Measuring and modeling of two-phase gap flow for oil-refrigerant mixtures in rotary positive displacement machines

旋转容积式机器中油-制冷剂混合物的两相间隙流的测量和建模

• 批准号: 531151785
• 负责人: Professor Dr.-Ing. Andreas Brümmer
• 金额: --
• 依托单位: Fachgebiet Fluidtechnik
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/531151785?language=en
• 关键词: Measuring; modeling; two; phase; gap

Oil-injected rotary positive displacement (RPDC) compressors such as twin-screw machines are widely used to compress refrigerants in HVAC (heating, ventilation, and air conditioning) systems. The efficiency of these fluid energy machines is determined to a significant extent by the unavoidable surge flows in front of a rotor lobe and the subsequent two-phase oil-refrigerant gap flow between the rotor and the housing. Within subproject A1, models for the one-dimensional calculation of the two-phase gap flows are being developed in the 1st funding period of the Research Unit FOR 5595. The governing effects, such as the outgassing of the refrigerant from the oil due to the pressure gradient in the gap or the moving gap boundary, are taken into account. At the same time, the local dissipation due to wall friction are resolved. Generic experiments of a rotating contour in a gas cylinder form the basis for this model development. The ratio of the frictional forces acting in the direction of flow to the inertial forces is systematically varied. Accordingly, the experiments are started with a rotating circular cylinder as contour (Couette-flow experiments) and varied towards a rotating rotor lobe contour (Couette-Poiseuille flow experiments with variable gap cross section). In the Couette-flow experiments, the driving torque is measured as a measure of the acting wall shear stress. In the Couette-Poiseuille experiments, the two-phase gap mass flow rate is measured together with the pressure distribution in the gap flow direction. The two-phase mixtures studied are first water with nitrogen (low solubility), then water with carbon dioxide (moderate solubility), and then n-decane with carbon dioxide (strong solubility). The complex thermophysical properties for these increasingly asymmetric fluid mixtures will be developed by the B group subprojects. Based on high-speed videos, the flow patterns in the gap are analyzed together with subproject A2 (Kriegseis) and transferred into flow pattern maps. Subsequently, approaches for the calculation of the inertial forces and wall friction forces acting in the flow direction will be established. The necessary models, e.g. for the slip between the gaseous and liquid phases, are developed together with subproject A2 and the high-resolution numerical flow simulation by subproject A3 (Schröder). Finally, with the validated approaches for the inertial and frictional forces, the sought two-phase oil-refrigerant gap mass flow rate and the gap dissipation for an imposed pressure drop across the gap can be calculated by numerically integrating the one-dimensional conservation equations per phase (separated two-phase flow model).

喷油旋转容积式（RPDC）压缩机（例如双螺杆机）广泛用于压缩HVAC（加热、通风和空调）系统中的制冷剂。这些流体能量机器的效率在很大程度上由转子凸角前面的不可避免的喘振流以及随后的转子和壳体之间的两相油-制冷剂间隙流确定。在子项目A1中，在研究单位FOR 5595的第一个资助期内，正在开发两相间隙流的一维计算模型。考虑了调节效应，例如由于差距或移动间隙边界中的压力梯度导致的制冷剂从油中的脱气。同时，解决了壁面摩擦引起的局部耗散问题。通用实验的旋转轮廓在气缸形成的基础上，这个模型的发展。作用在流动方向上的摩擦力与惯性力的比率是有系统地变化的。因此，实验以旋转的圆柱体作为轮廓（库埃特流实验）开始，并且朝向旋转的转子叶轮廓变化（具有可变间隙横截面的库埃特-普瓦耶流实验）。在库埃特流实验中，驱动扭矩被测量为作用壁剪切应力的量度。在Couette-Poiffille实验中，测量了两相间隙质量流率以及在差距流动方向上的压力分布。研究的两相混合物首先是水与氮气（低溶解度），然后是水与二氧化碳（中等溶解度），然后是正癸烷与二氧化碳（强溶解度）。这些日益不对称的流体混合物的复杂热物理性质将由B组子项目开发。基于高速视频，与子项目A2（Kriegseis）一起分析了差距中的流动模式，并将其转换为流动模式图。随后，将建立沿流动方向作用的惯性力和壁面摩擦力的计算方法。必要的模型，例如气相和液相之间的滑移，与子项目A2和子项目A3（Schröder）的高分辨率数值流动模拟一起开发。最后，利用惯性力和摩擦力的验证方法，可以通过对每个相的一维守恒方程进行数值积分（分离两相流模型）来计算所寻求的两相油-制冷剂间隙质量流率和差距两端施加压降的差距耗散。