Investigation on influence of nacelle chine of large civil transport aircraft on high-lift efficiency and on influence of relevant parameters

Carefully considering the landing configuration of a large civil transport aircraft, we apply the CFD computational method and mesh generation strategy, whose validity is confirmed by wind tunnel experiments conducted by us, to study the influence of nacelle chine on high-lift efficiency. The results show that the flow mechanism of nacelle chine is similar to that of large sweep delta wing. The intensity and the location of vortex flow, which are induced by nacelle chine, are the key elements of high-lift efficiency. Moving the vortex outer or downward or enhancing its intensity can increase high-lift efficiency. Through putting nacelle chine downward, the vortex will be moved downward and outboard of wing, but the influence of intensity will not show a monotonic way. The vortex will move upward and inboard of wing and its intensity will be enhanced by putting nacelle chine backward. Increasing the angle incidence or obliquity of nacelle chine can move the vortex upward and outboard of wing, and both of them can increase the intensity of vortex. Increasing the sweep angle (reducing the area near leading edge) of nacelle chine will move the vortex downward and outboard of wing, but its intensity will be reduced. Therefore, the influence of these parameters (location, angle of incidence and so on) upon high-lift efficiency are not monotonic. Getting the optimum parameter combination needs a lot of analysis of flow fields. Besides, the design of nacelle chine will be restricted by cruise configuration, the reverse thrust device and the structure of engines; they must be taken into consideration in design process.