turbo expo 2012 in copenhagen: reliable gas …files.asme.org › igti › news › 31751.pdfturbo...

Join more than 3000 professionals from over 50 countries for ASMETurbo Expo 2012 – a premier 5-day Technical Conference and a 3-day,premium exhibition of turbomachinery products and services supportedby leading companies in the industry, such as GE, ANSYS, CD-adapco,Dresser-Rand, and Pratt & Whitney.This year Turbo Expo is being held June11-15 at the Bella Center, in Copenhagen, Denmark. Register today atwww.turboexpo.org. Early registration discount ends May 14.

Keynote Speakers AnnouncedAl Brockett, Vice President, Engineering - Module Centers, Pratt & Whitney;

Mark Pearson, General Manager - Advanced Technology & Preliminary Design, GEAviation; and Henrik Stiesdal, Chief Technology Officer, Wind Power Business Unit,Siemens, will all speak at the opening keynote on Monday, June 11.

Don’t miss these Turbo Expo events:Career Development WorkshopsTaking place just before the conference begins, our Turbo Expo workshops

provide focused, fundamental training. Choose from seven courses to be heldSaturday and Sunday, June 9-10, 2012. See page 52 for more details and visitwww.turboexpo.org to register.

Annual Women’s DinnerWomen working in the turbomachinery industry who register for Turbo Expo

are eligible to attend our women’s networking reception and dinner. The dinner willbe held during Turbo Expo on Tuesday evening, June 12, 2012. This year the dinnerwill feature speakers Jeanne Rosario, Vice President of Aviation Engineering, GEAviation, and Nathalie von Siemens, Corporate Strategies, Strategy Development,Siemens Headquarters.

Special Networking Event for Young EngineersWhile attending Turbo Expo 2012, young engineers won’t want to miss a special

networking event on Wed., June 13, for rising engineers. This special networking eventwill give young engineers the opportunity to meet a variety of representatives fromthe turbomachinery industry as well as members of IGTI’s technical committees.Visit www.turboexpo.org today for more details and to register. Studentsqualify for discounted registration. R

April 2012 Global Gas Turbine News 47

ATLANTA, GEORGIA USA /// ASME INTERNATIONAL GAS TURBINE INSTITUTE

Volume 52, No. 2 • April 2012

In this issueTurbo Expo 2012

47View From the Chair

48Calendar of Events

48Best Paper Award...

Prediction ofAeroacoustic Resonance

in Cavites of Hole-Pattern Stator Seals

49-50Best Paper Award...

PerformanceOptimization of WindTurbine Rotors withActive Flow Control

(Part 1)

51ProfessionalDevelopment

52IGTI Committee MemberTerence Jones Honored

52As the Turbine Turns...

The Coming Single-Aisle, Narrow-Body

Aircraft Bonanza

53Turbo Expo 2013

54

Turbo Expo 2012 in Copenhagen:Reliable Gas Turbines Operating inExtreme Environments

A Special Thank You to OurTurbo Expo 2012 Sponsors!

PLATINUMGE

Rolls RoyceSiemens

SILVERANSYS

Pratt & Whitney

BRONZECD-adapcoNumeca

Solar TurbinesSouthwest Research

Institute

Additional SponsorsCambridge Flow Solutions

Dresser-RandMentor GraphicsParker Hannifin

IGTI SilverANSYS

IGTI BronzeSouthwest Research

Institute

Rosario has 15 years experience in enginedesign and 10 years in systems leadership,contributing to commercial, military, marine

and industrial product lines. Shecurrently directs the research,design, certification and in-service support of all engineprograms for commercial, militaryand industrial customers.

von Siemens joined the staff of Siemens AG in2005, and she is a Member of the Board of thevon Siemens family as well as of variousscientific and economic institutions.In her current position, she isfocused on the long-termdevelopment of the company.

48 Global Gas Turbine News April 2012

A SUPPLEMENT TO MECHANICAL ENGINEERING MAGAZINE

View From The ChairBy Klaus Brun, Ph.D., Chair, IGTI Board

Klaus Brun, Ph.D., is the Director of the Machinery Program and Southwest Research Institute in San Antonio, Texas.

JUNE 18, 2012 - JULY 6, 2012Gas Turbine Courses at Cranfield UniversityBedfordshire, UKhttp://www.cranfield.ac.uk/soe/shortcourses/gas-turbine/

June 18-22: • Combined Cycle Gas TurbinesJune 25-29: • Gas Turbine CombustionJuly 2-6: • Marine Propulsion Systems

JULY 30 - AUGUST 1, 201248th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibitand 10th International Energy Conversion Engineering ConferenceHyatt Regency | Atlanta, Georgia | www.aiaa.org

The objective for JPC 2012 is to identify and highlight how innovative aerospace propulsion technologiespowering both new and evolving systems are being designed, tested, and flown.

AUGUST 20-22, 2012Asian Congress on Gas Turbines 2012 (ACGT 2012)Shanghai Jiao Tong University | Shanghai, China |http://acgt2012.csp.escience.cn/dct/page/1

The ACGT 2012 will aim to provide an international forum for exchange of information related to gasturbine technology, especially among researchers in the Asian Region.

SEPTEMBER 10-14, 2012IGTI & SwRI Gas Turbine Training WeekTechnische Universität München | Munich, Germany | http://igti.asme.org

OCTOBER 17-18, 20126th International Gas Turbine Conference (IGTC-12)Brussels, Belgiumhttp://www.etn-gasturbine.eu/igtc.aspx

Organized by the European Turbine Network. this conference takes placebiennially, bringing together the whole value chain of gas turbine technology and research.

JUNE 3-7, 2013ASME Turbo Expo 2013San Antonio Convention Center | San Antonio, TexasIGTI’s flagship event comprises a major gas turbine conference and exhibition.

APRIL 18-20, 2012International Conference on Fan Noise, Technology and Numerical MethodsCongress Centre of CETIM | Senlis, FranceMore details: http://www.fan2012.org/

APRIL 30, 2012 - MAY 25, 2012Gas Turbine Courses at Cranfield UniversityBedfordshire, UKhttp://www.cranfield.ac.uk/soe/shortcourses/gas-turbine/

April 30 - May 25: • Mechanical Integrity of Gas TurbinesMay 14-18: • Gas Turbine PerformanceMay 14-18: • Gas Turbine Transient PerformanceMay 14-25: • Gas Turbine Performance and Component Technologies

JUNE 9-10, 2012ASME International Gas Turbine InstituteTE12 Turbo Expo Pre-conference WorkshopsBella Center | Copenhagen, Denmark

June 9: • Technology & Applications of Turbine Coatings• New!Gas Turbine Rotor Life Management

June 9 & 10: • New! Introduction to Optimization Methods and Tools for Multi-disciplinary Design in Turbomachinery• Advances in Turbines Aero-thermo-mechanical Design & Analysis

June 10: • New!A Primer on CHP Technologies• Basic Gas Turbine Metallurgy and Repair Technology• Gas Turbine Failure Analysis

JUNE 11-15, 2012ASME Turbo Expo 2012Bella Center | Copenhagen, Denmark | www.turboexpo.org

IGTI’s flagship event comprises a major gas turbine conference and exhibition.The 2012 advance program is now available online at www.turboexpo.org.

CALENDAR OF EVENTS

Dear fellow IGTI members, this is my last “View from the Chair.” In JulyThomas Sattelmayer of the Technical University of Munich will take over as chair ofthe IGTI Board. It has certainly been a very exciting and productive term, and I amproud to report that IGTI keeps on growing, not just in membership and Turbo Expoconference participation, but also in services to our IGTI members. My focus over thelast year has been on improving IGTI services, and we have been working onimplementing a number of new initiatives, such as more specialty conferences, anincreased number of educational events, more student scholarships, betterdissemination of Turbo Expo papers, and many others. For example, we recentlydoubled the number of scholarships for young engineers that study or work in gasturbine and turbomachinery fields. IGTI also held two very successful Gas TurbineTraining weeks in the last 12 months, one in San Antonio, Texas, and one in Hamburg,Germany. To increase IGTI’s exposure in the area of alternative energy, webinars wereheld on wind turbines and concentrated solar power plants.

We also welcome new board members in July: Geoff Sheard willbe the new Incoming Board Member and Philip Andrew will bethe new Member at Large. Ron Bunker and Pat Campbell willrotate off the IGTI Board; I want to thank both Ron and Pat fortheir many years of dedicated service. I also want to take thisopportunity to welcome our new IGTI Operations Director,Charity Golden. Charity has been hired to manage the Atlantaoffice because Mike Ireland (previous Managing Director of IGTI),

was recently promoted to ASME Director, Engineering Research and TechnologyDevelopment, and has relocated to the ASME New York office. Charity has a longand distinguished record of managing professional societies, and the entire IGTI

Board is glad she has agreed to join IGTI. We arelooking forward to working with her in ourcontinued effort to make IGTI a better organizationfor our members.We all know that ASME Turbo Expo 2012 is next,

and I am looking forward to seeing all of you inCopenhagen. This will be the largest Turbo Expo ever,with well over 1000 technical papers, panelpresentations, and tutorials. In addition to our manytechnical committee tracks, we have added specialtytracks on fans & blowers, supercritical CO2 applications,and concentrated solar plants. IGTI will continue tohighlight areas of current technical interest in the energyfield through specialty tracks at future Turbo Expos. Also,there will be another Gas Turbine Training week inGermany later this year. If you are interested inparticipating, please contact me or IGTI staff.As always, I want to thank all of you for your

continued support of IGTI. Without you, themembership, there would be no IGTI. R

Go to http://igti.asme.org to learn more about Charity Golden.

Charity Golden



AbstractA Reynolds-averaged Navier-Stokes (RANS) solver

developed in-house was used to simulate grazing channelflow past a cavity located in a channel. The objective ofthis investigation was to predict fluid instabilities in hole-pattern stator seals. The numerical results generated withthe RANS solver showed good agreement with thoseobtained using a commercial Large Eddy Simu lation(LES) code. In addition, the numerical results agreed wellwith experimental data. Rossiter’s formula, a popularsemi-empirical model used to predict fre quen cies of hole-tone acoustic instabilities caused by grazing fluid flow pastopen cavities, was modified using the RANS solver resultsto allow for its application to channel flows. This was doneby modifying the empirical constant k, the ratio of vortexvelocity and the freestream velocity. The dominantfrequencies predicted using the Rossiter’s formula withthe new k value matched well the experi mental data forhole-pattern stator seals. The RANS solver accuratelycaptured the salient features of the flow/acousticinteraction and predicted well the domi nant acousticfrequencies measured in an experi mental investigation.The flow solver also provided detailed physical insightinto the cavity flow instability mechanism. IntroductionFluid instabilities in hole-pattern and honeycomb

stator seals have been extensively investigated in recentyears.[1–3] The results of this body of research indicate thatrotor shaft vibrations are caused by cross-coupled forcesbetween the rotor shaft and the annular seal. Usually,these forces stabilize the rotor. However, under certainoperating conditions, a destabilizing effect can beencaused by an unexpected increase in friction factor withrespect to an increased rotor-seal clearance. Childs et al.[1]have linked this increase in friction factor to acousticfluid instabilities noticed in the hole-patterns of theannular seals. Unsteady pressure measurements at the baseof one of the cells showed that flow instabilities in thehoneycomb or hole-pattern cells cause this increase infriction factor. The oscillatory unstable cavity flow waslarge enough to interfere with the through flow.The fluid instabilities in hole-pattern stator seals are

produced when the flow between the rotor shaft andannular seals passes over the hole pattern of the annularseals. The holes in the annular seals act as cavities trappingpockets of recirculating fluid. The grazing flow generates aflow-acoustic feed-back loop within each cavity which inturn causes acoustic waves to emanate from the cavities.This phenomenon is similar to the bomb bay instabilitythat occurs at certain Mach numbers when the aircraftbomb bay door is opened. An overview of past studies ofcavity flow instabilities was compiled by Grace.[4]

Physics of Cavity FlowsFluid instabilities generated by the grazing flow past an

open cavity occur due to the interaction of shear layeroscillations within the cavity, vortices within the shear

layer and acoustic wavesradiating from the cavity. Asshown in Fig. 1, a boundarylayer forms along the wallupstream of the cavity andseparates from the wall as itreaches the leading edge of thecavity forming a shear layeracross the top of the cavity. The faster grazing flow in the channel passing over the slowerrecirculation in the cavity causes Kelvin-Helmholtz oscillations in the shear layer. Theseoscillations cause vortices to be shed from the leading edge of the cavity and alsopropagate them along the shear layer. The vortices propagate downstream and impingeon the trailing edge. The interaction between the vortices and the shear layer warps theshear layer causing its reattachment point to momentarily move down the cavity wallbelow the lip. The shear layer stagnates just below the trailing edge causing a brief periodof higher pressure. As the flow accelerates past the trailing edge of the cavity, an area oflow pressure is momentarily formed along the wall just downstream of the cavity edge. Asa result, an acoustic dipole is generated at the trailing edge, which radiates acoustic wavesin all directions. The acoustic waves that propagate upstream excite the shear layer at theleading edge of the cavity, which in turn causes the shedding of additional vortices. Thisvortex-acoustic interaction forms a feed-back loop which selectively amplifies adominant frequency.Rossiter[5] derived a semi-empirical

equation that predicts the dominantfrequency of the cavity flow instability, ƒ, where U is the freestream flow velocity,L is the length of the cavity, M is the Mach number, co and ct are the speed of soundoutside and inside the cavity respectively, g and k are empirical terms, and m is themode of the oscillation. Using experimental measure ments, Rossiter determined thatthe empirical terms are g = 0.25 and k = 0.66. Subsequent studies have reported kvalues as low as 0.57 while the value for g has remained consistent.[6]

Rossiter, as well as the majority of researchers utilizing Rossiter’s formula, studiedcavities open to the freestream with no influence of an opposing wall. For flow in hole-pattern stator seals the cavities are located within a channel where the opposing wall issituated in the proximity of the opening of the cavities. Consequently, Rossiter’sformula must be modified to account for the presence of the opposing wall. This wasdone using numerical results that were validated by experimental data.

RANS, LES and Experimental ResultsFor the numerical simulations the model for the hole-pattern seal was simplified to a

single, rectangular, two-dimensional cavity with a length and depth of 3.175 mm. Thecavity was located in a channel with a height of 0.7112 mm, which extended 22 mm (6.9cavity lengths) in front of and behind the cavity. The geometry was a simplified version ofthe experimental setup used at the Turbomachinery Laboratory at Texas A&MUniversity. The experiments were conducted for a hole pattern con taining severalhundred cavities. The simplified domain, with a single cavity, allowed for reasonablecomputation times while still capturing the necessary flow features.The inlet total pressure was 104,190 Pa, the exit static pressure was 101,325 Pa and the

total temperature was 305.4 K. The Reynolds number based on the cavity length was14,300. Each simulation was started from an initial condition with a uniform velocity of68 m/s parallel to the channel. These parameters were chosen to provide a flow with aMach number of approximately 0.2.Figure 2 shows a series of pressure contours illustrating a complete cycle of the cavity

flow mechanism described above. A vortex is shed from the leading edge of the cavityand increases in magnitude as it propagates along the shear layer. As the vortexapproaches the trailing edge of the cavity, a dipole is formed releasing an acoustic wave.As the original vortex impinges on the trailing edge, a second vortex is shed.

Fig. 1. Features of cavity flow.

(1)

Best Paper Award...This is the 2011 Structures and Dynamics Committee Best Paper Award Winner

Prediction of Aeroacoustic Resonancein Cavities of Hole-Pattern Stator Seals

By David N. Liliedahl, Graduate Research Assistant; Forrest L. Carpenter, Graduate Research Assistant; andPaul G. A. Cizmas, Professor, Department of Aerospace Engineering, Texas A&M University College Station, Texas

Velocity profiles are shown in Fig. 3 for five evenly spaced locations through thecavity. The velocity profiles produced with the LES and RANS simulations are nearlyidentical except near the bottom of the cavity.Simulations using the flow conditions described above predicted a dominant

frequency using RANS and LES of 20.95 kHz and 21.80 kHz, respectively. Thiscompares well with the experimental result of 21.75 kHz. This shows that, even thoughthe flow domain was significantly simplified, both types of numerical simulations wereable to accurately capture the important flow features and predict the dominantfrequency. This indicates that cross flow and cavity interactions are secondary effects forthe dominant frequencies. The computational time required by the RANS solver wasmore than one order of magnitude smaller than that of the LES solver.

Determination of Empirical Values for Rossiter’s FormulaIt was found that Rossiter’s formula (1) as reported in literature[5, 6] was not able to

accurately predict dominant frequencies. It was believed that the error was due to theinfluence of the opposing wall of the channel. Numerical simulations showed that thefeed-back mechanism for cavity channel flows was the same as that used to deriveRossiter’s formula. For this reason the form of Rossiter’s formula remained valid whileonly the value of one empirical variable, k, was modified.The empirical term k can be physically understood as the ratio between the

propagation speed of vortices and the freestream velocity. Originally, Rossiter found thevalue for k by fitting the equation to experimental results. Reported k values for opencavity flow range from 0.57 by Larcheveque et al.[6] to 0.66 by Rossiter.[5] Using CFD,however, the position of the vortices can be directly tracked throughout a given cycle.The velocity is then easily calculated giving the k ratio. Using the technique describedabove, the authors found the k ratio for channel cavity flow to be 0.52.Figure 4 shows pressure variation as a function of frequency for a Mach number at the

cavity leading edge of 0.166. Simulations were also run for a Mach number of 0.183. Thepressure variation calculated using the RANS predict dominant frequencies of 23.68kHz for Mach 0.166 and 26.32 kHz for Mach 0.183. The dominant frequency was alsocalculated with Rossiter’s formula (1) using the third mode, m=3. Two values of kconstant were used: Rossiter’s k=0.66 and the value calculated herein for channel flows,



k=0.52. Figure 4 shows a good match between thedominant frequency predicted by the RANS solver andRossiter’s formula with k=0.52, for both Mach numbers.A summary of the predicted dominant fre quencies isshown in Table 1.

ConclusionsA Reynolds-averaged Navier-Stokes (RANS) solver

developed in-house was used to simulate grazing channelflow past a cavity in a channel. The objective of thisinvestigation was to predict fluid instabilities in hole-pattern stator seals. The numerical results generated withthe RANS solver showed good agreement with thoseobtained using a commercial Large Eddy Simulationcode. In addition, the numerical results agreed well withexperimental data. Rossiter’s formula, a popular semi-empirical model used to predict frequencies of hole-toneacoustic instabilities caused by grazing fluid flow past opencavities, was modified using the RANS solver results toallow for its application to channel flows. This was doneby modifying the empirical constant k, the ratio of vortexvelocity and the freestream velocity. The corrected k valuewas obtained by tracking vortex position through a cycleof the flow. The dominant frequencies predicted using theRossiter’s formula with the new k value matched well theexperimental data for hole-pattern stator seals. TheRANS solver accurately captured the salient features ofthe flow/acoustic interaction and predicted well thedominant acoustic frequencies measured in anexperimental investigation. The flow solver also provideddetailed physical insight into the cavity flow instabilitymechanism.This work was sponsored by the Turbomachinery

Research Consortium. The authors thank Professor DaraChilds and Mr. Bassem Kheireddin of theTurbomachinery Laboratory at Texas A&M Universityfor providing the geometry, flow conditions, andexperimental results for the hole-pattern stator seal. R

References1. Childs, D.and Elrod, D., and Hale, K., 1989. “Annular honeycomb

seals: Test results for leakage and rotordynamic coefficients;comparisons to labyrinth and smooth configurations”. J. ofTribology(111), pp. 293–301.

2. Al-Qutub, A., Elrod, D., and Coleman, H., 2000. “A new frictionfactor model and entrance loss coefficient for honeycombannular gas seals”. Journal of Tribology, 122, July, pp. 622–627.S0742-4787(00)02102-0.

3. Iwatsubo, T., and Sheng, B. C., 1995. “Evaluation of seal effectson the stability of rotating fluid machinery”. International Journalof Rotating Machinery, 1(1), pp. 145–152.

4. Grace, S. M., 2001. “An Overview of Computational AeroacousticTechniques Applied to Cavity Noise Prediction”. AIAA Paper2001-0510.

5. Rossiter, J. E., 1966. Wind-Tunnel Experiments on the Flow overRectangular Cavities at Subsonic and Transonic Speeds. Tech.rep., Ministry of Aviation.

6. Larchevêque, L., Sagaut, P., Mary, I., Labbé, O., and Comte, P.,2003. “Large-eddy simulation of a compressible flow past a deepcavity”. Physics of Fluids, 15(1), January, pp. 193–210.

Mach RANSRossiter’s formula (1)

Channel k=0.52 Open k=0.66

0.166 23.68kHz 23.90 kHz 29.70 kHz

0.183 26.32 kHz 26.14 kHz 32.42 kHz

Fig. 3. Snapshot of velocity profiles generated withthe LES and RANS solvers; profiles located at fiveevenly spaced axial locations through the cavity.

Fig. 4. Pressure variation vs. frequency atM=0.166

Fig. 2. Pressure contours at time, t: (a) 0, (b) 12µs, (c) 24µs, (d) 36µs

(a) (b)

(c) (d)



Best Paper Award...The following is part 1 of a two-part article. This is the 2012 Wind Committee Best Paper Award Winner. Part II will be featured in the August issue of the GGTN.

Performance Optimization of Wind TurbineRotors with Active Flow Control (Part 1)

By G. Pechlivanoglou, C.N. Nayeri, C.O. Paschereit

Modern wind turbines have reached sizes andinstalled capacity levels previously unimaginable.Currently the largest rotors have diameters exceeding150m and installed capacities of more than 6MW. Thecombination of large rotor dimensions, turbulent inflowfield, terrestrial boundary layer profile and rotor yawmisalignment causes extremely high aeroelastic loads onwind turbine blades. In addition, the blades of modernwind turbines are extremely cost intensive components.Thus, a potential aerodynamic/aeroelastic load reductioncould be very beneficial for the cost competitiveness ofthe entire wind turbine.To reduce the loads and/or increase the performance

of modern wind turbines, many passive and active flowcontrol (AFC) solutions were investigated by the authors.After an extensive literature research on AFC solutionsbasic simulations were carried out to assess their potentialfor use on HAWT rotors. In a second phase the bestperforming AFC solutions were investigated in detailthrough experiments and numerical analyses (CFD) tocharacterize their performance. The experimental resultsof two solutions are presented in the following.

Flexible Trailing Edge FlapThe idea of the flexible flaps and the extension of that

which is the morphing wing goes back to the beginningof aviation and is related to the investigation of themorphing behavior of the bird wings. From the aero -dynamics point of view, the flexible flaps increase thecamber of the airfoil thus modifying the Kutta conditionfor the flow and the circulation of the airfoil. The feasi -bility of the utilization of modern flexible flaps for AFChas been investigated extensively for use on helicopterrotors as well as on aircraft wings. The imple mentation offlexible flaps on wind turbines is a point currently underextensive investigation with several research projectsfocusing on various implementation strategies of theconcept. Most of the research efforts focus on the imple -mentation of flexible flaps for load alleviation during windturbine operation rather than wind turbine power regu -lation which is the ultimate target of the current project.The integration of flexible flap modules into the wind

turbine blade structure is generally similar to theintegration of plain rigid flaps. However, in the case offlexible flaps and due to the fact that there is no need forimplementation of rotating shafts mounted at the sides ofthe flaps, it is possible to produce them in standalonemodules. The current flexible flap (Figure 1) concept wastested on a DU96W180 airfoil which was measured inthe wind tunnel. It was found that the flexible flapmechanism achieved very high control authority. Flapdeflections towards the pressure side (lift increase) causedsignificant lift and drag increase. Additional wind tunnelmeasurements with vortex generators (VGs) at 60%c(suction side) revealed that despite the smooth flapcurvature, the large flap deflection caused high pressuregradients, thus a large separation (i.e. high drag) on the

suction side. When deflected towards thesuction side (lift re duc tion), the flexible flapmas sively reduces the generated lift. At theangle of maximum Cl/Cd, where windturbine airfoils usually operate, the negativeflap deflection reduced the lift to zero. Such alarge lift variation would allow significantwind turbine power regulation thus reducingthe use of the traditional pitch system.

Active Gurney Flap / MicroFlapThe Gurney flap is a simple flat plate in the order of 1% of the chord length which is

located perpendicular to the pressure side of the airfoil at the trailing edge. When properlysized, the Gurney flap will increase the total lift of the airfoil while reducing the drag. Alift increase in the order of 13% for a Gurney flap size of 0.5%c with minimal to no dragpenalties for the low and moderate Cl values is usually expected. Serrated and slit Gurneyflaps (i.e. micro tabs) have also been investigated in order to eliminate the 2D vortexshedding from the solid Gurney flaps which can cause vibration and noise. Micro flapsand active Gurney flaps are suitable for the task of load alleviation mostly due to their fastactuation capabilities. The actuating mechanism in the case of micro flaps requires lowactuation forces due to the small size of the element. The integration of these elements inthe blade structure is a relatively simple process since the elements and their actuators arevery small and only minor changes need to be made in the blade structures.To achieve a significant load reduction during the operation of the wind turbine a fast

and reliable control and actuation system is needed. From the aerodynamic andmechanical point of view micro flaps are especially suitable for fast control and actuation.The active Gurney flap concept was tested in the wind tunnel by the authors underdynamic AoA variations to simulate unsteady inflow conditions. A high deflection microflap was actuated by four digital electric servos with a maximum deflection rate of360°/sec. A custom code was created to allow dynamic AoA variations of the test wingwith simultaneous dynamic force measurements. In this way, the wind tunnel forcebalance delivered a lift measurement input signal. An additional high precisionmechanical AoA sensor was attached to the wing assembly to extract accurate AoAmeasurements. This signal was used to feed an AoA variation pattern around a mean AoAposition and through the force measurements of the balance to calculate the optimalGurney flap deflection angle to stabilize the aerodynamic lift. Several actuation controlstrategies were tried during the tests in order to identify their performance differences.The AoA variation pattern during the dynamic tests with active Gurney flaps in the windtunnel was initially set as an adaptable white noise profile but also as a pattern similar tothe one extracted from aeroelastic wind turbine simulations. In this way the performance of the active Gurney flap system could be more easily

assessed for an actual wind turbine application. During the dynamic investigations variouscontrol strategies were tested, starting from standard PID controllers with semi-empiricalparameter tuning models (Ziegler Nicholson method), to DIC (Direct InverseControllers) with neural network tuning strategies and pure self learning neural networkcontrollers. The results of the closed loop measurements using the manually tuned PID-

Controller showed a reduc -tion potential for the dyna -mic lift loads in the range of70% (Fig. 2) as well as astable controller behavior.The DIC controller showeda load reduc tion of 36.8%,but also signi ficant improve -ment potential with respectto its fine-tuning. R

Fig. 1: Wind tunnel test blade with a pneumaticallyactuated high deflection flexible flap.

Fig. 2: Lift variation without (blue) and with (red) active Gurney flap element.



ASME IGTI Professional & Member Development

By Shirley Barton, IGTI Professional & Member Development Manager

Professional Development (continued)

2012 Turbo Expo Workshops Announced!Seven highly focused gas turbine training workshops arescheduled June 9-10, prior to the opening of Turbo Expo inCopenhagen, Denmark. Register now and learn how toimprove turbine design and efficiency!

➢ Technology & Applications of Turbine Coatings ➢ Gas Turbine Rotor Life Management➢ Advances in Turbines Aero-thermo-mechanicalDesign & Analysis

➢ Introduction to Optimization Methods & Tools for Multi-disciplinary Design in Turbomachinery

➢ Basic Gas Turbine Metallurgy and RepairTechnology

➢ A Primer on CHP Technologies ➢ Gas Turbine Failure Analysis

2012 IGTI and SwRI European Gas Turbine Training WeekIGTI and SwRI have scheduled another training week at theTechnische Universität München in Munich, Germany theweek of September 10, 2012.

➢ Introduction to Gas Turbines and CentrifugalCompressors

➢ Machinery Performance Testing andTroubleshooting

➢ Root Cause Failure Analysis of Gas Turbines➢ Rotor and Blade Dynamics

Instructors: Dr. Klaus Brun, David Ransom, SwRI; Dr. Rainer Kurz, Solar Turbines

For detailed information on upcoming trainingevents for the gas turbine industry, please visit theIGTI web site at http://igti.asme.org/

Member ServicesIGTI Student ScholarshipIGTI will award 10 scholarships of $2,000 each, to students who submit allthe required documentation and meet the qualifications. Applications willbe accepted from February 15, 2012 through April 15, 2012. Applicationswill be reviewed in June/July and the award winners will be notified inSeptember and receive their scholarship in October. For application andrequirements, please visit the following web page: http://igti.asme.org/Honors/

Please contact Shirley Barton, [email protected], regardinginformation on:

n Navigating IGTI's Technical Committee & Leadership Directory(Who's Who)

n Committee Member Updatesn Volunteer Opportunitiesn IGTI Awards and Scholarshipsn Training & Development

Professional DevelopmentIGTI/SwRI Training Week a Huge Success!IGTI partnered with SwRI for the 4th year to conduct a Gas TurbineTraining Week February 27 – March 2, 2012 at Southwest Research Institutein San Antonio. Attendees from eight countries participated in this event andattendance this year increased 225% since the first offering in 2009! This isincredible. It proves that face-to-face training is still in demand.

IGTI would like to thank SwRI and all of the following Instructors forsharing their knowledge, skills and time with all the engineers whoattended the Gas Turbine Training Week.

➢ Dr. Timothy C. Allison, SwRI ➢ Dr. Jeff Moore, SwRI ➢ Dr. Klaus Brun, SwRI ➢ Nathan W. Poerner, SwRI➢ Jason Gatewood, SwRI ➢ David Ransom, SwRI➢ Justin R. Hollingsworth, SwRI ➢ Dr. Harold Simmons, SwRI➢ Dr. Dan Hopkins, SwRI ➢ Dr. Sean Tavares, SwRI➢ Stephen M. James, SwRI ➢ Melissa Wilcox, SwRI➢ Andrew H. Lerche, SwRI

IGTI Committee Member Terence Jones HonoredIGTI Heat Transfer committee member, Professor Terry Jones, was recently awarded the prestigious

RAeS Silver Medal (Silver Medal by the Royal Aeronautical Society) for his lifetime contributions toAerospace. He led the University of Oxford Department of Engineering Science TurbomachineryResearch Group from 1988 to 2005, and was responsible for many engineering innovations, includingthe invention of the Isentropic Light Piston Tunnel (ILPT) used for turbine research.

The Royal Aeronautical Society has been honoring outstanding achievers in the global aerospaceindustry since 1909, when Wilbur and Orville Wright came to London to receive the Society’s first GoldMedal. In the years that have followed, honoring world aerospace achievers has become a permanenttradition of the Society. R

Professor Terry Jones (right) waspresented with his Silver Medal by thePresident of the Royal AeronauticalSociety, Mr Lee Balthazor. Copyright of the Royal Aeronautical Society.

If you have a topic you think will be of value to the turbine industry and would like to present it in a webinar format or a“face-to-face” format, please contact Shirley at [email protected].



engine offered, similar to the other 737 models. Boeing’s order book has also swelledsince the launch of the 737 MAX.All current and potential new SANB entrants have been enabled by one key factor:

the arrival of new engine technology from Pratt & Whitney and CFM International.Pratt & Whitney’s new entry is a high-bypass geared turbofan engine commonly

known as the Geared Turbofan (GTF). In the research phase since the early 1990’s, thedevelopment of the GTF started in earnest in 1998, with what is known as the PW8000.This essentially was an upgrade of the existing Pratt and Whitney PW6000 that replacedthe fan section with a fan hub-mounted planetary gearing system and a new single-stagefan. After several years of development the PW8000 essentially changed to the ATFIproject still using the PW6000 turbo-machinery but with a new gearbox and a single-stage fan. This led to the GTF program, which was based around a newly designed corejointly developed with MTU Aero Engines of Germany. In addition to the gearedturbofan, the current design includes a variable-area nozzle which offers additionaleconomic benefits. In July 2008, the GTF was renamed the PW1000G, the first in a newline of “Pure Power” engines. The PW1000G consists of a single-stage fan, three boosterstages, eight high pressure compressor stages, two high pressure turbine stages and threelow pressure turbine stages. Fan diameters vary from 56 inches for the MRJ to 81 inchesfor the A320neo and MS-21, with a 12:1 bypass ratio. The PW1000G will be 15% morefuel efficient and markedly quieter [4] than current engines used on regional and SANBjets. At this writing, Pratt & Whitney has conducted more than 1250 hours and 2800cycles of full engine testing of the CSeries and MRJ engines, with the PW1524G forBombardier completing its first flight test program in September 2012 after 25 flights and115 flight hours on the company’s 747 test bed.CFM International’s LEAP-X engine will power ABC (Airbus, Boeing and COMAC)

SANB aircraft. LEAP-X (Leading Edge Aviation Propulsion) will not have entry intoservice for the A320neo until 2015 and the COMAC C919 until 2016. Developmentwork, which started in 1999, must be completed before full engine testing begins. This willbe the first all-new engine to come from the GE Aviation/SNECMA 50/50 jointventure, since the 1974 start of design and development of their very successful CFM56,now at nearly 23,000 engines delivered.The mounting pressure to squeeze every last bit of efficiency and reliability out of

existing dual-spool turbofan engine design is evident in the development of CMFI’sLEAP-X. CFMI settled on the direct drive, two-stage high pressure turbine architectureand use of GE’s latest combustor technology to reduce NOx emissions to 50% of thelatest regulations. LEAP-X has a bypass ratio of 12:1, compared to 5:1 for currentengines. Fan sizes are increased from 63 to 68 inches on the 737MAX and from 68 to 78inches on the A320neo and C919. The turbine inlet temperature has been raised whilecooling and coating technology will keep metal temperatures similar to CFM56conditions. LEAP-X composite fan blades will be built using a 3D woven and resintransfer molding process, allowing thinner, lighter airfoils with better aerodynamics thanachieved with titanium. ...continued on page 54

Two trillion dollars (US) is a lot of money.That iswhat airplane builders are predicting as the size of themarket for single-aisle, narrow-body (SANB)commercial aircraft for the next twenty years. (See thebar charts below and [1].) If we use a rule-of-thumbestimate that 25% of the two trillion represents enginecosts, that puts the 20 year market for SANB aviation gasturbines at $500 billion — an average of $25 billion peryear. (The total commercial aviation gas turbine marketin 2010 was $21 billion [2].)The SANB market has been the most lucrative for

engine manufacturers. Boeing's 737 and Airbus’s A320families, powered by twin 30,000 pounds-thrust enginesfrom CFM International or from International AeroEngines number in the many thousands. About 7000Boeing 737's have been delivered since its introduction in1968, compared to about 5000 Airbus A320's since 1988.Of the 19,400 airplanes now in the worldwide airtransport fleet [1], according to Airbus [3], for aircraft above100 seats, 87% of all routes flown and 78% of all seatsoffered are in SANB airplanes.With the single-aisle jet liner market at record levels,

not surprisingly, new players want a piece of this Boeing/Airbus duopoly pie. Regional jet maker Bombardier isentering into the main line SANB market with its 110 –130 seat CSeries. China’s COMAC has launched its ownjet with its 150 seat C919. Other players include Russia’sUnited Aircraft that wants to stage a comeback with the150 – 200 seat MS-21 and Japan is developing the MRJ,a passenger jet aircraft seating 70–90 passengers,manufactured by Mitsubishi Aircraft Corporation, apartnership between majority owner Mitsubishi HeavyIndustries and Toyota Motor Corporation.With this much at stake, governments are playing a

prominent role in supporting their nationalmanufacturers. Both Airbus and Boeing have reliedextensively over the last few years on customer financingsupport from export credit agencies such as the U.S.Export-Import Bank. The Russian and Chinese jets aregovernment funded. Bombardier is getting Canadianand provincial government aid to develop the CSeries.In August 2008, Bombardier launched its CSeries with

the Pratt & Whitney’s Pure Power geared turbofan. InDecember 2010, Airbus launched its A320neo (newengine option) series, expected to enter into service in2016, featuring a choice of Pratt & Whitney’s PW1100GPure Power or CFM International’s LEAP-X engines.The neo series attracted so many airline customers with atremendous run up in orders (1226 at the end if 2011)that Boeing, in July 2011, was forced into making adecision to offer its new version of the extremely popular737 series, the 737 MAX with an expected entry intoservice in 2017 with the LEAP-X engine being the only

Featured Column: As the Turbine Turns...

The Coming Single-Aisle,Narrow-body Aircraft Bonanza

By Dr. Lee S. Langston, Professor Emeritus of Mechanical Engineering, University of Connecticut

COPYRIGHT © 2011 THE BOEING COMPANY

Technical ConferenceThe ASME Turbo Expo Technical Conference is

globally recognized as the most important annual,international event for gas turbine technology. It ishighly respected for presenting cutting edge, state of theart gas turbine technology from around the world,including contributions from academia and industry.The program scope has also been expanded to includerelated topics in solar, fans and blowers, supercriticalCO2 cycles and wind and steam turbine technology. Tooffer your work for publication in 2013, please note thatabstracts are due by August 27, 2012, with drafts dueOct. 29, 2012.

ExpositionTurbo Expo brings together the top players in the

turbomachinery industry. Exhibiting at Turbo Expo willmaximize your ROI by placing your company in frontof a focused target market, enabling you to generatehigh-quality leads to achieve your marketing objectives.Exciting brand-enhancing sponsorship packages are

also available! Packages are designed around yourparticular corporate goals and are an extremelyeffective way for your company to really stand out fromthe crowd–before, during and after the Show. To insure your company’s participation in the 2013

exposition, contact IGTI at +1-404-847-0072 x1646or via e-mail at [email protected]. R



Plan now to join 3,000 turbomachinery colleagues from around the world at TURBO EXPO, ASME’s premier turbine technical

conference and exposition, set for June 3 -7, 2013, in San Antonio, Texas, at the San Antonio Convention Center.

Turbo Expo 2013 highlights include:n A five-day Technical Conference that sets the world standard for turbine technology events

n A three-day, premium exhibition of turbine products and services supported by leading companies in the industry

n A dynamic keynote session featuring prominent industry leaders n A value-packed registration package that includes proceedings, access to all activities, PDH certificate of completion, and abundantnetworking opportunities, including receptions and daily lunches

n In-depth career development workshops providing fundamental study and efficient techniques

LeadershipLeading the organization of Turbo Expo 2013 are Executive Conference Chair

Bernhard Winkelmann, Conference Chair Dr. Seung Jin Song, Technical ProgramChair Dr. Timothy Lieuwen and Review Chair Professor Howard Hodson.Winkelmann is Manager of Product Strategies and Director of the Gas Compressor

Business at Solar Turbines in San Diego, CA. He has more than 20 years of experience inthe turbomachinery industry in Germany, Belgium, and the U.S. Song is a Professor of Mechanical and Aerospace Engineering at Seoul National

University in Seoul, Korea. His specialty fields are Aerodynamics and Fluid StructureInteractions in Turbomachinery; Power Plant System Design and Performance Analysis;and Stability of Refrigeration Systems. He was awarded the 2003 ASME Melville Medaland the 2009 Korean Fluid Machinery Association Scholar Award, among many honors.Lieuwen is a Professor at the School of Aerospace Engineering, Georgia Institute of

Technology, in Atlanta, GA. He is a former chair of the IGTI Combustion, Fuels, andEmissions technical committee and currently serves as associate editor of theProceedings of the Combustion Institute. In addition, he has taught professionaldevelopment courses and authored a variety of books and technical presentationsrelating to the field of Combustion.Hodson is a Professor of Aerothermal Technology and former Director of the

Whittle Laboratory at the University of Cambridge in the UK. He has received theASME Gas Turbine Award and the ASME Melville Medal and is a former chair of theIGTI Turbomachinery technical committee. He is also a Fellow of the ASME, the RoyalAcademy of Engineering and the Royal Aeronautical Society.

ASME Turbo Expo 2013 Set for San Antonio, Texas

The Most Important Conference for Turbomachinery Professionals

Presented by ASME International Gas Turbine Institute

June 3 -7, 2013ASME INTERNATIONAL GAS TURBINE INSTITUTE

phone +1-404-847-0072 | fax +1-404-847-0151 | [email protected]

www.turboexpo.org

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What about SANB aircraft development, beyond the next twenty years? NASA has launched a study under the subsonic fixed wing researchprogram seeking to identify and develop technologies that could achieve new breakthroughs in quieter and more efficient commercial aircraft thatwould enter service after 2025. New advances in open rotor engine technology can make airliners more fuel efficient, but still may face a noise problem.General Electric and Rolls Royce revived the open rotor concept in 2007, saying new advances could allow such a propulsion system to achievehigher fuel efficiency targets without being significantly noisier. To learn more about this important and evolving SANB market, I invite you to attend a panel session that Dr. Aspi Wadia of GE Aviation (who

contributed to this article) and I will be co-chairing at TURBO EXPO ’12 in Copenhagen on June 12, 2012. Panel members will includerepresentatives from General Electric, Pratt & Whitney, NASA, Boeing, Airbus, Bombardier and COMAC. R

References1. Boeing Commercial Airplanes, 2011, “Current Market Outlook 2011-2030” and Paris Presentation, June, 2011, www.boeing.com/commercial/cmo/.2. Langston Lee S., 2011, “Powering Ahead”, Mechanical Engineering Magazine,May, pp. 30-33.3. Airbus, 2011, “Delivering the Future, Global Market Forecast 2011-2030”, www.airbus.com/company/market/forecast/.4. Langston, Lee S., 2008, “Changing the Game”, Mechanical Engineering Magazine,May, 2008, pp. 26-30.

As The Turbine Turns . . . CONTINUED FROM PAGE 53

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