Kinetics of Ignition of n—Pentane in a Shock—Tube

ＫｉｎｅｔｉｃｓｏｆＩｇｎｉｔｉｏｎｏｆｎ－ＰｅｎｔａｎｅｉｎａＳｈｏｃｋ－Ｔｕｂｅ￥ＭｉｃｈａｅｌＤｖｉｎｙａｎｉｎｏｖ；ＡｌｅｘａｎｄｅｒＢｕｒｃａｔ（ＦａｃｕｌｔｙｏｆＡｅｒｏｓｐａｃｅＥｎｇｉｎｅｅｒｉｎｇ，Ｔｅｃｈｎｉｏｎ－ＩｓｒａｅｌＩｎ...     

A k－ε－PDF Two－Phase Turbulence Model for Simulating Sudden－Expansion Particle－Laden Flows

Ａｋ－ε－ＰＤＦＴｗｏ－ＰｈａｓｅＴｕｒｂｕｌｅｎｃｅＭｏｄｅｌｆｏｒＳｉｍｕｌａｔｉｎｇＳｕｄｄｅｎ－ＥｘｐａｎｓｉｏｎＰａｒｔｉｃｌｅ－ＬａｄｅｎＦｌｏｗｓＡｋ－ε－ＰＤＦＴｗｏ－ＰｈａｓｅＴｕｒｂｕｌｅｎｃｅＭｏｄｅｌｆｏｒＳｉｍｕｌａｔｉｎｇ...     

On The Analysis of Labyrinth Seal Flow Induced Vibration by Oscillating Fluid Mechanics Method

ＯｎＴｈｅＡｎａｌｙｓｉｓｏｆＬａｂｙｒｉｎｔｈＳｅａｌＦｌｏｗＩｎｄｕｃｅｄＶｉｂｒａｔｉｏｎｂｙＯｓｃｉｌｌａｔｉｎｇＦｌｕｉｄＭｅｃｈａｎｉｃｓＭｅｔｈｏｄ￥ＣｈｅｎＺｕｏｙｉ；ＪｉｎｇＹｏｕｈａｏ；ＳｕｎＹｏｎｇｚｈｏｎｇ（Ｄｅａｔｈ．ｏｆＴ...     

Boundary Layer Ignition of Hydrogen-Air Mixtures in Supersonic Flows

ＢｏｕｎｄａｒｙＬａｙｅｒＩｇｎｉｔｉｏｎｏｆＨｙｄｒｏｇｅｎ－ＡｉｒＭｉｘｔｕｒｅｓｉｎＳｕｐｅｒｓｏｎｉｃＦｌｏｗｓ￥Ｌ．Ｆ．Ｆｉｇｕｅｉｒａ；ｄａＳｉｌｖａ；Ｂ．Ｄｅｓｈａｉｅｓ；Ｍ．Ｃｈａｍｐｉｏｎ（Ｌａｂｏｒａｔｏｉｒｅｄ＇Ｅｎｅｒｇｅｔｉ...     

An Experimental Study on the Motion of Droplets in Flue Gas Humidification Activator with Pulse Laser Sheet Photography

ＡｎＥｘｐｅｒｉｍｅｎｔａｌＳｔｕｄｙｏｎｔｈｅＭｏｔｉｏｎｏｆＤｒｏｐｌｅｔｓｉｎＦｌｕｅＧａｓＨｕｍｉｄｉｆｉｃａｔｉｏｎＡｃｔｉｖａｔｏｒｗｉｔｈＰｕｌｓｅＬａｓｅｒＳｈｅｅｔＰｈｏｔｏｇｒａｐｈｙ￥ＫｅＪｉａｎｇ；ＸｕｃｈａｎｇＸｕ；Ｘｕｅｇ...     

Experimental and Numerical Investigation of Enhancement of Heat and Mass Transfer in Adsorbent Beds

ＥｘｐｅｒｉｍｅｎｔａｌａｎｄＮｕｍｅｒｉｃａｌＩｎｖｅｓｔｉｇａｔｉｏｎｏｆＥｎｈａｎｃｅｍｅｎｔｏｆＨｅａｔａｎｄＭａｓｓＴｒａｎｓｆｅｒｉｎＡｄｓｏｒｂｅｎｔＢｅｄｓＬｉｕＺｈｅｎｙａｎ；ＦｕＺｈｕｍａｎ；ＧｅＸｉｎｓｈｉ；ＳｕＹｕｅｈｏｎｇ；...     

Acoustic Wave Prediction in Flowing Steam-Water Two-Phase Mixture

ＡｃｏｕｓｔｉｃＷａｖｅＰｒｅｄｉｃｔｉｏｎｉｎＦｌｏｗｉｎｇＳｔｅａｍ－ＷａｔｅｒＴｗｏ－ＰｈａｓｅＭｉｘｔｕｒｅＸｕＪｉｎｌｉａｎｇ；ＣｈｅｎＴｉｎｇｋｕａｎ（ＳｔａｔｅＫｅｙＬａｂｏｒａｔｏｒｙｏｆＭｕｌｔｉｐｈａｓｅＦｌｏｗｉｎＰｏｗｅｒＥｎ...     

Numerical Simulation of a Negative Impulsive Wave

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆａＮｅｇａｔｉｖｅＩｍｐｕｌｓｉｖｅＷａｖｅＴｏｓｈｉａｋｉＳＥＴＯＧＵＣＨＩ；ＭａｎａｂｕＴＡＫＡＯ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｃｈａｎｉｃａｌＥｎｇｍｅｅｒｉｎｇ，ＳａｇａＵｎｉｖｅｒｓｉｔｙ，Ｈｏｎｊ...     

Numerical Simulation of the Flow over a Model of the Cavities on a Butterfly Wing

ＮｕｍｅｒｉｃａｌＳｉｍｕｌａｔｉｏｎｏｆｔｈｅＦｌｏｗｏｖｅｒａＭｏｄｅｌｏｆｔｈｅＣａｖｉｔｉｅｓｏｎａＢｕｔｔｅｒｆｌｙＷｉｎｇＲｏｄｒｉｇｕｅＳａｖｏｉｅ；ＹｖｅｓＧａｇｎｏｎ（ＵｎｉｖｅｒｓｉｔｙｄｅＭｏｎｃｔｏｎ，Ｃａｍｐｕｓｄ＇Ｅｄｍｕ...     

An Analytical Solution of Melting around a Moving Elliptical Heat Source

ＡｎＡｎａｌｙｔｉｃａｌＳｏｌｕｔｉｏｎｏｆＭｅｌｔｉｎｇａｒｏｕｎｄａＭｏｖｉｎｇＥｌｌｉｐｔｉｃａｌＨｅａｔＳｏｕｒｃｅ￥Ｗ．Ｚ．Ｃｈｅｎ；Ｓ．Ｍ．Ｃｈｅｎｇ；Ｚ．Ｌｕｏ；Ｈ．Ｑ．Ｚｈｕ（ＨｕａｚｈｏｎｇＵｎｉｖｅｒｓｉｔｙｏｆＳｃｉｅｎｃｅａｎ...     

太阳能固体吸收式制冰机的动态模拟——(Ⅰ)反应前锋模型

发展了两个太阳能固体吸收式制冰机的动态模拟程序,差别在于对反应器内的传热过程采用了不同的计算方法,其一采用反应前锋假设,其二采用有限差分方法求解非稳态的热传导方程。本文介绍反应前锋模型。     

A new method for simulating the combustion of a large biomass particle—A combination of a volume reaction model and front reaction approximation

Combining a volume reaction model and front reaction approximation is proposed to simulate the combustion of a large biomass particle. Two intraparticle processes—drying and char oxidation—are simplified as front reaction because they are transport controlled. The other intraparticle process—pyrolysis—is described as the volume reaction because it is controlled by both heat transfer and kinetics. A new numerical method based on the basic mechanism of the process is applied to mitigate oscillations of the solution of the front reactions. To compare the calculation results with the experimental results presented in the literature, combustion of cubic wood particles between 5 and 25 mm is chosen to test the new method. Drying, pyrolysis, char oxidation, vapor condensation, shrinkage of the process, heat transfer via conduction, diffusion, convection, radiation and mass transfer via diffusion, and convection inside particle are taken into account. Finite volumes attached to solid materials are used to discretize the domain and explicit method with variable time step is used to calculate the process. A program was written and the calculation showed that the conversion of a particle is almost independent of computational mesh from 10 cells on. However there is significant instability in the mass loss rate curve when the number of cells is less than 20. Predictions for different particle sizes, furnace temperatures and moisture contents were compared with measurements and they agree reasonably well. The results highlight the significance of pyrolysis kinetics on prediction. Thus, the front reaction model of pyrolysis assuming a constant reaction temperature of 773 K is sometimes inadequate. The proposed method also showed that moisture content and pyrolysis reactivity significantly affect the thickness of devolatilizing fuel.     

Sensitivity analysis of a biomass gasification model in fixed bed downdraft reactors: Effect of model and process parameters on reaction front

A detailed sensitivity analysis is performed on a one-dimensional fixed bed downdraft biomass gasification model. The aim of this work is to analyze how the heat transfer mechanisms and rates are affected as reaction front progresses along the bed with its main reactive stages (drying, pyrolysis, combustion and reduction) under auto-thermal conditions. To this end, a batch type fixed-bed gasifier was simulated and used to study process propagation velocity of biomass gasification. The previously proposed model was validated with experimental data as a function of particle size. The model was capable of predicting coherently the physicochemical processes of gasification allowing an agreement between experimental and calculated data with an average error of 8%. Model sensitivity to parametric changes in several model and process parameters was evaluated by analyzing their effect on heat transfer mechanisms of reaction front (solid–gas, bed–wall and radiative in the solid phase) and key response variables (temperature field, maximum solid and gas temperatures inside the bed, flame front velocity, biomass consumption and fuel/air ratio). The model coefficients analyzed were the solid–gas heat transfer, radiation absorption, bed–wall heat transfer, pyrolysis kinetic rates and reactor-environment heat transfer. On the other hand, particle size, bed void fraction, air intake temperature, gasifying agent composition and gasifier wall material were analyzed as process parameters. The solid–gas heat transfer coefficient (0.02 < correction factor < 1.0) and particle size (4 < diameter < 30 mm) were the most significant parameters affecting process behavior. They led to variations of 88% and 68% in process velocity, respectively.     

Modelling of the Absorption and Desorption Process of Chemical Heat Pumps

A simple model for the desorption and absorption process of the chemical heat pump is presented in this paper, It is based on the assumption of a definite reaction front. The results from m this model are compared with those obtained by finite difference method and it is observed that there is almost no difference between them.     

Mathematical and numerical model of solidification process of pure metals

This paper concerns the mathematical and numerical modeling of solidification process of pure metals. Such process takes place without development of “mushy zone”, which very often occurs during solidification of alloys. The model is based on the finite element method (FEM) and takes into account the existence of a sharp solidification front which moves according to time. The paper discusses how to include the conditions of continuity on the moving interface as well as the technique of front tracking based on the level set method (LSM). The paper also presents the results of computer simulations of the solidification process of pure copper. Two in-home solvers for one- and two-dimensional problems were built. Both of them are based on FEM. The correctness of the front tracking technique was checked by comparing the results obtained from 2D simulation to 1D simulation. Furthermore, the final calculation process was done for the two-dimensional area at different temperatures on the boundaries to demonstrate the effectiveness of the solver for a complex shape of the solidification front.     

Solar reforming of methane in a direct absorption catalytic reactor on a parabolic dish: II—Modeling and analysis

The CAtalytically Enhanced Solar Absorption Receiver (CAESAR) test was conducted to determine the thermal, chemical, and mechanical performance of a commercial-scale, dish-mounted, direct catalytic absorption receiver (DCAR) reactor over a range of steady state and transient (cloud) operating conditions. The focus of the test was to demonstrate “proof-of-concept” and determine global performance such as reactor efficiencies and overall methane conversion. A numerical model was previously developed to provide guidance in the design of the absorber. The one-dimensional, planar, and steady-state model incorporates the following energy transfer mechanisms: solar and infrared radiation, heterogeneous chemical reaction, conduction in the solid phase, and convection between the fluid and solid phases. Improvements to the model and improved property values are presented here. In particular, the solar radiative transfer model is improved by using a three-flux technique to more accurately represent the typically conical incident flux. A spatially varying catalyst loading is incorporated, convective and radiative properties for each layer in the multilayer absorber are determined, and more realistic boundary conditions are applied. Considering that this test was not intended to provide data for code validation, model predictions are shown to generally bound the test axial thermocouple data when test uncertainties are included. Global predictions are made using a technique in which the incident solar flux distribution is subdivided into flux contour bands. Reactor predictions for anticipated operating conditions suggest that a further decrease in optical density (i.e., extinction coefficient) at the front of the absorber inner disk may improve absorber conditions. Code-validation experiments are needed to improve the confidence in the simulation of large-scale reactor operation.     

Shrinking core discharge model for the negative electrode of a lead-acid battery

This article presents a shrinking core model for the discharge of porous lead particle at the negative electrode of a lead-acid battery by considering the reaction in a separate particle of the solid matrix. The model relates the shrinking unreacted lead core with the maximum amount of active material that can be reacted before termination of the discharge process due to poorly soluble low-conducting product. The developed model equations also incorporate the effect of double-layer capacitance and a dissolution–precipitation mechanism on the discharge process. The expressions for evaluating concentration and potential distributions as functions of time and distance are presented in three different models of a porous lead particle. For the simple case, equations are solved to achieve analytical expressions and where the coupled potential and concentration gradients with dissolution–precipitation mechanism are taken into account; the numerical method of lines is utilized to study the discharge behavior. The simulation outcomes are in good agreement when compared with the experimental data for discharge.     

A universal model of opposed flow combustion of solid fuel over an inert porous medium

In this study, a universal model is developed to examine the behavior of combustion wave observed in porous solid matters (e.g., smoldering, self-propagating high-temperature synthesis (SHS), diesel particulate filter (DPF) regeneration process). Analytical expressions of the combustion characters of solid combustible (e.g., diesel particulate matters trapped in a DPF) deposited over an inert porous medium are obtained employing large activation energy asymptotic taking into account the sensible transport processes; namely, heat transfer between the porous medium and gas phases, radiation heat transfer from the porous medium, heat loss from the porous medium to the environment, mass transfer of oxygen from the gas stream to the surface of solid fuel and the effective diffusion in modeling the species diffusion. Then it has been validated that the present model is applicable and adaptable for predicting the characteristics of smoldering combustion and thus SHS process. As a result, the features of combustion wave of the present phenomena would be useful to other processes. From practical point of view and for deep understanding of the behavior of combustion wave of these processes, we investigate the effects of various physical parameters over a wide range of conditions. We observe that the moving speed of the reaction front increases with the increase of porosity of the porous medium, mass transfer coefficient and initial fuel mass fraction; while it decreases owing to the increase of heat transfer rate from the porous medium to the gas, heat loss to the environment and radiative heat transfer. Furthermore, the results reveal that extinction tends to occur due to lower porosity of the porous medium, higher radiative heat transfer from the porous medium, higher heat transfer rate from the porous medium to the gas and higher heat losses from the porous medium to the environment. Even the observed near-extinction behavior in reaction front speed versus heat loss diagram is found to be similar what we got in gaseous premixed flame propagating through the porous medium. An extinction limit diagram has been presented as a function of radiation-conduction parameter and the gas flow velocity. In addition to, the impact of radiation and the combined effect of the inclusion of Knudsen diffusion and tortuosity are demonstrated in terms of the spatial temperature and species profiles to examine how these two parameters modify the reaction front structure. Furthermore, the governing equations have been solved numerically and it is observed that asymptotic analysis gives a good agreement with the numerical solution.     

Laser heating and surface evaporation

In the present study, laser heating of solid substrate and evaporation of the surface are considered. The numerical method is employed to predict the temperature field in the solid as well as in the vapor front. The absorption of incident laser beam by the evaporating front and by the solid is accommodated to account for the absorption process. It is found that temperature decays sharply across the solid–vapor interface due to the location of the laser power intensity, which moves with the interface towards the solid bulk as evaporation of the surface progresses. The recession velocity becomes high in the early evaporation stage and as the heating period progresses, recession velocity becomes almost steady. Consequently, the transient behavior of evaporation can be observed during the early evaporation period.