Dissertations

Fall 1995

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical and Industrial Engineering

Rong-Yaw Chen

John Vincent Droughton

E. S. Geskin

Robert P. Kirchner

MengChu Zhou

Abstract

Particle trajectory and deposition of two phase gas-solid flows in a convergent or divergent two-dimensional channel are investigated numerically in a wide range of parameters. For the fluid phase, a two dimensional, incompressible laminar fluid flow is considered in the analysis. The particle phase is a diluted suspension. The effects of inertia, gravity, viscous force and electrostatic image force are included in the computational model.

Both convergent and divergent channel flow are solved by the finite element method based on the software FIDAP. The flow separations will appear in a divergent channel and their separation positions are obtained in the computation. The governing equations of particle motion are built upon the Lagrangian trajectory method and are solved with the forth- order Runge-Kutta method. A computer simulation procedure is developed to find the trajectory of each particle entering a channel. Particle depositions are calculated based on the distance for a particle to reach the wall. Many computations for deposition are performed on combinations of different parameters, such as charge parameter Q, gravity parameter G, and inertia parameter S.

The ranges of parameters are θ=2.5° to 7.5°, S=0.01 to 100, G=0.01 to 100, Q=0.00001 to 10000, Re=100, and L/ho=40.

Results under the influence of inertia, viscous, gravity and image forces indicate that particle trajectory in a channel is dependent upon these combined effects. A closer initial particle position to the channel wall may not mean a faster moving to the wall. Either in a convergent channel or a divergent one, the maximum longest deposition distance keeps the range of Q/G=0.1 to 1, and their deposition distance curves are almost the same after Q/G<0.001. The influence due to varying image forces and gravity is important to the particle deposition fraction. Generally, Q/G is greater or equal to 10, the gravity effect to deposition can be neglected, while the charge effect to deposition fraction can also be neglected at Q/G<0.001. The deposition decreases with increasing S for all Q and G. The particle deposition fraction increases always with increasing X displacement and the channel angle effect to the deposition fraction is smaller as compared with other effects. As small divergent channel cases, the back flow effect can also be neglected in limited channel length ranges.

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