Experimental Study Of Boron Particle Combustion In Ducted Rocket

Elemental boron has high potential energy release on both volumetric and gravimetric, and is the first choice of solid fillers for fuel-rich propellant. In gas generators of solid ducted rockets, due to both hypoxia and low temperature, large amounts of boron particles can’t fully realize ignition and combustion. In secondary chambers, boron particles are mixed and combusted with air from the inlets. The study of ignition and combustion of boron particles in secondary chambers of solid ducted rockets is of important significance and great value, through which the inherent mechanism and control method of ignition and combustion of boron particles in secondary chambers can be revealed and achieved, and the foundation for further study on high efficient energy conversion of boric fuel-rich propellant in solid ducted rockets can be established. In the secondary combustion chambers of solid ducted rockets, boron particles are generally in convectional flow fields. In which, the ignition and combustion processes of boron particles are very different from those in relative static atmospheres. Both at home and abroad, the study of ignition and combustion of boron particles in secondary chambers is insufficient. In this paper, efforts on the innovations of experiment methods and combustion flow field diagnosis methods have been made, a series of boron particle combustion experiments have been carried out in secondary chamber conditions, analysis of the influence mechanism of flow field conditions in secondary chambers of solid ducted rockets on combustion efficiency of boron particles have been made.Boron particle combustion experiment methods under conditions of secondary chambers have been studied and an innovative experimental system has been developed. In the system, the working processes of a boric fuel-rich propellant ducted rocket containing a gas generator and a secondary chamber are mimicked by tests, and flow field conditions near in a real secondary chamber of a ducted rocket provided for experimental study on boron particle combustion. By a series of tests, the working characteristics of the designed boron combustion experimental system were studied.By several combustion flow field diagnosis methods including BO2 characteristic spectrum signal acquisition and secondary chamber flow field multi-point temperature and static pressure, total pressure measurement, the combustion processes of boron particles under secondary chamber flow field conditions have been experimentally studied. The secondary chamber flame was observed and BO2 characteristic spectrum radiation intensity was acquired under different secondary chamber flow field conditions. With the increase of the gas generator oxygen flow rate, the radiation intensity of BO2 characteristic spectrum enhances in the secondary chamber. But when the oxygen flow rate increases to a certain value, the radiation intensity decreased. In a constant working condition of the gas generator, with the increase of air flow rate, BO2 characteristic spectrum intensity monotonously increases in the secondary chamber. By analysis on changes of temperature, static pressure, total pressure and mach numbers, the distribution rule of the temperature, static pressure, total pressure and mach numbers at the head, mixing zone and burning zone of the secondary chamber was understanded.A sampling system has been designed. A series of boron particle combustion experiments have been carried out and condensed products were sampled with the sampling system. Based on the XRD and EDS analysis, the contents of the samples was analyzed quantitatively. The general reaction rate and local reaction rate of boron has been investigated and compared in different flow field conditions. As oxygen mass rate increased with a constant air mass rate, temperature, static pressure, total pressure, mach number and general reaction rate of boron particles increased at all sampling points. In the primary heating section, boron particles were partly oxidized. Most of the boron was oxidized in the afterburning section. The lowest boron reaction rate happened at the region around the air entrances, and the highest boron reaction rate point was at downstream locations. As the air mass rate increased while the oxygen and ethanol mass rate is kept constant, in the region between the air entrance and the nozzle of the afterburning section, temperature, static pressure, total pressure and general reaction rate of boron particles increase at all the sampling points as the air mass rate increases, but mach number decreases. It can be inferred an optimum air mass rate exists for the boron combustion.A model for combustion chamber flame radiation transfer process analysis has been established based on Monte Carlo method. And a reconstruction method three-dimensional temperature field of secondary chamber flame is developed. Through numerical simulation, the three-dimensional temperature fields of flame of cube and secondary chamber were reconstructed. The influence of detector position, quantity of radiation from each grid and other factors on reconstruction error was analyzed. Through the experiment, the flame images of secondary chamber were recorded under different working conditions. And the three-dimensional temperature fields were reconstructed. The three-dimensional temperature distribution of the secondary chamber has been obtained.The ignition and combustion processes of agglomerated boron particles have been experimental studied under the conditions of secondary chambers. According to the imaging principle of CCD, an identification method has been developed for boron particle ignition and combustion processes and flame structures with high speed images of the flames. Ignition and combustion characteristics of agglomerated boron particles in secondary chamber conditions were studied with the measurement results of flow field parameters and high speed images of the flames. The results show that the secondary chamber flow field conditions of high temperature and high oxygen concentration can promote the ignition and combustion of agglomerated boron particles. With secondary chamber flow field conditions of high temperature and low oxygen concentration, agglomerated boron particles do not ignition and combustion. If the oxygen concentration is increased, agglomerated boron particles can ignition and combustion. Under secondary chamber flow field conditions of low temperature, the effect of increasing the oxygen concentration is more obvious on the promotion of agglomerated boron particle ignition and combustion than raising the temperature. In the combustion process, the agglomerated boron particles were wrapped by bright white flame, the green light radiation intensity of which is strong. The gas may enter the agglomeration and react with internal boron particles. Before and after the test, size and shape of the agglomerated boron particles changed little.