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Dokumentenidentifikation EP1160439 01.02.2007
EP-Veröffentlichungsnummer 0001160439
Titel Strahlmischer für Strahltriebwerke
Anmelder The Boeing Company, Seattle, Wash., US
Erfinder Balzer, Ronald L., Bothell, Washington 98021, US
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 60125279
Vertragsstaaten DE, FR, GB
Sprache des Dokument EN
EP-Anmeldetag 07.05.2001
EP-Aktenzeichen 012016598
EP-Offenlegungsdatum 05.12.2001
EP date of grant 20.12.2006
Veröffentlichungstag im Patentblatt 01.02.2007
IPC-Hauptklasse F02K 1/46(2006.01)A, F, I, 20051017, B, H, EP
IPC-Nebenklasse F02K 1/48(2006.01)A, L, I, 20051017, B, H, EP   F02K 1/38(2006.01)A, L, I, 20051017, B, H, EP   

Beschreibung[en]

Jet engines can produce a high noise level if the velocity of the mass flow exiting the engine is non-uniform and high. For performance considerations, jet engines often have multiple nozzles with the mass flow exiting each nozzle at a different velocity. Since noise radiating from a jet's exhaust increases with the intensity and nonuniformity of the exhaust velocity, jet noise reduction concepts have historically focused on methods for rapidly mixing the flows and achieving a uniform velocity within a short distance of the nozzles.

Various flow-mixing devices have been employed in the past to achieve a uniform velocity within a jet's exhaust and to reduce the noise radiated from the exhaust flow. While those devices have been successful at reducing jet noise, the thrust, drag, and weight penalty associated with those devices have often been of a magnitude that the noise at constant aircraft performance has not been reduced. During the NASA Advanced Subsonic Transport (AST) Program (reference 1) sharp pointed, triangular shaped, extensions added to the sleeve of an external plug primary nozzle were tested and were found to reduce jet noise. A. D. Young et al (US patent 3,153,319) also developed extensions that when added to the trailing edge of nozzles reduced jet noise.

The primary difference between the above-described prior art and the hereinafter described invention is the rounding of the upstream intersection of the extensions with the nozzle and the rounding of the extension's trailing edge. Rounding has been found to enhance the reduction of low frequency noise while inhibiting an increase in high frequency noise. Increased high frequency noise has been a characteristic of the previous sharp edged devices even though they have reduced low frequency noise and have had a net acoustic benefit.

US-A-5,924,632 discloses a segmented nozzle extension for jet engines comprising a triangular shaped, curved extension of the nozzle sleeve, said nozzle extension having a semi-round valley and tip radius to prevent a rise in high frequency noise and loss of thrust.

EP-A-913567 discloses a segmented nozzle extension for jet engines comprising a triangular shaped curved extension of the nozzle sleeve, said nozzle extension having a semi round valley and tip radius to prefent a rise in high frequency noise and loss of thrust.

The present invention provides a segmented nozzle extension for a jet engine according to claim 1.

The present invention also provides a method for reducing noise radiated from a jet engine exhaust flow according to claim 2.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

0005 Figure 1 is a perspective view of a jet engine segmented mixing device with internal plug nacelle;

0006 Figure 2 is illustrative of a jet engine segmented mixing device with internal plug nacelle;

0007 Figure 3 is an aircraft jet engine segmented mixing device with mixed flow nacelle

0008 Figure 4 is a semi-round tip triangular planform showing of a segmented mixing device nozzle sleeve;

0009 Figure 4A is a sectional view taken along the lines A-A of Fig. 4 showing in more detail how the outer surface of the mixing device extensions curve inward towards the engine center line;

0010 Figure 4B is a sectional view taken along the lines B-B of Fig. 4 showing in more detail how the extensions having a planform shape create a streamwise vortex;

0011 Figure 5A is further illustrative of the present trapezoidal planform nozzle sleeve; and,

0012 Figure 5B is illustrative of streamwise vortex flow.

DETAILED DESCRIPTION OF THE INVENTION

0013 The present invention comprises a segmented mixing device which, when applied to the nozzle of a jet engine, enhances mixing between adjacent flows and reduces the noise radiated from the jet's exhaust flow. The device does so with a very small degradation in aircraft performance. The mixing device is a segmented, triangular or trapezoidal shaped, curved extension 1 to a nozzle's sleeve which results in a serrated trailing edge (see Figures 1, 2, and 3). This invention comprises: 1) A modification from the sharp pointed, triangular shaped, nozzle extensions evaluated in the hereinafter referenced NASA AST program to a semi-round, triangular or trapezoidal shaped planform (see Figures 4 and 5). 2) An application of the present nozzle extensions to internal and external plug primary nozzles of dual flow exhaust systems (see Figures 1 and 2). 3) An application of the nozzle extensions to secondary nozzles of dual flow exhaust systems (see Figures 1 and 2). 4) An application of the nozzle extensions to the nozzle of mixed flow exhaust systems and the flow splitter between the primary and secondary streams of those systems (see Figure 3). And, 5) an application of the nozzle extensions to the trailing edge of any surface separating adjacent flows wherein enhanced mixing is desired.

0014 The purpose of the present nozzle extensions 1 is to enhance the natural free mixing of the exhaust flows and to reduce the acoustic energy associated with the velocity differences between the streams in which they are imbedded. The presently configured nozzle extensions enhance the natural free mixing between adjacent streams by forcing the adjacent flows to penetrate into one another to a greater depth than that achievable with free mixing and therefore results in a more uniform flow in a shorter stream wise distance. The acoustic benefit of the extensions increases as the velocity differences between the streams increase. Two methodologies are employed to enhance mixing: 1) The outer surface of the extensions curve inward towards the engine centerline forcing the secondary (outer) flow into the primary (inner) flow (see Figure 4, sec A-A). 2) The extensions have a planform shape that creates a stream wise vortex that also enhances rapid mixing of the two streams (see Figure 4, sec B-B and Figure 5B). Outward turned segments can also be used to enhance mixing. However, the thrust losses for outward turned segments has been greater than for inward turned segments. The present concept however includes rounding to outward turned segments. 0015 Unlike the previous NASA AST configurations and the A. D. Young et al configurations described in U. S. patent 3,153,319, the extensions defined herein incorporate a planform with semi-rounded intersections with the baseline nozzle and semi-round trailing edges. The purpose of the upstream rounding is to increase the strength of the stream wise vortex by allowing the primary (inner) flow to exit the nozzle sooner and in a more radial manner. Rounding the upstream intersection also eliminates the stress concentrations and low fatigue life of the previous NASA AST and A. D. Young et al concepts. Rounding the extension's trailing edge separates the two stream wise vortexes and increases the circumferential surface area available for the secondary (outer) flow to penetrate the primary (inner) flow. In addition, rounding the trailing edge increases the average turning angle of the secondary flow resulting in greater penetration of the secondary flow into the primary flow and increased mixing of the two flows. Rounding has been found to enhance the reduction of low frequency noise while inhibiting an increase in high frequency noise. The increase in high frequency noise has been a characteristic of the previous designs. The nozzle extensions may vary in length, width, curvature, and count being only constrained by the geometry of the baseline nozzle.

References:

  1. 1. D. C. Kenzakowski, J. Shipman, S. M. Dash, J. E. Bridges, and N. H. Saiyed, AIAA-2000-0219, "Turbulence Model Study of Laboratory Jets with Mixing Enhancements for Noise Reduction", January 2000.
  2. 2. A. D. Young et al, U. S. Patent No. 3,153,319, "Jet Noise Suppression Means", October 20, 1964.


Anspruch[de]
Segmentierte Düsenverlängerung für ein Strahltriebwerk, umfassend eine segmentierte, trapezoidförmige, gebogene Verlängerung einer Düsenhülle, wobei eine Draufsicht der Düsenverlängerung eine gezackte Hinterkante umfasst, wobei die Düsenverlängerung eine halbrunde Mulde und eine halbrunde Spitze aufweist, wobei die Düsenverlängerung eine Außenoberflächen aufweist, welche sich nach innen, in Richtung einer Triebwerksmittellinie, biegt, wodurch ein äußerer Strom in einen inneren Strom gedrückt wird, was einen Wirbel in Strömungsrichtung erzeugt, wodurch ein rasches Mischen des äußeren Stroms und des inneren Stroms verbessert wird. Verfahren zur Verringerung von von einem Strahltriebwerkabgasstrom abgestrahlten Lärm durch Verbessern eines natürlichen freien Mischens zwischen benachbarten Gasströmen, umfassend die Schritte: Hinzufügen einer segmentierten, trapezoidförmigen, gebogenen Verlängerung einer Düsenhülle zu einer Gasströmungsbasisdüse, wobei eine Draufsicht der Düsenverlängerung eine gezackte Hinterkante umfasst, wobei die Düsenverlängerung eine halbrunde Mulde und eine halbrunde Spitze aufweist; und Konfigurieren der Verlängerung durch Biegen einer Außenoberfläche derselben nach innen in Richtung einer Triebwerksmittellinie, um einen äußeren Strom in einen inneren Strom zu drücken, was einen Wirbel in Strömungsrichtung erzeugt, wodurch ein rasches Mischen des äußeren Stroms und des inneren Stroms verbessert wird.
Anspruch[en]
A segmented nozzle extension for a jet engine comprising a segmented, trapezoidal shaped, curved extension of a nozzle sleeve, wherein a plan view of said nozzle extension comprises a serrated trailing edge, said nozzle extension having a semi-round valley and a semi-round tip, said nozzle extension having an outer surface curving inward, toward an engine centerline, thereby forcing an outer flow into an inner flow, which creates a stream wise vortex thereby enhancing rapid mixing of the outer flow and the inner flow. A method for reducing noise radiated from a jet engine exhaust flow by enhancing natural free mixing between adjacent streams of gases, comprising the steps of: adding to a gas flow baseline nozzle a segmented, trapezoidal shaped, curved extension of a nozzle sleeve, wherein a plan view of said nozzle extension comprises a serrated trailing edge, said nozzle extension having a semi-round valley and a semi-round tip; and configuring said extension by curving an outer surface thereof inwardly towards an engine centreline to force an outer flow into an inner flow, which creates a stream wise vortex thereby entraining rapid mixing of the outer flow and the inner flow.
Anspruch[fr]
Extension de tuyère segmentée pour un turboréacteur comprenant une extension incurvée, en forme trapézoïdale, segmentée d'un manchon de tuyère, dans laquelle une vue en plan de ladite extension de tuyère comprend un bord de fuite denté, ladite extension de tuyère ayant un creux demi-rond et une pointe demi-ronde, ladite extension de tuyère ayant une surface externe s'incurvant vers l'intérieur, vers une ligne centrale de moteur, forçant de ce fait un flux externe à l'intérieur d'un flux interne, ce qui crée un tourbillon longitudinal améliorant de ce fait le mélange rapide du flux externe et du flux interne. Procédé pour réduire le bruit rayonné d'un flux d'échappement de turboréacteur en améliorant le mélange libre naturel entre des courants gazeux adjacents, comprenant les étapes consistant à : ajouter à une tuyère de base de flux de gaz une extension incurvée, en forme trapézoïdale, segmentée d'un manchon de tuyère, dans laquelle une vue en plan de ladite extension de tuyère comprend un bord de fuite denté, ladite extension de tuyère ayant un creux demi-rond et une pointe demi-ronde ; et configurer ladite extension en incurvant une surface externe de celle-ci vers l'intérieur vers une ligne centrale de moteur pour forcer un flux externe à l'intérieur d'un flux interne, ce qui crée un tourbillon longitudinal améliorant de ce fait le mélange rapide du flux externe et du flux interne.






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