Non-intrusive sensing of air velocity, humidity, and temperature using TDLAS

Size: px

Start display at page:

Download "Non-intrusive sensing of air velocity, humidity, and temperature using TDLAS"

John Brooks
5 years ago
Views:

1 Non-intrusive sensing of air velocity, humidity, and temperature using TDLAS TDLAS: Tunable Diode Laser Absorption Spectroscopy Suhyeon Park Mechanical Engineering, Virginia Tech Advisor Dr. Lin Ma Aerospace and Ocean Engineering Mechanical Engineering Adjunct Virginia Tech

2 Outline Introduction: Concept of TDLAS measurement Velocity measurement Temperature measurement and non-uniform distribution analysis Water concentration tomographic inversion 2

- simultaneous measurement Non-intrusive in-situ real-time monitoring without

3 TDLAS for wind energy TDLAS sensor Real-time monitoring Flow info Research instrument Active control of wind turbines Velocity, humidity and temperature - simultaneous measurement Non-intrusive in-situ real-time monitoring without particle seeding Calibration-free accurate measurement Low cost, low maintenance 3

4 Fundamental theory of absorption spectroscopy Detector I t ( ) L Laser I o ( ) Beer - Lambert relation: τ ν = I t(ν) I o = exp[ k ν L] Measure k ν and P to infer T and X : k ν = f(t, X, P) 4

5 Principle of TDLAS measurement T temperature : inferred from the shape of spectra (the relative absorption strengthen of a cold and a hot line) X H 2 O concentration : inferred from the magnitude of the spectra after T) V flow velocity : inferred from Doppler shift between two beams with an angle T=2379 K X=0.347 T=1647 X=0.190 Cold Line Hot Line mm mm 5

6 Outline Introduction: Concept of TDLAS measurement Velocity measurement Temperature measurement and non-uniform distribution analysis Water concentration tomographic inversion 6

7 TDLAS Doppler velocimetry setup 50 θ Photodiode 1 Laser Diode 1343 nm Coupler Coupler Coupler 10 MZI Photodiode 2 Laser Diode 1392 nm Interferometer Air Flow Schematic of H 2 O absorption velocity measurement Tunable diode laser scans across optical frequency Mach-Zehnder interferometer converts time series data into frequency spectrum Two beams cross at angle 2θ and Doppler shift is measured 7

8 TDLAS velocity measurement demonstrated in a simple duct y Laser Air Flow x Experimental setup of TDLAS velocity measurement Averaged velocity in the y direction 8

9 Measured Doppler shift by TDLAS Voigt Fitting Parameters Voigt 1 Voigt 2 y 0, offset E E-03 x c, center E E-03 A, area E E-03 w G, Gaussian width E E-02 w L, Lorenzian width E E-02 9

10 TDLAS measured velocity in agree with hot wire velocity TDLAS velocity agrees well with averaged hot-wire velocity Averaging (i.e., effects of flow non-uniformity) will be more thoroughly investigated in the future 10

11 Outline Introduction: Concept of TDLAS measurement Velocity measurement Temperature measurement and non-uniform distribution analysis Water concentration tomographic inversion 11

12 Ambient air temperature measurement Absorbance Cold Laser Whole Range TDLAS cold line Simulation Measurement Wavenumber(cm -1 ) TDLAS Voigt cold Fitting line Measurement Voigt Fit Absorbance Hot Laser Whole Range Simulation Measurement TDLAS hot line Wavenumber(cm -1 ) TDLAS Voigt hot Fitting line Measurement Voigt Fit Identification of target lines Laser controller setting: Diode temperature T case,cold = 27.2 C T case,hot = 26.2 C Drive current control V mod = 1.7 V pp, ramp signal Temperature sensing Absorbance A cold = e-2 cm Wavenumber (cm -1 ) Absorbance A hot e-3 cm Wavenumber (cm -1 ) Room condition T = 23 C Measured temperature T M = 25 C (error = +2 K) 12

was manually traversed through a stable flat flame from a McKenna burner

13 Temperature ( C) Thermocouple measurement of flame temperature McKenna Burner and flame temperature measurement Thermocouple was manually traversed through a stable flat flame from a McKenna burner McKenna burner flame temperature was about 1200 C Position (mm) 13

Setup to demonstrate non-uniform temperature distribution TDLAS measurement was conducted for premixed burner flame Detector McKenna Burner Hot section Beam path Laser Non-uniform

14 Setup to demonstrate non-uniform temperature distribution TDLAS measurement was conducted for premixed burner flame Detector McKenna Burner Hot section Beam path Laser Non-uniform temperature distribution setup Goal: To see if TDLAS can resolve the non-uniform temperature and water concentration in the laser beam path Hot section: flame Cold sections: ambient air 14

15 Line-of-sight TDLAS measurement of Flame Temperature 0.05 Line Strength - Temperature Relation A cold A hot S hot /S cold 2 TDLAS measured temperature was 936 C Absorbance Signal ratio Ratio Discrepancy is due to temperature non-uniformity in the beam path 0 T Temperature (K) T = 1209 K = 936 C Possible solutions include nonuniform analysis or tomographic inversion. 15

16 Flame temperature distribution by TDLAS non-uniform analysis Case 1 TDLAS 1460 K TC 1489 K T (K) 1800 TC 1600 TDLAS x (mm) Non-uniformly distributed temperature is found by thermocouple (TC) and TDLAS measurement Case 2 TDLAS 1587 K TC 1588 K T (K) TC TDLAS TDLAS measured temperature distribution agrees with TC measurement x (mm) 16

T 2 T 2 Position (cm) Flame Valuable for practical implementation Practical flows are

17 Temperature (K) Non-uniform fitting procedure Temperature Distribution T 1 6 cm Fitting procedure demonstrated to find T1, X1, T2, X2 in hot section and cold sections 0 0 Side View T 2 T 2 Position (cm) Flame Valuable for practical implementation Practical flows are non-uniform Undesirable/difficult to mount sensors near hot flows Collimator McKenna Burner Detector 17

18 Example results from the fitting procedure TDLAS absorption spectrum T 1 = 1587 K, X 1 = Measurement Non-uniform Uniform Measurement Non-uniform Uniform Absorbance Absorbance Frequency, cm Frequency, cm -1 Our method exploits the shape (i.e., all the data points on the absorption lines) to obtain distribution information in nonuniform flows 18

19 Outline Introduction: Concept of TDLAS measurement Velocity measurement Temperature measurement and non-uniform distribution analysis Water concentration tomographic inversion 19

+ IS Beam 1 Beam 2 Collimator Laser beams cross at the jet for TDLAS velocity measurement with Doppler effect

20 TDLAS setup in high speed jet measurement Jet Sensors Traverser Lasers TDLAS measurement system is installed for high speed jet measurement Laser controller TDLAS setup installed at the high speed jet facility Detecter + IS Beam 1 Beam 2 Collimator Laser beams cross at the jet for TDLAS velocity measurement with Doppler effect Sensors are installed on a vertical traverser Detecter + IS Jet flow Collimator TDLAS sensors located at the jet 20

21 Water density of high speed jet obtained by traversing TDLAS XL (A.U.) x Ambient air Jet flow Ambient air Vertical Position(cm) TDLAS measurement in the high speed jet at Mach 0.65 Line-of-sight averaged water concentration measured by traversing the TDLAS sensor Conditions Ambient air: 25 C, X = Compressor supplied air: 17 C, X = Traversing step : 0.4 cm 21

22 Projection of non-uniform distribution Distribution X 1 X 1 5 cm X 2 0 r y TDLAS measurement by traversing is a projection of non-uniform distribution X 1 Front View X 2 Jet flow X 1 Water density projection should be reconstructed to distribution by tomography Collimator Detector Projection 0 y 22

23 Introduction to Abel inversion (Tomography in 1D) r l 1,1 l1,2 l 2,2 l 3,3 l 2,3 l 1,3 Abel inversion is used in axially symmetric geometry... X 3 X 2 X 1 The jet is divided into layers with different water density (X 1, X 2, X 3...) X = A -1 P Distribution can be obtained from TDLAS measured projection by Abel inversion X - Distribution A - Geometry P - Projection 23

24 1D tomography applied to TDLAS jet measurements 16 x 10-3 Reconstructed X (A.U) Ambient air Jet flow Ambient air Abel inversion is applied to TDLAS jet measurements Spatial distribution of water density in the jet is obtained r (cm) Spatial distribution of water density in the high speed jet at Mach

25 Conclusion TDLAS measurement of temperature, velocity, water concentration was demonstrated simultaneously Non-intrusive instantaneous measurement capabilities of TDLAS sensor can be utilized in research facilities and practical monitoring system of wind energy 25

26 Thanks! Suhyeon Park Department of Mechanical Engineering Virginia Tech, Blacksburg, 24060, VA Tel: (540)

Hefei

Hefei 2017 3rd International Conference on Computer Science and Mechanical Automation (CSMA 2017) ISBN: 978-1-60595-506-3 Experimental Study of Broadening Coefficients for the v3 Band of CO by Tunable Diode