Optimization Design And DEM Analysis Of Mixing Blades Of Concrete Mixer Truck

With the rise of the commodity concrete industry,the use of concrete mixer trucks has become increasingly widespread.Due to long-distance transportation of mixing trucks,Due to the long-distance transportation of the mixer truck,the ready-mixed concrete often suffers from the deterioration of the homogeneity in the transportation process,and serious segregation will occur.If such concrete is used for engineering construction,it will seriously reduce the quality of the project,and will undoubtedly bring a huge hidden danger to the safety of the project.The spiral mixing blade in the mixing drum is used as a core component and is closely related to the mixing quality of fresh concrete.Therefore,by studying the flow state of fresh concrete in the mixing drum,optimizing the stirring blades to enable them to fully stir the materials during the transportation process is of great significance for improving the stirring performance of the concrete mixing truck.Because it is not easy to observe the microscopic phenomenon during the flow of the concrete during the test,and there is an error in the manual operation,the numerical simulation method is used to analyze the optimized blade.The traditional numerical simulation is mostly based on Euler-Euler coupled two-fluid model.This method has low accuracy and can not express the characteristics of the discretization of aggregates,and has certain limitations.Therefore,the discrete element method is used to numerically simulate the optimized stirring blade,which is helpful to intuitively observe the particle homogeneity and the discharging condition.The main research contents of this article are as follows:1)Since the actual size of the mixing drum is too large,and the discrete element method has a certain limit on the order of particles,the scale of the mixing drum prototype needs to be scaled.The flow pattern of fresh concrete in a mixing drum is affected by gravity,elastic force,viscous force,etc.,and gravity is dominant.Therefore,in order to ensure similar flow before and after scaling,the corresponding motion parameters should obey the Newton's similarity rule,the Froude criterion.2)In order to improve the mixing and discharging performance of the mixer drum,this paper takes a 8 m~3 concrete mixer as the design basis,and optimizes the original design logarithmic spiral line as a linearly variable angle spiral line and a non-linearly variable angle spiral line.At the same time,in order to reduce the return rate,the rear cone blades are optimized as concave curved surfaces.After coloring the blades with Gaussian curvature,it was found that the fitting quality of the non-equal variable spiral blade and equal variable angle spiral blade can reach the G2 and G1 levels,and the smoothness is higher than the original design.3)This paper innovatively uses the“Hertz-Mindlin with JKR”contact model to represent the contact between particles.The model can better represent the interparticle adhesion behavior.The contact parameters of the model were calibrated using the GEMM Universal Database and the virtual test(slump,L-box test).The simulation results were in accordance with the actual situation.4)After comparative analysis of the simulation results,it is found that in the aspect of improving the agitation and the discharge homogeneity,non-equal variable spiral>equal variable angle spiral>logarithmic spiral.Although the discharge efficiency has improved,the effect is not obvious enough.Designing the rear cone section as a concave curved surface can significantly reduce the material return rate,increase the discharge efficiency,and have little effect on the change of the particle homogeneity.The combination of non-equal variable spiral and concave curved surface design can not only improve the discharge efficiency,but also improve the agitation and discharge homogeneity,which has certain guiding significance for practical engineering applications.