Dissertation > Excellent graduate degree dissertation topics show

Experiments on the Effect of Geometry Structure on the Gas-Solid Flow Pattern in a Circulating Fluidized Bed Riser

Author: ZhangXiMei
Tutor: WangQinHui；LuoZhongZuo
School: Zhejiang University
Course: Energy and Environmental Engineering
Keywords: Circulating fluidized bed Gas-solid flow Rectangular cross-section Bed structure The fiber particle concentration probe Particle image velocimetry
CLC: TK221
Type: Master's thesis
Year: 2010
Downloads: 72
Quote: 1
Read: Download Dissertation

Abstract

The circulating fluidized bed (CFB) as a clean coal combustion technology, both at home and abroad in recent years has spread rapidly. Currently, the circulating fluidized bed boiler is the development direction of the large capacity of the high-parameter, but there are some problems in the rapid development of the process to be studied to solve, such as large-scale circulating fluidized bed boiler dense phase zone structure, furnace exit, as well as secondary tuyere and other structural feature points of the furnace the furnace hydrodynamic characteristics. Built-section 350 × 480mm2, high 4.9m rectangular cross-section of the cold circulating fluidized bed test rig, good reflective properties of glass beads as the bed material, the use of high-speed photography combined with particle image velocimetry (PIV) technology PC6D dense phase zone structure, transition zone structure and bias export position structure feature points through the testing and analysis of particle velocity and concentration fields under different conditions of bed, on the bed and light reflective particles concentration probe Experimental study on influence within the solid flow behavior. The test results show that the dense phase region has a significant effect on the structure of the dense phase gas-solid flow characteristics. The radial distribution of the particle flow velocity and concentration in the dense phase region of the symmetric diverging type structure is substantially symmetrical, and the the unilateral back wall diverging type structure, the dense phase region of the particle flow rate and the concentration distribution of the front back wall direction showed a non-centrosymmetric distribution of bubbles and particles to the back wall of the diverging direction bias and more intense backmixing, the back wall of the the regional particle concentration was significantly higher than the front wall. Improve sectional velocity, the flow velocity of the particles increases, the particle concentration is reduced. With the increase in the rate of secondary air at the same time, an increase in the number of particles of the region of the bottom of the dense phase region, the particle concentration was increased. The back wall of the stepped structure of the transition region changes the flow field distribution in the region of the particles near the stepped region, the deflection of the particle flow phenomena is evident, especially in a partial area of ??the edge and the lower edge on the steps, the stepped structure of the particles radially movement have worsened, and up and down stairs at both ends, a large number of particles gathered collisions, the formation of a local high particle concentration area; prominent step layout by intense erosion of the high concentration of the particles. The layout of the transition zone of secondary air solid flow structure in the region also have a greater impact. Affected the flow of the particles of the transition zone is no longer present the typical ring-core structure, the particles of the side wall of the region with the secondary air jet flow, lateral flow velocity of the particles to the central area of ??the wall area of ??the particle concentration was significantly reduced, the center Regional concentration is increased, the uneven radial distribution of the particle concentration is significantly reduced. The secondary vent above the particle concentration of the cross-section a slight change with the increase in the rate of secondary air, but little change overall. Bias export layout of the exit area of ??the bed particles flow structure have a greater impact. Most of the left wall surface area of ??the particles close to the exit along the wall facing the back wall of the outlet flow, and only in the region close to the front wall of the flow of the typical side wall region particles decreased. Subject to export effect and the confining wall friction, easy to form a localized the particulate high concentration region, leading to the particle concentration of the surface zone of the rear wall is significantly larger than the other regions in the back wall at the outlet below. The front wall, the wall region particles by weak export effect, coupled with rectangular cross-section corner effect role, as well as intensive roof rebound down some of the particles, the particles of the corner of the left wall and the front wall. Weaken the export effect wall side Guabing before layout certain extent, there is a redistribution process by both particle flow structure of the wall surface area before the impact of hanging screen layout.

Related Dissertations

CLC: > Industrial Technology > Energy and Power Engineering > Steam Power Engineering > Steam boiler > Theory
© 2012 www.DissertationTopic.Net Mobile