Noise predictions of a hypersonic air transport vehicle concept during the landing and take-off cycle

The work described in this article is performed in the framework of the European project HIKARI [1]. The main objective of the HIKARI project is investigating the possibility of designing a high speed transportation aircraft in a joint cooperation between Europe and Japan. This article will describe the noise performance of a pre-cooled turbojet engine for high-speed transport for the landing and take-Off (LTO) cycle. Based on jet noise models, a noise analysis is carried out for a precooled turbojet (PCTJ) engine at certification points (ICAO Annex 16 [2]). A comparison is made with maximum allowable noise levels as provided by ICAO Annex 16 and where possible, certification noise levels of relevant aircraft that are available in open literature. To model the jet of the hypersonic passenger aircraft the semi empirical model of Stone [3] has been used. The jet noise model of Stone consists of a source model for mixing and shock noise. The implemented model has been verified with the measurement results and the predictions of Stone. These three dataset are equal, from which it can be concluded that the model has been implemented correctly. The proposed hypersonic jet has a rectangular shape with a bevel. This shape is not included in the jet noise model of Stone; this model is based on a circular jet. To compensate for this a shape correction is used based on measurements performed by Bridges [4]. The jet noise model of Stone and the shape correction based on Bridges are implemented in NLRs in-house prediction tool Enoise [5]. Enoise uses source models to predict the noise contribution as a function of time at user defined positions. The positions are defined on bases of the ICAO certification points. An ISA atmosphere, spherical spreading, atmospheric attenuation [6] and ground reflection [7] are taken into account. The simulations are based on the input values provided by JAXA for the jet. The flight paths for the LTO cycle are based on conventional take-off and landing procedures (e.g. acceleration/decelerate, climb/descent angle). The final take-off speed and the approach speed are provided by JAXA. The three certification procedures (flyover, lateral full-power and approach) have been simulated with Enoise. During the take-off procedure, for the modelled PCTJ engine, shock noise has the largest contribution in the forward arc. Mixing noise is dominant in the rearward arc. During the approach procedure there is no shock noise contribution, during this approach the jet Mach number is below 1. Once the final input values have been set, an updated calculation will be performed and the results will be evaluated with certification noise levels of relevant aircraft that are available in open literature.