Research on Dynamic Modeling and Parameter Influence of Adaptive Gun Head Jet System of Fire-Fighting Monitor

The jet medium of the adaptive gun head jet system of the fire-fighting monitor is generally a mixture of air and water. During the operation, the equivalent stiffness of the jet fluid fluctuates periodically or randomly due to the pressure pulsation of the jet system and the external excitation such as wind, thus the dynamic behavior of the adaptive gun head jet system of the fire-fighting monitor has typical nonlinear characteristics. In this paper, based on the assumption that the equivalent stiffness of the fluid fluctuates in type of simple harmonic motion, a nonlinear dynamic model of the jet system is established, and the model is solved by the multi-scale method. The influence of design parameters such as fluid pulsation frequency, air inlet rate and fluid pressure on the amplitude of the main resonance and combined resonance of the jet system is analyzed. Results show that the existence of the fluid pulsation frequency increases the resonance frequency range of the jet system. As to the influence of design parameters on the dynamic characteristics of the jet system, from the point of view of amplitude change, the air inlet rate has the greatest impact on the main resonance, and the fluid pulsation frequency has the dominant influence on the combined resonance. This research can provide theoretical support for the dynamic optimization of the adaptive gun head jet system of the fire-fighting monitor.