Study on the stability of gas-liquid-solid mixed jets in the three-phase jet fire monitor

The stability of gas–liquid–solid jets is a key factor affecting the performance of three-phase jet fire monitors. To elucidate the stability characteristics and interphase interaction mechanisms of mixed jets, a coupled CFD–VOF–DPM model was established to capture gas–liquid interface evolution and particle transport. The effects of gas–solid inlet pressure, powder-outlet configuration, powder-pipe diameter, and particle mass flow rate on jet stability were investigated. In addition, a mixed-jet experimental platform was developed based on similarity principles to validate the numerical model. The results show that three-phase jet stability is mainly governed by the competition between the penetration capability of the central gas–solid jet and the confinement capability of the annular water jet. Optimal jet collimation was achieved at a gas–solid inlet pressure of 20 kPa, whereas excessive pressure accelerated the premature breakup of the annular water jet. Compared with converging and diverging outlets, the straight-pipe outlet provided smoother velocity and pressure transitions, reduced radial particle dispersion, and strengthened the confinement of the annular water jet. A powder-pipe diameter of 25 mm achieved a favorable balance between particle penetration and water-jet confinement. Moreover, a particle mass flow rate of 0.01 kg/s improved particle-core collimation. These findings enhance the understanding of gas–liquid–solid jet stability and provide guidance for optimizing the operating parameters and nozzle configuration of three-phase jet fire monitors.