Abstract: The injection trajectory of compressed air foam is one of the key factors affecting foam extinguishing efficiency. In view of the lack of accurate foam jet trajectory model at present, a theoretical prediction model of compressed air foam through the trajectory of fire water spray is proposed based on particle kinematics, fluid mechanics, external ballistics theory and experimental data. In addition, the four order Runge-Kutta algorithm and MATLAB software is used to solve the differential equation of the foam jet micro element, and to simulate the theoretical trajectory of the foam jet. Furthermore, the influence of different parameters on the theoretical trajectory of the jet is explored. It is found that the predicted jet trajectory is basically consistent with the actual foam jet trajectory, and the kinetic differential equation is more accurate, which can provide a theoretical basis for the actual application of compressed air foam in lifting vehicles.

Key words: fire water monitor, foam jet, microbody dynamics, jet trajectory, air resistance