Unsteady side wall flows and heat transfer in a linear turbine cascade

目前叶轮机械在提高压比、减少叶片数、减小展弦比、高强度部分负荷运行等方面所做的努力，导致侧壁附近的流动对发动机整体性能的影响越来越大。尤其是这些流动对工作范围、损失和换热都有影响。虽然几十年来一直在研究，但对其发生机制仍未完全了解。因此，当前的技术进步强烈要求有足够的基础研究活动。德累斯顿理工大学、明尼苏达州立大学和波鸿州立大学的四个研究小组将通过仔细协调的模拟和实验来解决这一不足，以产生相关的结果。除了研究传热学和开发有方法的工具外，这个联合项目的一个主要目标是详细分析系统旋转的影响。在慕尼黑联邦武装力量喷气推进研究所项目部分(TV3)的框架下，对低压涡轮叶栅的端壁流动和换热进行了分析。所研究的非定常端壁流动包括端壁边界层、马蹄涡的形成、对端壁附近吸力面过渡的影响、端壁区域的产油量损失、端壁和叶片表面的换热及其对潜在冷却方式的影响。为了产生更真实的端壁流动，将在高速叶栅风洞中实施一种新的改进设置，其特点是额外插入端壁，这是获得显著结果的关键因素。实验将利用多种高空间分辨率(PIV)、高时间分辨率(CTA、Kulite)以及表面测量(TSP、Thermo-LC、Sher-LC)的流量测量方法进行。实验研究将得到数值模拟(URANS)的支持，URANS采用高保真热流模型，使用流动求解器轨迹。研究项目部分的科学目标是加深对周期性非定常流入与端壁流动、端壁边界层和换热相互作用机理的理解，并评价RANS方法对这些流动现象的预测能力。此外，与项目合作伙伴(特别是TV4)的调查结果的比较提供了关于线性叶栅和轴流涡轮机中流动现象的异同的信息。

Current efforts in turbomachinery to increase pressure ratio, reduce blade count, decrease the aspect ratio, intense part load operation, etc. lead to increasing influence of flows near the side walls on the overall engine performance. Especially the operating range, losses and heat transfer are influenced by these flows. The occurring mechanisms are not fully understood although being investigated since decades. Thus the current technological progress strongly requests adequate basic research activity. This deficit will be addressed by a joint research program of four research groups at TU Dresden, UniBw München und RU Bochum, by carefully coordinated simulations and experiments to produce relevant results. Beside the investigation of heat transfer and the development of methodical tools a major goal of this joint program is the detailed analysis of the effect of system rotation. Therefore a number of specially planed and adjusted configurations will be investigated and compared with each other.Within the framework of the project part (TV3) at the Institute of Jet Propulsion of the University of the Federal Armed Forces Munich, the endwall flow and heat transfer will be analyzed in a low pressure turbine cascade. The array of investigated aspects of the unsteady endwall flow include the endwall boundary layer, the formation of the horse shoe vortex, influence on suction surface transition near the endwall, loss production in the endwall region, as well as heat transfer to the endwall and blade surfaces and its effect on potential cooling methods. A new and improved setup, featuring an additional inserted endwall, will be implemented in the High Speed Cascade Wind Tunnel in order to produce more realistic endwall flow, which is a critical factor in attaining significant results. The experiments will be conducted utilizing a multitude of flow measurement methods with high spatial resolution (PIV), high time resolution (CTA, Kulite), as well as surface measurements (TSP, Thermo-LC, Shear-LC). The experimental investigations will be supported by numerical simulations (URANS) with high fidelity heat flux modeling, using the flow solver TRACE. The scientific goal of the research project part is to improve the understanding of the interaction mechanisms of the periodically unsteady inflow with the endwall flow, the endwall boundary layer and heat transfer as well as to evaluate the capabilities of the RANS method to predict these flow phenomena. Furthermore, comparisons of the investigation results with the project partners (especially TV4) provide information regarding the similarities and differences of flow phenomena in linear cascades and axial turbines.