REal-GAs effects on Loss mechanisms of ORC turbine flows (REGAL-ORC)

有机朗肯循环（ORC）动力系统为废热回收和环境友好发电提供了巨大的潜力，但是关于真实气体效应对ORC涡轮机膨胀机中的损失机制的影响知之甚少。只有更好地理解和模拟相关的非理想可压缩流体动力学现象，才能进一步提高ORC涡轮机效率。目前用于ORC设计的计算流体动力学（CFD）工具，基于雷诺平均Navier-Stokes（RANS）模型，受到许多臭名昭著的缺陷和不确定性的影响，大涡模拟（LES）或直接数值模拟（DNS）方法是一个有前途的工具，以提高我们对这些流动的基本理解。大涡模拟和直接数值模拟方法在可压缩真实气体流动中的应用是一个公开的挑战，由于高雷诺数的影响和复杂的热物理模型的要求，需要高质量的实验数据来验证，而这些数据目前还没有得到。本计画将以数值-实验相结合的方法，使用高精度数值解算器，新的有机蒸汽风洞试验设备和新一代热膜表面传感器。该项目将明确识别和量化真实气体对层流到湍流转捩、流动分离、激波边界层相互作用和尾流发展的影响，并最终确定它们对跨音速流态中损失机制的影响。将研究两种主要的试验配置，即平板上的流动和通过简化的涡轮机叶栅叶片的流动。流动特性，包括湍流量，将通过热线风速计，常规和聚焦纹影系统，皮托管和五孔探针，基于激光的风速测量，并通过新一代的小型化热膜表面传感器量身定制的有机蒸汽流的非常特殊的需求。由于理论/数值研究小组之间的密切合作，（巴黎，法国）和一个实验组（明斯特，德国）和微系统技术集团的支持（Ilmenau，德国），该项目将首次实现有机蒸气的几个重大进展，即：1）通过模拟和实验之间的交叉比较表征过渡和湍流行为; 2）深入了解叶片损失机制并评估数值模型捕获它们的能力; 3）开发专门为ORC涡轮机定制的创新型高保真CFD工具; 4）开发并发布新的热表面传感器，用于测量真实气体的非常薄的壁区域中的流动和湍流量。

Organic Rankine Cycle (ORC) power systems offer a great potential for waste heat recovery and environmental-friendly power generation but relatively little is known regarding the impact of real-gas effects on loss mechanisms in ORC turbine expanders. A further increase of ORC turbine efficiencies can only be achieved if relevant non-ideal compressible fluid dynamical phenomena are better understood and modeled. Computational fluid dynamics (CFD) tools currently used in ORC design, based on Reynolds-averaged Navier-Stokes (RANS) models, are affected by many notorious flaws and uncertainties, and large-eddy-simulation (LES) or direct-numerical-simulation (DNS) methods are a promising tool for improving our fundamental understanding of these flows. The application of LES and DNS methods for compressible real-gas flows in turbomachinery configurations is an open challenge, due to the high Reynolds numbers that come into play and the complex thermophysical models required and necessitates high-quality experimental data for their validation that are not available so far.Higher-order LES and wall-modelled LES methods for simulating organic vapor flows in turbomachinery will be developed in this project based on a combined numerical-experimental approach employing high-accurate numerical solvers, a new organic vapor wind tunnel test facility and a new generation of hot-film surface sensors. The project will explicitly identify and quantify real-gas effects on laminar-to-turbulent transition, flow separation, shock-wave-boundary layer interactions and wake development and, ultimately, their impact on loss mechanisms in the transonic flow regime. Two primary test configurations will be investigated, namely, the flow over a flat plate and though a simplified turbine cascade vane. Flow properties, including turbulence quantities, will be measured by means of hot-wire anemometry, conventional and focusing Schlieren systems, Pitot and five-hole-probes, laser-based anemometry, and by a new generation of miniaturized hot-film surface sensors tailored to the very special needs of organic vapor flows. Thanks to the close collaboration between a theoretical/numerical research group (Paris, France) and an experimental group (Muenster, Germany) and the support by a microsystem technology group (Ilmenau, Germany), the project will enable, for the very first time for organic vapors, several significant advances, namely: 1) characterization of transitional and turbulent flow behavior via cross-comparisons between simulations and experiments; 2) insight into blade vane loss mechanisms and assessment of the capability of numerical models to capture them; 3) development of innovative high-fidelity CFD tools specifically tailored for ORC turbomachinery; 4) development and release of new thermal surface sensors for measuring flow and turbulence quantities in the very thin wall region for real-gases.