Experimental Discussion on the Equipment of Loop Springs
The theoretical calculation formula obtains the calculation formula of the critical speed, the vertical direction and the theoretical productivity of the screw conveying device when the material is conveyed vertically by the force analysis and motion analysis of the material in the vertical conveying state. The critical speed refers to the material layer under the action of the coil spring, which will produce a vertical upward speed, but the minimum speed of the coil spring is the basis for determining the minimum speed of the coil spring conveying device. The calculation formula is as follows: nc=30Pgtan(A+B)r1L1/2(1) where: nc is the critical speed, rmin-1; L is the friction coefficient between the material and the inner wall of the feed pipe; r1 is the radius of the coil spring, m; B is the friction angle of the material and the coil spring; A is the spiral angle of the coil spring; g is the gravitational acceleration, ms-2.
When the actual rotational speed of the coil spring exceeds the critical speed, the circumferential speed at any point above it exceeds the maximum peripheral speed of the material particles at the critical point, thereby causing relative motion between the material particles and the coil spring. The vertical upward velocity of the material particles is vn=Pr60(nr-nc)sin(2A)(2) where: vn is the vertical velocity of the material particles, ms-1; nr is the actual speed of the coil spring, rmin-1 .
After determining the speed at which the material is transported vertically upwards, the theoretical productivity of the conveying device can be obtained Qth=367Qlvn (3) where: Qth is the theoretical productivity, kgh-1; Ql is the mass of the material line in the conveying pipe, kgm-1 , Ql=1000VQ/s; where Q is the volume mass of the material to be transported, kgm-3, s is the pitch of the coil spring, m, V is the volume of the material contained in a pitch length, m3.
Estimation of V value: It is assumed that during the conveying process, the material is not filled with the feeding pipe, but is thrown to the wall of the conveying pipe by the action of the coil spring, forming a material layer between the coil spring and the conveying pipe, such as omitting the spring The volume occupied by itself is the volume of the material in the length of a pitch s of V=P4s: D1 is the outer diameter of the conveying pipe, m; D is the wall thickness of the conveying pipe, m; D2 is the middle diameter of the coil spring m; d is the diameter of the spring wire, m; $D/2 is the thickness of the material driving layer from the inner diameter of the coil spring to the center of its rotation, which is related to the material properties. Here, when the material is corn, take $D=0.016m, and when the material is wheat, take $D=0.010m.
Of course, the vertical upward velocity of the material at different positions in the conveying pipe and the spatial distribution of the material in the pipe are related to the material characteristics, the state of the inner surface of the conveying pipe, the sectional shape and surface condition of the coil spring wire, and the rotation speed of the coil spring. The accuracy of the V value estimation needs to be verified by experiments.
Data processing and analysis 1) The critical rotational speeds of corn and wheat were 280rmin-1 and 285rmin-1, respectively. The critical speeds calculated by equation (1) were 269rmin-1 and 293rmin-1, respectively. The relative errors of the values ​​are 3.9% and 2.8%, respectively, which are basically similar, so equation (1) can be used as the theoretical basis for design calculation. 2) Under the condition that the structural parameters are determined, the theoretical productivity Qth is linear with the actual rotational speed nr of the helical spring, and Qth increases as nr increases (as known from equations (2) and (3)). The regression data of the test data in the table was linearly regressed to obtain the productivity Qr of the transported corn and wheat and the rotational speed nr of the coil spring.
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Packing
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