Numerical Study on Influence of Size and Number Density of Droplet on Spray Combustion Mode

Abstract

The spray combustion is applied to various practical combustors such as a diesel engine, a gas turbine, etc. However, the spray combustion is the very complicated, unsteady two-phase reactive physicochemical phenomenon composed of preheating, evaporation, mixing, ignition, combustion and quenching, etc. Chiu et al. have considered the spray combustion field with the concept of group combustion, and proposed that the group combustion can be classified into four modes in terms of group combustion number G. In this paper, using the numerical analysis with PSI-CELL model, we examined combustion process in three-dimensional heterogenous combustion field of fuel droplets and air, so as to improve Chiu's group combustion mode. We arranged many fuel droplets using random variables, and changed the size and the number density of droplets. We obtained the following results; 1) The group combustion is classified into six modes. 2) The initial equivalence ratio ϕ is needed to consider the influence of oxygen existing initially in the combustion field. 3) The group combustion mode can be organized by the initial equivalence ratio ϕ when the size of fuel droplet is small, while it can be organized by group combustion number G when the size of fuel droplet is large.