Combustion Theory and Modelling最新文献_第10页

Counterflow combustion waves in short samples of metal powders at natural filtration of oxygen 氧气自然过滤条件下金属粉末短样品中的逆流燃烧波

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-04-26 DOI: 10.1080/13647830.2022.2066024

A. Bayliss, E. Shafirovich, V. Volpert

{"title":"Counterflow combustion waves in short samples of metal powders at natural filtration of oxygen","authors":"A. Bayliss, E. Shafirovich, V. Volpert","doi":"10.1080/13647830.2022.2066024","DOIUrl":"https://doi.org/10.1080/13647830.2022.2066024","url":null,"abstract":"Combustion of a porous solid fuel is considered. An exothermic reaction takes place between the fuel and a gaseous oxidiser which is delivered to the reaction zone by filtration through the pores in the sample from an open end toward which the combustion wave propagates (counterflow filtration). The gas reacts with the solid fuel to form a solid product. The gas filtration is due to the pressure difference between the ambient pressure at the open end and the pressure in the reaction zone where the gas is being consumed (referred to as natural filtration). A 1D mathematical model based on equations describing conservation of energy, gas mass, solid reactant mass, and gas momentum, as well as an equation of state, and appropriate boundary and initial conditions is formulated and analytically studied taking advantage of the separation of length scales in the process. When the reaction zone is sufficiently far from the open end, the combustion wave propagates at a constant speed and has a time-independent structure, while when the reaction is close to the open end (closer than the filtration length), the structure of the combustion wave and its speed become time dependent. Both cases are discussed in the paper though the main emphasis is on short samples, in which the combustion wave is affected by the gas flow from the open end during the entire propagation process. A specific example of interest involves magnesium as the solid fuel and oxygen as the gaseous oxidiser.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"746 - 773"},"PeriodicalIF":1.3,"publicationDate":"2022-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45611452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

Reaction-Diffusion Manifolds including differential diffusion applied to methane/air combustion in strong extinction regimes 反应-扩散流形，包括应用于强消光条件下甲烷/空气燃烧的微分扩散

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-04-16 DOI: 10.1080/13647830.2022.2029947

P. Breda, Chunkan Yu, U. Maas, M. Pfitzner

{"title":"Reaction-Diffusion Manifolds including differential diffusion applied to methane/air combustion in strong extinction regimes","authors":"P. Breda, Chunkan Yu, U. Maas, M. Pfitzner","doi":"10.1080/13647830.2022.2029947","DOIUrl":"https://doi.org/10.1080/13647830.2022.2029947","url":null,"abstract":"Detailed chemistry simulations of turbulent reacting flows involving combustion of hydrocarbons can easily exceed the available computational resources, depending on the dimensions of the chemical system. Previous work of the authors showed how the combination of the Eulerian Stochastic Fields (ESF) model with tabulated chemistry based on 2-dimensional Reaction-Diffusion Manifolds (REDIM) provided a significant computational speed-up, compared to the finite rate ESF solver. In this work, the behaviour for flame F, featuring a strong degree of extinction, is further investigated. A comparison is performed for 2D and 3D databases, both using simplified and detailed transport, where the scalar dissipation rate is included as the third table parameter. The results show that the upstream sections are well captured by the REDIM built for detailed transport, while the downstream sections are better captured by the simplified transport database. While a 3D-REDIM based on simplified transport seems to be necessary to capture the extinction events, a 2D-REDIM with differential diffusion already provides satisfactory results. Overall, the use of a 3D-REDIM with differential diffusion better describes the global behaviour of flame F.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"451 - 481"},"PeriodicalIF":1.3,"publicationDate":"2022-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42748964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Effects of buoyancy on turbulent scalar flux closure for turbulent premixed flames in the context of Reynolds Averaged Navier–Stokes simulations 在Reynolds平均Navier-Stokes模拟中浮力对湍流预混火焰湍流标量通量闭合的影响

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-03-19 DOI: 10.1080/13647830.2022.2049881

A. Varma, U. Ahmed, N. Chakraborty

{"title":"Effects of buoyancy on turbulent scalar flux closure for turbulent premixed flames in the context of Reynolds Averaged Navier–Stokes simulations","authors":"A. Varma, U. Ahmed, N. Chakraborty","doi":"10.1080/13647830.2022.2049881","DOIUrl":"https://doi.org/10.1080/13647830.2022.2049881","url":null,"abstract":"The effects of body force on the statistical behaviour of turbulent scalar flux and its closure in the context of Reynolds Averaged Navier–Stokes simulations have been studied using Direct Numerical Simulations (DNS) of statistically planar turbulent premixed flames under different turbulence intensities and Froude numbers. An increase in body force magnitude in the case of unstable density stratification has been found to augment flame wrinkling, burning rate and gradient transport in comparison to a case without body force but with statistically similar unburned gas turbulence. By contrast, an increase in body force magnitude in the case of stable stratification reduces the flame wrinkling, burning rate and gradient transport in comparison to the flame without body force subjected to statistically similar unburned gas turbulence. Based on a-priori DNS analysis, an algebraic closure for turbulent scalar flux has been identified where the Froude number effects are explicitly accounted for. The body force has been found to have significant influence on the statistical behaviours and magnitudes of the terms of the scalar flux transport equation and this effect is particularly strong for the mean pressure gradient term in the scalar flux transport equation. Based on a detailed a priori DNS analysis, suitable model expressions have been identified for the turbulent transport, pressure gradient, dissipation and reaction rate-velocity correlation terms of the scalar flux transport equation by incorporating the effects of body force (e.g. Froude number effects) for improved model performance.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"686 - 711"},"PeriodicalIF":1.3,"publicationDate":"2022-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45148606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Inward swirling flamelet model 内旋小火焰模型

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-03-11 DOI: 10.1080/13647830.2022.2103452

W. Sirignano

{"title":"Inward swirling flamelet model","authors":"W. Sirignano","doi":"10.1080/13647830.2022.2103452","DOIUrl":"https://doi.org/10.1080/13647830.2022.2103452","url":null,"abstract":"A new rotational flamelet model with inward swirling flow through a stretched vortex tube is developed for sub-grid modelling to be coupled with the resolved flow for turbulent combustion. The model has critical new features compared to existing models. (i) Non-premixed flames, premixed flames, or multi-branched flame structures are determined rather than prescribed. (ii) The effects of vorticity and the related centrifugal acceleration are determined. (iii) The strain rates and vorticity applied at the sub-grid level can be directly determined from the resolved-scale strain rates and vorticity without a contrived progress variable. (iv) The flamelet model is three-dimensional. (v) The effect of variable density is addressed. (vi) The inward swirl is created by vorticity combined with two compressive normal strain components; this feature distinguishes the model from counterflow flamelet models. Solutions to the multicomponent Navier–Stokes equations governing the flamelet model are obtained. By coordinate transformation, a similar solution is found for the model, through a system of ordinary differential equations. Vorticity creates a centrifugal force on the sub-grid counterflow that modifies the molecular transport rates, burning rates, and flammability limits. Sample computations of the inward swirling rotational flamelet model without coupling to the resolved flow are presented to demonstrate the importance of the new features. Premixed, nonpremixed, and multi-branched flame structures are examined. Parameter surveys are made with rate of normal strain, vorticity, Damköhler number, and Prandtl number. The centrifugal effect has interesting consequences when combined with the variable-density field. Flow direction can reverse; burning rates can be modified; flammability limits can be extended.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"1014 - 1040"},"PeriodicalIF":1.3,"publicationDate":"2022-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42260821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Flame stabilisation by a highly conductive body: multiple steady-state solutions and time-dependent dynamics 高导电体的火焰稳定性:多重稳态解决方案和随时间变化的动力学

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-03-10 DOI: 10.1080/13647830.2022.2049370

V. Kurdyumov, C. Jiménez

引用次数: 2

Modelling extinction/re-ignition processes in fire plumes under oxygen-diluted conditions using flamelet tabulation approaches 用火焰表法模拟氧气稀释条件下火焰羽流的熄灭/再点燃过程

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-02-18 DOI: 10.1080/13647830.2022.2036373

Li Ma, F. Nmira, J. Consalvi

{"title":"Modelling extinction/re-ignition processes in fire plumes under oxygen-diluted conditions using flamelet tabulation approaches","authors":"Li Ma, F. Nmira, J. Consalvi","doi":"10.1080/13647830.2022.2036373","DOIUrl":"https://doi.org/10.1080/13647830.2022.2036373","url":null,"abstract":"The main objective of this article is to investigate the capability of the flamelet progress variable (FPV) model to capture the extinction processes observed in under-ventilated fire scenarios. To this end, large eddy simulation (LES) of the methane line fire plumes in oxygen-reduced environments down to global extinction, investigated experimentally at the University of Maryland (UMD), is performed. Two experimental burner configurations, that differ by the presence (anchored) or not (non-anchored) of an oxygen anchor to stabilise the flame base, are considered leading to two different extinction modes. Both the FPV and the steady laminar flamelet (SLF) model coupled with a presumed filtered density function (FDF) are considered. The Rank Correlated Full Spectrum k-distribution (RCFSK) model is used as a gas radiative property model. In both non-anchored and anchored scenarios, the FPV model reproduces with fidelity the evolution of the fire plume structure, radiative loss, and combustion efficiency with decreasing down to global extinction, without introducing any adjustable constant. The extinction in the non-anchored scenario occurs owing to flame-based detachment coupled to the generation of a buoyancy-driven vortex and is found to be very sensitive to the grid resolution in the near burner region. The present results suggest that these processes can be adequately resolved with a spatial resolution of 2.5 mm in this region. The SLF model, for its part, provides reliable predictions comparable to the FPV as long as no local extinction/re-ignition process occurs.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"613 - 636"},"PeriodicalIF":1.3,"publicationDate":"2022-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46377333","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

Nonlinear analysis of flame hydrodynamic instability at large gas expansion ratio 大气体膨胀比下火焰流体动力不稳定性的非线性分析

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-02-18 DOI: 10.1080/13647830.2022.2037720

S. Minaev, V. Gubernov

引用次数: 0

A Tsuji burner in a counterflow 逆流中的Tsuji燃烧器

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-02-18 DOI: 10.1080/13647830.2022.2036374

Brandon Li, A. L. Sánchez, F. Williams

{"title":"A Tsuji burner in a counterflow","authors":"Brandon Li, A. L. Sánchez, F. Williams","doi":"10.1080/13647830.2022.2036374","DOIUrl":"https://doi.org/10.1080/13647830.2022.2036374","url":null,"abstract":"This paper addresses the aerodynamics of a new type of Tsuji burner involving a cylindrical porous fuel injector of radius a placed at the centre of a planar air counterflow configuration with strain rate , with specific attention given to flows with large values of the Reynolds number , where ν represents the air kinematic viscosity. For cases in which the fuel-injection velocity is comparable to the characteristic counterflow velocity , the boundary layer is blown off from the cylinder surface, so that the flame is embedded in the thin twin mixing layers that form about the stream surfaces separating the outer air stream from the fuel stream. Molecular transport effects are confined to these mixing layers, while the flow structure outside is nearly inviscid, with the air-side velocity being potential, while the velocity found on the fuel side is rotational, because fuel injection generates vorticity through the requirement that fuel emerges normal to the cylinder surface. The inviscid flow is computed numerically, with use made of the streamfunction-vorticity formulation for values of the ratio of injection velocity to counterflow velocity , the only relevant parameter of the flow, ranging from small injection velocities to large injection velocities . Asymptotic methods are used to investigate the form of the solution for extreme values of Λ. In the limit of weak injection, the vorticity, scaling with , is confined to a thin near-cylinder boundary layer of thickness Λ that necessarily separates from the cylinder to form a cavity of finite size on both sides of the cylinder. In the opposite limit of strong injection, the vorticity needed to maintain the fuel flow normal to the porous cylinder is found to be small, of order , so that the flow is irrotational in the first approximation. The velocity distribution along the fuel-air interface is seen to determine the evolution of the diffusion flame, including the length of the stretched jet flames that develops along the counterflow centre plane.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"637 - 653"},"PeriodicalIF":1.3,"publicationDate":"2022-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48632932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Autoignition of isolated n-heptane droplets in air and hot combustion products at microturbine conditions 微涡轮条件下空气中分离正庚烷液滴和热燃烧产物的自燃

IF 1.3 4区工程技术

Combustion Theory and Modelling Pub Date : 2022-02-16 DOI: 10.1080/13647830.2022.2034976

Jiayi Wang, E. Mastorakos

{"title":"Autoignition of isolated n-heptane droplets in air and hot combustion products at microturbine conditions","authors":"Jiayi Wang, E. Mastorakos","doi":"10.1080/13647830.2022.2034976","DOIUrl":"https://doi.org/10.1080/13647830.2022.2034976","url":null,"abstract":"Spontaneous ignition of isolated n-heptane droplets with initial diameters of 20–100 is simulated using air at 4 atm and 700–1200 K, which includes the typical operating conditions of recuperated microturbines. Because some fuel droplets in a combustor may be sprayed or carried to near the recirculation zone, the simulations use a mixture of pure air and hot combustion products as the oxidiser. The flame structures, evaporation times, and autoignition times in both physical and mixture fraction spaces for the different conditions are presented and compared. The variables examined include the air preheat temperature, amount of dilution with hot products, initial fuel droplet diameter, oxidiser temperature, and oxygen concentration. The results show that droplets in pure air at microturbine conditions fully evaporate before ignition, suggesting that a prevaporised concept is suitable for microturbines. The dilution with hot combustion products decreases the ignition delay time mainly by raising the oxidiser temperature. Low-temperature chemistry does not have a significant effect on droplet ignition because adding even a small amount of hot combustion products can increase the oxidiser temperature to higher than the temperatures favourable for low-temperature kinetics. The cool flame is only observed for 100 droplets at low temperatures, but two-stage ignition is not observed.","PeriodicalId":50665,"journal":{"name":"Combustion Theory and Modelling","volume":"26 1","pages":"541 - 559"},"PeriodicalIF":1.3,"publicationDate":"2022-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41675261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 2

In the Theater of the Body. 身体剧场

4区工程技术

Combustion Theory and Modelling Pub Date : 2022-02-15 eCollection Date: 2022-01-01 DOI: 10.1093/schizbullopen/sgac019

Helene Cæcilie Mørck

引用次数: 0