Laser Diagnostics for Hypersonic Ground Test

Transcription

1 Laser Diagnostics for Hypersonic Ground Test Ronald K. Hanson and Jay B. Jeffries High Temperature Gasdynamics Laboratory Stanford University AFOSR/NASA, Review, June TDL sensors: vision/fundamentals 2. Sensing for UVa 3. Sensing for ATK 4. Advanced concepts for future needs CO 2, T for hydrocarbon fuel Normalized WMS to suppress noise Scanned WMS for simultaneous multi-parameter sensing 1

2 Vision for Laser Sensing in Hypersonic Propulsion Diode laser sensors offer prospects for time-resolved, multi-parameter, multi-location sensing for performance testing, model validation, feedback control Inlet and Isolator (velocity, mass flux, species, shocktrain location) Combustor (T, species, stability) Exhaust (T, species, UHC, velocity, thrust) Acquisition and Feedback to Actuators Fiber Optics Diode Lasers Project focuses on new tools and data for hypersonic ground test Develop, test, and validate at Stanford; targets are T, H 2 O, CO 2, O 2, V, & HCs Apply to ground test UVa Transition to application in ATK Future opportunities in other test facilities, flight? 2 6

3 Absorption Fundamentals: The Basics V I 0 TDL absorption: non-intrusive, time-resolved line-of-sight measurements I t L Unshifted line Multiplexed-cw-lasers Visible, NIR, extended NIR, mid-ir Doppler shifted lines Beer-Lambert relation It exp( k L) exp I o absorbance Spectral absorption coefficient k S( T ) ( T, P, i ) i Mass and momentum flux from and V Many-line data for non-uniform T(x), X i (x) Approaches: Direct absorption or WMS n i P L Shifts & shape of contain information (T,P, i ) V from Doppler shift of spectra Wavelength-multiplexing for multi-parameters Ratios of lines yield T T and yield i (mole fraction) or n i or 3 3

4 Injection current tuning I o Comparison of Direct Absorption and WMS (2f/1f) Direct Absorption 0.00 i i + Injection current Gas sample I t WMS 2f&1f Laser Intensity Signal WMS Signal Direct Absorption Scan Time(ms) WMS Scan Time (ms) Baseline fit for I o 2f Direct absorption: Simpler, if absorption is strong enough WMS: More sensitive especially for small signals (near zero baseline) Ratio of two WMS-2f signals provides T (same as direct absorption) WMS with TDLs improves noise rejection (especially for non-absorption losses) Since both 2f and 1f signals are proportional to I; 2f/1f independent of optical losses Absorbance Normalized 2f signal Direct absorption lineshape Wavelength (relative cm -1 ) WMS-2f lineshape Wavelength (relative cm -1 ) 4 4

5 Diagnostics to Support Dual-Mode Combustion Modeling Benchmark Measurements in Combustion Isolator Mach 2 Nozzle Combustor Tomography Extender & CARS TDL measurement planes UVa facility provides steady operation Stanford TDL diagnostics will target combustor and combustor inflow Time resolution (cw sensors allow frequency analysis) Spatial resolution Translate LOS (vertical) for spatial resolution Monitor at multiple locations: Inflow & three downstream Targets: H 2 O & T for H 2 fuel; CO 2 & T for HC fuel Future plans will add velocity 5

6 Stanford TDLAS Timeline for UVa Tests Measurement Campaign 1 (March 2010) UVa exit plane measurements Measurement Campaign 2 (November 2010) 2D-resolution measurements via windows in the combustor Inflow plane characterization (with steam injection) revealed window leaks Flame-holding instabilities led to window failure preventing combustion exps Plans for measurement campaign 3 (fall 2011) Complete 2D T and χ H2O measurements in combustor Final window design awaits combustion stability tests

7 Review of Year 1: Exit Plane Results Stanford UVa exit plane diagnostics LOS path-averaged T and χ H2O Comparison of direct absorption and WMS WMS increased sensitivity with reduced uncertainty Test Cases Validation of facility steam injection Simulated vitiation with 9% and 12% H 2 O H 2 -Air Combustion w/ ϕ=.33 Results show complete combustion at tunnel exit Mode Expected Value DA WMS 9% Steam K 860±30K 831±9K Exit value 9.1±0.4% 9.1±0.2% 9.1±0.1% 12% Steam K 875±50K 850±6K Exit value 12.0±0.5% 12.1±0.5% 11.5±0.1% H 2 /Air Combustion K 1802±94K 1765±41K =0.33 Exit value 13% 12.8±0.5% 11.5±0.1% 7

8 Review of Year 2 Measurements 2D measurement system Optics on computer-controlled translation stages Measurements at multiple axial locations (Y) Sub-mm spatial resolution on each plane (X) Measurement plan Combustor inflow measurements with steam injection (completed Nov 2010) Combustion measurements at 3 axial locations downstream of fuel injection Unstable flameholding and subsequent window failure delayed these measurements (planned for fall of 2011) Y X 8

9 Inflow-Plane Measurements Revealed T Gradient Distribution of LOS T transverse to inflow w/11% added steam Ramp wall Fuel injection 0.04 From Wall Opposite Fuel Injector Error Bars Represent ±1 from 500 samples average (0.5 seconds) Translating LOS for TDL Inflow measurement plane Gradient in T likely due to cold-air leak around window on ramp wall side Observation of unstable flameholding consistent with leak Next measurement campaign awaits successful/stable flameholding at UVaSCF (tentatively fall 2011)

10 Diagnostics to Support HyPulse Benchmark Measurements in Reflected Shock ATK GASL Mach 5-25 M5 Facility Nozzle Test Article Driver gas Air (test) gas Diaphragm 10

11 Diagnostics to Support HyPulse Benchmark Measurements in Inlet Flow exit Planned test conditions: P = 60 kpa T = 1700 K ms test time Ramp fuel injection H 2 fuel Need: data for CFD validation of combustion efficiency (completeness of combustion), fuel penetration, flow characterization, etc. Plan: Simultaneous T and χ H2O at multiple lines-of-sight at several axial locations in HyPulse hydrogen fueled combustor Challenge: High-speed (10-15ms test time), compact, multi-los sensor design Requires fast, sensitive sensor concepts Requires miniaturized optical components 11

12 Miniaturization of Optical System New Fiber Optics Enable Five LOS over 1 Flowpath Supersonic Air L~1 Exhaust H 2 Fuel Injector Ramp 5 Beam Paths Optical Fibers Five measurement LOS in each downstream plane Spatially-resolved measurements needed to validate model results Axial measurement plane locations monitored sequentially Challenge: Optical system engineering New fiber collimators designed, fabricated, and laboratory tested 12

13 Two-Color TDL Sensor for H 2 O and T T sensor validation in heated cell Heated cell Line selection Selected H 2 O features at nm and nm Database and sensor performance measured in Stanford heated cell Absorption measurement strategies Scanned-Wavelength Direct Absorption 20kHz bandwidth 1f-normalized WMS-2f 250kHz bandwidth w/ improved SNR 13

14 Stanford TDLAS Timeline for ATK Tests Completed (Spring 2011): Sensor design (line selection, measurement techniques and locations) Validation of spectroscopic database Fiber-coupled 3 mm collimation optics designed, fabricated and tested Remaining tasks (Summer 2011) Test article ATK Test sensor package in Stanford shock tube or expansion tube First HyPulse measurement campaign Planned for Fall

15 Continued Development of New Sensor Concepts Advanced sensor concepts to meet future needs in ground test at UVa & ATK 1. New sensor for CO 2,T needed for hydrocarbon fuels Demonstration measurements in shock tubes - Complete 2. 2/1f normalization strategy for WMS to suppress noise from non-absorption losses in transmitted intensity Demonstration measurements of gas T in presence of liquid aerosol- complete 3. New scanned-wms concepts for simultaneous, multi-parameter sensing based on refined model that accounts for simultaneous laser intensity and wavelength modulation needed for precision velocity Demonstration measurements in Stanford expansion tube just initiated 15

16 CO 2, T Sensor Using Extended-NIR Extended NIR Enables Large Increase in Sensitivity Access to CO 2 enabled by new DFB lasers for >2.5 m The band strength near 2.7 m is orders of magnitude stronger than NIR Many candidate transitions for optimum line pair (depending on T) 16

17 Extended-NIR Sensor for CO 2, T Strategy: Sense T by ratio of absorption by two CO 2 transitions 1%CO 2, L=10cm NIR Fiber-coupled Diodes Extended-NIR E = cm -1 E = cm -1 m 1. An optimum line pair (R(20) and P(70) was selected Isolated from H 2 O, wide separation in E 2. Validate in shock tube Demonstrate achievable precision 17

18 Shock-Tube Validation of Extended NIR CO 2, T Sensor Precision Time-Resolved T from WMS-2f/1f of CO 2 Validate fast, sensitive strategy for CO 2, T using a shock tube DFB laser Shock wave Test mixture InSb Detector Ratio of WMS-2f/1f signals for R(28) and P(20) CO 2 transitions 2f signal ratio P = 1.0 atm P = 2.0 atm 1 ~2743nm 2 ~2752nm Temperature [K] Ratio of WMS-2f signals sensitive to temperature, insensitive to pressure (1-2 atm) Sensor provides accurate and precise time-resolved temperature 18

19 Shock-Tube Validation of Extended NIR CO 2, T Sensor Temperature vs Time in Shock-Heated Ar/CO 2 Mixtures Temperature [K] atm, 2%CO 2 in Ar T ideal Reflected shock arrival Incident shock arrival Time [ms] Pressure [atm] Difference of Measured T & T 5 [K] K 0 K Reflected shock arrival Time [ms] Temperature data agree well with T 5 determined from ideal shock relations Temperature precision of 3 K demonstrated! Unique capability for real-time monitoring of T in reactive flows High potential for supersonic combustion applications 19

20 1f-normalized WMS-2f Improves SNR Accounts for Non-Absorption Transmission Loss Modulated TDL near 1392nm Pitch Lens Detector Fixed WMS-2f/1f Ambient H 2 O (T=296 K, 60% RH) L=29.5 cm, ~6% absorbance) 1f Magnitude 2f Magnitude nm, Partially Blocking Beam 1392 nm, Vibrating Pitch Lens 2f Magnitude 1f Magnitude 1f Magnitude 2f Magnitude f Magnitude 1f Magnitude 2f/1f Magnitude f/1f f/1f Magnitude f/1f Time (s) Time (s) Demonstrate normalized WMS-2f/1f No loss of signal when beam attenuated (e.g., scattering losses) No loss of signal when optical alignment is spoiled by vibration Normalized WMS-2f/1f signals free from window fouling and particulate loading 20 20

21 1f-Normalized WMS-2f for CO 2 with Scattering from Particles Validate in Aerosol-Laden Gases Aerosol shock tube experiment: 2% CO 2 /Ar in n-dodecane aerosol, L=10 cm P 2 =0.5 atm; P 5 =1.5 atm 2f/1f TDL sensor successfully measures T in presence of aerosol! May prove useful in silane-h 2 fueled combustion W. Ren, J.B. Jeffries, R.K. Hanson. Measurement Science and Technology 21 (2010) 21

22 New Extension of WMS Theory for TDLs Existing Strategy: Fixed- WMS Well-established: improves sensitivity and noise rejection High data rate & and facile real-time analysis Calibration-free with inclusion of laser tuning and spectroscopic models The Opportunity: Rapid scanning of WMS would allow simultaneous monitoring of i, T, & V 2f/1f spectra include lineshape information (T, P) The Problem: Rapid wavelength scanning with TDLs Simultaneous variation in and I from current-tuned TDLs distort laser WMS The Solution: New model includes phase shifts and non-linear signal coupling Experiments underway to validate new model 22

23 Planned Measurements to Demonstrate Scanned WMS Stanford Expansion Tube Supersonic flow facility capable of producing a wide range of flight conditions with realistic chemistry but with limited test time Test Section Driver Section Driven Section Expansion Section Dump Tank Pressure trace identifies well-characterized test time Test Section Pressure [kpa] Expansion Gas Arrival Test Gas Arrival Test Time End Time [ s] 23

24 Supersonic Demonstration of Scanned WMS Scanned WMS demonstration in Stanford expansion tube Flow model with configurable beam paths T, V, and X H2O data rate: 25 khz Demonstration experiments underway 24

25 Summary Summary and Acknowledgements Sensor and hardware for spatially-resolved gas T ready for dual Status: Measurement campaign planned fall 2011 Miniaturized, multi-path sensor for ATK nearly ready for shock tube/expansion tube validation Status: Validation test underway, planned campaign fall 2011 New sensor strategies New extended-nir CO 2, T sensor combustion efficiency for HC fuels 1f-normalization of WMS suppresses flow-field noise enabling technology New model for -scanned-wms high speed velocity, T, X H2O sensor Acknowledgements Collaborators: Goyne & McDaniel at UVa, Cresci & Tsai at ATK Current students: Chris Goldenstein, Ian Schulz, Wei Ren, Christopher Strand 25