A Semi-Analytical Model for Prediction of Wall Quenching Distances of Premixed Flames

2021 ◽  
Author(s):  
Huang Xia ◽  
Liu Weijie
Keyword(s):  
Analytical Model ◽  
Single Layer ◽  
Premixed Flame ◽  
Surface Radiation ◽  
Flame Surface ◽  
Incoming Flow ◽  
Conservation Of Energy ◽  
Factors Affecting ◽  
Quenching Distance ◽  
Flow Velocities

Abstract In order to predict the variation of the wall quenching distance of a premixed flame under different equivalence ratios and incoming flow velocities, a semi-analytical model applied to both lean single-layer flame and rich double-layer flame has been derived based on the conservation of energy in the quenching zone. In this model the flame surface radiation plays an important role. Factors influencing the radiation have been analyzed, respectively. The model indicates that the factors affecting the quenching distance in premixed flame are more complicated than that in single-wall flames or flames in tube. To fit the empirical coefficient in this model, a methane-air premixed flame quenching distance experiment under both lean and rich conditions has been performed. The comparison between the theoretical prediction and the experiment result shows that this semi-analytical model gives a suitable description of the quenching distance. The relative error of the quenching distance under different equivalence ratios and incoming flow velocities is less than ±15%.

Numerical Simulation of Premixed Propane/Air Flame Propagation Using a Dynamically Thickened Flame Approach

2013 ◽  
Vol 444-445 ◽  
pp. 1574-1578 ◽  
Author(s):  
Hua Hua Xiao ◽  
Zhan Li Mao ◽  
Wei Guang An ◽  
Qing Song Wang ◽  
Jin Hua Sun
Keyword(s):  
Numerical Simulation ◽  
Flame Propagation ◽  
Numerical Study ◽  
Vortex Motion ◽  
Combustion Process ◽  
Single Step ◽  
Premixed Combustion ◽  
Premixed Flame ◽  
Flame Surface ◽  
Arrhenius Kinetics

A numerical study of premixed propane/air flame propagation in a closed duct is presented. A dynamically thickened flame (TF) method is applied to model the premixed combustion. The reaction of propane in air is taken into account using a single-step global Arrhenius kinetics. It is shown that the premixed flame undergoes four stages of dynamics in the propagation. The formation of tulip flame phenomenon is observed. The pressure during the combustion process grows exponentially at the finger-shape flame stage and then slows down until the formation of tulip shape. After tulip formation the pressure increases quickly again with the increase of the flame surface area. The vortex motion behind the flame front advects the flame into tulip shape. The study indicates that the TF model is quite reliable for the investigation of premixed propane/air flame propagation.

The Dynamics of a Cantilevered Pipe Aspirating Fluid Studied by Experimental, Numerical and Analytical Methods

2010 ◽  
Author(s):  
Dana Giacobbi ◽  
Stephanie Rinaldi ◽  
Christian Semler ◽  
Michael P. Pai¨doussis
Keyword(s):  
Analytical Model ◽  
Low Flow ◽  
Computational Fluid Dynamics Cfd ◽  
Computational Structural Mechanics ◽  
Cantilevered Pipe ◽  
The Galerkin Method ◽  
Csm Model ◽  
Ocean Mining ◽  
Flow Experiments ◽  
Flow Velocities

This paper investigates the dynamics of a slender, flexible, aspirating cantilevered pipe, ingesting fluid at its free end and conveying it towards its clamped end. The problem is interesting not only from a fundamental perspective, but also because applications exist, notably in ocean mining [1]. First, the need for the present work is demonstrated through a review of previous research into the topic — spanning many years and yielding often contradictory results — most recently concluding that the system loses stability by flutter at relatively low flow velocities [2]. In the current paper, that conclusion is refined and expanded upon by exploring the problem in three ways: experimentally, numerically and analytically. First, air-flow experiments, in which the flow velocity of the fluid was varied and the frequency and amplitude of oscillation of the pipe were measured, were conducted using different elastomer pipes and intake shapes. Second, a fully-coupled Computational Fluid Dynamics (CFD) and Computational Structural Mechanics (CSM) model was developed in ANSYS in order to simulate experiments and corroborate experimental results. Finally, using an analytical approach, the existing linear equation of motion describing the system was significantly improved upon, and then solved via the Galerkin method in order to determine its stability characteristics. Heavily influenced by a CFD analysis, the proposed analytical model is different from previous ones, most notably because of the inclusion of a two-part fluid depressurization at the intake. In general, both the actual and numerical experiments suggest a first-mode loss of stability by flutter at relatively low flow velocities, which agrees with the results from the new analytical model.

scholarly journals A MODEL FOR IMPLEMENTING MONETARY AND BANKING POLICIES

2020 ◽  
Vol 9 (2) ◽  
Author(s):  
Aliaskar Baharloo ◽  
Fatah Sharifzadeh ◽  
Mahnaz Rabiei ◽  
Seyed Ahmad Hosseini Golafshani
Keyword(s):  
Analytical Model ◽  
Policy Making ◽  
Research Model ◽  
Factors Affecting ◽  
Statistical Sample

This research has addressed the pathology of the implementation of monetary and banking policies in Iran and identifying the factors affecting the implementation of these policies in the banking system.In this research, concurrent with collecting researches and studies performed about the factors affecting the implementation of policies, by conducting exploratory interviews with 20 experts in the field of policy-making and banking and monetary experts, 36 indicators affecting the implementation of monetary and banking policies in Iran were also identified. Afterwards, in order to fit the "proposed analytical model of implementing monetary and banking policies in Iran", 13 hypotheses were defined. Then, by selecting appropriate statistical sample and distributing the questionnaire among them, the fitness of the model was investigated. Finally, the proposed research model for implementing monetary and banking policies in Iran was fitted and confirmed, and out of 13 hypotheses, 2 were rejected and the rest were confirmed.

scholarly journals A validated predictive model of coronary fractional flow reserve

2011 ◽  
Vol 9 (71) ◽  
pp. 1325-1338 ◽  
Author(s):  
Yunlong Huo ◽  
Mark Svendsen ◽  
Jenny Susana Choy ◽  
Z.-D. Zhang ◽  
Ghassan S. Kassab
Keyword(s):  
Analytical Model ◽  
Fractional Flow Reserve ◽  
Coronary Stenosis ◽  
Coronary Flow ◽  
Energy Losses ◽  
Fractional Flow ◽  
Conservation Of Energy ◽  
Flow Reserve

Myocardial fractional flow reserve (FFR), an important index of coronary stenosis, is measured by a pressure sensor guidewire. The determination of FFR, only based on the dimensions (lumen diameters and length) of stenosis and hyperaemic coronary flow with no other ad hoc parameters, is currently not possible. We propose an analytical model derived from conservation of energy, which considers various energy losses along the length of a stenosis, i.e. convective and diffusive energy losses as well as energy loss due to sudden constriction and expansion in lumen area. In vitro (constrictions were created in isolated arteries using symmetric and asymmetric tubes as well as an inflatable occluder cuff) and in vivo (constrictions were induced in coronary arteries of eight swine by an occluder cuff) experiments were used to validate the proposed analytical model. The proposed model agreed well with the experimental measurements. A least-squares fit showed a linear relation as (Δ p or FFR) experiment = a (Δ p or FFR) theory + b , where a and b were 1.08 and −1.15 mmHg ( r 2 = 0.99) for in vitro Δ p , 0.96 and 1.79 mmHg ( r 2 = 0.75) for in vivo Δ p , and 0.85 and 0.1 ( r 2 = 0.7) for FFR. Flow pulsatility and stenosis shape (e.g. eccentricity, exit angle divergence, etc.) had a negligible effect on myocardial FFR, while the entrance effect in a coronary stenosis was found to contribute significantly to the pressure drop. We present a physics-based experimentally validated analytical model of coronary stenosis, which allows prediction of FFR based on stenosis dimensions and hyperaemic coronary flow with no empirical parameters.

Heat Transfer in Thermocline Storage System With Filler Materials: Analytical Model

2010 ◽  
Author(s):  
Wafaa Karaki ◽  
Jon T. Van Lew ◽  
Peiwen Li ◽  
Cho Lik Chan ◽  
Jake Stephens
Keyword(s):  
Heat Transfer ◽  
Solar Energy ◽  
Power Systems ◽  
Analytical Model ◽  
Storage System ◽  
Heat Transfer Fluid ◽  
Filler Materials ◽  
Initial Temperature Distribution ◽  
Conservation Of Energy ◽  
Concentrated Solar Energy

Parabolic trough power systems utilizing concentrated solar energy have proven their worth as a means for generating electricity. However, one major aspect preventing the technologies widespread acceptance is the deliverability of energy beyond a narrow window during peak hours of the sun. Thermal storage is a viable option to enhance the dispatchability of the solar energy and an economically feasible option is a thermocline storage system with a low-cost filler material. Utilization of thermocline storage facilities have been studied in the past and this paper hopes to expand upon that knowledge. The heat transfer between the heat transfer fluid and filler materials are governed by two conservation of energy equations, often referred as Schumann [1] equations. We solve these two coupled partial differential equations using Laplace transformation. The initial temperature distribution can be constant, linear or exponential. This flexibility allows us to apply the model to simulate unlimited charging and discharging cycles, similar to a day-to-day operation. The analytical model is used to investigate charging and discharging processes, and energy storage capacity. In an earlier paper [2], the authors presented numerical solution of the Schumann equations using method of characteristics. Comparison between analytical and numerical results shows that they are in very good agreement.

scholarly journals Housing Reproduction Strategy in Single-Industry Towns

2020 ◽  
Vol 11 (3) ◽  
Author(s):  
Irina Torgashina ◽  
Konstantin Demyanov
Keyword(s):  
Analytical Model ◽  
Economic Situation ◽  
Economic Potential ◽  
Factors Affecting ◽  
Reproduction Strategy ◽  
Single Industry ◽  
Definition Of ◽  
Financial Recovery ◽  
Functional Purpose ◽  
Housing Facilities

The research showed the contribution of domestic single-industry towns to the total GDP of the country. We identified the main features and the definition of a «single-industry town» or «mono-profile settlement» based on the perspective of its functional purpose. The research also analyzed and systematized factors affecting the decrease in the economic potential of domestic single-industry towns. We summarized a number of measures to achieve a stable socio-economic situation in the territory of a mono-profile settlement. The research pointed out the necessity of reproducing housing facilities in the context of the main areas of financial recovery of problematic single-industry towns. The possibilities and scope of specialized approaches developed specifically for the reproduction of housing in single-industry towns with low economic potential were investigated. The authors developed a universal analytical model to determine necessary volumes of housing reproduction within the framework of the policy of financial rehabilitation of mono-profile cities.

The effect of geometric parameters of PTL on oxygen transport in PEM electrolysis cell

2021 ◽  
pp. 095440622110380
Author(s):  
SZ Hoseini Larimi ◽  
A Ramiar ◽  
R Shafaghat ◽  
Q Esmaili
Keyword(s):  
Oxygen Saturation ◽  
Polymer Electrolyte Membrane ◽  
Single Layer ◽  
Operating Conditions ◽  
Transport Layer ◽  
Electrolysis Cell ◽  
Two Phase ◽  
Factors Affecting ◽  
Electrolyte Membrane ◽  
Layer Arrangement

In this study, two-phase flow of oxygen-water is studied by using numerical simulation in the Porous Transport Layer (PTL) of the Polymer Electrolyte Membrane Electrolysis Cell (PEMEC). The effect of thickness, porosity and multi-layer arrangement of PTL on the oxygen flow pattern and its removal from the PTL is investigated. The results showed the increase in the PTL thickness causes to increase the growth of the lateral paths from the inlet to the channel, which leads to increase the oxygen saturation in the PTL. It is also obtained that for PTL with different porosity, number and volume of occupied pores by oxygen in the PTL are the two main factors affecting the oxygen saturation and trade-off between them indicate the proper porosity to be used in different operating conditions. Furthermore, studies showed the use of two-layer PTL instead of single-layer can cause reduction in oxygen saturation in the proximity of reaction sites leading to a better operation of the electrolyzer.

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