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

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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