Abstract
The working medium of the adaptive gun head jet system of fire-fighting monitor is generally water containing a little bit of air. During the operation, the pressure pulsation of the fluid will cause the fluctuation of the equivalent stiffness of the gas-liquid mixed fluid, so that the motion of the fluid in the jet system has obvious nonlinear characteristics. In this paper, the nonlinear dynamic model of the jet system is established. The analytical expressions of the nonlinear vibration response of the jet system are derived via the multi-scale method. The main resonance and combined resonance of the jet system are determined. The results show that the external excitation frequency is the dominant frequency of the main resonance response of the jet system, and the combined frequency between the natural frequency of each order and the equivalent stiffness fluctuation frequency of the fluid unit has a small effect on the main resonance, and the maximum amplitude is 0.2592mm; the dominant frequency of the combined resonance response of the jet system is the combined frequency between the natural frequency of each order and the equivalent stiffness fluctuation frequency of the fluid unit, the system amplitude in combined resonance is smaller than that in the main resonance, and the maximum amplitude is 0.002532mm; the main resonance and the combined resonance will adversely affect the dynamic characteristics of the jet system. This research can provide a theoretical basis for the dynamic optimization of the adaptive gun head jet system of the fire-fighting monitor.
Highlights
The nozzle opening of the adaptive gun head of the firefighting monitor can be adjusted according to the inlet flow and pressure of the jet system, so that the fire-fighting monitor can operate in optimal condition under various flows and extinguish large fires quickly and efficiently [1]
When the external excitation frequency is close to the combined frequency between the natural frequency of each order and the equivalent stiffness fluctuation frequency of the fluid unit, the combined resonance of the jet system will occur
When the external excitation frequency is equal to the first natural frequency, the amplitude of the main resonance is the largest, which is 0.2592 mm
Summary
The nozzle opening of the adaptive gun head of the firefighting monitor can be adjusted according to the inlet flow and pressure of the jet system, so that the fire-fighting monitor can operate in optimal condition under various flows and extinguish large fires quickly and efficiently [1]. X. Yuan et al.: Nonlinear Dynamics of Adaptive Gun Head Jet System of Fire-Fighting Monitor fluid and pulse pulsations that ignore the viscosity of the fluid. Research on the parameter vibration of the adaptive gun head jet system of fire-fighting monitor considering the pressure pulsation of the fire pump, has not been carried out. Based on the assumption that the fluid pressure pulsation is a harmonic function, a dynamic model of the adaptive gun head jet system of fire-fighting monitor is established, and the main resonance and combined resonance response under the parameter vibration of the jet system are determined by the multi-scale method, which can provide a theoretical basis for dynamic optimization design of the jet system
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