スプライン断面を有する可変ノズルの音響・推力特性

抄録

This paper proposes a new concept of a noise reduction nozzle and describes the sensitivity analysis of the nozzle's acoustic and thrust characteristics. The proposed concept envisages a variable nozzle that enables a change in cross-section and reduction of noise by a single mechanism. Under takeoff conditions, the nozzle has a convergent shape with teeth and slots similar to those of a spline hub, which enables noise reduction. On the other hand, under cruise conditions, the shape of the nozzle can be altered from convergent to a clean convergent-divergent configuration. This concept has been validated by scale model tests in a jet noise facility, and the sensitivity of the acoustic and thrust characteristics has been analyzed using numerical analysis. The analysis revealed that the acoustic benefit depends on the depth of slot, and its frequency characteristics depend on the number of slot. Thrust loss strongly depends on the nozzle throat position and weakly depends on the number of slot. The proposed concept has the potential to provide significant acoustic benefits relative to the thrust loss, and the results of the sensitivity analysis enable us to design appropriate nozzle geometry.