Motion Mechanism of Coarse Particle on a Rotational Flow Pneumatic Conveying in Horizontal–Vertical Pipeline Based on Continuous Wavelet Analysis and Dynamic Mode Decomposition

This study involved a rotational flow conveying (installing rotational blades upstream of the particle inlet) of coarse particles. First, the particle velocity and concentration were measured to evaluate the suspension and acceleration ability of rotational flow by using the high-speed particle image velocimeter (PIV) and electrical capacitance tomography (ECT) system. And then, the particle pulsation velocities were analyzed to reveal the energy-saving mechanism of rotational flow based on the continuous wavelet transform (CWT) and dynamic mode decomposition (DMD) methods. The research results indicate that the dominant frequency of particle motion was reduced at the conveying upstream when employing rotational blades; high-frequency particle motion was attenuated, while low-frequency motion was amplified, enabling particles to effectively absorb airflow energy and enhance the fluctuations in particle motion. Otherwise, the transformation of particles from large-scale motion to small-scale motion is promoted at the conveying downstream for using rotational blades; the high-frequency small-scale motion of particles increased, and the motion of particles gradually tends to be stable.