密闭空间内典型可燃气体层流预混火焰传播动力学及其化学反应机理研究
发布时间：2018-10-16 13:43
【摘要】：密闭空间内层流预混火焰传播是可燃气体安全、内燃机应用和爆轰波理论等领域重要的燃烧科学与技术课题。如何有效地预防可燃气体的火灾爆炸(爆轰)事故,控制其发展蔓延和减轻事故危害,这些问题的解答需要科学研究作为依据。而内燃机领域也亟需基础的火焰传播数据和详细的化学反应机理来建立燃烧模型,以实现其自身结构的优化改进和对替代燃料的性能评估。因此,为了更加全面地揭示火焰发生、发展以及加速突变的本质规律和机理,深入剖析火焰内部反应区结构和物理化学过程,并建立综合完善的化学动力学模型,同时也为了积累更多有用的火焰传播基础数据,本文利用实验、理论和数值模拟手段对密闭空间内典型可燃气体层流预混火焰传播结构形态、火焰加速和突变动力学、层流火焰速度以及化学反应机理开展了细致严谨的科学研究。 本文首先对氢-空气和丙烷-空气预混火焰在封闭管道内的传播特性开展研究,内容包括火焰和超压动力学、火焰与诱导流场和压力波的相互作用等。高速纹影摄像技术用于捕捉和记录火焰位置和形态变化,高精度压力传感器用于探测管道内瞬时的压力变化特性。实验结果表明,封闭管道内预混火焰传播经历了复杂的形状变化,呈现出经典的或变形的Tulip结构,由于受到火焰加速和减速、壁面约束、边界层效应、压力波效应以及火焰诱导流场等影响,火焰裙边运动、火焰与壁面接触点运动、Tulip尖端运动和火焰尖端运动等都表现出明显的阶段性特征,Bychkov模型对基本运动参数(位置和速度)的预测并不理想,仅适用于火焰发展早期。所有工况都观察到了火焰尖端位置(速度)及压力脉动现象,只是频率和幅度各有不同。变形Tulip结构并不是封闭管道内氢-空气预混火焰特有的行为,在化学计量比(中=1)附近的预混丙烷-空气火焰中也有发现,且Tulip变形过程中都伴随着显著的火焰尖端速度脉动。压力波并不是火焰速度脉动及Tulip变形的诱因,但确实会起到促进作用；而壁面和边界效应,楔形挤压流、水力学不稳定性及火焰诱导流动的综合效应可能是主要物理起因。 随后我们利用圆柱形双燃烧室实验台,结合高速摄像和纹影技术,对C2碳氢燃料(主要是乙烷、乙烯和乙炔等)常压和高压层流火焰速度开展了实验研究和测量,并分析了当量比、初始压力和燃料分子结构对火焰传播的影响。常压实验结果与权威文献数据吻合得很好,并对一些历史数据较少且分散的工况做了补充和验证。对于不同燃料反应体系,二氧化碳稀释的作用机制明显不同。表观的,二氧化碳会抑制乙烯火焰以及富燃料乙烷火焰传播,但对于乙炔火焰以及贫燃料乙烷火焰几乎没有影响,表明其抑制作用被抵消。总体来说,USC Mech Ⅱ对层流火焰速度的定量预测不是很理想(特别是对高压火焰),仅能较好地反映火焰速度的变化趋势。 本文讨论分析了USC MechⅡ模型存在的问题和缺陷,进而以化学动力学领域最新的研究成果为基础,借助量子化学计算和实验测量等手段,建立了新的综合化学反应模型。实验验证表明新模型对常压和高压典型可燃气体层流预混火焰速度的预测能力相比USC Mech Ⅱ有了显著的提高。新模型为我们揭示了乙烷、乙烯、乙炔火焰体系的主要反应路径；发现了碳氢燃料火焰结构和燃烧行为之间很多相似之处；同时还指出了高压火焰体系中一些重要的基元反应以及火焰速度对反应速率常数的敏感度变化(相比常压情况)。二氧化碳稀释对火焰体系的化学和第三体效应,主要表现为抑制和促进两个矛盾方面。一方面,过量的C02会逆转反应CO+OH=CO2+H,并增强第三体反应H+O2(+M)=HO2导致体系H原子浓度降低；另一方面,作为强第三体,C02稀释同样也会加剧HCO的分解反应HCO (+M)=H+CO (+M),从而补偿一定的H原子损失。表观的二氧化碳稀释效果是这两种内在作用机制相互竞争和抵消的综合体现。乙炔火焰中由于反应CO+OH=CO2+H并不是产物C02主要生成通道,因而其重要性减弱,二氧化碳稀释的抑制和促进作用相互抵消；而乙烯和乙烷火焰速度对HCO分解反应速率常数的敏感度较低(反应重要性较弱,尤其是在高压下),因此火焰总体受到抑制。特别的,二氧化碳稀释对富燃料乙烷火焰体系的化学和第三体效应较弱,体系的热量和质量输运性质以及混合物组成和密度的变化是导致火焰减速的本质原因。与乙烷和乙烯火焰不同的是,0原子(而不是H原子)在乙炔火焰体系中起着决定性作用,其浓度变化将直接影响火焰传播行为。
[Abstract]:Laminar premixed flame propagation in confined space is an important topic of combustion science and technology in the fields of combustible gas safety, internal combustion engine application and detonation wave theory. How to effectively prevent the fire explosion (detonation) accident of combustible gas, control its development spread and alleviate the accident hazard, the answer of these questions need scientific research as the basis. In the field of internal combustion engine, it is necessary to establish combustion model based on flame propagation data and detailed chemical reaction mechanism, so as to realize optimization improvement of its own structure and performance evaluation of alternative fuel. Therefore, in order to reveal the essence rule and mechanism of flame generation, development and accelerating mutation more comprehensively, deeply analyze the structure and physical and chemical process of flame interior reaction zone, and establish a comprehensive and perfect chemical kinetic model. At the same time, in order to accumulate more useful flame propagation basic data, this paper uses experiment, theory and numerical simulation to simulate the structure, flame acceleration and mutation dynamics of typical combustible gas laminar premixed flame in confined space. The laminar flame velocity and chemical reaction mechanism have carried out detailed and rigorous scientific research. Firstly, the propagation characteristics of hydrogen-air and propane-air pre-mixed flame in closed pipelines are studied. The contents include flame and overpressure dynamics, flame and induced flow field and pressure wave. The high-precision pressure sensor is used to detect the instantaneous pressure change in the pipeline, and the high-precision pressure sensor is used for capturing and recording flame position and shape change. The experimental results show that the pre-mixing flame propagation in the closed pipeline has undergone a complex shape change, which presents a classical or deformed Tulp structure, which is affected by flame acceleration and deceleration, wall restraint, boundary layer effect, pressure wave effect and flame-induced flow field, etc. The motion, flame and wall contact movement, Tulp tip movement and flame tip movement all show obvious periodic characteristics. The prediction of basic motion parameters (position and velocity) by Bychbach model is not ideal, and it is only suitable for flame development. Earlier, the flame tip position (velocity) and pressure pulsation phenomenon were observed for all operating conditions, except for frequency and amplitude. The deformation of the Tulp structure is not characteristic of the hydrogen-air pre-mixing flame in the closed pipeline, and is also found in the pre-mixed propane-air flame near the stoichiometric ratio (= 1), and there is a significant flame tip speed during the Tulp deformation process. Pulsation. Pressure wave is not the cause of flame velocity fluctuation and Tulp deformation, but does play a promoting role; and the wall surface and boundary effect, wedge-shaped extrusion flow, hydraulic instability and flame-induced flow can be the main physics. Then we carried out experimental research and measurement on C2 hydrocarbon fuel (mainly ethane, ethylene and acetylene, etc.) at normal pressure and high pressure laminar flame speed by using cylindrical double combustion chamber experiment table, combined with high speed camera and image shadow technology. The equivalence ratio, the initial pressure and the molecular structure of the fuel are analyzed. The experimental results of atmospheric pressure are well coincident with authoritative literature data, and some historical data are less and dispersed. Replenishment and verification. For different fuel reaction systems, carbon dioxide dilution works Visible, carbon dioxide suppresses the flame propagation of ethylene and fuel-rich ethane, but has little effect on acetylene flame and lean-fuel ethane flame, indicating its suppression The effect is cancelled. In general, the quantitative prediction of laminar flame velocity by USC Mech II is not ideal (especially for high-pressure flame) and only better reflects flame speed. In this paper, the problems and defects of USC Mech 鈪，
本文编号：2274543
[Abstract]:Laminar premixed flame propagation in confined space is an important topic of combustion science and technology in the fields of combustible gas safety, internal combustion engine application and detonation wave theory. How to effectively prevent the fire explosion (detonation) accident of combustible gas, control its development spread and alleviate the accident hazard, the answer of these questions need scientific research as the basis. In the field of internal combustion engine, it is necessary to establish combustion model based on flame propagation data and detailed chemical reaction mechanism, so as to realize optimization improvement of its own structure and performance evaluation of alternative fuel. Therefore, in order to reveal the essence rule and mechanism of flame generation, development and accelerating mutation more comprehensively, deeply analyze the structure and physical and chemical process of flame interior reaction zone, and establish a comprehensive and perfect chemical kinetic model. At the same time, in order to accumulate more useful flame propagation basic data, this paper uses experiment, theory and numerical simulation to simulate the structure, flame acceleration and mutation dynamics of typical combustible gas laminar premixed flame in confined space. The laminar flame velocity and chemical reaction mechanism have carried out detailed and rigorous scientific research. Firstly, the propagation characteristics of hydrogen-air and propane-air pre-mixed flame in closed pipelines are studied. The contents include flame and overpressure dynamics, flame and induced flow field and pressure wave. The high-precision pressure sensor is used to detect the instantaneous pressure change in the pipeline, and the high-precision pressure sensor is used for capturing and recording flame position and shape change. The experimental results show that the pre-mixing flame propagation in the closed pipeline has undergone a complex shape change, which presents a classical or deformed Tulp structure, which is affected by flame acceleration and deceleration, wall restraint, boundary layer effect, pressure wave effect and flame-induced flow field, etc. The motion, flame and wall contact movement, Tulp tip movement and flame tip movement all show obvious periodic characteristics. The prediction of basic motion parameters (position and velocity) by Bychbach model is not ideal, and it is only suitable for flame development. Earlier, the flame tip position (velocity) and pressure pulsation phenomenon were observed for all operating conditions, except for frequency and amplitude. The deformation of the Tulp structure is not characteristic of the hydrogen-air pre-mixing flame in the closed pipeline, and is also found in the pre-mixed propane-air flame near the stoichiometric ratio (= 1), and there is a significant flame tip speed during the Tulp deformation process. Pulsation. Pressure wave is not the cause of flame velocity fluctuation and Tulp deformation, but does play a promoting role; and the wall surface and boundary effect, wedge-shaped extrusion flow, hydraulic instability and flame-induced flow can be the main physics. Then we carried out experimental research and measurement on C2 hydrocarbon fuel (mainly ethane, ethylene and acetylene, etc.) at normal pressure and high pressure laminar flame speed by using cylindrical double combustion chamber experiment table, combined with high speed camera and image shadow technology. The equivalence ratio, the initial pressure and the molecular structure of the fuel are analyzed. The experimental results of atmospheric pressure are well coincident with authoritative literature data, and some historical data are less and dispersed. Replenishment and verification. For different fuel reaction systems, carbon dioxide dilution works Visible, carbon dioxide suppresses the flame propagation of ethylene and fuel-rich ethane, but has little effect on acetylene flame and lean-fuel ethane flame, indicating its suppression The effect is cancelled. In general, the quantitative prediction of laminar flame velocity by USC Mech II is not ideal (especially for high-pressure flame) and only better reflects flame speed. In this paper, the problems and defects of USC Mech 鈪，
本文编号：2274543
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