EXPERIMENTAL STUDY ON AIR FLOW FIELD CHARACTERISTICS OF SUCTION METERING DEVICE

The vacuum seed metering device absorbs seeds by using the negative pressure generated by vacuum air flow. Therefore, it is of great significance to study the variation law of pyrolysis gas flow field to improve its seed metering performance. In this paper, the common disc and composite disc were selected as the research objects and tested on the indoor test-bed. The negative pressure was measured by U-type barometer, and the effects of fan speed, suction hole size, seed hole structure and air chamber thickness on the air flow field were studied. Firstly, the influence of fan rotation frequency on vacuum chamber negative pressure is studied, and the variation law of negative pressure in vacuum chamber and fan port of common disc and composite disc under the same frequency is compared. Secondly, the suction holes in the vacuum chamber were numbered, the negative pressure distribution of the suction holes was measured, and the influence of the number and diameter of the suction holes on the negative pressure of the vacuum chamber was studied. Finally, the negative pressure was measured at the distance of 0 to 10 mm from the suction hole to study the effect of seed hole structure on the air flow field. Moreover, increase the additional thickness of the vacuum chamber from 0 to 40 mm to study the influence of the chamber thickness on the distribution of the gas flow field. This paper makes a comprehensive experimental analysis on the influencing factors of air flow field of air suction seed metering device, necessary for future design of air suction seed metering device.

DESIGN AND TEST OF NEGATIVE PRESSURE CHAMBER ROTARY BUCKWHEAT SEED METERING DEVICE

A negative pressure chamber rotary precision seed metering device was designed to achieve the buckwheat precision sowing goal, solving the problems of traditional negative pressure chamber poor sealing and air suction seed metering device high power consumption. The planting plate of the device was fixedly connected with the shell of the air chamber forming a negative pressure chamber, which rotates around an axis. A planting plate suitable for buckwheat seed metering was designed. Single factor test and response surface test were carried out on the seed metering device. Results showed that the buckwheat precision seed metering achieved best performance when the negative pressure, suction hole diameter and rotation speed was 2.4 kPa, 2.0 mm and 25 r/min respectively. The qualified index, multiples index and miss-seeding index were respectively 88.32%, 7.35%, and 4.33%, which met the technical requirements of buckwheat precision sowing. The results of the study provided references for the design and application of buckwheat precision seed metering device.

Experimental Evaluation of Rootstock Clamping Device for Inclined Inserted Grafting of Melons

A grafting machine is a kind of machine that can quickly graft scion to rootstock instead of manual grafting. Currently, an inclined inserted grafting machine uses the mechanical clamping method, which can easily damage the rootstock seedlings due to its high stiffness, thus, reducing the success rate of grafting. This study proposed an effective, flexible clamping device for grafting. The suction hole diameter (HD), the negative pressure (NP), and the surface inclination angle (IA) of the clamping device were studied via a single factor experiment to obtain optimal parameter ranges. Optimal HD, NP, and IA were 2–3 mm, 4–8 kPa, and 10–20°, respectively. The orthogonal experiment results showed that the optimal parameter combination for maximum holding success rate was HD, 2.5 mm; NP, 6 kPa; and IA, 10°. The experimental verification was carried out using the optimal parameter combination, with a holding success rate of 98.3% and no damage. This study provides a reference for the optimal design of an inclined inserted grafting machine.

Theoretical Verification of Film Forming in Local Electroplating Process with Electrolyte Suction Tool

Electroplating has many applications, including surface hardening and metal thin film manufacturing. In conventional electroplating, the entire workpiece is immersed in the plating solution. Since the whole surface in contact with the solution is plated, a masking operation to remove the unnecessary plating film is required. This is especially applicable to local plating in the case of ornament plating, surface hardening method, among others. However, these additional processes result in substantial increase in processing time and cost. Earlier, we achieved maskless local electroplating with a smooth surface using a suction tool, in which the electrolyte was retrieved by a suction pump through a suction hole. Even so, formation of film on electroplating is yet to be verified by simulations. Herein, we performed experiments and simulations of the local electroplating by varying the processing time before comparing the results. Finally, the validity of the film forming was examined by discussing the results.

Aerodynamic Investigation on Performance Enhancement of NACA 2412 Airfoil with Suction Assistance

Advanced transport aircraft concept has active boundary-layer control by slot suction which reduces drag by stabilizing the laminar boundary. Thus, the prevention of transition and delaying the boundary layer separation will lead to a higher lift co-efficient. The influence of location and position of suction, suction flow rate and suction hole width on aerodynamic performance have greater influence. These examine the potential payoff for boundary-layer control as applied to the advanced-concept wings. An experimental work deals with the continuous normal suction from the wing upper surface effects on the aerodynamic forces. The wing model with NACA-2412 has been made to achieve normal suction from the wing upper surface by means of four slot channels. The results showed that the continuous normal suction can significantly increase the lift to drag force ratio and this ratio is increasing as the strength of suction increases. There is a convincing decrease in drag and pressure loss and an increase in max lift, which in turn improves the overall performance of the aircraft. While multi-hole suction control can reduce drag much more efficiently than single hole suction control, the position of the suction hole has a greater effect on reducing pressure losses than the suction flow rate.

Suction control of laminar separation bubble over an airfoil at low Reynolds number

A laminar separation bubble appears generally on the NACA2415 airfoil at low Reynolds number. In this paper, suction control of the laminar separation bubble over the NACA2415 airfoil at low Reynolds number are simulated. The effects of suction control on the flow field and the aerodynamic characteristics of the airfoil are focused on at different angles of attack. Numerical simulations show that employing the γ-Reθt transition model coupling the k–ω shear stress transport turbulence model can predict the laminar separation bubbles accurately. The results indicate that suction control can delay the transition, decrease the velocity gradient of the boundary layer and inhibit the production of the separation bubble. The effect of the suction control becomes better with the suction location getting closer to the separation bubble and the suction speed (the suction gas speed of suction hole) getting faster. The figure of merit is introduced to evaluate energy consumption of the suction control. In consideration of the economic effects, the suction control is suitable for the larger angle of attack situation at low Reynolds number.

Finite Element Analysis of Airflow Field for Vacuum Chamber in Air-Suction Seed Metering Device of No-Till Seeder

In order to study the impact of the different structures in the air-suction seed metering device of no-tillage planter on seeding performance, based on the structural characteristics of vacuum chamber in air-suction seed metering device of no-tillage planter, the air flow finite element analysis of air-suction seed metering device and experimental verification were did. Mainly the law of the distribution of airflow field and seeding performance of the vacuum chamber under the situation of the different distribution diameters of the suction hole were studied in this paper. The result shows that the adsorption performance is best when the suction hole distribution diameter is 150 mm. The conclusion can provide a reference for structural optimization and performance improvement of the air-suction seed metering device of no-tillage planter.