DYNAMICS OF LIQUID MOTION IN A NOZZLE OF A FIRE-EXTINGUISHING DEVICE
Purpose. Development of a mathematical model of liquid motion in a fire-extinguishing device nozzle and determination of its basic parameters. Methods. The analytical methods with application of the Bernoulli equation for unsteady-state flow, the flow continuity equation and the fluid dynamics equations. Results. The mathematical model of the liquid motion in the fire-extinguishing device nozzle has been developed. The regularities of mass rate variations, fluid velocity in the nozzle and on the nosepiece cut have been obtained, the fluid release time has been established. Scientific novelty. The non-linear differential equation of second order has been obtained which describes the fluid motion in the fire-extinguishing device nozzle and that differs by considering the rubber nosepiece resistance to be the resistance of an orifice in a thin wall with a rounded intake lip. Practical value. The proposed mathematical model makes it possible to simplify the calculation of the basic parameters of the dynamic process of the fire-extinguishing liquid motion in the device nozzle; to establish the relations between the design and operating conditions of the fire-extinguishing device. The derived dynamic characteristics, i.e. the law of liquid motion in the nozzle, liquid velocity and acceleration, mass rate of flow, reactive recoil force, liquid release time may be used for comparative assessment of different types of backpack fire-extinguishing devices.