Shock wave emission and evolution mechanisms in aerated cavitating aviation fuel flow in a converging-diverging nozzle

Fuel cavitation in an aircraft fuel system can lead to unexpected material degradation and damage to the fuel system components due to the violent collapse of cavitation bubbles near boundaries and the emitted shock waves. In this study, shock wave propagation and generation mechanisms in fuel cavitation are experimentally characterized in aerated cavitating flow in a converging-diverging nozzle via high-speed digital imaging and signal processing technique that we denote as synthetic schlieren. Two independent stationery and sustained mechanisms responsible for shock wave generation in the diverging section of the nozzle have been observed in the choked flow regime. A detailed systematic quantitative data is obtained to characterize shock wave intensity and velocity in aerated flow regimes of two jet fuels (JP5 and JP8) under different bubble injection rates, nozzle back pressures, and void fractions. A strong similarity is obtained between shock speeds from our experimental data and nonlinear solutions of the governing equations for nonbarotropic homogeneous flow. Results from our study shed some light on the complex physics of fuel cavitation and may lead to improved design of fuel system components.