One-Dimensional Modeling and Measurement of Pulsating Gas-Solid Flow in Tubes

Abstract

Pulsating turbulent gas-particle flow in a circular tube is investigated by both experimental and numerical methods. In experiments, the ensemble averaged centerline gas and particle velocities ate measured by using laser Doppler anemometry. The amplitude and the frequency of pulsations are controlled via the diameter and the RPM of a rotating butterfly valve. It was found that significant variations could be obtained along the axial position in the amplitude and the phase of the fluid velocity deviation from its mean. Both the amplitude and the phase shift behavior was a function of the imposed pulsating frequency and amplitude. Particle velocity measurements showed that the slip velocities between the fluid and particles are dependent on frequency and position along the axial direction. The experiments are simulated using a one-dimensional transient model which consists of one-dimensional compressible flow equations in an Eulerian, and particle momentum equation in a Lagrangian frame of reference. The explicit MacCormack method is used for the gas phase and Gear's method is used for the particle phase equations. An assessment of the one-dimensional, transient model is presented. It is shown that the experimentally observed dependence of both the fluid and the particle velocities on the frequency of forced oscillations as well as the significant variations with the axial distance can be simulated well by this simple model. The model can predict the instantaneous slip velocity between the fluid and solid particles in good agreement with measurements. This information is essential for combustion analysis of pulsed combustors utilizing pulverized coal.

KEYWORDS:

• Unsteady Flow
• Two phase
• Measurement
• Numerical Modeling
• Oscillating
• Pulse Combustion