Abstract:

Objective The stability of the airflow inside the channel affects the flow of cotton in the pipe, which in turn affects the subse quent detection and rejection of foreign fibers. The purpose of this paper is to reduce the fluctuation of airflow inside the transport channel and minimize the wall attachment phenomenon on the upper and lower walls of the channel by improving the structure of the transport channel, so that the cotton flow can be transported smoothly inside the channel and improve the efficiency and rejection accuracy of foreign fiber detection.

Method ANSYS software Fluent module is adopted to model the CS808 foreign fiber machine channel structure in equal scale, set the simulation parameters according to the actual working conditions of the foreign fiber machine, use computerized fluid dynamics simulation calculation, analyze the flow field characteristics of the original channel structure, and then propose two improvement options such as changing the curvature combined with the length of the inlet section and adding diffusers and simulate them, and draw velocity profiles to compare the effect before and after the improvement.

Results The simulation results show that: 1) due to the original cotton transport channel structure of the elbow, the pressure difference between the upper and lower walls of the place reached 23 Pa, the velocity field is disordered and the air velocity fluctuation is large, which is not conducive to the smooth transportation of the cotton flow. Therefore, it is proposed to improve the internal airflow stability of the channel by improving its own structural parameters and adding an external diffuser, respectively. 2) Reducing the angle of the bend and increasing the length of the inlet section of the cotton transport channel is conducive to reducing the coverage of the high and low pressure imbalance region at the bend of the channel, which can effectively reduce the velocity difference between the upper and lower walls at the bend, so that the airflow can restore smoothness more quickly. And the quantitative analysis of the channel shows that reducing the angle of the bend is better than changing the length of the channel inlet section to improve the stability of the airflow. 3) In the second optimization scheme, first, three different types of nozzles were screened as the diffuser in this paper; and then the design of the structural parameters of the diffuser into the cotton channel entrance section and simulation analysis, it was found that the addition of the diffuser of the cotton channel can effectively reduce the pipeline wall effect, and will control the flow of cotton in the pipe. It is found that the additional diffuser can effectively reduce the wall effect of the pipe, control the cotton flow in the middle of the pipe, and the pressure and velocity imbalance phenomenon at the bends is significantly improved; in order to reduce the diffuser caused by the resistance caused by the wall transition is not smooth, the section optimization is carried out for the shrinking and expanding diffuser surface, and the double arc tangent section with the smallest coefficient of resistance is screened as the optimal diffuser from the three section improvement schemes; finally, it can be seen that the added diffuser can be used as the optimal diffuser through the simulation experiments. Finally, through simulation experiments, it can be seen that the airflow in the cotton transport channel with the addition of the double arc tangent section diffuser can be stabilized 0.3 m earlier than that in the original cotton transport channel.

Conclusion The unreasonable structure of the original cotton transport channel is the main reason for the fluctuation of cotton flow velocity. By changing the angle of the bend combined with the length of the inlet section and adding a taped and expanded diffuser can effectively reduce the degree of velocity fluctuations inside the pipe and significantly shorten the distance to restore smooth airflow, to a certain extent, to ensure the efficiency of the subsequent detection and rejection of cotton foreign fibers. The degree of improvement of the efficiency of foreign fiber detection and rejection in the practical application of the improvement scheme proposed in this paper needs to be further verified in theory and practical application.

Key words: foreign fiber sorting machine, cotton transport channel, structural optimization, diffuser, airflow stability, cotton, foreign fiber