Experimental analysis on particle fluctuation velocity in a horizontal air–solid two-phase pipe flow having a dune model

ABSTRACT

To further elucidate the mechanism of energy-conserving conveying in horizontal pneumatic conveying with the dune model, the high-speed particle image velocimetry is applied to measure particle fluctuation velocity near the minimum conveying velocity of the conventional pneumatic conveying. This study focuses on the effect of mounting dune models on the horizontal pneumatic conveying in terms of power spectrum, autocorrelation coefficients, two-point correlation coefficients, fluctuation intensity of particle velocity, skewness factor, and probability density function. It is found that the power spectrum peaks with the dune model are larger than those of the nondune system, suggesting the acceleration and suspending efficiency of the dune model, especially dune models mounted at the bottom of the pipe. Meanwhile, the profiles of particle fluctuation velocity intensity indicate that the large particle fluctuating energy is generated due to mounting the dune model so that the particles are more easily accelerated and suspended. This is one of the important reasons why the mounted dune model results in a low pressure drop and low minimum conveying velocity. Based on the distribution of skewness factor and probability density function, it is found that the particle fluctuation velocities of all cases follow the Gaussian distribution in the lower and middle parts of the pipe. The particle fluctuation velocities in the case of the dune models mounted at the bottom of the pipe obey the Gaussian-type fluctuation more.

KEYWORDS:

• Dune model
• high-speed PIV
• intensity of particle fluctuating velocity
• minimum conveying velocity
• pneumatic conveying
• power spectrum
• probability density function
• skewness

Acknowledgment

The experiments were conducted at Professor A. Rinoshika’s laboratory at Yamagata University, Japan. The first author wishes to acknowledge support given to him by Natural Science Foundation of Jiangsu Province of China (No. BK20140512) and Scientific Research Foundation for Returned Overseas Chinese Scholars, State Education Ministry.