| Pond aquaculture occupies a high proportion in China’s aquaculture industry.Centrifugal feeding machine has the advantages of wide casting range,strong timing and quantification,and good stability.It is the most widely used in pond aquaculture.Due to the structural characteristics of the centrifugal feeding machine,feed particles will be broken in the process of its work,which will not only cause feed waste and raise the cost of breeding,seriously affect the economic benefit,but also the residual broken feed will pollute the water,threatening the normal growth of breeding bodies.However,there is no literature on the systematic study of feed crushing rate of centrifugal feeding machine at present.In view of this situation,this paper studies the influencing factors and laws of feed crushing caused by the main components of centrifugal feeding machine(feeding mechanism and feeding mechanism),and the main contents and results are as follows:(1)In view of the lack of reliable and accurate feed contact parameters for simulation in existing literature,"cylinder lifting method" was adopted to carry out virtual calibration of feed particle contact mechanical parameters,and the optimal combination of feed particle contact parameters was obtained through experimental optimization: The static friction coefficient between feeds was 0.34,the dynamic friction coefficient between feeds was 0.163 and the static friction coefficient between feeds and mechanisms was0.353.(2)A single feed particle bonding model was established,and a single feed particle of no.2 shrimp was determined by calculation to be composed of 88 small particles with a diameter of 0.2mm and bonding bonds that could bear certain normal and tangential forces.The mechanical parameters of the bond were obtained by uniaxial tensile compression test and calculation.(3)In order to reduce the amount of calculation and improve the efficiency while ensuring a certain simulation accuracy,the particles are scaled according to the similarity theory.The variation of each physical quantity before and after scaling was deduced.The average force stability value of feed particles under the original particle size of the centrifugal feeder was taken as the measuring standard,and the force stability value of feed particles under the 2～5 times magnification was compared and analyzed,and the reasonable magnification factor was determined to be 4 times.(4)The force of no.2 shrimp feed on the feeding plate of centrifugal feeding machine was analyzed,the differential equation of motion was established,and the factors that might affect the feed particle breakage were screened out,such as the speed of feeding plate,the radius of curvature of the feeding plate,the dip Angle of the feeding plate,the number of the feeding plate,the height of the feeding plate and the radial position of the feeding plate.In order to verify the feasibility of the simulation test,the simulation test data was compared with the actual test data under the conditions of different rotation speed and inclination Angle of the spinner.Then USES the EDEM discrete element simulation software,with the above six factors as variables,the centrifugal cast feeder on the single factor experiments on institutions,analysis of each factor for breakage and spilled feed distance,blanking effect and the influence of uniformity,it is concluded that feed broken rate are presented,with the increase of the three smaller first,then the law of the larger;The scattering uniformity is related to the radial position of the blanking,the closer the blanking position is to the edge of the disk,the worse the uniformity is.The scatter Angle depends on the radius of curvature of the floor.The larger the radius of curvature is,the larger the scatter Angle is.The casting distance is related to the radial position of the blanking,the rotational speed and the inclination Angle of the blanking tray.In order to obtain the feeding mechanism with lower crushing rate,orthogonal test was designed to establish the quadratic regression equation between feed crushing rate and three factors.It was found that the structural factors that had significant influence on feed crushing were the feeding plate inclination Angle,the number of accelerating ribs and the radius of curvature of ribs.Response surface analysis shows that the interaction between the radius of curvature is the most obvious.After optimization,the optimal parameters of the casting plate are as follows: the inclination Angle of the casting plate is12.8°,the number of ribs is 6,and the radius of curvature of the ribs is 71.5mm.In order to verify the effectiveness of the optimization,the cast plate was processed according to the combination of the optimized parameters,and the experimental results showed that the feed crushing rate decreased 38.8% on average after the optimization,and it was more obvious when the speed was higher than 15 r/s.(5)Use EDEM simulation software to carry out single-factor simulation test on spiral feeding mechanism and vibration feeding mechanism(eccentric feeding mechanism with guide groove and vibration motor feeding mechanism with box installation)common in centrifugal feeding machine,and analyze the reasons and laws affecting the crushing rate.It was found that the rotation speed of screw conveying mechanism had no significant effect on feed crushing rate.The feed fragmentation rate increased firstly and then decreased with the increase of the filling rate.When the filling rate was greater than 80%,the feed fragmentation rate appeared to be blocked.Screw clearance had a significant effect on feed crushing,and the feed crushing rate decreased with the increase of screw clearance.For vibrating cutting mechanism,with the increase of vibration amplitude and frequency,feed trough eccentric vibrating and container install vibration motor type blanking mechanism effect on the breaking rate are increasing state and container install vibration motor type blanking mechanism under different amplitude and frequency values for crushing the feed rate is significantly higher than the guide chute eccentric vibrating;The feeding efficiency of the vibration motor type is the highest,followed by the eccentric vibration type of the guide groove and the screw conveying type.(6)Simulation tests were carried out on feeding machines with three different feeding modes,and the results of the single mechanism breakage rate test were compared and analyzed.It was found that the feed throwing distance was only related to the structure parameters and speed of the feeding mechanism;The feed scattering uniformity was only related to the feeding mechanism,and the effect of feeding mechanism could be ignored.Eccentric vibrating feeder with guide groove can have higher working efficiency while taking into account lower crushing rate. |
