Combustion Of Boron-Based Propellent In The Secondary Combustion Chamber And Structure Optimization Of A Solid Ramjet

This thesis studies the combustion of boron-based propellant in the secondary combustion chamber of a solid ramjet, and optimizes the structure of secondary combustion chamber. It includes parametric modeling with the help of Ansys Workbench, exploring the ignition process of single boron particle, researching the two-phase combustion of boron-based propellant in the secondary combustion chamber by the secondary development of Fluent, and optimizing the structure of secondary combustion chamber by using parametric modeling.The results of the gas-phase indicate that:there is a high temperature backflow region in the head of secondary combustion chamber, while the temperature near the central axis is relatively low. There is a big eddy structure near the fuel inlet and a relatively small eddy near the air inlet.The research on the ignition of single boron particle indicates that:reducing initial particle diameter, reducing initial oxide layer thickness, increasing environment temperature and increasing mole fraction of oxygen and water vapour will shorten ignition time. Initial particle diameter, environment temperature and mole fraction of oxygen will have significant influence on ignition time within a certain range, while there will be the "marginal effect" beyond a certain range. Ignition time increases linearly with the increase of initial oxide layer thickness, while increasing mole fraction of oxygen dose not obviously reduce ignition time.The research on the two-phase combustion of boron-based propellant in the secondary combustion chamber indicates that:particles near the central axis of secondary combustion chamber ignite slower than these on the contact area of fuel and air. Particles quickly melt near their ignition position. Because of low concentration of oxygen, particles near the central axis of secondary combustion chamber burn relatively slow. With the increase of initial particle diameter, the ignition position is unchanged, while the combustion efficiency decreases significantly. With the increase of initial oxide layer thickness, the ignition position moves backward significantly, while the combustion efficiency decreases slightly.The optimization of the structure of secondary combustion chamber based on parametric modeling indicates that:parametric modeling can quickly achieve the optimal structure of secondary combustion chamber, which will improve the combustion efficiency.