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An Experimental Investigation of Ground Effect on a Quad Tilt Rotor in Hover

机译：悬停四倾斜转子的地面效应实验研究

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摘要

The performance of a 0.031 geometrically scaled fuselage/wing model of a Quad Tilt Rotor (QTR) operating in helicopter mode while hovering in-ground effect (IGE) and out-of-ground effect (OGE) was experimentally studied. The effect of ground proximity was tested by varying the height of the model above the ground. Measurements included download on the airframe; thrust, torque, and rpm of the rotors; and static pressures along the centerline of the bottom of the fuselage. Fixed-pitch propellers were used to model the rotors. The downwash distributions of the rotors were measured and compared well with large-scale V-22 rotor measurements. Tuft flow visualization was used to identify the physical processes causing changes in the download and static pressure measurements. The uncertainty of the measured quantities was determined to 95% confidence levels. A significant download (9 ± 0.5% of the rotor thrust) was observed in hover, OGE. The download reduced substantially IGE and become an upload (8.5 ± 0.5% of the rotor thrust) when the wheels of the QTR were on the ground. Flow visualization and pressure measurements suggest that the upload IGE is caused by the interaction of the wakes from the four rotors that are turned parallel to the ground and meet under the fuselage. The measured download, coupled with power measurements, indicate that for a given power the available vehicle thrust significantly increases IGE.
机译：实验研究了直升机在悬停地面效应（IGE）和地面效应（OGE）的同时，以直升飞机模式运行的0.031几何比例缩放的机身/机翼模型的性能。通过改变模型在地面上方的高度来测试地面邻近性的影响。测量包括在机身上的下载；转子的推力，转矩和转速；沿机身底部中心线的静压力。使用固定螺距螺旋桨对转子进行建模。测量了转子的向下冲洗分布，并与大型V-22转子测量结果进行了很好的比较。簇流可视化用于识别导致下载和静压测量值发生变化的物理过程。测定量的不确定度确定为95％置信度。在悬停状态（OGE）上观察到大量下载（转子推力的9±0.5％）。当QTR的轮子在地面上时，下载量大大降低了IGE，并变成了上载（转子推力的8.5±0.5％）。流量可视化和压力测量表明，上载IGE是由四个与地面平行并在机身下方汇合的旋翼的尾流相互作用引起的。所测量的下载量与功率测量值一起表明，对于给定的功率，可用的车辆推力会显着增加IGE。

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