【作者】 廖钦；

【导师】 徐胜利；

【作者基本信息】 中国科学技术大学 ， 流体力学， 2009， 博士

【摘要】 本文目的是研究煤油气溶胶及其裂解产物的点火延时和自点火现象。在新研制的两相激波管中,利用反射激波后气流,以瞬态压力和高分辨率发射或荧光测量为主,测量了点火延时并研究了自点火现象。主要内容如下:（1）第一章简要介绍了本文研究背景和相关的国内外研究进展、主要内容等。（2）第二章主要介绍了两相激波管研制和实验状态调试。包括激波管部件设计和安装、煤油雾化方法、煤油粒径Mie散射测量,给出了缝合接触面运行状态的计算和调试结果,并确认了实验时间。（3）基于压力和OH基自发光信号测量结果,第三章给出了煤油及其裂解产物点火延时测量结果。●考察了温度T、压力p和当量比φ对点火延时τ_ig的影响。对于T=1163K～1653K、p=0.1、0.3和0.6MPa、φ=1煤油/空气溶胶,τ_ig约为0.10ms～6.36ms。当T相同,τ_ig随p升高而减小,拟合得到τ_ig=4.75×10^-7p^-1.16exp（17360/T）,其中,τ_ig、p、T的单位分别为ms、MPa、K。对p=0.1MPa、T=1348K～1940K、φ=0.5、1和2的煤油裂解产物/空气混合物,τ_ig约为0.07ms～5.04ms。当丁相同,τ_ig随φ增大而减小。拟合得到τ_ig=1.45×10^-7φ^1.85exp（24950/T）。对不同压力和当量比的点火延时数据进行归一化处理,ln(τ_ig)和温度T均满足线性分布,这为比较不同条件的点火延时数据提供了途径。●对不同p的煤油/空气,p越大,发生爆燃对应的临界温度越低。对不同φ的煤油裂解产物/空气,φ越大,发生爆燃对应的临界温度越高。比较煤油及其裂解产物点火延时数据后发现,爆燃对应的点火延时均小于1ms。（4）针对不同压力、当量比的煤油及其裂解产物,第四章给出了自点火瞬态流场自发光成像、OH-PLIF、CH/OH基发射光谱测量结果,表征了火焰产生、传播特征和火焰内部结构。●当p=0.1MPa、0.3MPa、0.6MPa和φ=1,测量了煤油/空气溶胶自点火燃烧流场自发光成像,给出不同温度的自点火流场火焰结构和特征,显示了不同的高、低温点火机理。对于低温点火,在点火起始阶段,诱导区出现多个随机分布的火核,火核扩展、融合形成火焰面,并向反射端面传播。对于高温点火,在点火起始阶段,靠近反射端面形成了火核。当点火温度T＞1600K时,点火直接自从反射端面开始。●对相同φ、不同T的煤油裂解产物/空气,其自点火图像与煤油类似。当φ=0.5,火焰区图像表明:当T=1536K～1568K,仍为弱点火模式。当T=1700K,点火起始阶段为爆燃,火焰在传播过程中追赶反射激波,并在观察窗内赶上反射激波形成爆轰。当T=1850K,点火起始阶段在反射端面就形成了爆轰,火焰呈狭窄的带状。●针对激光器（YAG+DYE）预热后再起动,定性地测量了首次脉冲激光能量,确定了达到激光能量稳定的最大间隔时间,解决了OH-PLIF系统和激波管运行的时间同步控制问题,给出了煤油裂解产物自点火流场OH-PLIF测量结果,确认了湍流火焰内部的三维结构。●测量了自点火流场CH基（CH₄/空气、波长431nm）、OH基（H₂/O₂、波长308nm）自发辐射的瞬态光谱特征谱线,与LIFBASE计算结果进行了比较,给出了拟合的辐射温度。（5）第五章给出了全文总结和下一步研究工作建议。本文主要特色和创新为:（1）提出“管外预混”和“循环进气”思想,研制了两相激波管、配套的雾化燃料形成和进气系统,保证了煤油气溶胶在低压段进气和静置的均匀性,为低饱和蒸汽压的液态碳氢燃料两相点火提供了新的途径。激波管所模拟低温点火的压力、温度等均和超燃发动机燃烧室参数接近。（2）测量了煤油/空气溶胶、煤油裂解产物/空气混合物的点火延时,为超燃发动机燃烧室设计提供了基础性的数据。（3）结合点火延时和点火燃烧流场自发光图像,揭示了煤油气溶胶及其裂解产物高、低温的不同点火机理。（4）将PLIF方法用于自点火燃烧流场诊断,较好地解决了激波管运行、PLIF系统的时间同步控制难题,获得了火焰内部时间、空间高分辨率的自由基荧光图像,为探索点火阶段的火焰结构和湍流燃烧机理提供了新方法,也为点火燃烧流场在线诊断应用先进光谱成像方法提供了基础。（5）本文得到的点火延时数据和自点火流场光谱图像,对于化学动力学机理验证和煤油超燃发动机（scramjet）和脉冲爆轰发动机（PDE）燃烧室设计有意义。更多还原

【Abstract】 In this thesis,auto-ignition phenomena of kerosene aerosol and cracked kerosene were experimentally studied to obtain ignition delay and high resolution images of radical emission and fluorescence behind a reflected shock wave.Pressure and temperature can be changed in a wide range by changing Mach number of an incident shock wave.The works are summarized as follows:（1） In chapter one,related background and progress,as well as some topics in this thesis are briefly introduced for ignition studies.（2） In chapter two,an aerosol shock tube was developed for ignition studies, including its design and assembly,fuel atomization,aerosol inlet,SMD（Sauter mean diameter） measurement by Mie scattering.Finally,long test time was confirmed in conditions of tailored contact surface at low temperature.（3） In chapter three,ignition delay timeτ_ig was obtained at different equivalence ratioφ,pressure p and temperature T based on detected the time histories of pressure and OH-emission.τ_ig is ranged from 0.10ms to 6.36ms for stoichoiometric kerosene aerosol when pressure ranged from 0.1MPa to 0.6MPa and temperature from 1163K to 1653K.Andτ_ig decreases as p increases under the same temperature,τ_ig is fitted asτ_ig=4.75×10^-7p^-1.16exp（17360/T）.Whereτ_ig, p and T are in units of ms,MPa and K.τ_ig is ranged from 0.07ms to 5.04ms for atmospheric cracked kerosene,when temperature is ranged from 1348K to 1940K andφfrom 0.5 to 2.Andτ_ig increases asφincreases under the same temperature.Asφincreases,τ_ig deceases but ignition temperature increases,τ_ig is fitted asτ_ig=1.45×10^-7φ^1.85exp（24950/T）.Regression on logarithm In(τ_ig) shows good linearity to T at different pressure and equivalence ratio.This provides a way to analyze the ignition delay at different pressure and equivalence ratio.According to the pressure time history,the critical temperature of deflagration increases as p decreases orφincreases.Andτ_ig is less than 1ms for the cases in which deflagration occurs.（4） In chapter four,images of emission and OH-PLIF were got at different pressure and equivalence ratio for kerosene aerosol and its cracked products. Instantaneous emission spectrum of CH and OH were also presented.These results show detailed flame structure and its propagation with time marching. When p is 0.1MPa,0.3MPa and 0.6MPa respectively,emission images were obtained for stochiometric kerosene aerosol at different temperature.At initial stage of ignition,the images illustrate distinguished mechanism at high and low temperature.In the case of low temperature,several flame kernels locate randomly in induction zone.Then,kernels recombine and merge into a large zone and propagate outwards,especially to reflected end of shock tube.This means that auto-ignition doesn’t take place in vicinity of the reflected end.In the case of high temperature,kernels move to the end as temperature increases. Finally,kernels locate at the end whenever temperature is greater than 1600K. Furthermore,approximate images and similar mechanism were observed for cracked kerosene at different temperature whileφis kept unchanged.Weak ignition mechanism is still kept when temperature is ranged from 1536K to 1568K.If temperature is higher than 1700K,flame can overtake shock front and deflagration appears in test section.When temperature up to 1850K,detonation occurs accompanying with incoming flows and flame completely combines with shock front at the end.In this chapter,the energy of first laser pulse was qualitatively measured to check whether laser can reach its steady state after re-firing.Usually,re-firing is necessary for laser external triggering in a shock tube.The maximum time interval was determined to keep laser steady state.After solving difficulties of synchronization,OH-PLIF can be successfully obtained and detailed flame structure can be seen in cracked kerosene air mixture.Instantaneous emission spectrum of CH（CH₄/air mixture,wavelength 431nm） and OH（H₂/O₂ mixture,wavelength 308nm） were detected and compared to those calculated by LIFBASE software.The radiation temperature was also fitted by LIFBASE.（5） In chapter five,some conclusion and proposals for future studies were presented in this thesis.Some fresh ideas and methodology are listed as follows:（1） To suggest kerosene atomized outside shock tube and aerosol filled into shock tube by a special inlet device.By this way,homogeneous aerosol can be obtained in a shock tube.This provides a new way to study ignition phenomena of hydrocarbon fuels with low vapour pressure.In this thesis,almost the same pressure,temperature and fuel aerosol are provided which correspond to those in a scramjet combustor.（2） Ignition delay time of kerosene and its cracked fuels at different conditions is measured and collected which is key important for design of engine combustor.（3） Emission imaging of combustion field shows that ignition mechanism at low temperature is quite distinguished from that at high temperature for both kerosene and its cracked products.（4） OH-PLIF images were obtained for combustion field of cracked kerosene while synchronization is solved among shock tube,laser and ICCD camera.The images of emission and fluorescence demonstrate flame structure at high time and space resolution.This provides more information to understand turbulence flame.PLIF is successfully extended to diagnose ignition phenomena in a shock tube.（5） The ignition delay and spectroscopy images are key important to verify fuel chemistry kinetics.Also,these are beneficial to design the combuster of scramjet and pulsed detonation engines.更多还原