内充气吹式玉米排种器工作性能EDEM-CFD模拟与试验

针对内充气吹式排种器组合气嘴低位安装对供气系统气流稳定性要求高、田间作业适应性差的问题,为优化内充气吹式排种器结构、改善工作性能,运用EDEM-CFD耦合分析方法,采用玉米籽粒粘结颗粒模型,以气嘴安装位置、工作压强和前进速度为试验因素进行正交试验优化仿真,提取关键参数充种极限速度和充种时长为评价指标进行分析,结果表明气嘴安装位置、工作压强和前进速度对充种极限速度影响显著而对充种时长影响不显著,充种极限速度和充种时长在0.05水平上呈显著负相关关系,较大充种极限速度和较短充种时长有利于提高排种器充种性能;对不同作业状态下的合格率、重播率、漏播率等作业指标进行分析表明气嘴安装位置在中位时合格率和充种极限速度呈显著正相关,低位和高位时因清种效果不佳导致合格率和充种极限速度呈负相关,中位时排种效果较佳。为验证仿真结果,进行气嘴安装位置和工作压强的全因素试验,结果表明,气嘴安装位置为中位时作业效果最佳,合格率大于90%,明显优于低位、高位状态,与仿真结果一致;在确定组合气嘴中位安装结构参数下,进行工作压强、前进速度的全因素试验,结果表明,前进速度为5~10 km/h、工作压强为4.5~5.5 k Pa时,排种器合格率较高,均为90%以上,该区间各工作参数下对合格率影响不显著。

EDEM-CFD simulation and experiment of working performance of inside-filling air-blowing seed metering device in maize

Abstract: The qualified index of original inside-filling air-blowing seed metering device could reach above 85% when working pressure was more than 5 kPa. In order to reduce the working pressure and energy consumption of fan and optimize the working effect of inside-filling air-blowing seed metering device, the installation position of combined compressed air nozzle was adjusted at first to make it as close as possible to the hole. The qualified index of seed metering device was only 82.73% when the working pressure was 2.5 kPa, and qualified index was reduced when increasing or reducing working pressure. Thus it can be seen that the installation position of combined compressed air nozzle has a significant influence on the sowing effect of seed metering device. In this paper, the bonded particle model was used to model maize based on theory of discrete element method, and the coupling analysis method of EDEM-CFD was applied to simulate the influence of different air nozzle installation positions on the working performance of inside-filling air-blowing precision seed metering device. Installation positions of combined air nozzle of structural parameter, inlet velocity and working speed of working parameter were selected as experimental factors, particle filling limiting velocity and filling time were used as evaluating indicators, the orthogonal experiment was carried out to optimize working performance of seed metering device. The results of variance analysis of filling performance showed that the influence of three factors on filling limiting velocity was significant (P<0.05) and on filling time was not significant (P>0.05). The primary and secondary factors that affect the filling limiting velocity was working speed > inlet velocity > installation position of combined air nozzle. A significant negative correlation (P<0.05) was found between filling limiting velocity and filling time and Pearson correlation coefficient was -0.785 (P=0.012). The results of variance analysis of cleaning performance showed that three factors had no significant (P>0.05) effect on qualified rate, reseed rate and leakage rate, but qualified index and filling limiting velocity were negatively correlated (P<0.05) when the combined air nozzle was in upper or lower position. The qualified index and filling limiting velocity was significantly positive correlation (P=0.01), the Pearson correlation coefficient was 1.00 and the significant level was 0.005. Therefore, in order to adapt to different working parameters of seed metering device, first of all, the installation position of combined air nozzle of structural parameters was optimized as the middle position. Bench test was performed to validate the simulation results. Double factor test of working pressure and installation positions of combined air nozzle was in progress when the working speed was 6 km/h, and compared with first generation seed metering device. Experimental results showed that the reseed rate of the installation position of combined air nozzle was lower than mille, but the upper position was opposite. The leakage rate of the middle installed position was better than the installation position of combined air nozzle and also was better than the installation position of combined air nozzle at the lower and upper positions. That is, the seed metering device has the best effect when the installation position of combined air nozzle was the middle, and the qualified rate of seed metering device was higher than 90% under all working pressure. The double factor test was carried out when the installation position of combined gas nozzle was at the middle with working speed of 4-12 km/h and working pressure of 3-7 kPa. Results showed that the seed metering device was easier to reseed at lower working pressure and lower working speed, it was easier to leakage at higher working pressure and higher working speed. On the whole, the qualified rate of seed metering device was higher than 90% under suitable working conditions.