Yoshiya Nakamura

Low Noise FEGV Designed by Numerical Method Based on CFD

This paper describes a low noise FEGV (Fan Exit Guide Vane), which is designed by a fan noise prediction method based on CFD. Fan noise is predicted by a hybrid scheme, which is the combination of three-dimensional CFD and three-dimensional linear theory. Characteristics of noise sources are investigated in some kinds of FEGV shapes. High amplitude areas spread not only along the leading edge but also in the span-wise positions along the mid-chord. It is found that high amplitude areas around the mid-chord make an important role in noise generation, and appropriate aft-ward swept angle and span-wise distribution of leaned angle could reduce the amplitude of the noise sources keeping aerodynamic performance. A fan noise test for fan scale models has been conducted at an anechoic test facility in IHI Mizuho to demonstrate noise reduction and performance of low noise FEGV. Noise reduction can be achieved keeping aerodynamic performance compared to conventional straight FEGV.Copyright

Investigation of Acoustic Modes Generated by Rotor-Stator Interaction

This paper describes characteristics of the unsteady loadings on the stator surface generated by fan rotor-stator interaction and acoustic modes in a fan duct. Three-dimensional unsteady CFD analysis and three-dimensional linear theory method were performed to predict the unsteady loadings, and the both results agree well. The remarkable point is that the high amplitude areas arrayed in the span-wise direction on the mid-chord were observed. It can be shown that three-dimensional linear theory, which is useful for parametric study due to an advantage of less calculation time, has a potential to predict the characteristics of the unsteady loadings, although it includes some assumptions. Through parametric study, it is found that the high amplitude areas arrayed on the mid-chord are amplified suddenly as parameters satisfy a condition. The parameters were identified, and it comes to be clear that the characteristics of the unsteady loadings are much influenced by the high amplitude areas and their amplification. It is also found that as the rotor-stator spacing is stretched, the amplitude of the unsteady loadings does not attenuate monotonously, but attenuates with oscillating. Not only the amplitude of the unsteady loadings but also the array of them on the mid-chord affects the acoustic power levels, because it makes the specific radial mode dominant. Up to 10dB difference can be found whether the dominant mode is “cut-on” or “cut-off”. It can be said that to understand the characteristics of the unsteady loadings on the mid-chord is very important to reduce and control the fan noise generated by rotor-stator interaction.

Mixer-Ejector Noise Characteristics with Aerodynamic Performances

A 2D mixer-ejector nozzle device with the acoustically lined wall has been developed for jet noise reduction to achieve the noise level equivalent to ICAO Annex 16 Chapter 3 regulation with minimum thrust losses. In order to investigate flight effects on noise reduction and thrust losses, flight model test were made at the CEPRA19 anechoic wind tunnel in France. Upstream flow conditions of mixer such as velocity profile and temperature profile were simulated as close as the real engine. In this report, some of above experimental test results are presented including noise reduction characteristics by the porous ceramic matrix composites acoustic liner inserted to the ejector shroud and the trend of thrust losses of the mixer ejector nozzle in forward flight. NOMENCLATURE CEPRA19 anechoic wind tunnel CMC acoustic liner EPNL effective perceived noise level [EPNdB]

Development of High Speed Jet Noise Suppression System

Mixer ejector nozzle devices in scale have been developed for the target to reduce the noise level equivalent to ICAO Annex 16 Chapter 3 regulation with minimum thrust losses. On this paper, a parametric study of mixer ejector nozzle configurations with acoustic liner has been conducted acoustically assuming at static to flight speed. Then upstream nozzle conditions of the mixer with velocity profile and temperature profile were simulated to the uniform flow. For high temperature (HOOK) jet core condition, acoustic liner performance tuned at inner surface of ejector were very important to reduce jet mixing noise generated by mixer lobes inside the ejector especially. Mixer ejector configurations were changed by focusing the mixer shape and mixer lobes number and lobes numbers were important not only enhance of mixing but also attenuation by acoustic liner. Also heat resistive material which was made by porous CMC (ceramic matrix composites) was applied to the acoustic liner and the noise attenuation were ranked with the other existing liner. The mixer ejector noise suppression device including porous ceramic acoustic liner has been defined for the HYPR90-TURBO sub-scale (1/2.6) demonstrator engine which is planned to be tested for noise in the summer of 1997.

Large Eddy Simulation Analysis of Lobed Mixer Nozzle

Large Eddy Simulation (LES) was applied to predict the mixing characteristics of a lobed mixer nozzle analysis. LES was first validated by using experimental data of a convergent-divergent nozzle (CD nozzle) flow. Then, the LES results of the lobed mixer nozzle with a ejector duct were evaluated by comparing with measured data. LES analysis provided more reasonable agreement than Reynolds-averaged Navier Stokes (RANS) analysis.

Development of Mixer-Ejector with Ceramic Acoustic Liner

The capability of jet noise reduction by using mixer ejector nozzle with ceramic acoustic liner was demonstrated in the engine noise test under the international research program on the future SST/HST propulsion system called HYPR sponsored by Japanese government. In the initial phase of the program the engine cycle and the configuration was selected considering that one of a critical issue for the next generation SST is a engine noise which is a strong function of the exhaust jet velocity. Through the series of model tests in the anechoic wind tunnel, the configuration of mixer ejector for the engine noise demonstration test was selected by optimising design parameters of mixer lobe, ejector duct, and acoustic liners to achieve maximum noise reduction with minimum thrust loss. Useful data such as far field noise shape, induct acoustic signals, jet noise source distribution, and the effect of mixer ejector with and without acoustic liner were obtained and the noise control technology for the next generation SST was developed through the program. It was found that the improvement of the acoustic liner material is one of the most important area for the mixer ejector configuration as a noise suppresser.