Numerical analysis of the ignition and gas-phase flame evolution of pulverized coal based on online experimental diagnostics

IF 5.6 2区 工程技术 Q2 ENERGY & FUELS Journal of The Energy Institute Pub Date : 2024-09-27 DOI:10.1016/j.joei.2024.101843
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Abstract

A transient ignition model employing a reduced chemical mechanism was developed to investigate the ignition characteristics and the gas-phase flame evolution of pulverized coal particles. The chemical percolation devolatilization (CPD) model was chosen to simulate the devolatilization process, and its accuracy was validated using a high-temperature entrained-flow reactor. Additionally, a novel method was introduced to cross-validate the single-particle simulation results with real-time OH-PLIF experimental measurements of particle streams, particularly at a large particle spacing ratio. The ignition mode was determined using the ignition delay time and volatile burnout time. Results show that as the oxygen volume fraction increases from 5% to 50% at a temperature of 1800 K, the ignition mode transitions from homogeneous ignition (GI) to heterogeneous ignition (HI). Notably, the same ignition mode was observed regardless of whether GI was defined using gas-phase temperature or OH levels. In the homo-heterogeneous ignition mode, the gas-phase flame intensity, characterized by OH levels, increases rapidly, then decreases, and re-increases slightly. The sequence of gas-phase reactions initiates with volatile combustion, followed by the co-combustion of residual volatiles and newly generated CO, and culminates in the combustion of CO itself. Online experimental findings confirmed that CO originates from char oxidation. Throughout this process, the gas-phase flame front extends outward until the volatiles are consumed.
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基于在线实验诊断的煤粉着火和气相火焰演变的数值分析
为了研究煤粉颗粒的着火特性和气相火焰演化,开发了一种采用还原化学机制的瞬态着火模型。选择化学渗滤脱碳(CPD)模型来模拟脱碳过程,并使用高温内流反应器验证了其准确性。此外,还引入了一种新方法,将单颗粒模拟结果与颗粒流的实时 OH-PLIF 实验测量结果进行交叉验证,尤其是在颗粒间距比较大的情况下。利用点火延迟时间和挥发燃烧时间确定了点火模式。结果表明,在温度为 1800 K 时,当氧气体积分数从 5% 增加到 50% 时,点火模式从均质点火 (GI) 过渡到异质点火 (HI)。值得注意的是,无论使用气相温度还是羟基水平来定义 GI,都能观察到相同的点火模式。在同质异相点火模式下,气相火焰强度(以羟基水平为特征)会迅速增加,然后减弱,最后再略微增加。气相反应的顺序由挥发物燃烧开始,然后是残余挥发物和新生成的 CO 共同燃烧,最后是 CO 本身的燃烧。在线实验结果证实,CO 源自炭氧化。在整个过程中,气相火焰前沿一直向外延伸,直到挥发物消耗殆尽。
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来源期刊
Journal of The Energy Institute
Journal of The Energy Institute 工程技术-能源与燃料
CiteScore
10.60
自引率
5.30%
发文量
166
审稿时长
16 days
期刊介绍: The Journal of the Energy Institute provides peer reviewed coverage of original high quality research on energy, engineering and technology.The coverage is broad and the main areas of interest include: Combustion engineering and associated technologies; process heating; power generation; engines and propulsion; emissions and environmental pollution control; clean coal technologies; carbon abatement technologies Emissions and environmental pollution control; safety and hazards; Clean coal technologies; carbon abatement technologies, including carbon capture and storage, CCS; Petroleum engineering and fuel quality, including storage and transport Alternative energy sources; biomass utilisation and biomass conversion technologies; energy from waste, incineration and recycling Energy conversion, energy recovery and energy efficiency; space heating, fuel cells, heat pumps and cooling systems Energy storage The journal''s coverage reflects changes in energy technology that result from the transition to more efficient energy production and end use together with reduced carbon emission.
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