Numerical Simulation Of Base Heating Environment On A Strap-On Launch Vehicle With Plumes

As the pressure is low at the bottom of a aircraft, there may be backflow of the engine plume,which will heat the rocket base. Compared to a single core rocket, the flow field and the temperature distribution of a strap-on launch vehicle are more complex, because there is strong cross-interference between the core engine plume and booster engines plume, and the free stream of the gap also has interruption to some degree. The thermal environment of the bottom is crucial to the safety of equipments on the base. Thermal protection materials should not only meet the requirement of heat resistance but also have small weight and cost. Ground experiments of base heating environment of a rocket are full of difficulties and need a great deal of cost. With the development of computational fluid dynamics and the improvement of computer performance, numerical simulation has become an effective means of fluid flow study.In this paper, the numerical simulation method is applied to study the thermal environment in the bottom of the rocket, and it is focused on heat conduction of nozzle wall and heat convection of plume.Several boosters are bundled on the core rocket and there is a distance between the core and every booster, both the number of boosters and the distance have an influence on rocket base heating environment. The result proves that, both variables(number and distance) in the study have a greater impact on the bases of boosters than the core about temperature and heat flux. The maximum heat flux will be lager when there are four boosters within the scope of the study. As the distance increases, the maximum heat flux will firstly increase and then decrease at the bottom of the base and the outer bottom of boosters, while it is opposite at the inner bottom of boosters.The influence on the base heating environment by different flight altitude and velocity and different operating pressure of the core engine was studied. The result shows that, different flight conditions have a greater impact on the base of boosters than the core. The base temperature will increase and the base heat flux will decrease if the flight altitude increases. However, when the flight velocity increases, the maximum base temperature and the amplitude of temperature variation along the radial will firstly decrease and then increase. As for the maximum base heat flux, it will firstly increase and then remain the same. As the operation pressure of the core engine increases, the base temperature and the base heat flux will change more slowly. On the core base, the maximum temperature increases, while on inner base of boosters, the maximum temperature decreases and the maximum heat flux increases.Instability of the combustion leads to flow field oscillation, and this has little influence on the overall base of the rocket, while on the other side, it has obvious effect on the temperature of the inner bottom of intermediate position of boosters. Along the axis of the rocket, the oscillation curves of temperature and pressure of both axis and wall of the chamber gradually become smoother, and their response time is longer, in addition, frequencies of temperature and pressure are in consistence with that of pressure oscillation in the chamber inlet. For the chamber axis, profiles of temperature and pressure along axial coordinate is similar, while they are different for the chamber wall and the pressure amplitude is an order of magnitude larger than temperature amplitude. When the axis coordinate is constant, the pressure oscillation amplitudes on the axis and the wall appear little different, while temperature amplitude on the axis is above three times more than that on the wall.