Abstract: An initial geometry for a nacelle provides an intake at the upstream end of the nacelle and an exhaust at the downstream end of the nacelle. The intake has in flow series, an intake lip and a diffuser. The intake lip has a highlight defining the boundary between the inner and outer surfaces of the intake lip. On all longitudinal sections containing the axis of the engine (i) the inner and outer surfaces are tangency matched at the highlight, and (ii) the inner and outer surfaces have their maximum curvatures at the highlight.

Abstract: A method of designing a nacelle for a gas turbine engine includes defining an initial geometry for the nacelle, pivoting, at each of one or more positions on a highlight and in a plane of a respective longitudinal section, a front portion of a section of an intake lip lying in the respective longitudinal section about the highlight, and obtaining an altered geometry for the nacelle by adjusting surfaces of the intake neighboring the pivoted front portion to smoothly blend the surfaces of the pivoted front portion to unadjusted surfaces of the intake further removed from the pivoted front portion.

Abstract: A nacelle for a gas turbine engine has an intake at the upstream end of the nacelle and an exhaust at the downstream end of the nacelle. The intake has, an intake lip and a diffuser. The diffuser has a main diffuser section and an optional shorter straight wall diffuser section. The main diffuser section is bounded by an inner wall of the nacelle, the inner wall curving in the airflow direction of the engine. On each longitudinal section containing the engine axis, at the downstream end of the main diffuser section the inner wall has a non zero curvature. Thus each circumferential position on the inner wall at the downstream end of the main diffuser section has a curvature defined by a respective radius of curvature. However, one or more of the radii of curvature differ from the others of the radii of curvature.

Abstract: An initial geometry for a nacelle provides an intake at the upstream end of the nacelle and an exhaust at the downstream end of the nacelle. The intake has, in flow series/an intake lip and a diffuser. The intake lip has a highlight defining the boundary between the inner and outer surfaces of the intake lip. On all longitudinal sections containing the axis of the engine (i) the inner and outer surfaces are tangency matched at the highlight, and (ii) the inner and outer surfaces have their maximum curvatures at the highlight.

Abstract: A nacelle for a gas turbine engine has an intake at the upstream end of the nacelle and an exhaust at the downstream end of the nacelle. The intake has, an intake lip and a diffuser. The diffuser has a main diffuser section and an optional shorter straight wall diffuser section. The main diffuser section is bounded by an inner wall of the nacelle, the inner wall curving in the airflow direction of the engine. On each longitudinal section containing the engine axis, at the downstream end of the main diffuser section the inner wall has a non zero curvature. Thus each circumferential position on the inner wall at the downstream end of the main diffuser section has a curvature defined by a respective radius of curvature. However, one or more of the radii of curvature differ from the others of the radii of curvature.

Abstract: An initial geometry for a nacelle provides an intake at the upstream end of the nacelle and an exhaust at the downstream end of the nacelle. The intake has in flow series, an intake lip and a diffuser. The intake lip has a highlight defining the boundary between the inner and outer surfaces of the intake lip. On all longitudinal sections containing the axis of the engine (i) the inner and outer surfaces are tangency matched at the highlight, and (ii) the inner and outer surfaces have their maximum curvatures at the highlight.