This paper explores the effect of speed ratio and axial spacing between high aspect ratio, low speed contra-rotating pair rotors on their aerodynamic performance. The blades were designed with a low hub-tip ratio of 0.35 and an aspect ratio of 3.0. Numerical and experimental studies are carried out on these contra-rotating rotors operating at a Reynolds number of 1.258 × 105 (based on blade chord). The first and second rotors were designed to develop a pressure rise of 1100 Pa and 900 Pa, respectively, for total mass flow rate of 6 kg/s when both operating at a design speed of 2400 rpm. The performance of the fan was evaluated based on variations of total pressure and flow angles at off-design operating conditions. The measurementsof total pressure rise, flow angles etc. are taken upstream of the first rotor and in between the two rotors and downstream of the second rotor. The performance of the contra rotating stage is mainly influenced by the axial spacing between the rotors and speed ratio of both the rotors. The study reveals that the aerodynamics of the contra-rotating stage and stall margin is significantly affected by both the speed ratio as well as the axial spacing between the rotors. It was found that with increasing the speed ratio, the strong suction generated by the second rotor, improves the stage pressure rise and stall margin. Lower axial spacing changes the flow incidence to the second rotor and thereby improves the overall performance of the stage. This however, is accompanied by an increased noise level. The performance is investigated at different speed ratios of the rotors at varying axial spacing. Detailed numerical simulations have been conducted using ANSYS CFX13 using mixing plane approach between rotors. Numerical simulations are compared with experimental results at off-design conditions. These results are validated using the experimental data. Numerical simulations are expected to provide deeper insight into the flow physics of contra-rotating rotors which may be difficult to capture experimentally.
展开▼
机译：本文探讨了高长宽比，低速对转双转子之间的速比和轴向间距对其气动性能的影响。叶片的轮毂尖端比低，为0.35，长径比为3.0。对以1.258×105（基于叶片弦）的雷诺数运行的这些对转转子进行了数值和实验研究。当两个转子均以2400 rpm的设计速度运行时，第一转子和第二转子的压力上升分别设计为1100 Pa和900 Pa，总质量流量为6 kg / s。根据非设计运行条件下总压力和流角的变化评估了风扇的性能。总压力上升，流角等的测量是在第一转子的上游，两个转子之间以及第二转子的下游进行的。反向旋转级的性能主要受转子之间的轴向间距和两个转子的速比的影响。研究表明，反向旋转级和失速裕度的空气动力学特性受速比以及转子之间的轴向间距的影响很大。发现随着速度比的增加，第二转子产生的强劲吸力改善了级压力上升和失速裕度。较小的轴向间距改变了流向第二转子的流量，从而提高了平台的整体性能。然而，这伴随着噪声水平的增加。在不同的轴向间隔下，在转子的不同速比下研究性能。使用ANSYS CFX13使用转子之间的混合平面方法进行了详细的数值模拟。将数值模拟与非设计条件下的实验结果进行了比较。使用实验数据验证了这些结果。数值模拟有望为对转转子的流动物理学提供更深入的了解，而这在实验上可能很难捕获。
展开▼
