Aeronautics Space Space Agency Transport Energy. Hot-wire measurements of a Counter Rotating Turbo Fan (CRTF) Robert Meyer, Lars Enghardt

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1 CAV-Workshop 010 DLR German Aerospace Research Center Aeronautics Space Space Agency Transport Energy Hot-wire measurements of a Counter Rotating Turbo Fan (CRTF) Robert Meyer, Lars Enghardt Institute of Propulsion Technology Engine Acoustics Division (Berlin) 1/19

2 Outline DLR and the Department of Engine acoustics Hot-wire measurements in Counter Rotating Turbo Fan Rig (CRTF) /19

3 DLR Sites and Employees employees working in 9 research institutes and facilities at 9 sites in 7 field offices. Offices in Brussels, Paris and Washington. Hamburg Bremen Neustrelitz Trauen Berlin- Charlottenburg Braunschweig Berlin-- Adlershof Göttingen Köln-Porz Bonn Sankt Augustin Engine Acoustics Division Darmstadt Sites of the Institute of Propulsion Technologies Lampoldshausen Stuttgart Oberpfaffenhofen Weilheim 3/19

4 Mission DLR Institute of Propulsion Technology Increase in efficiency (resource management and reduction of operational costs) Minimization of environmental impact (pollutant and noise emission) Acceleration of product development cycles Rolls-Royce TRENT 500 Siemens Power Generation V94.3A 4/19

5 Organization of the Institute Institutefür of Antriebstechnik Propulsion Technology (AT) Prof. Dr.-Ing. Reinhard Mönig Komponenten Components Cross-sectional Querschnittsfunktionen tasks Engine Triebwerk Dr.-Ing. Andreas Döpelheuer Fan and und Compressor Verdichter Dr.-Ing. Eberhard Nicke Combustor Brennkammer Dr.-Ing. Christoph Hassa Turbine Dr.-Ing. Prof. Peter-Anton Dr.-Ing. Ingo Gieß Röhle (komm.) Engine Triebwerksakustik Acoustics Prof. Dr.-Ing. Lars rer. nat. Enghardt Lars Enghardt (komm.) Engine Triebwerksmesstechnik Measurement System Dr.-Ing. Christian Willert Numerical Numerische Methods Methoden Dr.-Ing. Dirk Edmund Nürnberger Kügeler Combustor Brennkammertest Test Dipl.-Ing. Christian Fleing Zentrum Center for für Verbrennungstechnik Combustor Technology 5/19

6 Main Work Topics/ Structure of the Department of Engine Acoustics in Berlin Lead: Lars Enghardt Turbomaschinery Acoustics Numerics/ Modelling Combustion Noise Active/Passive Flow Control Acoustic Data- and Mode analysis Source localisation Indoor-, Inflight- und Flyover-Measurements Jet Noise Active Noise Control Numerical Acoustic and Software Development (CAA) Source modelling and directivity Design to noise Combustor sound fields Optical measurement technique Entropie- and vortex noise Liner (hot and cold) Combustor instabilities Turbulence research Hot wire measurements Secondary flows Drag reduction Efficiency improvements Compressor flows 7 Researcher U. Tapken/ H. Siller 5 Researcher S. Guerin 6 Researcher F. Bake 3 Researcher R. Meyer Infrastructure, Consulting: 8 Employees Overall: 9 Employees Located on campus of the Technical University of Berlin (TU-Berlin) since 1956, Staff: 9 ( Scientists) plus students More than 50% of personal supported by external funding Very close cooperation with the Institute of Fluid Mechanics and Technical Acoustics of TU-Berlin 6/19

7 Main Strategic Direction Department of Engine Acoustics Important role (acoustic competence) in the development of system competence for aero-engines and gas turbines Support of research and development activities in turbo-machine acoustic with TRACE Cooperation with nacelle aerodynamics to predict and consider acoustical integration effects (system competence) Enhanced integration of research and development activities with other DLR- Institutes (especially Aerodynamics and Flow Technology and Atmospheric Physics) Strategic alliances with national and international universities Strategic alliances with selected industrial partners and enhanced cooperation with respect to Design-to-Noise in industrial R&D programs 7/19

8 European Community research program VITAL Collaborative research Project VITAL Environmentally Friendly Aero Engines ; 53 Partners gathering all major European engine manufacturers and national research institutes. Aim: Reduction of Aircraft noise and CO emission The aero-acoustic performance of three fan module concepts was tested in sub project (Direct Driven Turbo Fan, Geared Turbo Fan and the Counter Rotating Turbo FAN) DLR Project Task: Measurements of the unsteady flow field at the inter-stage section of a Counter Rotating Turbo Fan (CRTF) of a fast rotating compressors. Two fans rotating in opposite directions, allowing even lower rotation speeds, since the two fans split the loads involved. Hot-wire test have been performed on high speed 1/4-scale CRTF model 8/19

9 Hot-wire measurements of a Counter Rotating Turbo Fan (CRTF) Main challenging aspects: 3D velocity field Unsteady flow structures Highly fluctuating velocities Benefit: (periodic & stochastic fluctuations) Verification of the successful design of new compressor concepts. Validation of the numeric flow calculation code (CFD) and numerical acoustic simulation (CAA) Database for the numerical acoustics to improve the models for coupling acoustics and aerodynamics (modeling & prediction group) w Geschwindigkeit [m/s] v Hot-wires HW 1 HW +3 HW 4 u Fan Fan 1 resampelte machinenkoordinaten 54per_3probe_081113_7_U1 time signal mean average Rotorumfangsposition [ ] 9/19

10 Principles of the hot-wire technique Flow velocity U cooling Velocity U Wire voltage E Current I Electric current Sensor (thin wire) wire electric resistance Sensor dimensions: length ~1 mm diameter ~5 micrometer Wire supports (St.St. needles) E² =A+B*U n with n 0.5 wire temperature Sensor wires: platinum-plated tungsten wires with a diameter of d = 9-1 µm wire lengths l =.4 mm wire heated during operation to constant temperature (resistance). overheat factor: = 1.8 ( T 10 K). frequency range: f = 0-0 khz. 10/19

11 resampelte machinenkoordinaten 54per_3probe_081113_7_U1 Rotorumfangsposition [ ] time signal mean average Analysis procedures Measured raw data Calibration Calculation of effective velocities X-probe correlation?????? Rotor trigger interpretation Phased locked averaging Analysis: Mean velocities (phase averaged) Turbulence levels Spectra Analysis Geschwindigkeit [m /s] Flow field: 3D velocity field Highly fluctuating velocities 11/19

12 Methods of analysis Calculation of mean and fluctuating velocities U ( t) = U ( t) + u'( t) Trigger pulses (1 per ref.) Geschwindigkeit [m/s] rotation 1 rotation Instantaneous velocity Mean velocity Velocity U(t) Rotorumfangsposition [ ] Fluctuating velocity Phase-locked averaging (PLA) technique Statistical averaging locked on rotor rotations U(t) in [m/s] G e s c h w i n d i g k e i t [ m / s ] Instantaneous velocity 95 Mean average Rotorumfangsposition [ ] Methods of analysis: U (t) U (t) 1/19

13 DU/Ucirc Phase locked averaged velocities CRTF 1 Results: 54% rotor speed w v HW 1 HW +3 HW 4 u Axial U-component behind rotor Axial U-component behind rotor Radial V-component behind rotor 1 0 Time averaged circumferential position Circumferential W-component behind rotor Circumferential W-component behind rotor 1 13/19

14 Methods of analysis Turbulence levels v HW +3 HW 4 w u Turbulenzgrad--Nominal_54per_3probe_081113_7.bin Tu uw behind Rotor Tu uw = 1 ( u' ( U + w' ) + W ) Turbulence levels Sonde A10 UV Sonde B06 UW Sonde B08 UW Tu uw behind Rotor 1 Tu uw = 1 ( u' ( U Tu uv behind Rotor 1 + w' + W ) ) 3% Tu uv = 1 ( u' ( U + v' ) + V ) time CRTF 1 Results: 54% rotor speed 14/19

15 Methods of analysis Spectral Analysis: Power spectral density v HW w u 1. BPFR1 Power spectral density w 10. BPFR1 v HW u frequency Probe position: Axial: between two Rotors, Radial: 10 mm from outer casing Spectrum is influenced by wall boundary layer probe vibration 1. BPFR frequency Probe position: Axial: between two Rotors, Radial: 86 mm from outer casing Spectrum is influenced by core flow CRTF 1 Results: 54% rotor speed 15/19

16 Flow between rotor 1 and rotor Axial mean flow velocity U v HW +3 w u U component correlated with rotor 1 U component correlated with rotor - Upstream influence D U /Ucirc= D U/ Ucirc= CRTF 1 Results: 54% rotor speed 16/19

17 Flow between rotor 1 and rotor Radial (V) and circumferential (W) velocity (correlated with rotor 1) v HW +3 w u Radial flow velocity V Circumferential velocity W D V/Ucirc = 0.07 W/U_circ=018 CRTF 1 Results: 54% rotor speed 17/19

18 Summary In the counter rotating turbo fan hot-wire probes were placed in front of the first rotor, between both rotors and behind the second rotor. The measurements were conducted at three operating conditions of the compressor fan stage, relevant to noise issues (approach, takeoff/sideline and takeoff/cutback). With the DLR hot-wire measuring technique, unsteady flow structures of fast rotating compressors (e.g. the wake of each individual rotor blade) can be measured and analyzed in detail. The averaged mean vectors as well as the fluctuation components of the velocity are determined, which allows the local turbulence distribution of the flow behind the rotating blades to be calculated. These hotwire data results verify on the one hand the successful design of the new compressor concepts and offer on the other hand valuable information for the validation of the numerical flowcalculation code (CFD) to be applied. In addition, the results deliver a valuable data base for the development and future use of numerical acoustic simulation (CAA) tools, in particular to improve models for coupling acoustics and aerodynamics. In future, this will enable an improved noise and efficiency prediction already in the early stage of the fan modules design process. 18/19

19 Thank you for your attention Questions? Details to the project will be published on the ASME-Conference 010 Paper: GT The project is supported by the European Community within the Research Program Environmentally Friendly Aero Engines (VITAL) 19/19