Effect of backpressure on the film thickness inside liquid swirl injector

The film thicknesses of liquid swirl injector under different backpressures were studied theoretically and numerically. A loss coefficient model including friction effect on liquid/gas interface was established based on classical theory. It shows that the theoretical model is not sufficient to show variations of film thickness under different backpressures. The numerical simulations were conducted with a swirl axi-symmetric model to solve Navier-Stokes equations coupled VOF(volume of fluid) equation on an adapted grid, showing that the decreased mean velocity in the transition region near liquid/gas interfaces in liquid film is a contributing factor to the increase of the film thickness.