Analysis Of Cold-flow Mixing Effect And Combustion Efficiency Of Afterburning Chamber Of Solid Rocket Ramjet

Afterburner is an important component of solid rocket ramjet. Its property plays asignificant role in the integrity of solid rocket ramjet. At present，boron is often used in SolidRamjet Rocket（SRR） as additive for oxygen-poor propellants because of its high volumecalorific value and high-quality heat value. But it can’t be ignited and reacted completely inthe fuel gas generator where there is lack of oxygen and is low temperature. So the hot gaswill take lots of boron particles into the afterburner. Since the particles stay in the afterburnerfor just a short time, in order to organize better secondary combustion and increasecombustion efficiency of the afterburner, it is very crucial to study the mixing combustionbetween particles and gas.By the application of CFD software, especially particle trajectory model，the mixing ofgas-particle two-phase flows in the afterburner is studied in the case of cold flow firstly justfor providing reference and foundation of the following case of inner combustion flow fieldcomputation in SRR with chemical reaction. Influence of many different SRR structures suchas different air inlet angles, particle inject angles, hot gas inject angles and nozzle locations,air inlet spacing together with the factors such as particle diameters, hot gas mass flow rate,etc to the mixing of particle and gas is computed. Mixing degree and dimensionless particleconcentration is used to quantitatively evaluate the gas-particle mixing extent. The resultsshow that: There exist highly complicated flow field where many back flow regions andvortices can be found in the afterburner. The strong3-D property can also be seen in theabove flow field. With the increase of air inlet angle, the back flow region in the head ofafterburner is squeezed. The vortex moves upward and its strength is also enhanced. Thegas-particle mixing degree increases; the smaller the particle diameter, the more favorable themixing because of its better flow with fluid; the change of hot gas injection angle can promptthe mixing more effectively because such change can strengthen the interaction between theair jet and hot gas jet. So increase hot gas injection angle in some range (far from the side ofair inlet) is better for the mixing. The shorter the distance between nozzle location and airinlet, the better the mixing. Keeping the location of frontal air inlet unchanged and changingthat of rear air inlet could see better mixing in the head of afterburner but less oxygen content.In the case of latitudinal angle180o, particles can disperse in the whole afterburner whichresults in better mixing in the case of90o.Next the combustion in the afterburner is numerically simulated. k-εturbulence model and rapid one step reaction is adopted. The influence of change of particle diameters,air-fuel ratio, total temperature of air incoming flow and inject angles of fuel-rich gas tocombustion efficiency is investigated. The results show that: the smaller the particle diameter,the stronger its flowing with the fluid and the longer its stay time in the afterburner. Thus thecombustion efficiency can be improved; increase of air-fuel ratio increase and totaltemperature of incoming air can enhance the injection length of air and keep the airdistribution mean and the mixing of oxygen and fuel more desirable. In the above case, hotgas is no longer at one side of the afterburner, instead, it enter the center region of theafterburner and reacts with the oxygen and so the combustion efficiency of gas and particlesgoes up significantly; change of hot gas injection angle can strengthen the contact of oxygenand gas and particle phase; which brings about significantly increase of the combustionefficiency.