基于静压变化的隧道风管漏风计算方法

Calculation Method for Tunnel Air Duct Leakage Based on Static Pressure Variation

目前施工通风计算中,往往将风管百米漏风率取为1个固定值进行计算,而工程实际中漏风率会随着风管内外的静压差变化而变化,为此,通过试验测试和理论分析相结合,提出1种充分考虑静压差和风量沿程变化影响的漏风率计算方法。首先,基于漏风率测试试验结果,拟合漏风率和风管内静压的关系式;然后,将风管分段处理,从出口段开始对风量、静压、漏风率等参数进行迭代计算;最后,求出整段长风管的漏风率。基于该方法进行通风距离、风管直径和海拔高度对漏风率的影响分析,结果表明:风管百米漏风率与管内静压呈正相关;在风管距离较长时,分段迭代的漏风计算方法更为合理;通风距离增长,风机须提供的静压升高,平均百米漏风率随之增大;风管直径增大,风管内的通风阻力减小,风机须提供的静压降低,平均百米漏风率随之减小;海拔越高,需风量越大,风机须提供的静压升高,平均百米漏风率随之增大。

In current construction ventilation calculation,100-meter air leakage rate of the air duct is often calculated as a fixed value,while the air leakage rate in the actual project will change along with the variation of static pressure differences inside and outside the air duct.Therefore,a calculation method for air leakage rate is proposed through combining experimental tests with theoretical analysis,which can fully consider the influence of static pressure difference and air volume variation along the path.Firstly,based on the results of the air leakage rate test,the relational expression of air leakage rate and static pressure in the air duct is fitted.Then,the air duct is processed in segments,and the parameters such as air volume,static pressure,air leakage rate are iteratively calculated from the outlet section.Finally,the air leakage rate of the entire long duct is obtained.Based on this method,the impact analysis of ventilation distance,duct diameter and altitude regarding air leakage rate is carried out.The results show that there is a positive correlation between air leakage rate and static pressure in the air duct.When the distance of air duct is long,the segmented iterative air leakage calculation method is more reasonable.As the ventilation distance increases,the static pressure provided by the fan increases,and the average 100-meter air leakage rate of the air duct increases accordingly.As the air duct diameter increases,the ventilation resistance in the air duct decreases,the static pressure required by the fan decreases,and the average 100-meter air leakage rate of the air duct decreases.The higher the altitude,the greater the air volume required,the higher the static pressure that the fan needs to provide,and the average 100-meter air leakage rate of the air duct increases accordingly.