Theoretical Investigation and Its validation of Unsteady State Combustion Phenomena in Limited Non-Uniform Space

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This study was conducted for the establishment of understanding and generalizing spray diffusion combustion, which is commonly used in variety of combustion systems. Study was made for the two major topics : (1) combustion similarity, and (2) air-entrainments in spray flames. Here combustion similarity means that flow pattern and flame distribution develop similarly in differently sized combustion systems.The possibility of combustion similarity in differently sized spray combustion engines was theoretically investigated based on the analysis of governing equations of diffusion combustion. Because of this theoretical background, heat release rates and thermal efficiency can be predicted from scale model experiments. Based on an analysis of NO formation and the wall temperature of the combustion chamber, an algorithm to predict emissions and thermal loads were established. An experiment was then performed to compare predictions based on scale model experiments and results with large engines. The results showed good agreement with the theoretical predictions. Three dimensional computer simulation of combustion also supported the scale model experiments.Next theoretical formulation and its experimental validation for air entrainment changes in fuel spray combustion were performed. THe theory predicts air entrainment changes for a variety of swirl speeds, numbers of nozzle holes, nozzle diameters, engine speeds, injection speeds and fuel densities. Experiments were performed in order to compare theoretical predictions and experimental results in variety size of engines. All results showed good agreement with the theoretical predictions for shallow-dish piston engines.The study provides understanding of spray diffusion combustion and theories which are applicable for design and development of combustion systems.