| The greenhouse is an important vegetable and fruit cultivation facility in China.At present,the area of China’s greenhouses ranks first in the world and continues to grow,however,the comprehensive mechanisation level of greenhouses is only 33%,which has seriously restricted the stable development of greenhouse cultivation.Fertilization as one of the most important aspects of greenhouse planting,at present,the application of organic fertilizer in the greenhouse mainly relies on manual work,high intensity,low efficiency,so the development of greenhouse organic fertilizer fertilizer machinery is particularly necessary.In this paper,a centrifugal type of organic fertilizer spreading machine is designed to address the problem of low mechanization of organic fertilizer spreading in plastic greenhouses for strawberry cultivation commonly used in southern Jiangsu Province.The specific research and conclusions are as follows.(1)In order to provide a research basis for the design of the machine structure and subsequent simulation tests,the material properties of the organic fertiliser selected for the test were determined,obtaining a moisture content of 19.42%,a bulk density of 0.512 g/cm~3and a resting angle of 33.12°.The mass distribution of organic fertiliser of different particle sizes was obtained and the shape of the organic fertiliser was found to be predominantly spherical through morphological observations.The organic fertiliser simulation parameters for the test were calibrated by a combination of simulation and physical tests,and the calibration values for each factor were obtained as follows:recovery coefficient 0.62,static friction coefficient 0.96 and JKR surface energy 0.01 J/m~2.(2)In order to determine the overall structure of the centrifugal type organic fertiliser spreader,the structural composition of the machine was determined and the key components of the spreader were designed and analysed according to the agronomic requirements for spreading organic fertiliser in greenhouses and the basic dimensions of the greenhouses.The maximum critical speed of the churn is 222 r/min;the cone angle of the fertiliser disc is 3°,the diameter is 430 mm and the height above the ground is 500 mm;the inclination of the upper baffle of the baffle is 60°.(3)In order to obtain a more symmetrical and uniform distribution pattern of organic fertiliser,single-factor tests and orthogonal tests were carried out with the blade position angle,the number of blades and the disc speed as test factors,and the average angle of the fertiliser distribution pattern(hereinafter referred to as the average angle)and the coefficient of variation of the lateral uniformity as indicators.The results of the one-way test showed that the mean angle decreased with increasing blade position angle,with the smallest being85.93°at 45°.The coefficient of variation also decreased with increasing blade position angle,with the smallest being 19.93%at 45°.87.94°,the coefficient of variation decreases with the increase of the number of blades and then increases,the minimum value is taken at the number of blades for 3,16.56%;the average angle with the increase of the disc speed does not change significantly,the maximum value and the minimum value is only 2.49°,the coefficient of variation gradually decreases with the increase of the disc speed,at the disc speed of 700 r/min,the minimum coefficient of variation is 21.87%The minimum coefficient of variation was 21.87%at a disc speed of 700 r/min.The results of the orthogonal tests show that the optimal combination of structure and operating parameters is 29°blade position angle,2 blade numbers and 694 r/min disc speed,where the average angle is 90°and the coefficient of variation of the transverse distribution uniformity is 16.28%,the average angle in the bench test is 90.14°and the coefficient of variation is 16.72%,which is basically consistent with the optimisation results.(4)In order to further improve the fertiliser spreading uniformity of the fertiliser spreader,the factors affecting the spreading uniformity of the fertiliser spreader were determined according to the designed baffle structure and the fertiliser movement characteristics,such as the lower baffle inclination angle,the distance between the upper baffle and the centre of the disc and the forward speed,and single-factor tests and orthogonal tests were conducted using EDEM simulation software.The results of the single-factor test showed that the coefficient of variation of the horizontal uniformity of organic fertiliser decreases and then increases with the increase of the lower baffle angle,and the coefficient of variation is the smallest at 40°of the lower baffle angle(10.23%).The coefficient of variation decreases and then increases with the increase of the forward speed,and the smallest coefficient of variation is 11.41%at the forward speed of 0.6 m/s.The results of the orthogonal test showed that the optimum combination of parameters was 39.42°for the lower baffle angle,317.98 mm for the distance between the upper baffle and the centre of the disc,and 0.59 m/s for the forward speed,which resulted in a coefficient of variation of 10.16%for the lateral distribution uniformity of organic fertiliser.(5)In order to verify the rationality of the optimisation of the parameters of the fertiliser spreading disc and the material stopper,a trial production and performance test of the whole machine was carried out.The results of the verification test showed that the average angle of the static distribution pattern of organic fertiliser was 91.30°at a blade position angle of 29°,a blade number of 2 and a disc speed of 694 r/min,and the coefficient of variation of the transverse distribution uniformity was 16.56%.The distribution pattern is basically symmetrical and has the best transverse uniformity.The dynamic test results show that with the lower baffle angle at 40°,the distance between the upper baffle and the centre of the disc at 318 mm,and the advance speed of the fertiliser at 0.6 m/s,the coefficient of variation of the transverse distribution of the fertiliser is at a minimum of 11.24%,which meets the requirements of the fertiliser spreading uniformity. |
