Abstract: The flow characteristics and pressure drop of gas-coal mixtures under high pressure and concentration through a Venturi with different structures, including diameter ratio(0.44, 0.55, 0.7), convergence angle (2.5°, 5°, 9°), diffuser angle (2.5°, 8°, 13°) and throat length (23d, 43d, 80d) were investigated in the dense phase pneumatic conveying of pulverized coal system. A similar trend but a varied degree in non-dimensional pressure distribution for the gas-coal mixture through different Venturis was observed. The most remarkable influence parameter was diameter ratio, which had the greatest influence on pressure drop. The increase in pressure drop of the Venturi and remarkable increase in pressure drop in the diffuser were observed with the decrease of diameter ratio. The major role of other structural parameters was to change pressure distribution inside the Venturi, while having little influences on total pressure drop. The greatest convergence pressure drop for the convergence angle series occurred in the 2.5°. There was little difference of convergence pressure drop between 5° and 9° under high pressure and concentration. The greatest throat pressure drop for the throat length series occurred in the 80d. The least diffuser pressure drop for the diffuser angle series occurred in the 8°. By introducing solids momentum flux, an empirical equation of pressure drop of gas-coal mixture through the Venturi was established. It showed good prediction with deviations from most experimental value within 30%.

Key words: Venturi, fuel, two-phase flow, pressure drop, pneumatic conveying

摘要： 研究粉煤密相气力输送系统高压、高浓度煤粉通过不同节流比(0.44、0.55、0.7)、收缩角(2.5°、5°、9°)、扩张角(2.5°、8°、13°)、喉段长度(23d、43d、80d)的文丘里管的流动特征和压差特性。结果表明,不同结构参数的文丘里管的量纲1化压力分布趋势一致,但程度不一。其中节流比影响最为显著,并最直接地影响煤粉流经文丘里管的压差。节流比越小,总压差越大,扩张段压差显著增大。其他结构参数在各自的结构序列下主要改变文丘里管内压力分布,而对总压差改变不大。2.5°收缩角的收缩段压差最大,高浓度体系下5°和9°收缩角的收缩段压差差别不大。80d喉段长度的喉段压差最大。8°扩张角的扩张段压差最小。引入固相动量通量,获得本系统内煤粉流经文丘里管的压降经验方程,大部分实验点的计算偏差在30%以内,方程计算效果较好。

关键词: 文丘里管, 燃料, 两相流, 压差, 气力输送