high speed air breathing propulsion_2011 year in review

8/12/2019 High Speed Air Breathing Propulsion_2011 Year in Review

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AIAA High Speed Air Breathing Propulsion Technical Committee

High Speed Air Breathing Propulsion -2011 Year in Review

by Dora Musielak December 1, 2011

Despite unforeseen challenges, economic woes, and natural disasters, 2011 was a pivotal year forhigh-speed air-breathing propulsion. What will we remember? The following are highlights ofsome of the most important events that shaped this technology in 2011.

X-51A Waverider Aiming High and Fast!

The X-51A waverider 1 attempted its second

powered flight on June 13,2011. At 40.3 seconds afterlaunch, the hypersonicvehicle experienced acombustor/inlet un-startand it continued to flycontrolled, but unpowered,for an additional 97seconds before impactingthe Pacific Ocean.Exceptional telemetry datawas acquired all the way tosplashdown.

The X-51A vehiclessub-systems worked asexpected: B-52 safeseparation, boost, boosterseparation, guidance andcontrol, flight actuators, battery power sub-system, fuel system pressurization, and flight testinstrumentation.

1 The X-51A program is a collaborative effort of the U.S. Air Force Research Laboratory (AFRL ), the DefenseAdvanced Research Projects Agency (DARPA ), Boeing , and Pratt & Whitney Rocketdyne . The 7.9 m-long X-51AWaveRider, fueled by JP- 7 jet fuel and powered by Pratt & Whitney Rocketdynes SJY61scramjet engine , achievedaviation history May 26, 2010 by making the longest-ever scramjet-powered flight.
http://www.af.mil/information/factsheets/factsheet.asp?id=17986http://www.af.mil/information/factsheets/factsheet.asp?id=17986http://www.wpafb.af.mil/http://www.wpafb.af.mil/http://www.wpafb.af.mil/http://www.darpa.mil/http://www.darpa.mil/http://www.darpa.mil/http://www.boeing.com/http://www.boeing.com/http://www.boeing.com/http://www.pw.utc.com/products/pwr/pwr.asphttp://www.pw.utc.com/products/pwr/pwr.asphttp://www.pw.utc.com/products/pwr/pwr.asphttp://www.pratt-whitney.com/media_center/press_releases/2010/12_dec/12-6-2010_7812834.asphttp://www.pratt-whitney.com/media_center/press_releases/2010/12_dec/12-6-2010_7812834.asphttp://www.pratt-whitney.com/media_center/press_releases/2010/12_dec/12-6-2010_7812834.asphttp://www.pratt-whitney.com/media_center/press_releases/2010/12_dec/12-6-2010_7812834.asphttp://www.pw.utc.com/products/pwr/pwr.asphttp://www.boeing.com/http://www.darpa.mil/http://www.wpafb.af.mil/http://www.af.mil/information/factsheets/factsheet.asp?id=17986


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The X-51 investigation team concentrated on assessing both inlet (forebody/inlet isolator)and engine characteristics that were not as expected from data gathered both on the ground andon first flight. During boost, the flow through the inlet started (began flowing air) at a laterthan expected Mach number, and higher than anticipated combustion-driven pressures were seenduring the engine start sequence. Inlet/forebody geometry, fuel system delivery to combustor,

and clean air combustion characteristics (vs. ground combustion vitiation effects) were allexamined as possible causes for the un-start. It is likely that several separate causal factorscombined to cause the un-start. An extensive fault tree was developed with appropriatetests/analyses identified to aid in fault tree node closure.

Pratt & Whitney Rocketdyne and Boeing built four X-51A flight test vehicles with the program goal of reaching Mach 6 in scramjet power. Two vehicles remain. In developing newhypersonic propulsion concepts like the hydrocarbon-fueled scramjet, all test flights are deemedsuccessful in the sense that every attempt is an opportunity to find anomalies that need to beaddressed before the next flight. We agree with Mr. Charlie Brink, the Air Force ResearchLaboratorys X -51A program manager, who once said Every time we test this new and excitingtechnology we get that much closer to success.

Aerojet's TriJet Hypersonic Engine A New Idea

Aerojet unveiled a novel combined-cycle propulsion concept to achieve seamless operation fromMach 0 to 6+. Known as TriJet engine, the turbine-based combined cycle (TBCC) concept isattractive for high speed ISR/Strike Platform applications, bridging the existing thrust gap

between available turbojets and dual-mode ramjet/scramjets with an ejector ramjet.The TriJet enhanced TBCC propulsion system consists of a common 3D inward-turning

inlet with simple variable geometry, feeding compressed inlet air to three synergisticallyinteracting propulsion systems: an Off-the Shelf (OTS) heritage turbojet, a State-of-the-Art

(SOA) ejector ramjet (ERJ), and a near SOA core-burning dual-mode ramjet (DMRJ). In contrastto classical wall burning, core-burning combustion is initiated in the combustor center and not atthe combustor wall. Experiments have shown that this concept reduces the heat load to the wall

by 40- to 50%. The TriJet has two exhaust nozzle systems: one nozzle for the turbine engine onlyassuring minimal changes to its heritage design, and one nozzle that combines the effluents ofthe ERJ with the DMRJ. Using a patented concept called Sustained Aero Choke (SAC), thesecond nozzle is used for thrust enhancement in the Mach regime 2.5 to 4.5 where the DMRJ

produces little or no thrust.
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Dr. Adam Siebenhaar, Director of Hypersonic Propulsion at Aerojet, stated that theinnovative Aerojet TriJet has three significant attributes exceeding competing TBCC solutions:(1) Positive thrust margins can be achieved over the entire Mach 0 to 6+ flight regime withoutnew high risk technological innovations; (2) Sustained cruise speed capability in the Mach 3 to 4range to extend vehicle operating range, and the associated ability to make turning maneuvers

more practical; and (3) The option to configure and extensively operate a single enginedemonstrator vehicle up to Mach 4 with an available Turbine Engine and a State-of-Art EjectorRamjet. Dr. Siebenhaar further added that this robust vehicle can then be equipped with a largescale scramjet and used for envelop expansion into the higher Mach flight regime, therebyovercoming the ground test facility limitations as they exist now and the foresee able future.

TriJet Impacts

With the TriJet Aerojet has envisioned a propulsion system which delivers high thrustover the entire flight regime of an ISR/Strike mission capable platform:

The currently existing TBCC issues are eliminated by the TriJet as follows:

Small Transonic Thrust Margin - Turbojet thrust is assisted with ERJ thrust. Thrust Gap to DMRJ - ERJ and SAC provide reliable thrust. DMRJ Cruise Thermal Management Margin - Core-Burning provides robust margin. No full scale ground test facilities available - Two step approach:

o Build Mach 6+ Platform and at first operate w/ OTS TE and SoA ERJ up to Mach 3.5.o Install DMRJ and Use Vehicle for Envelope Expansion in Flight.

Payload dispense at Mach 6 - Low dynamic pressure ( Q) flight regime can be reliablyachieved with the primary thrusters of the ERJ which can produce thrust independent of Q .

The TriJet propulsion concept has the potential to advance high-speed intelligence, surveillanceand reconnaissance (ISR) or strike aircraft. TriJet is believed to be mature enough to initiate a

program with a subscale demonstrator; it just needs a customer ready to team up with Aerojet.

Fli ht Re ime: Mach 0 to 6+OTS Turbo et: M 0.0 to 2.5

SOA ERJ: M 0.0 to 4.5

SAC: M 3.4 to 4.5

Near SOW DMRJ: M 3.5 to 6+

Step 1: Learn Howto Operate Vehiclew/ TE & ERJ

Step 2: InstallDMRJ & ExpandEnvelo e in Fli ht


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AFOSR/NASA National Center for Hypersonic Combined Cycle PropulsionImproving the Future of Hypersonic Flight

The National Center for Hypersonic Combined Cycle Propulsion (CHCCP) 2, funded by AFOSRand NASA, completed its second year of research. Under the direction of Dr. James McDaniel,

professor at the University of Virginia (U.Va), the objectives of the CHCCP Center are to seekan improved physical understanding and modeling capability of three combined-cycle flowregimes: turbine-to-ramjet mode transition, ramjet-to-scramjet mode transition, andhypervelocity operation.

In addition to U.Va, the CHCCP is comprised of teams from industry, government, andacademia, including Boeing , ATK GASL , the National Institute of Standards and Technology (NIST), North Carolina State University , the University of Pittsburgh , George WashingtonUniversity , Cornell University , Stanford University , Michigan State University , and the StateUniversity of New York at Buffalo . Several members of the AIAA High Speed Air BreathingPropulsion Technical Committee (HSABPTC) are also part of the CHCCP working group.

To date, researchers at the CHCCP Center havedeveloped a dual-mode combustion wind tunnel tosimulate Mach 5 flight conditions, incorporating newlaser diagnostic tools such as TDLAS and PIV. Modelingof experimental data uses both RANS and LES/RANSmethods. Researchers are also developing advanced FDFmethods and chemical kinetic models are developed tocompute hypersonic turbulent reacting flows. Thefollowing are highlights of the most recent resultsachieved by the different CHCCP team members.

In the low-speed mode transition, the inlet modetransition (IMX) facility at NASA Glenn provided datawhich was modeled by Boeing, in both the supersonicmode and the back-pressured mode simulating a turbinein the flowpath. North Carolina State Universitydeveloped an immersed boundary technique forsimulating the flow through bleed passages in the inlet,used to control shock-boundary-layer interactions.

In the high-speed mode transition, the Universityof Virginia developed a unique dual-mode combustionwind tunnel which simulates Mach 5 flight conditions.The tunnel is an electrically-heated clean-air facility that

was designed with optical access for non-intrusive measurements. Measurements of hydrogen-aircombustion were conducted at the facility at conditions in which the reaction transitions fromscramjet mode to ramjet mode, increasing the fuel equivalence ratio. Modeling of the data was

2 The CHCCP is one of three NASA/AFOSR centers funded to advance research in air-breathing propulsion,materials and structures, and boundary layer control for aircraft that can travel at Mach 5 and faster. The jointinvestment of $30 million over five years has the objective of supporting basic science and applied research thatimproves our understanding of hypersonic flight.
http://seas.virginia.edu/research/hypersonic/overview.phphttp://seas.virginia.edu/research/hypersonic/overview.phphttp://seas.virginia.edu/research/hypersonic/overview.phphttp://www.boeing.com/http://www.boeing.com/http://www.gasl.net/http://www.gasl.net/http://www.gasl.net/http://www.nist.gov/index.htmlhttp://www.nist.gov/index.htmlhttp://www.ncsu.edu/http://www.ncsu.edu/http://www.pitt.edu/http://www.pitt.edu/http://www.gwu.edu/http://www.gwu.edu/http://www.gwu.edu/http://www.cornell.edu/http://www.cornell.edu/http://www.stanford.edu/http://www.stanford.edu/http://www.msu.edu/http://www.msu.edu/http://library.buffalo.edu/http://library.buffalo.edu/http://library.buffalo.edu/http://facilities.grc.nasa.gov/http://facilities.grc.nasa.gov/http://facilities.grc.nasa.gov/http://library.buffalo.edu/http://library.buffalo.edu/http://www.msu.edu/http://www.stanford.edu/http://www.cornell.edu/http://www.gwu.edu/http://www.gwu.edu/http://www.pitt.edu/http://www.ncsu.edu/http://www.nist.gov/index.htmlhttp://www.gasl.net/http://www.boeing.com/http://seas.virginia.edu/research/hypersonic/overview.php


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done by NCSU with both RANS andLES/RANS methods. Measurementswere made in the tunnel by StanfordUniversity using the Tunable DiodeLaser Absorption Spectroscopy

(TDLAS) technique, and by UVa usingStereoscopic Particle ImagingVelocimetry (SPIV). Of particularinterest is the effect of combustion onfuel-air mixing. SPIV images revealedthat the streamwise vorticies generated by the ramp fuel injector, which are responsible forefficient fuel-air mixing, are weakened due to pressure rise in the base of the fuel injector.

Additional laser diagnostics available for flowfield measurements are the UVa TunableDiode Laser Absorption Tomography (TDLAT) technique and the George WashingtonUniversity Coherent Anti-Stokes Raman Spectroscopy (CARS) technique. Upcomingexperiments will utilize a cavity

flameholder for ethylene-aircombustion.In the hypervelocity regime,

utilizing the NASA HYPULSEfacility, ATK/GASL constructed amodel of the UVa flowpath designedfor optical access. Non-intrusivemethods to be used in HYPULSEinclude TDLAS and fuel-plumeimaging (FPI). Researchers plan toobtain measurements at Mach 5 for comparison with the UVa facility, and later at Mach 7 and 10conditions.

Fundamental computational modeling being utilized by the CHCCP Center include production-level RANS techniques, state-of-the-art LES/RANS techniques, and the developmentof advanced filtered density function (FDF) techniques. LES/RANS, developed by NSCU,employed a blending function to transition from the LES of the flowfield to the RANS nearwalls. An advanced FDF technique, termed energy-pressure-velocity-scalar (EPVS), wasdeveloped by the University of Pittsburg and Michigan State University for turbulent combustingflows.

The University of Buffalo utilized Direct Numerical Simulation (DNS) to provide datautilized by the LES/RANS and FDF solution methodologies. UVa derived skeletal and reducedreaction models for ethylene combustion and conducted experiments on counterflow combustorextinction and ignition limits. Cornell University derived computationally-efficientimplementation of ethylene combustion using rate-controlled constrained equilibrium (RCCE)and in-situ adaptive tabulation (ISAT) methodologies for incorporation in LES/RANS andadvanced FDF models. NIST conducted experiments to provide detailed chemical kinetic datafor hydrocarbon fuels of interest in hypersonic propulsion.


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Hypersonic Propulsion Research at CUBRC State-of-the Art Ground Testing

At CUBRCs LENS II long -duration shock tunnel, a full-scale X-51 vehicle equipped with ageneric scramjet flowpath was tested at duplicated Mach 6 flight conditions. During the pastyear, measurements have been made of the thrust, drag and lift were conducted in the clean air

environment.A unique soft suspension system wasdeveloped to free fly the X-51 modelduring the 80+ ms of the flow duration inthe tunnel. Extensive heat transfer and

pressure measurements were madethrough the engine and over thesimulated engine seals. A combined setof measurements provided new uniquecode validation data for a range offueling conditions.

Fundamental studies of mixingand combustion were also conducted atCUBRC in a large-scale combustion ductwith a HIFiRE-like flowpath to examinethe mixing and combustion processes in aMach 5 to 7 scramjet environment. Thesestudies are being conducted in

conjunction with detailed DES/LES computations being performed at the University ofMinnesota.

The Aerothermal/Aero-optic

Evaluation Center (AAEC) atCUBRC operates the LENSsupersonic and hypersonic testfacilities for ground testing offull-scale missiles up to 30 ftin length at fully duplicatedflight conditions from Mach3.5 to Mach 30.

The LENS ground testcapability consisting of theLENS I and LENS II reflected

shock tunnels and the LENSX expansion tunnel, whichhave been constructed duringthe past 15 years, provide the world's most advanced facilities for high Reynolds number testingin hypervelocity flows. The LENS facilities have been used in the study of interceptors, scramjetand ramjet engine performance, dynamic booster stage and shroud separation, shuttle ascent andreentry, planetary reentry to Earth and Mars and other bodies in the solar system, jet and divertthruster interaction, plume interactions, and many other applications.
http://www.cubrc.org/WebModules/ServiceCategories/hypersonic.aspxhttp://www.cubrc.org/WebModules/ServiceCategories/hypersonic.aspx


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Air Breathing High Speed Propulsion in Japan Right On Track

The international community had a share of setbacks and triumphs. On March 11, a massive M9

class earthquake shook the north-east area of Japan, taking more than 15,000 lives anddestroying buildings, cars, ships and airplanes. At the end of July, nearly 5 thousand people werestill missing. Tohoku University and the Kakuda Space Center of the Japan AerospaceExploration Agency (JAXA) are located in the affected region. These two centers lead Japan'swork in high-speed air-breathing propulsion research. Fortunately, no casualties were reported in

both sites, and damages to the facilities were minimal.Kakuda Space Center, JAXA's hub for high-speed air-breathing propulsion R&D, did not

report human losses and damage to buildings was minor, considering the magnitude of thequake. The director of the center, Mr. Keiichiro Noda, was grateful to receive a letter ofsympathy from Mr. Charles Bolden, Jr., NASA Administrator. By mid-year, routine R&Dactivities at the Kakuda Center resumed.

Crack in the road - JAXA s Kakuda Space Center Mr. Justin Tilman, NASA Japan Representative, and Mr. Keiichiro Noda,(March, 2011) - Courtesy of Dr. Kanda. Director, Kakuda Space Center (June 28, 2011).

Japanese researchers succeeded in measuring the second mode pressure fluctuations of the boundary layer transition using a 7-degree half-angle cone model, 1100-mm long, at a highenthalpy flow condition in JAXAs High Enthalpy Shock Tunnel (HIEST) 3. The measurementmainly focused on observation of the second mode instability in the transition process underhypersonic high-enthalpy flow with high-speed pressure transducers.

Recently, Dr. Takeshi Kanda, lead researcher at JAXA and international member of theAIAA HSABPTC, proposed a prediction method for boundary layer transition using aconservation law approach 4 that covers from subsonic to hypersonic speed flow region. Theincreasing ratio of the boundary layer thickness to the laminar boundary layer thickness at the

3 Tanno, H., et al., AIAA Paper 2011-3889.4 Kanda, T., Trans. JSASS, Vol. 54, No. 183, 2011, pp. 7-15.
http://www.tohoku.ac.jp/english/http://www.tohoku.ac.jp/english/http://www.jaxa.jp/about/centers/kspc/index_e.htmlhttp://www.jaxa.jp/about/centers/kspc/index_e.htmlhttp://www.jaxa.jp/about/centers/kspc/index_e.htmlhttp://www.tohoku.ac.jp/english/


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transition is introduced. Several equations for laminar and turbulent boundary layers are used to predict the transition Reynolds number. The effect of the momentum deficit at the leading edgeis also incorporated in this approach assuming compressible flow conditions. The calculatedtransition Reynolds number shows reasonable agreement with the experimental results. Underthe compressible flow conditions, the calculation simulates the bucket of the transition Reynolds

number with a Mach number, the change in the transition Reynolds number due to wall cooling,and the increase in the transition Reynolds number with increase in the bluntness Reynoldsnumber. Dr. Kanda and his collaborators at JAXA plan to include this prediction method in thedesign and test of hypersonic propulsion technologies.

A 7 deg half-angle cone model used in the boundarylayer study at HIEST(JAXA).

As we end 2011, let us reflect on the advances made but with a look at the future of high speedair breathing propulsion. Let us imagine a future where hypersonic vehicles streak through thesky at many times the speed of sound around the world, and envision spaceplanes that combinescramjets with rockets to make access to space more viable. Let us now speed into the future!

Acknowledgements

The author is grateful to the following people for their contribution to this article.

Mr. Charles Brink - Air Force Research LaboratoryDr. Adam Siebenhaar - AerojetProfessor James McDaniel - University of VirginiaDr. Takeshi Kanda - Japan Aerospace Exploration Agency (JAXA)Dr. Michael Holden - CUBRC

high speed air breathing propulsion_2011 year in review

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