Space--time VMS flow analysis of a turbocharger turbine with isogeometric discretization: computations with time-dependent and steady-inflow representations of the intake/exhaust cycle
Space--time VMS flow analysis of a turbocharger turbine with isogeometric discretization: computations with time-dependent and steady-inflow representations of the intake/exhaust cycle
复制标题
具有等几何离散化的涡轮增压器涡轮的时空 VMS 流动分析：进气/排气循环的时间相关和稳定流入表示的计算
DOI：
10.1007/s00466-019-01722-2
复制
发表时间：
2019
影响因子：
4.1
通讯作者：
Zhang Yutong
中科院分区：
文献类型：
--
作者：
Otoguro Yuto;Takizawa Kenji;Tezduyar Tayfun E.;Nagaoka Kenichiro;Avsar Reha;Zhang Yutong
在涡轮增压器-涡轮流动分析中遇到的许多计算挑战已经通过一套集成的时空(ST)计算方法来解决。核心计算方法是ST变分多尺度(ST-VMS)方法。ST框架总体上提供了较高的精度，而ST-VMS的VMS特征解决了与非定常流动的多尺度性质相关的计算挑战。ST框架的移动网格特性使得在转子表面附近进行高分辨率计算成为可能。ST滑移界面(ST-SI)方法实现了旋转转子的移动网格计算。覆盖转子的网格随之旋转，旋转网格和其余网格之间的SI精确地连接解决方案的两侧。ST等轴测分析能够更准确地表示涡轮机几何形状，并提高流动解决方案的精度。使用ST/NURBS网格更新方法可以精确表示网格旋转。通用的NURBS网格生成方法使其更容易处理复杂的几何图形。SI还通过精确连接在非匹配网格上计算的解决方案的两侧，在一般情况下提供网格生成灵活性，从而允许在计算中使用非匹配NURBS网格。计算分析需要涵盖整个进气/排气循环，由于转速高，这比涡轮旋转周期长得多，所需的长时间是额外的计算挑战。作为解决这一挑战的一种方法，我们在这里建议通过插值法从与不同流量下的一组稳定流入计算相关的效率来计算进气/排气循环的透平效率。由进气/排气循环的随时间变化和恒定流入的计算结果表明，效率相当好。这表明，通过一组稳定的流入计算来预测涡轮机的性能是解决与多时间尺度相关的挑战的好方法。
Many of the computational challenges encountered in turbocharger-turbine flow analysis have been addressed by an integrated set of space–time (ST) computational methods. The core computational method is the ST variational multiscale (ST-VMS) method. The ST framework provides higher-order accuracy in general, and the VMS feature of the ST-VMS addresses the computational challenges associated with the multiscale nature of the unsteady flow. The moving-mesh feature of the ST framework enables high-resolution computation near the rotor surface. The ST slip interface (ST-SI) method enables moving-mesh computation of the spinning rotor. The mesh covering the rotor spins with it, and the SI between the spinning mesh and the rest of the mesh accurately connects the two sides of the solution. The ST Isogeometric Analysis enables more accurate representation of the turbine geometry and increased accuracy in the flow solution. The ST/NURBS Mesh Update Method enables exact representation of the mesh rotation. A general-purpose NURBS mesh generation method makes it easier to deal with the complex geometries involved. An SI also provides mesh generation flexibility in a general context by accurately connecting the two sides of the solution computed over nonmatching meshes, and that is enabling the use of nonmatching NURBS meshes in the computations. The computational analysis needs to cover a full intake/exhaust cycle, which is much longer than the turbine rotation cycle because of high rotation speeds, and the long duration required is an additional computational challenge. As one way of addressing that challenge, we propose here to calculate the turbine efficiency for the intake/exhaust cycle by interpolation from the efficiencies associated with a set of steady-inflow computations at different flow rates. The efficiencies obtained from the computations with time-dependent and steady-inflow representations of the intake/exhaust cycle compare well. This demonstrates that predicting the turbine performance from a set of steady-inflow computations is a good way of addressing the challenge associated with the multiple time scales.