Scale-resolving Simulations of Multicomponent Nozzle Flows

多组分喷嘴流的尺度解析模拟

• 批准号: 517046958
• 负责人: Professorin Dr.-Ing. Andrea D. Beck
• 金额: --
• 依托单位: Institut für Aerodynamik und Gasdynamik (IAG)
• 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/517046958?language=en
• 关键词: Scale; resolving; Simulations; Multicomponent; Nozzle

The project investigates in detail the injection and mixing processes of hydrogen in air, as they occur in direct injection systems. Due to the high inlet pressure, an underexpanded supersonic flow is established, in which a complex interaction of shock systems and turbulence occurs. This influences the mixing location and species distribution; likewise, a significant effect of thermodynamic parameters is to be expected. Uncertainties in inflow or nozzle geometry contribute to the complex, nonlinear behavior. This not only affects combustion but may also be part of the causal chain of intermittent cyclic variations. The characterization of these mixing processes as a function of the identified parameters is the goal of this subproject. For this purpose, high-resolution large eddy simulations of underexpanded hydrogen injections are performed. The resolution of the energy-carrying scales in space and time is absolutely necessary to capture the multiscale-multiphysics effects as well as the intermittent phenomena. Here, the coexistence of turbulent regions and shock systems pose great challenges to numerics. Additionally, the disparity of the occurring scales (e.g., more than 3 orders of magnitude lie between nozzle throat and diameter) cannot be represented with computational grids with globally constant grid spacing, even on high-performance computers. Therefore, state-of-the-art high-order methods with adaptation capabilities are used here, which can adapt the local grid resolution to the occurring scales. These methods are extended in this project for multi-component flows. With these methods, the nozzle flow as well as the subsequent mixing can be resolved with unprecedented accuracy and compared to the experimental results. Based on this methodology, the influence of the thermodynamic parameters (equation of state, diffusion approach) is further investigated in cooperation with numerical and experimental partner projects. The resulting high-resolution flow fields as well as the particle trajectories of passively advected tracer particles will be coupled to the combustion simulation code, taking into account the parallelization requirements. On the one hand, this will close the simulation chain from the nozzle to the combustion, and on the other hand, it will allow a joint investigation of the occurring variations (by correlation analysis as well as tracers). Multi-level and multi-fidelity methods are used to validate the results against changes in the nozzle flow. Overall, this project should contribute to a reliable and highly accurate mapping of hydrogen injection and mixing and thus to a contribution to the prediction of cyclic fluctuations and to a better understanding of their causes.

该项目详细研究了直接喷射系统中氢气在空气中的喷射和混合过程。由于入口压力高，形成了欠膨胀的超音速流，其中发生激波系统和湍流的复杂相互作用。这会影响混合位置和物种分布；同样，热力学参数也会产生显着影响。 流入或喷嘴几何形状的不确定性会导致复杂的非线性行为。这不仅影响燃烧，还可能是间歇性循环变化因果链的一部分。将这些混合过程的特征描述为已确定参数的函数是该子项目的目标。为此，对膨胀不足的氢气注入进行了高分辨率大涡流模拟。空间和时间上的能量承载尺度的分辨率对于捕捉多尺度多物理效应以及间歇现象是绝对必要的。这里，湍流区域和激波系统的共存对数值计算提出了巨大的挑战。 此外，即使在高性能计算机上，所出现的尺度的差异（例如，喷嘴喉部和直径之间超过3个数量级）也无法用具有全局恒定网格间距的计算网格来表示。因此，这里使用最先进的具有适应能力的高阶方法，可以使局部网格分辨率适应发生的尺度。这些方法在该项目中针对多组件流进行了扩展。通过这些方法，可以以前所未有的精度解析喷嘴流量以及随后的混合，并与实验结果进行比较。基于该方法，与数值和实验合作伙伴项目合作进一步研究热力学参数（状态方程、扩散方法）的影响。考虑到并行化要求，所得的高分辨率流场以及被动平流示踪粒子的粒子轨迹将耦合到燃烧模拟代码。一方面，这将关闭从喷嘴到燃烧的模拟链，另一方面，它将允许对发生的变化进行联合研究（通过相关分析和示踪剂）。使用多级和多保真度方法来验证喷嘴流量变化的结果。总体而言，该项目应有助于绘制可靠且高度准确的氢气注入和混合图，从而有助于预测循环波动并更好地了解其原因。