消防炮自适应炮头射流系统自由振动分析

消防炮自适应炮头可根据流体压力和流量变化自动调整炮口开度，从而提高消防炮的射流性能，快速高效地扑灭大型火灾。但炮头末端的自适应机构使射流系统具有流固耦合特性，在高速高压作用下，射流系统可能会发生振动乃至共振，进而影响灭火效率。考虑射流系统中流体域和固体域间的流固耦合效应以及炮头内连续体芯杆和端盖与其他离散结构间的连续离散耦合效应，通过集中质量法确定了芯杆和端盖结构的刚度矩阵，采用集中参数法建立了消防炮自适应炮头射流系统的动力学模型及方程。对射流系统进行了自由振动分析，确定了系统各阶固有频率及模态振型，分析了流体初始体积含气量和流体压力对系统固有频率的影响规律。由样机模态试验可知，理论与试验确定的一阶固有频率偏差仅为0.51%，验证了消防炮自适应炮头射流系统动力学模型的准确性。本项研究可为消防炮自适应炮头射流系统的动力学优化提供理论依据。

Analysis of Free Vibration of Adaptive Head Jet System of Fire Water Monitor

The adaptive head of the fire water monitor can automatically adjust the muzzle opening according to the change of fluid pressure and flow rate. Thus, the jet performance of fire water monitor can be improved, and large fires can be put out quickly and efficiently. However, the adaptive mechanism at the end of the adaptive head makes the jet system have the characteristics of fluid-structure coupling. And under the action of high speed and high pressure jet, the vibration even resonance of the jet system may occur, which will affect the efficiency of fire extinguishing. Considering the fluid-structure coupling effect between the fluid and solid domains in the jet system and the discrete-continuum coupling effect between the core rod and end cap of the continuous body and other discrete structures in the adaptive head, the stiffness matrix of the mandrel and end cap structure is determined by the lumped mass method and the dynamic model and equation of the adaptive head jet system of fire water monitor are found by the lumped parameter method. The free vibration analysis of the jet system is carried out, and the natural frequencies and mode shapes of the system are determined. The influence of initial volumetric gas content and fluid pressure on the natural frequency of the system is analyzed. According to the modal experiment of the sample machine, the error between the theoretical and experimental result of first-order natural frequency is only 0.51%, which verifies the accuracy of the dynamic model of adaptive head jet system of fire water monitor. This research can provide the theoretical basis for the dynamic optimization of the adaptive head jet system of the fire water monitor.