Ignition model of boron particle based on the change of oxide layer structure
| Autor: | Xu Hu, Chunbo Hu, Yi Hua Xu, Zhuoxiong Zeng, Wen Ao, Xiaofei Zhu |
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| Rok vydání: | 2019 |
| Předmět: |
Materials science
Mechanical Engineering General Chemical Engineering Oxide Evaporation Analytical chemistry chemistry.chemical_element Autoignition temperature Combustion law.invention Ignition system chemistry.chemical_compound chemistry law Particle Physics::Chemical Physics Physical and Theoretical Chemistry Boron Water vapor |
| Zdroj: | Proceedings of the Combustion Institute. 37:3033-3044 |
| ISSN: | 1540-7489 |
| DOI: | 10.1016/j.proci.2018.07.016 |
| Popis: | The oxide layer of boron particle is generally regarded as a two-layer structure the inner layer is B2O3 and the outer is (BO)n. However, under lower temperature, a tiny layer of B2O3 can be generated at the surface of the (BO)n and form a three-layer structure during the ignition process, which has been proven by experimental phenomenon. Accordingly, a parameter xo is adopted to represent the thickness of the outer B2O3(l) layer (outermost layer), and a simplified kinetic and diffusion model for the ignition process of boron particles in dry and wet atmosphere is developed with considering the generation and consumption process of the outermost layer. The ignition process is divided into two parts (ignition delay and first-stage combustion) by the parameter xo. The ignition temperature is defined as the particle temperature at the moment that xo reaches 0. When xo > 0, the particle is under the ignition delay process, and the evaporation product is B2O3(g). When xo = 0, the particle turns to the first-stage combustion process. (BO)n is exposed to the environment, the evaporation products are B2O2(g) and B2O3(g), and the particle is under the two-layer structure. The oxygen diffusion inward is available during these two processes. The ignition time which is predicted by this model is in good agreement with published experimental data. Under a real ramjet condition, higher ambient temperature and concentration of water vapor can reduce both the maximum value of xo and the ignition time. The ignition temperature decreases with higher water vapor concentration, but increases with the higher ambient temperature. |
| Databáze: | OpenAIRE |
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