Numerical investigation of the behaviour of confined, impinging jets with assessment of advanced concepts to reduce unsteady pressure fluctuations in gas turbine testing facilities

大型试验室被用来评估现代喷气发动机的性能。MDS航空支持公司是这些测试单元的领先设计和制造商。他们观察到，当大型发动机在其中以高流量运行时，设施中一些部件的压力波动幅度大，频率低。随着时间的推移，这些严重到足以对组件造成损坏。这将导致测试单元停机以进行维修，这对MDS及其客户来说是不希望的。该项目将研究减少非定常压力波动的方法，并将导致与产生和控制压力波动幅度的空气流动行为有关的新知识。****该问题与射流撞击有关，但与之相关的几何形状和流速在过去并没有得到广泛的研究。为了解决这一问题，将采用双管齐下的方法：一方面，将进行调查，以确定受压力波动最直接影响的部件形状的变化如何改变波动幅度；同时，将对潜在的物理过程进行更基础的研究，这将产生无源器件的设计建议，这些器件可以添加到测试单元中，以防止或减轻压力波动。这两种方法都将采用测试单元中气流的数值模拟。特别是，一种非常精确但复杂的模拟方法，称为大涡模拟，将被用来捕捉相关物理过程的细节。各种设计思想和修改将通过这些模拟进行评估，以确定哪些具有最大的潜在效益，以及为什么

Large test cells are used to evaluate the performance of modern jet engines. MDS Aero Support Corporation is a leading design and manufacturer of these test cells. They have observed large amplitude, low frequency unsteady pressure fluctuations on some of the components in the facilities when large engines are operated in them at high flow rates. These are significant enough to cause damage to the components over time. This leads to test cell downtime for repairs which is undesirable for MDS and their customers. This project will investigate approaches to reduce the unsteady pressure fluctuations and will also lead to new knowledge related to the air flow behaviour which gives rise to and governs the magnitude of the pressure fluctuations.****The problem is related to jet impingement, but the geometry and flow speeds which are relevant have not been extensively studied in the past. To try to solve the problem, a two-pronged approach will be employed: on one hand, an investigation will be carried out to determine how changes to the shape of the components most directly affected by the pressure fluctuations can alter the fluctuation magnitudes; simultaneously a more fundamental study of the underlying physical processes at play will take place and this will yield design proposals for passive devices which could be added to the test cells to prevent or mitigate the pressure fluctuations. Both approaches will employ numerical simulations of the air flow in the test cell. In particular, a very accurate but complex simulation approach called Large Eddy Simulation will be used to capture the details of the relevant physical processes. Various design ideas and modifications will be assessed using these simulations to determine which have the most potential benefit, and why.**