独立窨井内氮气惰化设备进气参数优化设计

Optimal design of inlet parameters of nitrogen inerting equipment in independent well

为了探究独立窨井中氮气惰化设备进气参数(进气流量、进气位置、进气角度)变化对惰化效果的影响规律,构建了独立窨井三维模型并进行网格划分,使用CFD方法对窨井充氮惰化过程进行数值模拟。分析惰化过程中窨井内氧气体积分数平均值、氧气体积分数最大值随时间的变化规律,探究惰化最终时刻窨井内氧气分布及流场分布特点。结果表明,增大进气流量、平吹进气、窨井下部进气均有利于将窨井内氧气体积分数降低至临界安全氧浓度以下,形成较大不易耗散的涡旋使窨井内部氮气分布较均匀,具有较好的惰化效果。使用正交试验分析3个进气参数对窨井内氧气体积分数降低效果的影响,从主到次依次为进气角度、进气流量、进气位置,确定以临界安全氧体积分数为判据的惰化效果最佳的进气参数组合:进气速度为12 m/s,下部位置位于窨井下部,进气角度为平吹进气。该进气参数组合可将窨井内氧气体积分数降低至6.17%,远低于临界安全氧体积分数14.4%,具有最好的惰化效果。研究成果可为窨井内氮气抑爆设备进气参数设计提供理论依据。

This study aims to explore the influence of the inlet parameters(nitrogen inlet flow rate, nitrogen inlet position, nitrogen inlet angle) on the nitrogen inerting device in the independent inspection well. A three-dimensional model of the independent inspection well was built and meshed, and the CFD method was used to numerically simulate the nitrogen-filling inerting process in the well. The average value of the oxygen volume fraction in the well and the maximum oxygen volume fraction change with time were analyzed, and the characteristics of oxygen distribution and flow field distribution in the well at the final moment of inerting were explored. The results show that increasing the inlet flow rate, flushing nitrogen, and flushing nitrogen in the lower part of the well are all beneficial to reduce the oxygen volume fraction in the well to below the critical safe oxygen concentration, forming a larger and difficult-to-dissipate vortex to distribute nitrogen more uniform in the well, resulting in a better inerting effect. An orthogonal test was used to analyze the effect of three inlet parameters on the reduction effect of oxygen volume fraction in the well. The results of range and variance analysis show the effect sequence: nitrogen inlet angle> nitrogen inlet flow> nitrogen inlet position. The critical safe oxygen concentration is used as the criterion to determine the nitrogen inlet parameter combination with the best inerting effect: 12 m/s nitrogen inlet speed, flushing nitrogen, and flushing nitrogen in the lower part of the well. This combination of nitrogen inlet parameters can reduce the oxygen volume fraction to 6.17%, which is much lower than the critical safe oxygen concentration and has the best inerting effect. The research results can provide a theoretical basis for the design of the nitrogen inlet parameters of the nitrogen inerting equipment in the well.