Nonlinear Dynamics of Adaptive Gun Head Jet System of Fire-Fighting Monitor

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. INDEX TERMS Fire-fighting monitor, adaptive gun head, jet system, nonlinear vibration, dynamics.

Impact of Firefighting Sprays on the Fire Performance of Structural Steel Members

“…The influence of discharge flow and pressure [20], air resistance [21] and mean vector-velocity fields [22] on performance of water monitor systems have been evaluated. Also, several other studies have investigated the non-linear dynamics of the jet sprays from water monitors [23][24][25][26][27]. However, there is a need for characterizing the water distribution patterns from water monitor sprays to aid the development of computational models of fire suppression.…”

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

“…Therefore, the stiffness of fluid is the function of the fluid pressure. Similar to the fluid pressure, the fluctuation of the equivalent fluid stiffness can be expressed as: The regular mode ψ and the spectral matrix Λ of the system are known, after regularizing the dynamic equation of parametric vibration of the jet system by referring [9], we can get:…”

“…There are three kinds of pressure pulsation components in the fire pump: random pulsation, blade-passing frequent pulsation and rotation frequent pulsation [9]. The pressure pulsation of the fire pump is closely related to the relative movement of the impeller and guide vane of the pump, and is affected by the secondary flow and cavitation in the pump.…”