Theoretical And Experimental Investigations Of Potato Soil Separation On Swing Separation Sieve

Swing separation sieve was viewed as the core component of the potato soil separation in the rod chain-swing screen type potato digger.The performance of potato digger directly depended on the work characteristics of swing separation sieve.Hence,to improve the performance of the rod chain-swing screen type potato digger,it was the key to study the theory and experiment of the potato soil separation on swing separation sieve.In this paper,we studied the movement process of potato relative to separation sieve,potato collision damage,kinetic characteristics of potato relative to separation sieve,potato soil separating mechanism of swing separation sieve,and optimization of separation sieve parameters using the combination of theoretical analysis and experimental research.The main investigated contents were as follows:1.Using the high speed camera and the acceleration sensor to synchronously capture the movement of the potato image and separation sieve acceleration data on different crank rotational speed and sieve inclination.And the correction coefficients between experimental and theoretical acceleration value of separation sieve were calculated.Based on the correction coefficients,the study established the mathematical model of the velocity of potato relative to separation sieve and discussed the relative motion process of the potato.Finally,the analytic results were verified by the high speed camera image.The results showed that there were three kinds of different movement processes of potato relative to separation sieve under different separation parameters:(1)the continuous movement process of slip forward and slide back;(2)the continuous movement process of slide forwards,move off the screen surface,slide forwards and move back;(3)the movement process of slide forwards,move away from the screen surface and slide backward.The forward movement distance of potatoes is larger than the reverse movement distance in the three kinds of processes,which satisfied the requirement of conveying potatoes to the sieve tail.The results of high speed image analysis were in agreement with the results of theoretical analysis.2.Applying the potato collision test device and the collision acceleration test system to collect collision acceleration of potatoes on different initial height,potato mass,potato internal temperature and impact material.The potato collision displacement-time curve was obtained by processed the acceleration data.According to the viscoelastic characteristics of potatoes,the paper established the dynamic model of collision between potatoes and rod,deduced the displacement formula of potatoes collision and obtained the parameters of the potato collision displacement model by the sinusoidal model regression,such as the natural angular frequency and the damping ratio of the damped system.The displacement model of potatoes collision predicted the depth of collision damage of potatoes,where the relative error between the predicted value and the experimental value was less than 8.8%indicating the correct and effective establishment of collision displacement model of potatoes.Considering the depth of collision damage as the damaged evaluation index,internal temperature of potato,initial height,potatoes mass and collision material as experimental factors,the orthogonal experiment was carried out.The main order of the factors affecting the collision damage of potatoes was analyzed.Based on the collision displacement model,the influence of the test factors on the collision damage was analyzed.Then,the thresholds value of potatoes collision damage was measured for different potatoes mass,temperature and material.The results indicated that the primary factors on the potatoes collision damage first were initial height and potatoes mass,and then potatoes internal temperature and collision material.Worthy mentioning was four factors had significant effect on the damaged depth.3.According to the distribution characteristics of the potatoes soil mixture,the sieve surface with the surface length of 600mm～1000mm was used as the no-soil sieving surface,and the sieve surface in the range of 100mm-600mm was served as the soil sieving surface.For the case of single potato,the processed software of Motion Analysis based on the Track Eye(TEMA)was used to deal with the moving images of the potato relative to separation sieve in the field experiment.Then we obtained kinematic parameters,like displacement,velocity and threw height of potato relative to sieve on the no-soil sieving surface and the soil sieving surface,due to the kinematic parameters changes of the crank speed,sieve angle and the machine forward speed.The experimental results also were compared with theoretical analysis.Thus,the measured results shows that the fluctuation of the front and rear displacement of potatoes relative to the sieves on the soil sieving surface is higher than that on the no-soil sieving surface.With the increment of quantity of soil,the fluctuation of the front and rear displacement of potatoes relative to the sieves was increased.The theoretical and experimental values of the absolute velocity and maximum throwing height relative to the separation sieve of the potatoe are going up with the increased crank rotational speed and the sieve inclination,but those were decreased with the machine forward speed increased.4.The experimental shot the distribution of potatoes soil mixture on the side and upward direction of swing separation sieve under the different crank rotational speed,sieve inclination and the machine forward speed using the high speed camera and digital camera.According to the high speed image,the distribution thickness of potatoes soil mixture on the separation sieve was obtained.And we interpreted the number of pixels in the area of the potatoes soil mixture and the separation sieve image via applying photo-shop software.The method of the number of pixels of the potatoes soil mixture divided by the number of pixels in the area of separation sieve was used to calculate the coverage rates of potatoes soil mixture on the separation sieve.Through analyzing the data,we got the various regulations of the distribution thickness and coverage rates of potatoes soil mixture on the separation sieve with the varied parameters of separation sieve.The results shows that the correlation coefficients between the crank rotational speed,the sieve inclination,the machine forward speed and distribution thickness are-0.846,-0.98,0.988 respectively,whilst the correlation coefficients between the crank rotational speed,the sieve inclination,the machine forward speed and coverage of potatoes soil mixture are-0.993,-0.969,0.992 respectively.The rates of obvious and abrasion are used as the performance of separation sieve to get the various relationships between performance and parameters of separation sieve.The effects of the parameters on the performance of the separation sieve are analyzed by combining the movement characteristics of potato relative to separation sieve and the variation of thickness and coverage of potato soil mixture.It is pointed out that the reason for the high rate of abrasion is due to the drastic fluctuation of the front and rear displacement of potatoes relative to the sieves,when the crank rotational speed is 180r/min.And the range of parameters of separation sieve for optimizing test are that the crank speed is 180r/min-230r/min,the sieve angle is 7.7°～21.1°,the machine forward speed is 1.69km/h～2.3 7km/h.5.The crank rotational speed,screen surface inclination and machine forward speed are the test factors.The rate of obvious and abrasion were used as the evaluation index to establish the regression mathematical model between the indexes and the factors by applying Box-Behnken response surface test method.Then,the influence of significant factors and interaction between factors on the evaluation index was analyzed,thus optimizing the structure and working parameters which affecting the separation performance of the swing separation sieve.The results showed that the interaction between sieve surface inclination and machine forward speed,and crank rotational speed influenced extremely the rate of obvious and abrasion.The primary and secondary order of the effect of the factors on the obvious rate and the abrasion rate were:crank rotational speed,screen surface inclination,machine forward speed.The crank rotational speed of 230r/min,screen surface inclination of 21.1°,machine forward speed of 2.03km/h were the best combination factors.The obvious rate and abrasion rate were 98.94%and 0.21%respectively after optimizing test.The obvious rate was increased by 1.68%,and the abrasion rate was decreased by 9.6%compared with that before optimization.The combination of optimized parameters had the better applicability in the ridge of the soil and the sandy soil.