The Theoretical Design Of The Rice Churning Cutter And The Study On Mechanized Puddling Operations

Puddling plays a key role in mechanized paddy farming.The quality of the puddled soil affects rice transplanting and field management.Traditional soil management and puddling was composed of many field operations which wasted long time and resources.Conservative farming requires that traditional soil tillage system be replaced with new machines.Recent year market has provided puddling machines derived from rotary tillers.However,as agronomical expectations for puddling is largely differed from rotatory tilling,technical specifications on the puddling knife is apparently contrasted with rotary knife.A welldesigned puddling knife is a key guarantying better performance of puddling machines.Unfortunately,there is still a lack of theoretical guideline on the design method for puddling knifes.Apart from the design of puddling knife,optimized design on the whole puddling machine should also be compatible with agronomic requirement on mechanized puddling.High quality puddled soil is only possible with the combination of puddling machines and a well-designed agronomy.Again,system optimization of the two is not well established.Quality of the puddled soil is assessed with limited indicators,e.g.straw cover density.The overall quality state of the puddled soil layer is difficult to be quantified.As different combinations of puddling knifes with field operations may result into different agronomy of puddling,there is thus another need to perform system evaluation on the resource efficiency and economy of each puddling operations.In this research,mechanized puddling is investigated and defined,based on which,the design method for puddling knife is proposed.Inverse engineering method was applied for the design of puddling knife,with which 3D modelling of a puddling knife was constructed and parameterized.Then a testing platform was constructed for the testing on puddling knives.A field plot experiment was conducted to evaluate and compare the performance of puddling and rotary tilling knives.Puddling depth stability,straw distribution and quantity,energy efficiency etc were measured.These measured indices were used for the evaluation on the validness of the puddling knife design theory.In the final stage,whole-scale field testing on both the puddling machine and a rotary tiller were conducted.The two mechanized field operations were compared and assessed for agronomic evaluation on suitable puddling in South China paddy fields.Details of the research is listed below:1.The design theory and indicators of puddling knife was proposed.The inverseengineering approach was used in conjunction with 3D digitizer and SolidWorks 2017 for the construction of puddling knife models.Performance of puddling and straw burial was considered along with the geometry,wedge angle of the side edge surface of the puddling knife.Depending on these characteristic specifications the wedge cutting mechanism was defined and thus wedge angle of the side knife surface was specified as the angle between the rotating surface of the point on the knife edge and the tangent surface of the side knife edge surface at the same point.The identified wedge effect for puddling intrusion is thus the key feature differed from a rotary knife.L-shaped puddling knife has a wedge angle<20o,while its dynamical wedge angle is less than static wedge angle by 3-10o.2.Original cropping conditions(Soil Physical Properties,Straw Stubble Status)affect puddling performance(puddling depth stability,straw burial and energy consumption).Thus a field investigation on the soil awaiting for puddling was conducted.Results showed that straw density was 490.42 kg/Mu.Soil bulk density and soil porosity differed largely from one layer to another.Soil physic in the 0-5 cm soil layer was similar with the 5-10 cm layer.Those in the 10-15 cm layer was similar with 15-20 cm layer.Soil water content increased steadily in the 0-20 cm layer,which was positively correlated with soil bulk density.Soil hardness increased linearly in 0-12.5 cm depth,below which it changed insignificantly.Overall,the investigated area revealed a feature of loosened state in the top soil and a dense state in the depth.3.The design parameters of the puddling knife was analyzed and evaluated with an insitu testing rig in the field,results from which was used as a reference for agronomic assessment on the puddling operations.A puddling knife and a rotary knife was compared and the performance of the two was assessed with National Puddling Standard(GB/T 246852009),including the parameterization on puddling depth stability,straw distribution,and energy consumption etc.Results showed that L-shaped puddling knife performed better than rotary knife.Torque requirement of L-and S-shaped puddling knives were less than rotary knife.The wedge design of puddling knife significantly increased straw burial performance.While tillage depth stability is less than IT225 rotary knife.Optimal rotary speed was found with 300-400 rpm using a 2-3 cm depth of flooding water.4.Performance difference between different puddling operations were assessed based on field testing,different flooding treatments and different puddling machines.Considering both the quantified transplanted rice performance and soil ped size distribution,soil microrelief and straw distribution,field performance of different puddling operations were evaluated.Results showed that moldboard ploughing,rotary tilling and no-till treated soils behaved similarly with respect to the changes of soil hardness along the time.A power exponential function can be applied to quantify this change.If evaluated with soil ped size,plowing+flooded rotor tilling+puddling provided the best soil quality as compared with other operations.Soil aggregates content in the 0-10 cm layer constitutes the major part of the soil.No-till puddling consumed 1.715 kg/Mu fuel,which was the least among the treatments.As for straw burial,better results were observed as compared with no-till puddling.Although the no-till puddling and no-till deep rotor tilling+puddling performed poor in the tillage depth uniformity,they were still satisfactory in agronomic perspective.