负压钻井液振动筛气液喷射器性能的数值模拟研究

随着石油钻井技术的发展，传统钻井液振动筛不能满足现有工程需求，因此提出了一种新型负压钻井液振动筛。气液喷射器是负压钻井液振动筛的核心设备，通过它在筛网下方形成负压区域，使钻井液受振动和负压的复合作用，增大钻井液透过筛网的能力，因此其性能直接影响负压振动筛的处理效率。为了提高负压振动筛的工作效率，需要对气液喷射器的结构和工况进行合理设计。运用流体动量守恒方程，推导出恒定流动状态下气液喷射器混合室的动量方程及其性能计算方程。运用计算流体力学方法对气液喷射器内部复杂的两相流动过程进行数值模拟，并通过对比数值模拟结果与理论计算结果来验证数值模型的合理性。对不同引射流体液体体积分数、工作气体压力、喷嘴距和喷管面积比下气液喷射器的喷射效果进行数值模拟，结果表明气液喷射器的工作参数和结构参数对其喷射系数和真空度有极大的影响。根据模拟结果可知，在引射液体体积分数为30%、工作气体压力为300 kPa、喷嘴距为60 mm、喷管面积比为3.484的情况下，气液喷射器的性能达到最佳。研究结果为负压钻井液振动筛中气液喷射装置的设计和现场应用提供了理论依据。

Numerical simulation study of the performance of gas-liquid ejector in negative pressure drilling fluid shale shaker

Processing capacity of traditional shale shaker can t meet the existing engineering requirements with the rapid development of petroleum drilling technology. Therefore, a new type of negative pressure drilling fiuid shale shaker is proposed. The gas-liquid ejector is the core equipment for the negative pressure shale shaker. The negative pressure area is formed under the screen by using the gas-liquid ejector, which makes the drilling fluid be subjected to a combination of vibration and negative pressure, and enhances the ability of the drilling fluid passing through the screen. The performance of the gas-liquid ejector directly affects the processing efficiency of the negative pressure shale shaker. In order to obtain a considerable working efficiency of the negative pressure shale shaker, it is necessary to design a structure and the working condition for ejector reasonably. The fluid momentum conservation equation was applied to the gas-liquid ejector in the negative pressure shale shaker, and the momentum equations of the gas-liquid mixing chamber under constant flow conditions were deduced as well as the computational performance equation of the gas-liquid ejector.The complex two phase flow in the gas-liquid ejector was simulated by computational fluid dynamics method (CFDM). The rationality of the numerical model was verified through comparison of the numerical simulation results and theoretical calculation results. Jet performances of gas-liquid ejector under different liquid volume fractions of ejected fluid, working gas pressures, nozzle distances and nozzle area ratios were simulated.It was found that the working parameters and structural parameters of the gas-liquid ejector had a great influence on its injection coefficient and vacuum degree. According to the simulation results, the ejector performance was optimal when the liquid volume fraction of ejected fluid was 30%, the working gas pressure was 300 kPa, the nozzle distance was 60 mm, and the nozzle area ratio was 3.484. The research results provide a theoretical basis for the design and field application of gas-liquid injection devices in negative pressure shale shaker.