引用本文:赵晓玉,李昌,李思语,刘鹏飞,韩兴.超音速火焰喷涂(HVOF)多相流瞬时演化机理及敏感性分析[J].中国表面工程,2024,37(1):148~159
ZHAO Xiaoyu,LI Chang,LI Siyu,LIU Pengfei,HAN Xing.Transient Evolution Mechanism and Sensitivity Analysis of Multiphase Flow in HVOF Thermal Spraying[J].China Surface Engineering,2024,37(1):148~159
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超音速火焰喷涂(HVOF)多相流瞬时演化机理及敏感性分析
赵晓玉, 李昌, 李思语, 刘鹏飞, 韩兴
辽宁科技大学机械工程与自动化学院 鞍山 114051
摘要:
以航空煤油为燃料的超音速火焰喷涂(HVOF)技术在制备 WC-Co 涂层方面具有独特优势。目前对 HVOF 热喷涂稳态过程的研究无法揭示燃料液滴在燃烧室中的动态燃烧行为。液体燃料进入燃烧室前需要雾化,量化揭示燃料燃烧反应瞬时演化机理是优化喷涂工艺的关键。基于 JP5000 喷枪建立 HVOF 热喷涂过程瞬时演化数值模型。将煤油液滴破碎、气化过程、 燃烧反应焰流与喷涂粒子直接耦合。采用双向耦合欧拉-拉格朗日方法跟踪连续相和离散相,以 realizable k-ε 湍流模型、一步反应涡耗散模型(EDM)表述喷涂燃烧焰流特性。通过 KHRT(Kelvin-Helmholtz Rayleigh-Taylor)破碎模型描述航空煤油液滴破碎过程。基于可靠性理论,综合分析煤油液滴直径、氧气 / 燃料比率及反应物质量流量对喷涂粒子飞行行为的影响。结果表明:氧气 / 燃料比率对粒子温度影响程度最大,煤油液滴直径对粒子速度影响最大。HVOF 瞬时演化模型可以直观呈现燃料的动态行为及喷涂粒子的飞行特性,可为优化热喷涂工艺提供参考和理论支撑。
关键词:  超高音速火焰喷涂(HVOF)  多相流  瞬时演化  灵敏度分析
DOI:10.11933/j.issn.1007-9289.20230319001
分类号:O242.21
基金项目:辽宁省应用基础研究计划(2023JH2/101300226);辽宁科技大学研究生科技创新项目(LKDYC202216)
Transient Evolution Mechanism and Sensitivity Analysis of Multiphase Flow in HVOF Thermal Spraying
ZHAO Xiaoyu, LI Chang, LI Siyu, LIU Pengfei, HAN Xing
School of Mechanical Engineering and Automation, University of Science and Technology Liaoning,Anshan 114051 , China
Abstract:
High-velocity oxygen fuel (HVOF) thermal spraying is an emerging technology for surface modification with a low cost and short cycle for preparing coatings that can deposit metal and ceramic powders on different substrate surfaces. The use of liquid kerosene can save fuel under high-power outputs. Before entering the combustion chamber, kerosene fuel was atomized using a coaxial stabilizer. The degree of atomization directly affected the combustion efficiency, which in turn affected the particle temperature and velocity. The transient solution of HVOF spraying visually presents the fragmentation, evaporation, and combustion processes of fuel droplets and more accurately reflects the change in the flame flow characteristics. Quantitatively demonstrating the transient evolution characteristics of thermal spraying is important for optimizing the spraying process. Presently, most studies have been carried out on the steady state in HVOF thermal spraying, which does not demonstrate the transient evolution of the multiphase flow. In this study, a numerical model of the transient evolution of HVOF thermal spraying was established using a JP5000 gun. The effects of the fragmentation and gasification processes of the kerosene droplets and flame flow on the flight characteristics of the particles were comprehensively considered. The continuous and discrete phases were tracked by a two-way coupled Eulerian-Lagrangian method, where the flame flow was considered as the continuous phase and tracked by the Eulerian method, whereas the WC-12Co particles and kerosene droplets were regarded as the discrete phase and tracked by the discrete phase. The realizable k-ε turbulence model and eddy dissipation model (EDM) with the one-step reaction were used to express the flame flow characteristics. The KHRT (Helmholtz Rayleigh) Taylor fragmentation model was used to describe the fragmentation process of aviation kerosene droplets, revealing the interaction between the evaporation and fragmentation of droplets, flame flow, and particle swarm during spraying. The effects of the kerosene droplet diameter, oxygen / fuel ratio, and reactant mass flow rate on the flight characteristics (temperature and velocity) of the particles were evaluated based on the reliability theory. The results showed that HVOF thermal spraying has the characteristics of highly nonlinear and transient evolution. The flame flow shows irregular turbulent behavior from ignition to combustion and obvious regularity as the combustion proceeds. As the particle size decreased, the particle flight trajectory became more concentrated, which was conducive to the heating and acceleration of the particles. The flight temperature and velocity of the particles decreased with an increase in the particle size. The temperature and velocity of the flame flow were high in the barrel, the particle residence time was short, and the heating and acceleration efficiencies were limited. Therefore, the temperature and velocity of particles were low in the barrel and rapidly increased in the air domain, which was because the Mach cone at the gun outlet played a vital role in heating and acceleration of the particles. Particles impacting the substrate in the molten state produce significant melt deformation, which is critical for the formation of high-quality coatings. During impact, the velocity of the particles should be as high as possible at a suitable temperature. This causes the particles to undergo significant deformation at the moment of impacting the substrate, improving the bonding strength of the coating and substrate and reducing the porosity of the coating. Owing to the effect of the high pressure in the combustion chamber, kerosene droplets aggregate to form large droplets, which gather near the fuel inlet in the form of a suspension. The surface of the suspension droplets underwent fragmentation and evaporation, and evaporation occurred in the same region as fragmentation. The influences of the reactant mass flow rate, oxygen / fuel ratio, and fuel droplet diameter on the particle temperature and velocity were demonstrated by sensitivity calculations. The combination of numerical modeling and sensitivity analysis is the most cost-effective means of optimizing the thermal spraying process and provides a theoretical reference for parametric optimization.
Key words:  high-velocitg oxygen fuelc(HVOF)  multiphase flow  instantaneous evolution  sensitivity analysis
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