Research On Bucket Attitude And Sprinkler Process Of Firefighting Helicopter Based On CFD Method

Firefighting helicopter drop water with bucket is an efficient way to control fire situation quickly.In order to solve the problems of visual blind areas and insufficient accuracy in the observation of bucket attitude in the process of bucket sprinkling,this thesis explores more possibilities for the analysis of bucket attitude and drop point of firefighting helicopter based on CFD method.Firstly,the sliding mesh method is used to simulate and verify the hovering rotor.On the basis of verifying the feasibility of the method,numerical simulation of UH-60 rotor forward fly downwash flow field was carried out,and the simulation results verified that the influence of rotor downwash flow on the attitude of the bucket could be ignored at a certain forward fly speed.Secondly,the scaled model of a helicopter slung load is established according to Froude’s similarity criterion.Parameters such as hanging mass and center of gravity position are compiled using user-defined functions.The overset mesh method was used for numerical simulation of hanging swing,and the simulation attitude data was in good agreement with the wind pressure balance angle and wind tunnel experimental data.It is proved that the CFD method is feasible for the simulation of hanging swing.Subsequently,the imitation BB-7590 bucket model was established.The simulation method of hanging swing was used to simulate buckets with different rope lengths and different residual water in different stages,and the corresponding attitude data was recorded to provide data support for the analysis of bucket sprinkler process.In addition,the simulation verified that the additional tail fin of the bucket has good stability enhancement effect.Then,the attitude data combined with the discrete phase model is used to carry out the numerical simulation of the drop point.The horizontal distance between the initial sprinkler point and the first drop point that touches the ground was obtained through post-processing.A scaled sprinkler test platform was built with the speed adjustable racing car as the power source.The bucket sprinkler was controlled by the steering gear module,and the drop point of the sprinkler was recorded by the camera to verify the numerical simulation results.The horizontal distance difference between the initial sprinkler point and the first point that touches the ground of the numerical simulation and the sprinkling experiment platform is0.08 m,which proved that the established sprinkling simulation model has certain ability to predict and simulate the sprinkling point,and provided a reliable analysis method for realizing accurate sprinkling.Finally,summarizing all the work contents,and looks forward to the difficulties and emphases of future work.