive amount of inner gases, so the pollutant emission reduction system is complicated and the cost is high. IGCC is promising because coal is gasified before utilization. However, the coal gasifier mostly operates in gas environments, so special equipments are needed for the purification of the raw gas and CO2 emission reduction. Coal and supercritical water gasification process is another promising way to convert coal efficiently and cleanly to H2 and pure CO2. The gasification process is referred to as "boiling coal in water" and pollutants containing S and N deposit as solid residual and can be discharged from the gasifier. A novel thermodynamics cycle power generation system was proposed by us in state key laboratory of multiphase flow in power engineering (SKLMFPE) of Xi'an jiaotong University (XJTU), which is based on coal and supercritical water gasification and multi-staged steam turbine reheated by hydrogen combustion. It is characterized by its high coal-electricity efficiency, zero net CO2 emission and no pollutants. A series of experimental devices from quartz tube system to a pilot scale have been established to realize the complete gasification of coal in SKLMFPE. It proved the prospects of coal and supercritical water gasification process and the novel thermodynamics cycle power generation system. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

关键词： Coal

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Phenomenon of fog formation and flow characteristics of droplet-vapor-gas mixture in a cooler-condenser

Phenomenon of fog formation and flow characteristics of drop...

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ASME 2019 International Mechanical engineering Congress and Exposition, IMECE 2019

作者： Gu, Hongfang Guo, Qiwei Li, Changsong Zhou, Qing State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an Shaanxi China

ISBN: (纸本)9780791859452

Fog formation occurs in the process of condensation in the presence of non-condensable gas if the bulk temperature is lower than its saturation temperature (supersaturated). The phenomena of fogging is the formation of small condensate particles mixing with the vapor/gas stream, which creates potential problems of the vapor/gas/condensate separation and environmental pollution. Therefore, understanding of fogging mechanism and prevention of fog droplet entrainment are one of technical concerns for design and operation of cooler-condensers in the process industry. This paper presents the experimental study and numerical simulation of shell-side condensation with fog formation using a mixture of steam/non-condensable gas. The experimental data were collected on the two tube bundles (modified plastic tubes and stainless steel tubes). Using a high-speed photograph technique, the phenomenon of fog formation and flow characteristics of vapor/droplet transport were recorded over a wide range of test conditions. The numerical analysis of film and dropwise condensation, fog formation and droplet particle transport were simulated using different tube geometry and material, and flow velocity of air/droplet mixture. Based on simulation results, a new droplet trapping parameter is proposed to assess the optimal parameters of heat exchanger structural and operation conditions. Comparisons show that the numerical analysis results have a good agreement with experimental data and observations. These findings provide fundamental approach to account for the effect of fog formation, film and dropwise condensation, and droplet transport crossflow in cooler-condensers. Copyright © 2019 ASME.

关键词： Drops

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Melt droplet fragmentation behavior during fuel-coolant interaction 18

Melt droplet fragmentation behavior during fuel-coolant inte...

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18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2019

作者： Li, Gen Feng, Haobo Wen, Panpan Zhang, Jun Wang, Jinshi Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

During a severe accident of nuclear reactor, the fuel-coolant interaction occurs at the relocation stage of corium melt. Such a mode of contact can result in vigorous thermal interactions, intense steam generation and, potentially, steam explosions. The thermal processes, in their turn, largely depend on hydrodynamic behavior. When melt is pouring into coolant pool, the melt jet fragments into large droplets or blobs, named the primary breakup. The droplets or blobs will experience secondary breakup as a result of shock wave at steam explosion. Either the primary or secondary breakup is governed by interface hydrodynamic instabilities. The droplet size distribution, which affects fuel-coolant areas, is important for evaluating heat transfer and debris coolability. In this study, we modelled melt drops deformation and fragmentation using a meshless Lagrangian MPS method. Fragments amount and size distribution were compared under different Weber numbers, and fragments drag coefficient were also analyzed. The results indicate that the melt drops breakup process could be divided into two phases: initial deformation and fragmentation phase governed by flow inertial force and the subsequent fragments coalescence phase under the impact of fluid surface tension. Fragments amount increased in fragmentation phase but decreased in coalescence phase. A large amount of fragments has a normalized diameter of 0.01 - 0.03, but a small amount of large size fragments (d/d0 > 0.04) also appeared as the crescent-shaped melt broke up and small fragments coalesced. The drag coefficient decreased with time during drop deformation period, and then reached a stable value. It has no significant difference among cases with different Weber numbers. © 2019 American Nuclear Society. All rights reserved.

关键词： Hydrodynamics

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