Elucidation of combustion mechanism of fuel sprays by optical diagnostics and modeling of spray flows

水谷和Akamatsu：喷雾液滴群燃烧假说的定量验证相位多普勒风速计光学的优化设计使我们能够讨论液滴簇的瞬时特性，并估计在各种群燃烧模式下每个液滴簇燃烧的修正群燃烧数G_C。发现火焰中所有液滴团簇的g_c值平均值落在Chiu等人定义的外团或内团燃烧模式范围内，这与之前的实验观察结果很好地吻合。Katsuki：喷雾燃烧液滴行为的统计建模我们开发了湍流中液滴行为的模型，用于实际燃烧器中喷雾燃烧的数值预测。在该模型中，用拉格朗日跟踪法确定了代表一组液滴的计算包的轨迹，并通过溶胶预定的气相场确定。与PSI-Cell模型相比，欧拉方程更符合欧拉方程，液滴的速度波动和湍流弥散使用概率密度函数进行了统计表征和计算。该模型在提供适当的液滴局部尺寸分布和估计气相与液滴之间的相互作用方面不需要太多的包裹。因此，与传统的随机方法相比，计算效率显著提高。Nakajima和Ikeda：喷雾研究中相位多普勒技术的误差估计。本研究的目的是探讨狭缝位置效应、测量体积大小效应和火焰前诱发的数据偏差等附加因素。利用两套PDA进行了三种实验。结果表明，狭缝位置位移效应对测量结果的不确定度有很大影响，特别是在高数据速率下。初始阶段狭缝位置的光学对准是最重要的影响因素，使用两个PDA接收光学器件可以显著改善这种狭缝位置偏移效应。在低数据速率下，质量通量的测量不确定度值较大。在高数据速率下，小液滴的检出率表现出测量体积尺寸效应。Hosokawa：循环分辨喷雾结构PDA测量采用循环分辨PDA测量，并将测量数据按液滴尺寸分组，研究空气辅助喷射器喷雾过程中液滴的循环分辨流动和动力学变化、液滴尺寸特征及其波动。周期分辨PDA测量观测到速度的大周期变化。由于剪切诱导涡结构引起的流动振荡也被观察到。少

Mizutani and Akamatsu : Quantitative Verification of Group Combustion Hypothesis for Spray DropletsThe optimized design of phase Doppler anemometer optics enabled us to discuss instantaneous characteristics of droplet clusters and to estimate the modified group combustion number G_C for each droplet cluster burning in various group combustion modes. It was found that the G_C-value averaged over all droplet clusters in the flame fell within the range of the external or internal group combustion modes so defined by Chiu et al., which was in good accordance with the previous experimental observations.Katsuki : Statistical Modeling of Droplet Behavior for Spray CombustionWe have developed a model of droplet behavior in turbulent flows for numerical prediction of spray combustion in practical combustors. In the proposed model, the trajectory of a computational parcel representing a group of droplets is determined by Lagrangian tracking method through the predetermined gas-phase field by sol … More ving Eularian equations as in PSI-Cell Model, Velocity fluctuation and turbulent dispersion of droplets are statistically characterized and calculated using a probability density function. This model does not required so many parcels in providing adequate local size distribution of droplets and in estimating the interaction between gas-phase and droplets. Therefore, the computational efficiency is significantly improved in comparison with the conventional stochastic methods.Nakajima and Ikeda : Error Estimations on Phase Doppler Technique for spray research.The purpose of this study is to investigate additional factors in such as slit location effect, measurement volume size effect and flame-front induced data bias. Three kinds of experiment were curried out using two sets of PDA.The results show that the slit location shift effect causes a significant measurement uncertainty, especially in high data rate. The optical alignment of the slit location at the initial stage is the most important factors, and this slit location shift effect can be improved dramatically using two PDA receiving optics. The measurement uncertainty of the mass flux at low data rate yields large value. The measurement volume size effect can be seen in detection rate of small droplet at high data rate.Hosokawa : Cycle-Resolved PDA Measurement of Size-Classified Spray StructureCycle-resolved PDA measurement was performed and measured data was classified into droplet size groups in order to investigate detail and time-dependent droplet dynamics of spray by an air-assist injector, those are cyclic resolved flow and droplet dynamics variation, size-classified droplet characteristics and its fluctuation. Large cyclic variation of velocity was observed by the cycle-resolved PDA measurement. Flow oscillation due to shear induced vortex structure is also observed. Less