| In order to improve the range of long range fire water cannon,this paper analyzes the internal flow field,outflow field and recoil of water cannon.The optimization of the internal structure is the key,especially for the straightener,elbow and nozzle structure optimization.So that the water cannon will achieve the longest range.The second is to improve the external structure.The main contents of this paper are as follows:(1)Through the simulation of the original water cannon model simulation,it found that the nozzle flow is disorder.There are tangential and axial velocity components,resulting in nozzle jet water column prematurely broken.So the rectification and optimization of the key structure of the water cannon is very necessary.Firstly,the nozzle shrinkage angle and the nozzle outlet cylindrical section with micro-rectification are analyzed.The structural design and flow field analysis are carried out to determine the optimal shrinkage angle of the nozzle and the length of the nozzle section.resulting in premature crushing of the nozzle jet water column,and the rectification and optimization of the key structure of the water cannon.(2)The optimal length of the straight tube was obtained by the method of orthogonal test and numerical simulation of the flow field,with the consideration of operational balance and structural minitype In order to determine the placement and the number of deflector,a detailed analysis of the 180 ° elbow was carried out to confirm the speed offset caused by the elbow and to find out the relationship between the offset and the elevation angle of the cannon.The best deflector for good elbow flow is located near the inner wall of the elbow.(3)In order to obtain a better nozzle flow,it is critical to place straightener in straight.In this paper,the cross section shape,the inlet and outlet transition mode,the influence of the length of the straightener on the internal flow field are studied.the Pressure loss,outlet velocity distribution,outlet turbulent kinetic energy and outlet axis speed are taken as the evaluation criteria.The more the number of straightener is divided,the better the rectification effect is,and the better the range is.Considering the ribs of ordinary straighteners haing a large number of impact losses,this paper designs a spiral honeycomb straightener with double-layer circular straightener and hexagonal flow channel with spiral fins.From the flow chart,the pressure loss and the comparison with the ordinary rectifier,it found that when the installation angle is equal to the liquid flow angle,the loss of the straightener and the loss of water tanker inlet and outlet pressure is minimal,and the energy loss is less.Compared with the ordinary straightener,the part of the tangential and radial velocity of spiral honeycomb straightener in the spiral flow channel drainage can be converted into axial velocity,which can get a larger outlet average velocity.At the same time,the influence of three different pitch changes on the performance of the straightener is studied by means of experiment and simulation.After installing the spiral straightener,the loss of the straightener and the total loss of the water cannon is smaller than that of the ordinary ones,which can effectively improve the range for the straightener design to provide technical reference.(4)At the end of this paper,the outflow field of the water cannon is analyzed,and the reliability of the simulation method is verified by a calculate example.After the analysis of the internal flow field above,the best water cannon structure was obtained.At the same time,the influence of the elevation angle and the nozzle velocity distribution on the jet is analyzed,and the velocity distribution good for jets of the nozzle is obtained.On the basis of this,the hydrodynamic coupling analysis is carried out on the recoil of the water cannon,which proves that the water cannon structure designed in this paper can meet the requirements of the actual work. |
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