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On the figure of merit and streamwise flow of a propulsive rotor with synthetic jets

机译：用合成射流的推进转子的优点和流动流程图

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Increasing the figure of merit of propulsive rotors for vertical takeoff and landing (VTOL) vehicles is critical to improving the hover efficiency and flight endurance of rotorcraft. In this paper, a new flow control scheme is proposed where 60 synthetic jet actuators are utilized on a large-scale propulsive rotor and the jets' velocity is increased from the blade root to the blade tip in order maintain constant levels of momentum coefficient per blade module. The three-bladed rotor measures 2.58 m in diameter and contains a NACA 0012 airfoil with zero blade twist distribution. The rotor was tested at speeds of 250, 500, 750 and 1,000 revolutions per minute (RPM) and blade pitch angles of 2, 5, and 8 degrees. Rotor thrust and power were measured using a high-capacity load cell and current sensor, and the streamwise flow was measured using phased-locked laser Doppler velocimetry (LDV) techniques at two measurement planes near the blade root and near the blade tip along the suction surface of the airfoil. Two flow control schemes were tested and compared; the new constant momentum coefficient (constant C-mu) and non-constant C-mu where the synthetic jet velocity is held constant throughout the rotor blade. When all 20 synthetic jets per blade are activated, it was found that constant C-mu improves low-speed rotor performance in terms of figure of merit, FM and thrust coefficient, C-T at 250 RPM, while non-constant C-mu is marginally superior at higher rotor speeds. When both flow control schemes are applied for just the blade root module, an increase in performance compared to the baseline is observed at rotor speeds of 750 and 1000 RPM, however different values of FM and C-T are achieved for each scheme. Near the blade tip the boundary layers undergo transition to turbulent flow combined with an increasing degree of adverse pressure gradient with rotor speed and blade pitch angle. Under these conditions where the normalized streamwise velocity profiles show significant velocity deficit in the near-wall flow, synthetic jets provide some momentum to delay separation as quantified by the boundary layer shape factor. (C) 2021 Elsevier Masson SAS. All rights reserved.
机译：增加推进转子的品质因数为垂直起飞和着陆（VTOL）的车辆是提高旋翼飞行器的悬停效率和耐力飞行关键。在本文中，一个新的流控制方案，提出了其中60合成射流致动器被使用于大规模推进转子和射流速度从叶片根部，以便增加叶片尖端保持每个刀片动量系数的恒定水平模块。的三叶片转子措施2.58米直径并且含有NACA 0012翼型具有零叶片扭曲分布。转子以每分钟（RPM）和2，图5和8度的叶片桨距角250，500，750和1000转的速度进行测试。转子的推力和功率使用高容量的负载传感器和电流传感器检测，并且使用相控锁定激光多普勒测速仪（LDV）技术测定顺流流量在两个测量平面附近的叶片根部和沿着吸入叶片尖端附近翼型件表面。两个流动控制方案进行了测试并比较;新的恒定动量系数（常数C-MU）和非恒定C-亩其中合成射流速度在整个转子叶片保持恒定。当每个刀片所有20个合成射流被激活时，人们发现，常数C-亩改善品质因数方面的低速转子的性能，FM和推力系数，CT以250RPM，而非恒定C-mu是轻微优越在较高的转子速度。当两个流动控制方案被应用于只是叶片根部模块，增加性能与基线相比，在750和1000rpm的转子转速观察到，但是FM和C-T的不同的值对于每个方案来实现的。靠近叶片尖端的边界层迁移为紊流与转子速度和叶片桨距角反向压力梯度的增加程度结合。在这些条件下，其中的归一化流向速度曲线显示在近壁流显著速度逆差，合成射流提供一些动力到延迟分离由边界层形状因子进行定量。 （c）2021 Elsevier Masson SAS。版权所有。

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