Study On Water Jet Characteristics Of Fire Water Monitor

With the acceleration of urbanization process,the hazards of urban fires are more serious,and higher requirements are put forward for the performance of fire fighting and extinguishing.Fire water monitor is an important component of sprinkler system,which is the core component of transforming pressure potential energy into kinetic energy.The direct current fire water monitor has the advantages of long range,large flow and easy processing,and is widely used in various fire extinguishing equipment and places.With the support of the national key research and development project(grant number 2016YFC0802908),theoretical analysis,numerical simulation and experimental research are combined to study the characteristics of the jet flow field of direct current fire water monitor in this paper.The jet of fire water monitor is a type of low pressure and non-submerged water jet.For the water jet characteristics of fire water monitor,the structural and dynamic characteristics of the water jet are analyzed theoretically.A jet experimental system of fire water monitor is designed and built,and the external jet image of fire water monitor is obtained by a high-speed camera.Based on the basic law of computational fluid dynamics,the water jet computing model of fire water monitor is established,and it is used to simulate the internal and external flow field characteristics of the jet.The results show that in the external area of fire water monitor,due to the interaction of gas-liquid interface,atomization will occur on the jet surface and the atomization area will gradually increase with the increase of jet distance.The theoretical analysis,experimental observation and simulation results are in good agreement.By means of experiment and numerical simulation,the characteristics of external jet of the direct current fire water monitor under different jet pressures and nozzle structure parameters were studied.The results show that the jet pressure has a great influence on the clustering and surface fluctuation characteristics of the jet.With the increase of jet pressure,the diffusion angle of the jet,the range of surface fluctuation,and the cone angle of the jet increases.Excessive pressure is not conducive to maintain the stability of jet.The nozzle contraction angle ? and the length of steady flow section l have little influence on the jet flow,while the outlet diameter d is the key structural parameter affecting the radial velocity distribution and the flow rate of the jet.The increase of the outlet diameter is not conducive to the stability of the jet.Aiming at the development law of surface wave of fire water monitor,the surface wave of jet is captured by high speed microscopic and continuous imaging technology in this paper,and the surface structure parameters of the jet were quantitatively measured and analyzed by image processing technology.Based on the obtained variation of the wavelength and wave amplitude of the jet surface,the relationship between the wavelength,as well as wave amplitude of water jet and the Weber number is discussed.It is found that with the increase of Weber number,the structure scale of jet surface wave gradually changes from regular large-scale structure to random small-scale structure,and the average wavelength decreases.With the increasing jet distance,the average wavelength and wave amplitude of water jet surface gradually increase,and the growth rate at low Weber number is less than that at high Weber number.The research results of this paper will help to deepen the understanding of the jet characteristics of fire water monitor,and the relevant conclusions can provide some reference for the structural design and performance optimization of fire water monitor.