Jet Noise Reduction for High Speed Exhaust Systems

2008 ◽  
Author(s):  
Steven Martens ◽  
Ludwig Haber
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
High Performance ◽  
Jet Noise ◽  
Military Bases ◽  
The Past ◽  
Business Jet ◽  
Mixing Characteristics ◽  
Difficult Challenge ◽  
Exhaust Systems

Jet noise has been an environmental issue since the advent of jet aircraft. The past five decades have seen much research into solving this very difficult challenge for a variety of applications. The Supersonic Transport (SST), High Speed Civil Transport (HSCT), and a variety of supersonic business jet (SSBJ) applications all face significant jet noise challenges. Jet noise from high performance military aircraft has also received growing attention. The continuous drive to higher specific thrust results in increasing jet noise levels. Compounding this is that many military bases, Naval in particular, are located in desirable locations on the coast, and surrounding communities are encroaching closer to these bases. In this paper we will conduct a survey of some jet noise reduction technologies for high-speed exhaust systems investigated in the past, as well as some of the implementation issues associated with them. Specific technologies aimed at changing the mixing characteristics of the jet plume after it leaves the nozzle will be discussed in detail, including chevrons and fluidic injection. Other noise reduction technologies, such as the inverted velocity profile, and fluid shield can also change the mixing characteristics of the jet plume. This includes the added benefit of noise reflection or shielding. Measured data will be presented to show the effect these technologies have on high-speed jets.

Adaptation of the Beveled Nozzle for High-Speed Jet Noise Reduction

AIAA Journal ◽  
2011 ◽  
Vol 49 (5) ◽  
pp. 932-944 ◽  
Author(s):  
K. Viswanathan ◽  
M. J. Czech
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Jet Noise

High-Speed Jet Noise Reduction Using Microjets on a Jet Engine

2004 ◽  
Author(s):  
Brenton Greska ◽  
Anjaneyulu Krothapalli ◽  
Nathan Burnside ◽  
William Horne
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Jet Noise ◽  
Jet Engine

Simultaneous Noise and Performance Measurements for High-Speed Jet Noise Reduction Technologies

2009 ◽  
Author(s):  
Dean Long ◽  
Steven Martens
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Near Field ◽  
Jet Noise ◽  
Source Distribution ◽  
Test Facility ◽  
Wave Radiation ◽  
Far Field ◽  
Shock Cell ◽  
Field Noise

Model scale tests are conducted to assess the Noise/Performance trade for high speed jet noise reduction technologies. It is demonstrated that measuring the near field acoustic signature with a microphone array can be used to assess the far field noise using a procedure known as acoustic holography. The near field noise measurement is mathematically propagated producing an estimate of the noise level at the new location. Outward propagation produces an estimate of the far field noise. Propagation toward the jet axis produces the source distribution. Tests are conducted on convergent/divergent nozzles with three different area ratios, and several different chevron geometries. Noise is characterized by two independent processes: Shock cell noise radiating in the forward quadrant is produced when the nozzle is operated at non-ideally expanded conditions. Mach wave radiation propagates into the aft quadrant when the exhaust temperature is elevated. These results show good agreement with actual far field measurements from tests in the GE Cell 41 Acoustic Test Facility. Simultaneous performance measurement shows the change in thrust coefficient for different test conditions and configurations. Chevrons attached to the nozzle exit can reduce the noise by several dB at the expense of a minimal thrust loss.

Acoustics measurements of military-style supersonic beveled nozzle jets with interior corrugations

2016 ◽  
Vol 16 (1-2) ◽  
pp. 21-43 ◽  
Author(s):  
Russell W Powers ◽  
Dennis K McLaughlin
Keyword(s):  
Noise Reduction ◽  
Acoustic Field ◽  
High Speed ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Operating Conditions ◽  
Military Aircraft ◽  
Azimuthal Dependence ◽  
Penn State ◽  
Mixing Noise

Increasingly powerful and noisy military aircraft have generated the need for research leading to the development of supersonic jet noise reduction devices. The hot, high speed supersonic jets exhausting from military aircraft during takeoff present a most challenging problem. The present study extends prior research on two methods of noise reduction. The first is the internal nozzle corrugations pioneered by Seiner et al. and the second is the beveled exit plane explored most recently by Viswanathan. A novel research idea of creating fluidic corrugations similar to the nozzle corrugations has been initiated by Penn State. To further the understanding and analysis of the fluidic corrugations, the present study focuses on the flow field and acoustic field of nozzles with two, three, and six conventional, hardwalled corrugations. The effect of the combination of the internal corrugations with a beveled nozzle is explored. The results show that significant noise reductions of over 3 dB of the mixing noise and the broadband shock-associated noise can be achieved. The combination of the beveled nozzle and the internal nozzle corrugations showed that there is less azimuthal dependence of the acoustic field than for the purely beveled nozzle. The combination nozzle was shown to reduce the noise over a wider range of polar angles and operating conditions than either the purely beveled nozzle or the purely corrugated nozzle.

Prediction, Experiments and Optimization of High-Speed Jet Noise Reduction Using Fluidic Inserts

2014 ◽  
Author(s):  
Philip J. Morris ◽  
Dennis K. McLaughlin ◽  
Russell W. Powers ◽  
Matthew J. Kapusta
Keyword(s):  
Noise Reduction ◽  
High Speed ◽  
Jet Noise

The generation of sound in turbulent motion

2008 ◽  
Vol 112 (1133) ◽  
pp. 381-394 ◽  
Author(s):  
G. M. Lilley
Keyword(s):  
Noise Reduction ◽  
Turbulent Flows ◽  
High Speed ◽  
Experimental Studies ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Aerodynamic Noise ◽  
Turbulent Shear ◽  
Noise Generation ◽  
Physical Mechanisms

Abstract The present paper reviews and discusses the physical mechanisms of noise generation and reduction in turbulent flows with their applications towards aircraft noise reduction at takeoff and on the approach. This work began in 1948 when Lilley undertook an experimental investigation into the source of jet noise as a necessary precursor to finding methods for the reduction of high speed jet engine noise on civil jet airliners. Westley and Lilley completed this experimental programme in 1951, which included the design of a range of devices for high speed jet noise reduction. It was about this time that similar studies on jet noise were being started elsewhere and in particular by Lassiter and Hubbard in USA. The major contribution to the subject of turbulence as a source of noise came from Sir James Lighthill’s remarkable theory in 1952. In spite of the difficulties attached to theoretical and experimental studies on noise from turbulence, it is shown that with the accumulated knowledge on aerodynamic noise over the past 50 years, together with an optimisation of aircraft operations including flight trajectories, we are today on the threshold of approaching the design of commercial aircraft with turbofan propulsion engines that will not be heard above the background noise of the airport at takeoff and landing beyond 1-2km, from the airport boundary fence. It is evident that in the application of this work, which centres on the physical mechanisms relating to the generation of noise from turbulence and turbulent shear flows, to jet noise, there is not one unique mechanism of jet noise generation for all jet Mach numbers. This author in this publication has concentrated on what appears to be the dominant mechanism of noise generation from turbulence, where the mean convection speeds of the turbulence are subsonic. The noise generated at transonic and supersonic jet speeds invariably involves extra mechanisms, which are only briefly referred to here.

Influence of Microjet Condition on Characteristics of Supersonic Jet Noise and Flow Field

2012 ◽  
Author(s):  
Ryuichi Okada ◽  
Toshinori Watanabe ◽  
Seiji Uzawa ◽  
Takehiro Himeno ◽  
Tsutomu Oishi
Keyword(s):  
Flow Field ◽  
Noise Reduction ◽  
High Speed ◽  
Supersonic Jet ◽  
Jet Noise ◽  
Experimental Investigations ◽  
Acoustic Measurements ◽  
Supersonic Transport ◽  
Supersonic Jet Noise ◽  
Supersonic Aircraft

Jet noise reduction is essential for environmentally-friendly civil transport. Since jet noise becomes very intense in the case of supersonic aircraft, noise reduction is crucial topic for the realization of next-generation supersonic transport. In the present study, experimental investigations were performed to clarify the effect of microjet injection on supersonic jet noise and flow field. The experiments were focused on supersonic jet with Mach number up to 1.47, which was generated from a rectangular nozzle with high aspect ratio. Far-field acoustic measurements were conducted for widely ranged microjet conditions to understand the influence of the condition on characteristics of supersonic jet noise and flow field. For understanding the unsteady behavior of the flow field and the relation with noise reduction, flow field visualization was performed with schlieren technique using a high-speed camera.

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