Tomas alaric paper_mec_e200

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Technical report project for MEC E 200 during my spring-summer term 2012. First tech. paper I have written.

Primarily focused on the design and development of a new aircraft engine nozzle for quiet supersonic flight.

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  • Cool read, partner.
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  • Quiet airplanes would be a nice thing to see, or not hear I suppose.
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  • Great report Alaric! Hopefully they'll get that figured out!
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Tomas alaric paper_mec_e200

  1. 1. Improvements in EngineNozzle Design within theField of Supersonic Flight Alaric Tomas 2nd year Mechanical Engineering student June 18th, 2012 1
  2. 2. Abstract:NASA’s Fundamental Aeronautics Supersonics Project has revealed an interestingdevelopment in the field of aeronautic engineering: an inverted velocity-profile nozzle. This is anozzle device to be fitted to end of new engines to improve efficiency and noise reduction.Developed by GE Aviation, this device will sport supreme supersonic noise reduction potentialalong with excellent aerodynamic performance. Utilizing a specialized flow arrangement with asupplemental fluid shield, this new design will potentially allow for major improvements in thefuture of commercial supersonic flight.Introduction:In late 2003 the last commercial supersonic passenger jet, the “Aérospatiale-BAC Concorde,”was retired from service due in part to a dwindling economic interest and the ceaselesscomplaints of noise pollution [1]. However, recent developments in advanced flow design toolshave allowed for a influx in development by NASA and industry. This research is primarily aimedat creating a new supersonic passenger jets with specialized nozzles that will produce minimalnoise pollution, improve fuel efficiency, and as a result be more economically feasible [2]. Initialdevelopments in this field have been greatly aided with advancements in computational fluiddynamics (CFD) for complex flow interaction. This allows for detailed modeling of the flowthrough the aircrafts engine inlet flow and exhaust systems. As a result of these developmentsGE Aviation has developed the inverted velocity-profile nozzle, a key component for the newsupersonic passenger jet project.Methods:One of the primary developments spawned from the advancements in CFD is the developmentof the Adaptive Versatile Engine Technology (ADVENT) program by the Pentagon’s researchproject, the Versatile Affordable Advanced Turbine Engines (Vaate). The primary result of thisproject is new high efficient and adaptive jet engines that can vary airflow throughout thedifferent flow paths in the engine [3]. Traditionally, most jet engines have two flows, a hot innercore and a cooler bypass. With the ADVENT engine, however, a new cool third stream flow hasbeen introduced. This allows for, among other things, a stream dedicated to noise reduction, afeature well used by the inverted velocity profile nozzle.In prospective normal operation, this new nozzle has an unorthodox method for thearrangement of the two main stream flows. After passing through the engines and entering the 2
  3. 3. nozzle, the cooler slower inner flow is directed through the center of the output flow whilst thefast main hot flow is routed around the outside, this is opposite of traditional jet engines. Noisefrom a jet engine is typically caused by faster exhaust violently shearing with slower ambient air[4], hence this method seems counter-intuitive. However the placement of the fast hot flows onthe outside allows for faster mixing of the air resulting in a quick reduction of peak velocity. Thequicker shear time caused by the initial violent mixing causes an increase in high frequencynoise, but a reduction in the principal low frequency noise. This low frequency noise results inthe “rumbling” sound of typical commuting aircraft, a common public complaint.[5] Fig 1. Prototype drawing of ADVENT engine showing stream routes and nozzle placement (circa 2007) (Note: Figure shown for visualization purposes, does not show current design layout) [6].To reduce the new high frequency noise, a fluid shield, which is a thin layer of flow underneaththe engine, was implemented with the design of the nozzle [7]. This fluid shield works byoffsetting some of the flow provided by the ADVENTs third stream, and directing it underneaththe output stream to reflect the high frequency noise caused by the initial inversion of the twomain flows. This development has many useful properties; one being that the fluid shieldsposition can be adjusted to direct the reflected noise. This allows for sideways noise reductionat the airport and ground noise reduction when the aircraft is in aerial operation. An addedadvantage of the fluid shield is that the flow can be toggled on, for noise sensitive areas, and offin other areas, to reduce the losses caused by the changed direction of flow. 3
  4. 4. Fig 2. Fluid shield vent design and placement on a previous generation jet engine (Circa 2005) [8].Results:The current results of the new inverted velocity-profile nozzle have been positive. Tests haveshown that the new nozzle has significant acoustic benefits, along with having excellentaerodynamic performance. However, most of the numerical statistics of the nozzle itself are notavailable to the public as of yet.However, since the fluid shield has had the benefit of previous years or research, numericalstats are available. The potential acoustic suppression of an engine equipped with a fluid shieldhas been in the range of 4 to 8 effective perceived noise dB [9].Conclusion:The inverted velocity-profile nozzle has many valuable features that can be potentially utilized inthe future of supersonic air travel. It has a unique inverted flow design that allows for a majorcutback in low frequency noise, leaving only high frequency noise. This noise is then reflectedtowards a less sound sensitive area via a thin fluid shield generated by the third stream inADVENTs new engine design. The active nature of the fluid shield allows for greater acousticflexibility in flight and on the tarmac. Overall, the further development and refinement of thisnozzle will be an asset that will pave the way for quieter, more efficient, and economicalsupersonic travel. 4
  5. 5. References:[1] Robert M Allen, “Legal and Enviromental Ramifications of the Concorde”. Available from:http://heinonline.org/HOL/LandingPage?collection=journals&handle=hein.journals/jalc42&div=28&id=&page= (Accessed on June18, 2012).[2] Main stem article: Guy Norris, Graham Warwick, “NASA Focuses Supersonic Effort On Low-Boom Propulsion”. Available from: http://www.aviationweek.com/Article.aspx?id=/article-xml/AW_06_04_2012_p50-461842.xml&p=4(Accessed on June16, 2012).[3] Unknown, “The ADVENT of a Better Jet Engine?” Available from:http://www.defenseindustrydaily.com/the-advent-of-a-better-jet-engine-03623/ (Accessed onJune18, 2012).[4] Ilan Kroo and Juan Alonso, “Noise”. Available from:http://adg.stanford.edu/aa241/noise/noise.html (Accessed on June18, 2012).[5] D. J. Bodony and S.K. Lele, Low frequency sound sources in high-speed turbulent jets.Available from http://ctr.stanford.edu/ResBriefs06/23_bodony.pdf (Accessed June 27,2012).[6] Bill Sweetman, Aviation Week article on B-2 engine improvements. Available from:http://aviationweek.typepad.com/ares/2007/05/baby_b2.html (Accessed on June 27, 2012).[7] Rudolph A. Mangiarotty , “Controlling jet noise with a fluid shield”. Available from: http://asadl.org/jasa/resource/1/jasman/v69/iS1/pS117_s4?bypassSSO=1 (Accessed onJune18, 2012).[8] Salikuddin, M.; Mengle, V. G.; Shin, H. W.; Majjigi, R. K., “Acoustic and Aero-MixingExperimental Results for Fluid Shield Scale Model Nozzles”. Page 16 Available from:http://ntrs.nasa.gov/search.jsp?R=20050080678 (Accessed on June19, 2012).[9] Salikuddin, M.; Mengle, V. G.; Shin, H. W.; Majjigi, R. K., “Acoustic and Aero-MixingExperimental Results for Fluid Shield Scale Model Nozzles”. Page 507, 6., Available from:http://ntrs.nasa.gov/search.jsp?R=20050080678 (Accessed on June19, 2012). 5

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