Abstract
Owing to its low flame temperature and high airflow velocity, the activated combustion high-velocity air-fuel (AC-HVAF) spraying process has garnered considerable attention in recent years. Analyzing the velocity field, temperature field, and composition of AC-HVAF spray coatings plays a vital role in improving the quality of coatings. In this study, an actual spray gun is adopted as a prototype, and the radial air inlets are introduced to improve the reaction efficiency so that the chemical reaction can be completed in the combustion chamber. Furthermore, a complete three-dimensional (3D) model is established to examine the effects of radial inlets and porous ceramic sheet on the combustion and flow fields. The hexahedral cells are used to discretize the entire model for reducing the influence of false-diffusion on the calculation results. The gas flow field is simulated by the commercial Fluent software, and the results indicate that the porous ceramic sheet effectively reduces the turbulent dissipation of the airflow with a good rectification effect (the ceramic sheet ensures a consistent airflow direction). The radial inlets and the porous ceramic sheet promote the formation of vortex in the combustion chamber, increase the residence time and stroke of the gas in the combustion chamber, and improve the probability of chemical reactions. In addition, it is observed that the stability of velocity for the airflow is strongly related to the airflow density.
Highlights
The activated combustion high-velocity air-fuel (AC-HVAF) spraying is a novel surface spraying process developed on the basis of high velocity oxygen-fuel (HVOF) spray coating process [1]
Several studies have focused on understanding the formation mechanism of AC-HVAF coatings, the high airflow velocity and the difficulty in measuring physical quantities pose a significant challenge for further research
The structure of spray gun and the spraying principle of other spraying such as HVOF spraying [18,19,20,21,22,23,24,25,26,27,28,29,30,31,32], plasma spraying [33,34,35], and cold spraying [36] are extremely different from HVAF spraying, the related simulation studies provided a useful reference for this study on AC-HVAF spraying
Summary
The activated combustion high-velocity air-fuel (AC-HVAF) spraying is a novel surface spraying process developed on the basis of high velocity oxygen-fuel (HVOF) spray coating process [1]. Jiang et al assumed that fuel and air were fully mixed and regarded the small holes on the ceramic sheet in the spray gun as the gas inlets to establish a 3D model Based on this model, the airflow velocity, temperature, pressure, and other parameters under a certain mass flow rate were obtained, which were used to simulate the flight process of particles [16]. To resolve the above issues, the porous ceramic sheet is used in the simulation to examine its influence on the combustion, and radial compressed air inlets are added to the wall of the combustion chamber to enhance the vortexes, thereby promoting the chemical reaction.
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