引射器的性能受几何尺寸影响,相关设计方法给出的结果差异较大,存在设计点偏离严重的问题.针对小膨胀比煤层气气井引射需要,利用基于气体动力学理论的索科洛夫经验公式对引射器进行初步设计,并通过CFD方法对其关键结构尺寸进行数值优化,得到关键结构参数如喷嘴间距、混合室直径、混合室长度及扩压室长度等对引射器性能的影响规律.对比分析理论设计和模拟优化得到的引射器几何尺寸,发现CFD方法优化后的引射器等熵效率较理论设计高出13%左右,并通过实验验证引射器在偏离设计工况时,等熵效率急剧降低,表明数值模拟设计的引射器效率最高,在工程上为偏离设计工况的引射器设计提供了参考.%The ejector′s performance could be affected easily by the geometric dimension, and different design methods would lead to quite different results, the design point would be seriously deviated.In order to meet the needs of ejection in coal-bed methane with small expansion ratio, the gas ejector is designed according to the Sokolov empirical formulas which are based on aerodynamics theory, and the key structural dimensions are simulated and optimized by CFD method.The influence rule of the ejector′s key structural parameters, such as the nozzle distance, the mixing chamber diameter, the mixing chamber length and the diffuser chamber length on the ejector performance is obtained.By comparing the results of theoretical design and numerical simulation, the isentropic efficiency of the ejector which was optimized by CFD method is about 13% higher than that of using theoretical design.Then, it is verified through experiments that the isentropic efficiency of the ejector will sharply reduce when the operating condition deviates from the design condition.It is proved that the ejector designed by numerical simulation has the higher efficiency, which provides reference to the design of ejector deviating from the design point in engineering.
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