Multi-component cavitation modelling for the numerical flow simulation of real fluid mixtures in hydraulic systems

在液压系统中，通常使用复杂的流体混合物，例如液压油或燃料。这些混合物由数百种不同的组分组成，其流体和传输特性取决于局部混合物的组成。假设对于气泡动力学和空化，根据气泡周围的环境条件，气泡内和气泡周围的轻和重挥发性组分发生局部燃料分离，类似于液滴蒸发。最近的CFD方法使用的空化模型不能解释这种分离。因此，它们反映了汽蚀的发生，例如仅在燃料中发生的汽蚀不够充分。该项目的目的是开发一个多组分单气泡动力学模型，该模型描述了球形气泡的传热传质和相变，从而捕获了流体混合物的分离。简单的流体混合物用离散模型来处理，而真实的混合物则用基于连续热力学的多组分模型来处理。此外，还模拟了多组分混合流体中空气的释放和吸收与空化的相互作用。对具有代表性的注油和油压系统测试用例进行了验证和应用。在第一步中，即使是多组分单气泡模型的应用也有助于更好地理解流体混合物、气泡动力学、空气释放和空化侵蚀之间的因果关系。在第二步中，它针对的是后续项目，重点是用于三维CFD的多组分空化建模。

In hydraulic systems, usually complex fluid mixtures e.g. hydraulic oils or fuels are utilized. These mixtures consist of several hundred distinct components whose fluid and transport properties depend on the local mixture composition. It is assumed that for bubble dynamics and cavitation, in dependence on environmental conditions around the bubble, a local fuel segregation of the light and heavy volatile components within as well as around the bubble occurs, similar to droplet evaporation. Recent CFD methods use cavitation models that do not account for this segregation. Therefore, they reflect the occurrence of cavitation e.g. in fuels only insufficiently. The aim of the proposed project is the development of a multi component single bubble dynamics model that describes the heat and mass transfer as well phase change of spherical bubbles component-wise and therefore captures the fluid mixture segregation. Simple fluid mixtures are treated with a discrete model and real mixtures as e.g. fuels by a multi component model based on continuous thermodynamics. Furthermore, the interaction between air release and absorption with cavitation in multi-component fluid mixtures is modelled. The validation and application is performed on test cases which are representative for injection and oil hydraulic systems. In a first step, even the application of the multi-component single bubble model serves for a better understanding of the cause and effect chain between fluid mixture, bubble dynamics, air release and cavitation erosion. In a second step, it is aimed at a subsequent project with the focus on multi component cavitation modelling for 3D CFD.