Simulation And Experiment Research On Temperature Reduction Of Rocket Engine Jet By Water Injection

With the development and application of the new generation of carrier rocket, aneffective thermal protection for the gas flow-guided channel and other launching equipmentson the ground is one of the most important factors for a successful launch. Water injectioninto a jet flow is the most direct and effective way to slove the problem with reference to thesuccessful experience of foreign large launch site. However, the key problem to adoptingwater cooling scheme is how to design the water injection mode and injection parameters.For what we need to have a clear underatanding of the mechanism of cooling water first.Based on the launching of new carrier rocket, a sub-scale model was designed. With whichboth the numerical simulation and experiment method were used to study the water coolingprocess and the effect. The following aspects were included in the main work:1. A program to solve vaporizing process is written according to the study of thevapourizing mechanism of liquid water. Based on the Mixture multiphase model, theunsteady gas-liquid two-phase multiphase flow field model was established. According tothe calculation model, a free jet flow and water injection flow field was simulated and the3-D simulation results had shown clearly the effect with water injection. Comparing with theexperimental results, the numerical calculation model has higher precision and reliability.With which the physical phenomenon of water injection into the jet flow could be describedaccurately. Based on the calculation model, the Finite-Rate Chemistry model was coupled tosimulate the afterburning phenomenon. The result showed that: for a free jet flow, thetemperature on the edge of the flow field in where the afterburning happened increasedsignificantly. However, with water injection, the effect is not obvious because of the gasstream was waapped in the center region by a large amount of water vapor.2. On the premise of a fixed total water injection with double pipe, the flow fieldstructure and the cooling effect were studied with the water flow velocity. The calculationresult shows that the mainstream will be desformed and appear bifurcation, an a secondarybifurcation will be occur with the increase of water injection quantity.before the bifurcationphenomenon appears in the flow, the axial temperature of the main stream decreasedexponentially with the increase of water injection momentum. In the critical state, it reachesthe best cooling effect. Beyond the critical state, the cooling effect will be decreased with the increase of the water injection quantity and the flow velocity, the secondary bifurcation willoccour as the ultimate state.3. The cooling effect and the flow structure are researched with the change of the waterpipe number under two conditions, which is the fixed water quantity for a single pipe and thefixed total water quantity with a relatively small value. It shows that: in the first condition,the axial temperature increases exponentially with the number increased, there is an oppositechange with the result by changing the velocity of water injection.in the second condition,the cooling effect and the flow structure hasn’t changed significantly.4. In the four pipe water injection condition and on the premise of the mainstreamstructure has a small change, the cooling effect was studied with the change of the total waterquantity. The result shows: improve the total quantity while maintaining the waterpipesectional area constant, the cooling effect on the mainstream is different, water cooling isrealized on the surface of the gas flow with less water injected at a low velocity. On thecontrary, a relatively large quantity of water injected at a high flow rate will decease thetemperature both in the core area and on the surface at the same time. According to optimizingdesign, the water injection parameters can both meet the cooling requirmentswhile reducingwater amount.5. Aiming at the optimization design, a sub-scale model of the gasflow-guided channelwas added on the test equipment.both the numerical simulation and experimental methodwere used to test the thermal protection effect for the gas flow-guided channel. On this basis,the dynamic laying method was used to simulate the rocket taking off process. As the resultshown: water injection into the jet flow can effectively achieve the thermal protection. On theguilding cone surface where the mainstream impacted, temperature value from900K down to500K, the average temperature of the gas flow in the gasflow-guided channel also decreasedsignificantly, in the outlet the temperature value decreased from600K to400K. During thetaking off process, the cooling effect has little changed. However, a large mount of watervapor generated and flow with the mainstream into the gasflow-guided channel, which cangreatly influence the drainage unobstructed.