Effect of Number and Spacing of Pre-cooled Turbojet Engines on Takeoff Noise of Hypersonic Transport

Abstract

The pre-cooled turbojet (PCTJ) engine which will be installed in a hypersonic transport has been studied in the Japan Aerospace Exploration Agency. The takeoff noise reduction is one of the most important technical issues in the development of a high-speed propulsion. Engine/airframe integration is quite important in terms of not only the propulsion performance but also the acoustics radiation. In this study, the effect of the engine number, engine spacing and ramp length on the noise radiation characteristics from the multiple jet is investigated. Acoustic data for the ramp, sidewall and cowl directions are acquired. For sidewall direction cases, the sound intensity is not proportional to the number of engines; smaller than simple expectation since nearby jet shields the noise from the far side jet. For cowl direction cases, the sound intensity is also smaller than simple expectation since turbulent kinematic energy generation is hindered between the neighboring jets.