容积式油气混输泵内固体颗粒破坏性弱化机理研究

Multiphase pump units are considered as the key equipments in the multiphase pumping technology. Currently, most of displacement multiphase pumps which are widely used in the oil fields are sensitive to the sand particles contained in the working fluids. Due to the destructive behavior of sand particles, the positive-displacement multiphase pumps face the operation problems of high failure rate, short operation life and poor performance stability. Former solution of this problem focused on the improvement of abrasion resistance of the pump components by improving the material and processing technology. However, it has been proved that this method is ineffective in controlling the destructive behavior of sand particles and increasing the pump’s tolerance to sand particles fundamentally. In this project, a new idea is presented based on the early studies on the synchronal rotary multiphase pump. The solution of the problem above will be found from the studies on the motion and the destructive behavior of sand particles in the pump chambers. Particularly, the dynamic characteristics and spatial distribution of sand particles in the pump working chambers will be firstly studied and the essential relation between the structural parameters of working chambers and the retention ratio of sand particles will be revealed. Moreover, the effect of sand particles on the thermodynamic process of pump will also be studied and the essential relation between the geometric parameters of leakage gaps and the pump efficiency will be revealed. Finally, the above fundamental study will clarify the weakening mechanism of the destructive behavior of sand-particles for the design optimization of pump structural parameters. Thus the self-discharge mechanism of solid particles will be enhanced and the destructive effect of the sand particles on the pump operation will be weakened through the improvement of the pump structural parameters. In this way, the pump’s tolerance to sand particles will be improved effectively.

油气混输泵是油气混输技术的关键设备。目前，在国内外油田中广泛应用的容积式油气混输泵抗砂能力较差，砂粒对混输泵腔体及密封间隙的破坏致使混输泵运行时存在故障率高、寿命短、性能稳定性差等问题。以往解决该问题的思路均专注于通过改变部件材料及改进处理工艺来对抗固体颗粒的磨损破坏，并不能从根本上控制并削弱固粒自身的破坏性。本项目在前期对新型同步回转式油气混输泵研究的基础上，从混输泵腔内固粒的运动及与固粒破坏行为相关联的内在规律入手，首先对混输泵腔内固体颗粒的动力学特性及空间分布进行研究，揭示腔内固粒滞留率与工作腔结构之间的本质联系；同时研究固体颗粒对混输泵热力过程的影响，揭示在固粒扰动下间隙尺寸与混输泵效率的本质联系。通过以上基础性研究，构建用于混输泵结构参数优化的固粒破坏性弱化机理，利用混输泵结构参数的改进来增强固粒的自行排出机制并从源头上削弱固粒的破坏性，最终切实有效地提高混输泵的抗砂能力。

目前，容积式油气混输泵普遍存在抗砂能力较差、性能稳定性不高的问题，限制了我国油气混输技术的发展。本项目针对同步回转式油气混输泵的数值模拟与实验研究，探究容积式混输泵内固体颗粒破坏行为与混输泵结构参数间的本质联系，利用优化结构参数来削弱固粒的破坏性，从而提高混输泵的长时运行性能与可靠性。首先，建立了全含气率下同步回转式混输泵内间隙流动模型，该模型能够准确计算混输泵的内部泄漏流量，从而准确预测不同工况下混输泵的流量曲线；理论模拟与实验结果表明，工作流体中的固粒并不在混输泵的转子径向间隙内聚集，却对混输泵转子端面间隙泄漏影响突出，为此利用了PTFE接触型密封对混输泵端面进行了改进，在对混输泵总功耗影响较小的前提下，有效削弱了固粒对转子端面间隙密封的破坏，提升了混输泵的效率与可靠性。其次，建立了全含气率范围内同步回转式混输泵的热动力学模型，该模型能够准确计算混输泵在不同工况下的动态参数与宏观性能参数；理论模拟与实验结果表明，在输送含固粒气-液流体时，同步回转式混输泵的宏观性能参数与常规气-液流体工况时差别较小，而混输泵的效率主要由进口含气率决定；对于容积式混输泵，为了适用于任意含气率的工况，不存在高压封闭容积，为此在处理高含气率流体时，因高压流体的回流造成了大量额外的能量损失，致使混输泵的效率处在较低的水平。此外，进行了混输泵结构参数优化设计，获得了混输泵腔体优化设计准则，并根据气-液工况下混输泵腔内流场模拟结果，改进了混输泵吸入孔口设计，不仅增加了混输泵内固粒的自行排出率，同时提升了混输泵的长时运行效率。