Simulation and neural network analysis of spreading the oblique fuel jet impinging onto concave walls

Abstract

A series of numerical simulations of oblique-jet impinging onto concave walls are carried out to gain insight into the formation process of the liquid fuel film in a liquid film cooling thrust chamber. Moreover, the influence of jet and wall surface parameters on spreading the fuel film is investigated. The volume-of-fluid method is employed to capture the spreading process of liquid film formation after an oblique jet impacts the curved surface. Furthermore, the neural network model is developed to analyze the effects of jet diameter (0.2 mm ≤ d ≤ 0.6 mm), jet velocity (15 m/s ≤ v ≤ 20 m/s), impingement angle (15°≤β ≤ 30°), equilibrium contact angle (45°≤θe≤75°), curvature radius (22.5 mm ≤ R ≤ 67.5 mm), and surface roughness (3.2 μm ≤ Ra ≤ 16μm) on the fuel film's spreading length and maximum width based on Radial Basis Function. The results show that the liquid fuel film gradually stabilizes from upstream to downstream during spreading and the circumferential spreading of the liquid film is at its greatest when all the forces in the circumferential direction are in equilibrium. The jet diameter has the most significant effect on film spreading among jet parameters. Doubling the jet diameter at least doubles the film width and length. The effect of jet angle and velocity on film spreading is also magnified at larger jet diameters. Compared to other surface parameters, a change in the wall contact angle has the most marked effect on the spreading of the film. Lastly, the wall radius of curvature between 40 mm and 50 mm is more favorable for obtaining larger film lengths.