Experimental and Analytical Study on the Liquid Film by Jet–Wall Impingement

Liquid film cooling by jet–wall impingement on the combustor wall is commonly used in small rocket engines. The heat transfer mechanism inside the liquid film is closely related to the film flow. Therefore, we establish a comprehensive analytical model with reasonable assumptions for the liquid film flow by inclined jet–wall impingement, and we validate it through a series of experiments. It is found that the predicted liquid film dimensions agree well with the experimental results. As the impingement angle increases from 30 to 60 deg, the shape of the liquid film turns from an oval to a circle. With the increase of the impingement velocity from 7.8 to 15.6 m∕s, the width, length, and area of the liquid film increase. The wall roughness R_a ranges from 6.3 to 0.025 μm, which shows negligible effects on the liquid film dimensions. As the surface tension increases from 36.03 to 67.13 mN/m and the viscosity increases from 1 to 6.72 mPa ⋅ s, the dimensions of the liquid film decrease. The effect of viscosity is more significant than surface tension within the scope of this experiment. Finally, an empirical correlation for the three investigated film dimensional parameters is proposed.