Simulation and experiment of distributors of different outlet types of pneumatic collection and discharging systems based on CFD-DEM coupling

doi:10.12398/j.issn.2096-7217.2024.01.001

Abstract

Abstract:

Pneumatic centralized seeding technology has the advantages of high seeding efficiency， wide adaptability and low seed damage. In the study， it was found that the type and structural parameters of the seed distributor had a great influence on the seeding uniformity of the pneumatic centralized seeding system. In this study， M-type， T-type and Y-type seed distributors were proposed respectively， and the overall structure and working principle of the pneumatic collection system were expounded. Taking wheat as the research object， the force and motion analysis of the seed particle group in the distributor under the action of airflow was carried out. Based on the CFD-DEM gas-solid coupling method， the simulation models of wheat seeds and distributors were established respectively. Taking the coefficient of variation of the uniformity of each row displacement as the index， the simulation test of the influence of different outlet types on the performance of the distributor was carried out， and the M-type seed distributor was determined as the optimal structure. On this basis， the influence of different outlet pipe inclination angles， top cover cone angles， inlet diameters， fillet radius and airflow velocity on the uniformity of the internal flow field of an M-type seed distributor was studied by single factor experiment， and the significant factors and their horizontal range were determined. The orthogonal test of three factors and three levels was carried out with the factors of outlet pipe inclination angle， top cover cone angle and fillet radius. The optimal structural parameters of the M-type seed distributor were determined by response surface analysis with the variation coefficient of uniformity of each row displacement as the index. The bench and field verification tests were carried out on the experimental farm of Northwest A & F University. The simulation and experimental results show that compared with the T-type and Y-type seed distributors， the M-type seed distributor significantly improves the seeding quality of wheat seeds， and the coefficient of variation of seeding uniformity is reduced by 7.41% and 3.72%， respectively. When the cone angle of the top cover is 117.03° and the angle of the outlet pipe is 59.50°， the corner radius is 69.46 mm， the uniformity of the seed distributor is the best， and the coefficient of variation of the uniformity of each row is 6.05%. The absolute errors between the simulation results of the M-type seed distributor and the bench and field test results were 1.00% and 1.55%， respectively. The research provides reference and technical support for the design of a pneumatic collecting and discharging system.

Key words: pneumatic centralized system, seed distributor, CFD-DEM coupling, field experiment

CLC Number:

S223.2

LI Guichuan, LI Haiyu, YANG Shaopeng, HUANG Yuxiang, GAO Xiaojun, FU Zuoli. Simulation and experiment of distributors of different outlet types of pneumatic collection and discharging systems based on CFD-DEM coupling[J]. Journal of Intelligent Agricultural Mechanization, 2024, 5(1): 1-11.

Figures/Tables 17

References 29

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	Item	Details	Index	Value
CFD	Materials	Fluid/air	Density/(kg·m^-3)	1.225
	Materials	Fluid/air	Viscosity/(kg·m^-1·s^-1)	1.789×10^-5
	Boundary conditions	Solid/PLA	Density/(kg·m^-3)	1 250
		Velocity-inlet	Velocity magnitude/(m·s^-1)	28
		Turbulence	Turbulence intensity/%	4
		Turbulence	Hydraulic diameter/mm	50
		Flow-outlet	Outlet type	Flow-outlet
		Wall	Wall motion	Stationary wall
		Wall	Shear condition	No slip
DEM	Materials (wheat seeds)	Particle	overall dimensions/mm	7.01×3.47×3.20
			Thousand-grain weight/g	48.96
			Water content/%	10.80
			Poisson’s ratio	0.41
			Shear modulus/Pa	4.79×10⁷
			Density/(kg·m^-3)	1 350
		wall	Poisson’s ratio	0.35
			Shear modulus/Pa	1.3×10⁹
			Density/(kg·m^-3)	1 250
	Interaction	Particle-particle	Coefficient of restitution	0.47
			Coefficient of static friction	0.55
			Coefficient of rolling friction	0.28
			Interaction contact model	Hertz-Mindlin
		Particle-wall	Coefficient of restitution	0.50
			Coefficient of static friction	0.22
			Coefficient of rolling friction	0.16
			Interaction contact model	Hertz-Mindlin
	Particle	Particle generation	Particle radius/（mm×mm×mm）	7.00×3.20×3.20
			Factory type	Dynamic/unlimited number
			Generation rate/（s^-1）	2 000

	Item	Details	Index	Value
CFD	Materials	Fluid/air	Density/(kg·m^-3)	1.225
	Materials	Fluid/air	Viscosity/(kg·m^-1·s^-1)	1.789×10^-5
	Boundary conditions	Solid/PLA	Density/(kg·m^-3)	1 250
		Velocity-inlet	Velocity magnitude/(m·s^-1)	28
		Turbulence	Turbulence intensity/%	4
		Turbulence	Hydraulic diameter/mm	50
		Flow-outlet	Outlet type	Flow-outlet
		Wall	Wall motion	Stationary wall
		Wall	Shear condition	No slip
DEM	Materials (wheat seeds)	Particle	overall dimensions/mm	7.01×3.47×3.20
			Thousand-grain weight/g	48.96
			Water content/%	10.80
			Poisson’s ratio	0.41
			Shear modulus/Pa	4.79×10⁷
			Density/(kg·m^-3)	1 350
		wall	Poisson’s ratio	0.35
			Shear modulus/Pa	1.3×10⁹
			Density/(kg·m^-3)	1 250
	Interaction	Particle-particle	Coefficient of restitution	0.47
			Coefficient of static friction	0.55
			Coefficient of rolling friction	0.28
			Interaction contact model	Hertz-Mindlin
		Particle-wall	Coefficient of restitution	0.50
			Coefficient of static friction	0.22
			Coefficient of rolling friction	0.16
			Interaction contact model	Hertz-Mindlin
	Particle	Particle generation	Particle radius/（mm×mm×mm）	7.00×3.20×3.20
			Factory type	Dynamic/unlimited number
			Generation rate/（s^-1）	2 000

Factors	Level
The inclination of outlet pipe θ₁/(°)	50, 55, 60, 65, 70
The cone angle of the top cover θ₂/(°)	100, 120, 140, 160, 180
The inlet diameter D_r/mm	56, 58, 60, 62, 64
The fillet radius R/mm	62, 66, 70, 74, 78
The pneumatic conveying speed V_c/(m·s^-1)	28, 30, 32, 34, 36

Factors	Level
The inclination of outlet pipe θ₁/(°)	50, 55, 60, 65, 70
The cone angle of the top cover θ₂/(°)	100, 120, 140, 160, 180
The inlet diameter D_r/mm	56, 58, 60, 62, 64
The fillet radius R/mm	62, 66, 70, 74, 78
The pneumatic conveying speed V_c/(m·s^-1)	28, 30, 32, 34, 36

Level	The inclination angle θ₁/(°)	The cone angle θ₂/(°)	The fillet radius R/mm
-1	55	100	66
0	60	120	70
1	65	140	74