Experimental study of exhaust noise generated by pulsating flow downstream of pipe end

Higashiyama, Junji; Iwamoto, Junjiro

doi:10.1016/s0389-4304(98)00038-1

Cited by 11 publications

(14 citation statements)

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“…Understanding shock-vortex loop interaction phenomena are important for noise detection/reduction in high speed flows [20][21][22] and the automobile exhaust flow fields [23][24][25]. Since the early 1990s, there have been experimental, numerical, and theoretical investigations of shock wave interaction with vortex rings [20-22, 26, 27].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional shock wave distortion in shock-square vortex loop interaction

Ukai

Zare‐Behtash

Kontis

et al. 2016

Experimental Thermal and Fluid Science

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Abstract:Understanding of the three-dimensional shock wave-vortex loop interaction phenomena plays a key role in noise reduction. This study focuses on the three-dimensional shock wave distortion and propagation phenomena in a near-field supersonic jet. Shock-square vortex loop interaction was experimentally investigated in a square cross-sectional open-end shock wave generating tube at an incident shock Mach number of 1.39 ± 0.05. A square vortex loop impinged on a reflected shock wave from a wall located in front of the nozzle end. The planar reflected shock wave transforms into either a concave or convex distorted shape due to the opposing high-speed flow emitted from the nozzle corner. The convex shaped shock wave scatters towards the outside of the vortex loop, whereas the concave one converges towards the centre of the vortex loop. The concave shaped shock wave results in shock wave focusing. In shock-square vortex loop interaction, the shock wave is locally focused along the axis of the nozzle corner. Keywords:Shock wave interaction; square vortex loop; shock wave focusing 2

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Section: Introductionmentioning

confidence: 99%

Three-dimensional shock wave distortion in shock-square vortex loop interaction

Ukai

Zare‐Behtash

Kontis

et al. 2016

Experimental Thermal and Fluid Science

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“…Estas técnicas se aplican en general a medidas de intensimetría acústica [119,148,166] (medidas realizadas con antenas focalizadas sobre las diferentes fuentes bajo estudio), o bien medidas directas de vibración mediante acelerómetros [179]. Además de estas técnicas, en la actualidad se está aumentando el empleo de técnicas de análisis espectral tiempo-frecuencia, como transformadas de Wavelets [53], de Hilbert o incluso el uso de distribuciones de Wigner [74]. Estasúltimas técnicas, permiten obtener una mayor información sobre los mecanismos de generación sonora, ya que, dan información no sólo de su característica espectral (amplitud, frecuencia), sino también de su comportamiento en el tiempo: estacionario o transitorio.…”

Section: Fuentes De Ruido En El Motorunclassified

“…Por otro lado, a esta generación sonora contribuye la interacción existente entre el flujo subexpandido en esta sección y los anillos vorticales generados en su entorno [74]. Este fenómeno presenta cierta complejidad debido a su carácter de patrón de flujo no estacionario, caso en el que no resulta trivial separar su contribución de la correspondiente a las propias fluctuaciones del flujo.…”

Section: Fuentes De Ruido En El Motorunclassified

“…Es este un problema suficientemente complejo y relevante, si se tiene en cuenta que lo que se pretende es disminuir el ruido emitido teniendo en mente cualquier efecto negativo que un cambio en la línea de escape puede tener sobre las prestaciones del motor [74]. deben tener en cuenta varios factores asociados a su problemática particular.…”

Section: Fuentes De Ruido En El Motorunclassified

“…Enél coexisten diferentes fuentes tales como el motor de combustión interna alternativo, la interacción con el aire circundante, la contribución del sistema motriz, y la interacción de las ruedas con el firme que se transmiten al habitáculo a través de la suspensión [74]. En este trabajo nos centraremos en el estudio de la contribución del motor, que ya es en sí un problema suficientemente complejo, eliminando de este modo, contribuciones como la del flujo alrededor del cuerpo del automóvil, que debido a las altas velocidades que adquiere el flujo es considerada como una de las fuentes principales del ruido del tráfico.…”

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Contribución al estudio y caracterización de la generación de ruido de flujo en el sistema de escape.

Verdú¹,

Concepción²

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The studies of the vehicle noise emissions has been acquired a great relevance over the last few years for two reasons: (1) the increased social sensitivity to environmental contamination phenomena among which acoustic contamination is found, and (2) to the highest market requirements (higher "capability"vehicles at the same time as more comfortable ones: acoustic comfort).Within the complexity of the vehicle acoustic generation phenomena in this doctoral thesis, we will focus on one of the engine contributions: the exhaust noise. This component of noise is the result of two different phenomena: pulsating noise originated in the gas exchange process in the cylinders, and the flow noise induced by the turbulence phenomena developed by the mean flow that goes through the exhaust system. From these two phenomena the core of our study is flow noise and its prediction, under the motivation that as well as the pulsating noise being extensively studied and there being some prediction methods in it, the flow noise is unknown to a great extent. To this we should add, that while the pulsating noise contribution, main source, has been reduced the flow noise contribution has become more and more important in exhaust noise. The relevance of flow noise contribution is associated with its interaction with the acoustics in the system (it could amplify the main source contribution) and the existence of mufflers that work as flow noise generation sources.For the flow noise contribution study, the present doctoral thesis has been structured in six well-defined chapters.In the first chapter there is a summary of the different contributions that can be distinguished in the overall vehicle emitted noise. The importance of the flow noise study is justified from the present state of knowledge in this subject, and also the methodology bases used to perform it.In the second chapter, an experimental procedure for the estimation of the volume velocity fluctuation at the open end of the exhaust tailpipe of an internal combustion engine is presented. The different physical mechanisms involved in the emission process are analysed through the introduction of a realistic emission model. The possibility to consider that the pulsating component of the noise and the flow noise are decoupled to a certain extent is established, which means that this last component is generated by a mean "steady" flow superimposed to a pulsating flow. 8Once the possibility of studying the contribution of flow noise generated during the exhaust process as a steady flow effect has been justified. In the third chapter an experimental technique, sound intensity from in-duct measurements, is presented to analyse it. This technique allows the study of the flow noise generation by the individual component of an exhaust system (useful in the automotive industry) on a cold flow test bench. The proposed technique also allows to separate and to know the contributions in the final radiated noise of the internal and external sources of the muffler.Once the experimental pr...

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Noise reduction by using smoothed corner at a duct exit

Shen

Chen

2005

Shock Waves

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Experimental study of exhaust noise generated by pulsating flow downstream of pipe end

Cited by 11 publications

References 0 publications

Three-dimensional shock wave distortion in shock-square vortex loop interaction

Three-dimensional shock wave distortion in shock-square vortex loop interaction

Contribución al estudio y caracterización de la generación de ruido de flujo en el sistema de escape.

Noise reduction by using smoothed corner at a duct exit

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