Analysis of air suction structure for cotton fiber length detection: Simulation and experiment

Air suction structure is an important part of cotton fiber length detection device. In this study, a structure for fixing cotton tufts by air suction was designed. Internal flow fields were established in the suction port and suction chamber of the suction structure by FLUENT software. Through the single-factor test, taking the velocity nonuniformity coefficient S_v of plane P0 and the surface average velocity V_a of plane P1 as evaluation indexes to select main variables (the length L and width W of the suction port and the horizontal distance Z between the central axis of the air source pipe and the suction port) and their value ranges. The response surface method was used to carry out simulation tests, and a dual-objective optimization model was established. The optimal suction model with high wind velocity and high flow field uniformity was determined (L = 125.24 mm, W = 8 mm, and Z = 90 mm). Finally, an orthogonal experiment was designed to determine the optimal working parameters of this structure, with the velocity V of the rear suction port and the distance X from the front end of the suction port to the cotton tuft as experimental factors, and the included angle α of the tangent lines at the two ends of the cotton tuft as evaluation index. The experiment results showed that when the V was 12 m/s and the X was 15 mm, α was the minimum, and the fiber straightening performance was the optimal.