To address the problems of high breakage rates, high entrainment losses and many unthreshed kernels when harvesting high moisture content maize seeds, a high moisture content maize seed threshing test was designed based on a multifunctional seed harvester stand designed by this group.In order to determine the optimum operating parameters of the threshing unit, single-factor experiments and orthogonal tests were carried out using the threshing drum speed, concave plate clearance and feed rate as test factors and the crushing rate, unthreshing rate, entrained loss rate and trash content rate as test evaluation indicators.The optimum combination of test factors obtained for the harvesting of maize at 32% to 34% moisture content was a drum speed of 346.55r/min, a concave plate clearance of 44.39mm and a feed rate of 9.739Kg/s.After repeated experiments on the bench, the test results with optimum parameters were 6.311% crushing rate, 0.187% unthreshing rate, 0.912% entrained loss rate and 4.251% impurity rate, at which point the crushing rate was the lowest and the other three met national standards.

Aiming at the problems of the low efficiency of manual pesticide application in the greenhouse, the narrow operating space of plant protection machinery, and the possibility of poisoning the pesticide applicators due to the closed space, a high-pressure atomization spraying equipment for the greenhouse was designed. The spraying equipment adopts two-way communication between PLC and HMI to realize the adjustment of atomization pressure and atomization flow, and the control equipment completes automatic spraying. To determine the best working parameters of the spraying equipment, orthogonal tests were conducted with atomization pressure and atomization nozzle aperture as the test factors and the coefficient of variation of the fog volume distribution as the evaluation index. The optimum combination after parameter optimization was determined to be as follows: atomization pressure of 4 MPa, atomization nozzle aperture of 0.4 mm. The test results under the optimal parameters showed that the spray distribution coefficient of variation was 10.5%, and the uniformity of fog volume distribution was good to meet the requirements of spraying in greenhouses.

Aiming at the current problem of the high rate of impurity and loss in the cleaning device of corn seed harvesters in China, this paper took the cleaning device of 4YZL-6 self-propelled corn seed harvester as a sample and analyzed the movement law of the material on the sieve. Box-Behnken response surface experimental design theory was used for the orthogonal tests. Wind inlet angle, airflow velocity, and crank angular velocity were selected as influencing factors, and the impurity rate and loss rate as the evaluation index of operation quality. A regression mathematical model between each influencing factor and indicator was established, and the model was also integrated and optimized. The optimal parameter combination was obtained as follows: the wind inlet angle was 37.95o, the airflow velocity was 11.3 m/s, and the crank angular velocity was 4.1 r/s. The corresponding impurity rate was 0.87% and the loss rate was 0.34%. Verification tests were conducted on the optimization results, and the test results showed that under the optimal combination of parameters, the impurity rate was 0.89% and the loss rate was 0.35%. The relative errors of each evaluation index and its model prediction were 2.29% and 2.94%, respectively.

To better analyze the distribution law of airflow in the wind sieve type cleaning device, this study took the cleaning device of Yafeng 4YZL-6S corn seed harvester as an example and conducted numerical simulation and comparative analysis of the airflow field inside the cleaning device under the sieve plate opening scales of 12, 16 and 20 mm using CFD software. The numerical simulation showed that the distribution of airflow velocity above the sieve surface was uniform at a sieve plate opening scale of 16 mm. Airflow velocity measurements were performed on the test prototype using an anemometer to verify the accuracy of the numerical simulation results. The simulation test results were supplemented by field trials, which showed that when the speed of the cleaning fan was 1200 r/min and the sieve plate opening scale was 16 mm, the impurity rate in the field harvest of the operating machinery was 1.03% and the loss rate was 1.91%. The operating effect met the standard of mechanized corn grain harvesting. This paper can provide a reference for the design and working mechanism research of corn seed harvester cleaning devices.

It is urgent to study the damage mechanism of corn kernels and find ways of reducing the rate of kernel breakage in mechanical threshing. This paper, by studying the mechanical curves and deformation characteristics of corn kernels with different moisture contents, points out the brittle mechanical characteristics of corn kernel damage fracture with low moisture content, and clarifies the the variation law of mechanical properties of kernels with moisture contents. The experimental data of fatigue load - fatigue life curves of corn kernels with different moisture contents were described by the power function equation. At the same time, the fatigue life and damage characteristics of kernel with different moisture content were analyzed, and the accuracy of the fitting equation was verified. Through mathematical statistical analysis, the normal distribution curve of fatigue life was fitted, and the variation law of normal distribution curve with moisture content and fatigue load was determined.