Experimental Study On Characteristics Of Dust Produced By Axial Flow Threshing Of Rape

The threshing device is an important working part of the rape combine harvester,and it is also the main source of dust during the rape harvesting process.During the mechanical harvesting of rapeseed,the threshing device will produce a large amount of dust while crushing the rapeseed plants to achieve effective threshing.A large amount of dust generated by threshing is directly discharged outside the machine,which seriously endangers the health of workers and pollutes the environment.The heat deposited at the heat source of the machine blocks the heat and causes fire.Harvesting equipment has become an important direction for agricultural machinery research and development.Aiming at the problem of dust hazard,this paper carried out an experimental study on the dust generated by the operation of the rape threshing threshing device.Explored the relationship between threshing device operating parameters and the peak dust concentration and threshing loss,obtained the optimal working parameter combination of threshing device and some physical characteristics of threshing and dust production,and carried out green harvesting for the formulation of subsequent crop harvest dust reduction and dust removal programs for reference.The main research contents of this article include:(1)Analysis of rapeseed harvesting environment.At present,my country’s rape harvesters are still mainly small and medium-sized,and the cab is mostly open,and the dust generated during harvest will directly contact the operators.The respiratory dust concentration and the total dust concentration at the cab during the harvest of rapeseed machinery were tested.The test results showed that the peak value of the respiratory dust concentration was 68.5 mg/m3,the average value was 28.3 mg/m3,and the peak value of the total dust concentration was 144.3 mg/m3,With an average value of 60.9 mg/m3,and each dust concentration value far exceeds the time-weighted average allowable concentration of grain dust 4mg/m~3.(2)The structural composition and working principle of the grain threshing device were analyzed,and the physical and chemical characteristics and hazards of productive dust were established.The overall research plan for the rape threshing axial threshing dust production test was established.According to the use of threshing equipment for rape in my country,a longitudinal axial flow spike-toothed threshing device was designed for threshing and dust production test.For the collection of threshing dust production,a threshing dust collection filter bag is designed and the supporting use of threshing dust concentration detection equipment is improved,so as to detect and analyze the physical characteristics of threshing dust concentration,dust production,particle size distribution and other physical characteristics.(3)The relationship between the moisture content of rape,the speed of threshing drum and the amount of dust produced by threshing was tested.The dust generated by threshing is collected and sieved through the combination of the dust collection filter bag and the layered screen,and the obtained dust sample is weighed after balancing the moisture.The results show that:the moisture content is negatively correlated with the amount of dust produced.With the decrease of the moisture content,the amount of dust produced increases by a multiple;the non-positive correlation between the drum speed and the amount of dust produced After rising,it decreases.Use a laser particle size analyzer to detect the particle size distribution of the collected dust samples.The test results showed that the sample particle size ranged from 20μm to 1800μm,the median diameter was 686.2μm,and combustible dust and combustible fly floc were present at the boundary of 500μm.(4)In order to ensure that the dust concentration detection data is representative and can accurately reflect the threshing dust production situation,the dust concentration detection position is selected.Establish a coordinate system on the threshing stand,according to the axial distribution of the extracted material under the concave screen of the roller,select the axis cut plane of X=700 mm as the dust concentration detection plane.According to the distribution of the peak value of respirable dust concentration in the detection plane and the interference of each detection point with the outside world,the coordinate point(700,700,0)is selected as the dust concentration detection point.(5)Experimental study on the threshing platform for rape threshing.According to the analysis results of rape threshing and dust production,the drum rotation speed,threshing gap and nail spacing were selected as the test factors to carry out a single factor test,and the variation rules of threshing loss rate and peak value of respirable dust concentration with each test factor were obtained.In order to explore the relationship between the operating parameters of the threshing device and the threshing loss rate and the peak value of respirable dust concentration,the test factors of the drum rotation speed,threshing gap and nail pitch were used,and the threshing loss rate and the peak respirable dust concentration were used as the test indicators Three-dimensional quadratic regression orthogonal rotation combination test.A regression model between each factor and threshing loss rate and peak value of respirable dust concentration was established,and the influence of each factor on the index was analyzed and optimized.The test results show that the order of the influence of various factors on the threshing loss rate is:threshing gap>drum speed>nail pitch;the order of the influence of each factor on the peak of respiratory dust concentration is:nail pitch>threshing gap>drum speed.The optimized parameters obtained in the experiment are:drum rotation speed 548r/min,threshing gap 19.4 mm,nail pitch 150 mm.The verification test of the optimal parameters obtained from the test showed that the threshing loss rate was 0.47%,the peak respirable dust concentration was 31.62 mg/m3,the relative error of threshing loss rate was 2.13%,and the relative error of the peak respirable dust concentration was 4.59%.The relative error is small and the optimization model is reliable.