Rongqing Liang's research while affiliated with Dezhou University and other places

In this study, to obtain the contact parameters of particulate materials accurately and quickly in residual film mixture after sieving, the contact parameters of particulate materials were calibrated via a physical test and simulation test. By using the self-made dynamic angle of a repose measurement test bench, the dynamic angle of repose of the particulate materials was measured at 41.32°, and the standard deviation was 1.33°. A discrete element simulation of the dynamic angle of the repose test was performed via an EDEM screening experiment design through a simulation of a combination of different parameters, with the dynamic angle of repose as the response value. Through simulation experiments, three significant influencing factors, as well as the level range of each factor, were confirmed. By using the response surface experiment, a mathematical model of the dynamic angle of repose and the three most influential parameters was created. The analysis of variance showed that the determination coefficient R2 and the correction determination coefficient R2adj were 0.9824 and 0.9598, respectively. The model had a good fit. The variable coefficient was 2.06% and the lack of fit was non-significant, which showed that the regression model was very significant, and the dynamic angle of repose could be predicted according to the model. By solving the optimization for the mathematical model, the optimal combination of parameters with three important influencing factors were obtained. The results showed that the coefficient of the static friction between soil and soil was 0.38, the coefficient of the rolling friction between soil and soil was 0.08, and the coefficient of the static friction between cotton residue and cotton residue was 0.33. The relative error of the dynamic angle of repose between the simulation with the optimal parameter combination and the physical test value was 2.64%. The results could provide a reference for the calibration of the discrete element model parameters of other agricultural particulate material, as well as provide a theoretical basis for the design of related collecting and conveying machinery.

The accuracy of the material parameter settings directly affects the reliability of the results of the discrete element method simulation. It is necessary to calibrate the relevant parameters to obtain accurate discrete element simulation results when separating the cotton stalk particles from the residual film after crushing. The repose angle of the chopped cotton stalk particles was used as the response value to calibrate the contact parameters between particles. Physical tests measured the intrinsic particle and contact parameters between the cotton stalk particles and the contact material, which provided data for the simulation tests. According to the biological structure characteristics of cotton stalk, the discrete element method model of cotton stalk particles was constructed by bonding the elements of nonequal-diameter basic particles. Based on the response surface methodology, the stacking test of particles was simulated. The response model between the contact parameters and repose angle was established, and the effect law of the single-factor terms and interaction terms on the repose angle was analyzed. The optimal combination of contact parameters was obtained through the single-objective and multi-variable optimization methods. Finally, the contact parameter combination was verified by a simulation test of the repose angle. The results showed that the average relative error of the repose angle between the simulation test and the physical test was 1.04%, which verified the accuracy of the calibrated contact parameters and the reliability of the simulation test. These parameters provide a basis for the discrete element simulation study of cotton stalk motion in the separation process of cotton stalks and residual film and the subsequent gas–solid coupling simulation research.

The dynamic characteristics of the cotton stalks during the cutting process were analyzed, and the key parameters (e.g. the number of teeth, rotating speed and cutters gap) of multi-edge toothed cutting device that affect the cutting of cotton stalks were determined. Based on the designed cutting device, central composite design method and regression variance analysis method were applied to build the distributed characteristic model of the cotton stalk length in the mixture of mechanically recovered residual films and impurities after shredding, and the optimal combination of parameters was obtained. The influence law of the key parameters as well as their obvious interactions on the distribution characteristics of the cotton stalk length was analyzed, and the optimal combination of parameters of the cutting device was obtained. The average error between the physical test value and model predicted value under the same condition was 7.54%, which indicated that the test results were basically the same as the model prediction.

The friction characteristic parameters of cotton stalks are important basic physical parameters required to establish the crushing mechanics model and study the separation machinery of film residue mixtures. In this paper, the friction characteristics of cotton stalks were studied using response surface methodology, and the influence of the variation in contact materials, sampling location, and moisture content on the static sliding friction coefficient (μs) and stable static rolling angle (φs) were analyzed. The results show that the contact materials, sampling location, and moisture content significantly influence the μs and φs. When the contact material is cotton stalk bark, the μs and φs values of cotton stalks are maximum. When the sampling location of the cotton stalk changes from top to bottom, the μs increases and φs decreases, respectively, while the moisture content has an opposite influence on the μs and the φs. The model coefficient of the μs and the φs indicates that the influencing factors have a high degree of explanation for the influence on the μs and φs. This study on the friction characteristics of cotton stalks can provide theoretical references and basic parameters for the separation technology research and equipment development of film residue mixtures.

The theoretical model for the power consumption of the device that shreds a mixture of residual mulch film and impurities was constructed using the theoretical method, and the key factors affecting shredder power consumption were obtained. Through a central composite design, regression analysis and analysis of variance, a relational model was constructed among the number of multi-edge toothed cutters, the clearance between multi-edge toothed cutters and between multi-edge toothed cutters and stationary blades, the speed of high-speed toothed rollers, the speed difference between high-speed and low-speed toothed rollers, and the shredding power consumption. Under the same key parameter values of the cutting device, the error between the predicted value of the shredding power consumption obtained from the model and the measured value of the verification test was 9.76 %, which proved that the established cutting power consumption model had good reliability. The research results can provide a theoretical basis for the research on the technology and equipment development for shredding the residual film and impurity mixture.