Study On Flow Field Numerical Simulation And Trajectory Of Steady Flow Fire Water Monitor

With the development and the progress of the global economy,urban construction is becoming more and more perfect.The building land landing in the urban areas is becoming scarce,making buildings grow in size and density,which greatly increases the difficulty of firefighting.Once a fire occurs in such a building,it is easy to form a huge and catastrophic fire accident.The difficulty in extinguishing the fire will be increased,and huge human casualties and property losses will also occur.Therefore,it is especially important to optimize the internal structure of fire water monitor and improve its trajectory prediction model to improve the fire extinguishing ability of fire water monitor and to achieve accurate positioning of the fire source.The shape of the inner contour of the nozzle has a great influence on the jet stability and the range.In order to determine a better shape of the inner contour,the fluid domain of three inner contour nozzles is geometrically constructed in the pre-processing software Gambit.Modules and grids are divided,and boundary conditions are defined.The model is imported into Fluent to set parameters for the fluid domain,and preliminary preparation work for the simulation analysis of fire water monitor in the later stage is made.A multi-phase flow simulation analysis is performed on fire water monitor with nozzles of three kinds of inner contour curve,and the pressure distribution,velocity distribution,turbulent kinetic energy distribution,phase distribution,and the cross-sections of the longitudinal section and the nozzle outlet at the exit location of the fire nozzles are determined.The possibility of cavitation is discussed based on the analysis of the velocity and turbulent kinetic energy,especially on the analysis of the absolute pressure inside the nozzle.After a comparative analysis,it is determined that the inner contour curve in the form of a sinusoidal curve has a better overall performance.A new jet trajectory theoretical model based on air resistance is proposed,which divides the jet trajectory into two phases,namely ascending and descending.At the same time,two cross-sectional area change coefficients and two angular acceleration coefficients are added to the model to make the simulated jet trajectory be in line with the actual situation.The composition of the air resistance coefficient is analyzed.The fourth-order Runge-Kutta method is used to calculate the theoretical model of the jet trajectory.Based on the above-mentioned jet trajectory model,the two sets of water jet trajectories of the U.S.TFT company are taken as examples,and the theoretical model calculation results are compared to determine the maximum error of range and shot height.The undetermined parameters of the jet trajectory model can be fitted and predicted by the exponential function,and the jet trajectory error calculated from the predicted coefficient is within the acceptable range.Experiments are carried out with a certain type of fire water monitor in Xugong Group,and the jet trajectories at different elevation angles are determined.Through the comparison of experiments and simulations,the correctness of the jet trajectory model of fire water monitor and exponential function as a coefficient fitting function are verified.