Turbine Broadband Noise Predictions Using Linearised Frequency Domain Navier-Stokes Solvers

Ricardo Blázquez-Navarro,Roque Corral

doi:10.3390/ijtpp6040042

Abstract

A linear frequency domain Navier-Stokes solver is used to retain the influence of turning, thickness, and main geometric parameters on turbine broadband noise. The methodology has been applied to predict the broadband interaction noise produced by a representative low-speed low-pressure turbine section. The differences in the spectra with respect to those yielded by state-of-the-art flat plate based methodologies are up to 6 dB. The differences are caused by multiple effects that semi-analytical methodologies do not account for. The most important are blade thickness and turning, which have been studied separately to quantify their impact on the broadband noise footprint. The influence of changing the turbine operating conditions has been discussed as well. The outlet sound pressure level scales with the third and second power of the inlet and outlet Mach number, respectively, for constant turbulence intensity, within most of the frequency range considered.

Highlights

Since the last decade, there has been an increasing concern regarding the impact of turbine-generated broadband noise in the context of civil aviation
Regarding turbine noise sources break-down, Serrano et al [2] quantified experimentally the relative importance of turbine broadband noise, which can result in being dominant in many operating points and designs and there is a need of industrial methods to predict it accurately
A baseline operating point, OP1, which can be considered as the On-Design conditions, has been run

Summary

Introduction

There has been an increasing concern regarding the impact of turbine-generated broadband noise in the context of civil aviation. Nesbitt [1] described what he considered a ’turbine noise storm’ caused by the confluence of several design choices. Their reduced blade-count and solidity, the removal of acoustic liner treatments to reduce engine weight, and the reduction of noise emissions by other engine components. Regarding turbine noise sources break-down, Serrano et al [2] quantified experimentally the relative importance of turbine broadband noise, which can result in being dominant in many operating points and designs and there is a need of industrial methods to predict it accurately. Turbulent wakes generated by a turbine row (see Figure 1) impinge on the downstream one, giving rise to acoustic waves with a broadband energy content

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Conclusion