Study On Boron Particles Ignition And Combustion And Its Enhancement Methods

With both high potential volumetric and gravimetric energy release, boron is regarded as the best fuel for high-energy density propellant on ducted rocket.Boron-based fuel-rich propellant contains more boron particles, which cannot achieve full ignition and combustion for poor oxygen and low temperature in the primary motor.The ignition and combustion of fuel-rich gas containing large amounts of boron particles completes in secondary combustion chamber mixed with air. The dwelling time of boron particles in secondary combustion chamber is only a few milliseconds.Within such a limited period of time, the second combustion must be well organized to achieve rapid ignition and efficient combustion. Therefore, it will lay the foundation for efficient energy conversion of boron-based fuel-rich propellant on ducted rocket to study the process of ignition and combustion of boron, to reveal its inner mechanism and control mode, and to explore the promoting methods of boron ignition and combustion. All of these have both important theoretical significance and application value.On the basis of review of domestic and overseas related research, a theoretical study on boron ignition and combustion is conducted. A one-dimensional model about the ignition process of boron particle in boron-based propellant ducted rockets is proposed to systematically analyse the variation law and causes of Stefan flow, with the consideration of the gas flow around the boron particle, the heat transfer and the mass transfer between the boron particle and the surroundings. And a one-dimensional model about the combustion is also proposed, taking account of the effects of vapor diffusion and gas-solid/liquid two-phase chemical reaction kinetic factors.The effects of ambient pressures, temperature, and oxygen concentration on the ignition and combustion of boron particles is investigated.To study the collisional process of the boron particles in afterburner of the ducted rocket, force analysis on the particles during collision in a microcosmic scale was given in this paper. Based on the computational model of viscous force and collisional force,which are the two main forces that have effects on the collisional process, numerical simulation on movement of the particles in the afterburner was conducted and analysis of results of the collision was performed from a mechanical angle. Results indicate that in the first collision, boron particles with the same size are easy to agglomerate, the smaller the particles the more obvious. One-dimensional model on ignition of boron particles agglomerate is thus developed to analyse the effects of ambient pressures,temperature, oxygen mass fraction and the size of agglomerate on the ignition process of boron particles agglomerate.Based on the analysis of domestic and overseas experiments and research materials,experimental method of boron ignition and combustion is developed, and its preliminary feasibility is verified. The parametric variation regulation of the temperature and mass of boron particles ignition process obtained from Xenon lamp heating experimental platform and differential scanning calorimetry. Thermal gravimetric analysis shows that the ignition temperature of boron particles agglomerate is lower than that of single particle, and decrease with the increase of agglomerate diameter, which further verifies the correctness of the model on the ignition of boron particle agglomerate preliminarily.The experimental research on combustion enhancing methods is conducted tentatively. An experimental research on ignition properties of the mixture of boron and magnesium using xenon lamp heating system and thermal gravimetric test is conducted.The results show that the addition of magnesium will shorten the delay time of ignition,while has little effect on the ignition temperature of boron. According to experiments conducted, a model on ignition of zero-dimensional boron and magnesium agglomerate is created. The analysis of the model indicates that the addition of magnesium will shorten the delay time of ignition and accelerate the ignition of boron.