Elucidation of Detailed Structure of fuel sprays by Advanced optical diagnostics and the Combustion Mechanisms

Katsuki和Akamatsu：喷雾火焰的宏观燃烧行为和光学测量为了更好地了解喷雾火焰的燃烧行为，采用激光层析成像技术对喷雾火焰中的液滴团进行了可视化测量，并采用一种新开发的多色集成卡塞格伦接收光学系统（MICRO）对局部OH化学发光和CH带发射进行了同步测量。利用氩离子激光器和高速数字CCD摄像机，研究了燃烧过程中液滴团簇及其瞬态结构的时间序列平面图像。通过同时观察预混喷雾火焰中的液滴团和局部化学发光，证实了由于优先火焰传播，喷雾流的某些部分非常迅速地消失，这在气态预混火焰中常见，而喷雾流的其他部分在长时间内存活以形成液滴团，消失 关于我们 Nakajima和Ikeda：通过激光诊断和局部荧光来阐明喷雾结构本研究的目的是研究喷雾燃烧中液滴动力学和湍流之间的相互作用。该研究项目分三个阶段进行。首先，基于相位多普勒风速仪（PDA）在高速数据采集条件下获得的液滴速度和尺寸信息，对湍流特性、火焰稳定机理、混合气形成和液滴蒸发进行了研究。其次，利用粒子图像测速技术（Particle Image Velocimetry，PIV）测量了液滴的瞬时空间结构、速度分布、不同粒径的液滴速度，并开发了“多强度层PIV”系统。最后，通过对OH^*、CH^*、C2^* 的局部化学发光测量，阐明了流体动力学与化学反应之间的关系。利用该技术可以在高的时间和空间分辨率下观察到从外部燃烧到内部燃烧的转变。Fujimoto和Senda：非稳态蒸发喷雾中的混合物形成过程本研究的对象是非稳态蒸发场中的自由柴油喷雾。在前人对柴油机非蒸发自由喷雾研究的基础上，分析了高温高压场中蒸发喷雾的形成过程和结构。提出了蒸发喷雾的结构模型。在实验分析中，主要采用激基复合物荧光法研究了喷射压力和环境气体密度对自由喷雾结构形成过程的影响。在数值分析中，采用KIVA-II程序中改进的TAB模型，分析了油滴颗粒、燃料蒸气浓度、颗粒速度和环境气体速度的空间分布。最后，本文提出了一种改进的TAB模型与DVM相结合的混合模型，对喷雾的环境气流和内部涡流进行了数值分析。少

Katsuki and Akamatsu : Macroscopic combustion behavior of spray flames and the optical measurementIn order to better understand the combustion behavior of spray flames, simultaneous measurements of droplet cluster visualization using laser tomography and local OH chemiluminescence and CH-band emission using a newly developed optical probe system named the Multi-color Integrated Cassegrain Receiving Optics (MICRO) are applied to a premixed-spray flame. Time-series planar images of droplet clusters and their transient structures during combustion are examined using an Ar-ion laser and a high-speed digital CCD camera. By observing the droplet clusters and local chemiluminescence simultaneously in the premixed-spray flame, it is confirmed that some portions of the spray stream disappear very rapidly due to preferential flame propagation, which is often seen in gaseous premixed flames, while other portions of the spray stream survive over a long period to form droplet clusters, disappearing … More gradually from their outermost portions, which seems similar to a diffusion-flame.Nakajima and Ikeda : Elucidation of spray structure by laser diagnostics and local chemiluminescenceThe purpose of this research was to investigate interaction between the droplet dynamics and turbulent flow in spray combustion. This research project was conducted in three phases. First of all, turbulent flow characteristics, flame holding mechanism, mixture formation and Droplet evaporation were discussed based upon the droplet velocity and size information acquired by phase Doppler anemometry (PDA), which was measured at very high data acquisition rate. Secondly, particle image velocimetry (PIV) was applied to measure instantaneous spatial structure, velocity distribution, droplet velocity of different size by size discriminating PIV, as we call 'Multi-Intensity-Layer PIV', developed. Finally, local chemiluminescence measurements of OH^*, CH^*, C2^* were performed to elucidate the relation between the fluid dynamics and chemical reactions. The transition from external to internal group combustion was observed in high temporal and spatial resolution by this technique.Fujimoto and Senda : Mixture formation process in unsteady vaporizing spraysThe object of this study is free diesel spray in unsteady and evaporative field. We analyze formation process and structure for evaporating spray in high temperature and pressure field based on the previous studies on results of non-evaporating free diesel spray. Also, we propose a structural model of evaporating diesel spray. In the experimental analysis, we mainly research the effects of injection pressure and ambient gas density on the formation process of free spray structure with exciplex fluorescence method. In the numerical analysis, the spatial distributions of droplet parcels, fuel vapor concentration, parcel velocity, and ambient gas velocity are analyzed by a modified TAB model of KIVA-II code. Finally, we propose a hybrid model which consists of a modified TAB model and DVM, for numerically analyzing both ambient gas flow and inner vortex flow of spray. Less