Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows

Hsu, Paul S.; Patnaik, Anil K.; Gord, James R.; Meyer, Terrence R.; Kulatilaka, Waruna D.; Roy, Sukesh

doi:10.1007/s00348-010-0961-6

Cited by 28 publications

(18 citation statements)

References 66 publications

(116 reference statements)

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“…Also note that the increase in the pulse duration of the higher PRR pulses may also decrease the LIDT (LIDT ∂  -0.5 ). 11,20 The coupling efficiency (i.e., the ratio of input-beam energy to output-beam energy) of the tapered fiber is ~80%, which is higher than that of the standard 550-m-core MSIF (~70%). The 80% coupling efficiency is achieved under the condition of a 6% power penalty due to fiber tapering.…”

Section: B High-power Tapered-fiber Beam-delivery Systemmentioning

confidence: 98%

“…The LIDT (tested at 10 Hz) of the tapered, fiber-optic beam-delivery system is approximately a factor of seven higher than that of the conventional fiber-optic beam-delivery system (standard multimode fiber with conventional coupling method (bulk optics)). 11 Because the large-aperture tapered fiber is capable of coupling the full-pulse energy output from the high-speed PIV laser (~7 mJ/pulse at 1 kHz, ~5.5 mJ/pulse at 5 kHz, ~3.3 mJ/pulse at 10 kHz), the LIDT of the silica fiber was tested with a 550-m-core, multimode step-index fiber (MSIF). In our experience the damage-threshold intensity of the two fibers should be very similar.…”

Section: B High-power Tapered-fiber Beam-delivery Systemmentioning

confidence: 99%

“…[10][11] In previous studies several low-repetition-rate (~10 Hz), fiber-coupled PIV systems have been developed using these fibers for detection of gas-flow velocities. [12][13][14][15][16][17][18][19] The primary challenge in the development of a fiber-coupled PIV system is delivery of sufficient laser pulse energy (~10-30 mJ at 10 Hz) through the silica fiber for PIV particle illumination.…”

Section: Introductionmentioning

confidence: 99%

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Development of fiber-coupled high-speed particle image velocimetry (PIV) for flow fields measurements in gas turbine engine hardware

Hsu

Jiang

Caswell

et al. 2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

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We demonstrate the design and implementation of a fiber-optic beam-delivery system using a large-aperture, tapered step-index fiber for high-speed PIV in turbulent combustions flows. The tapered fiber in conjunction with a diffractive-optical-element (DOE) fiber-optic coupler significantly increases the damage threshold of the fiber, enabling fiber-optic beam delivery of sufficient nanosecond, 532-nm, laser pulse energy for high-speed PIV measurements. The fiber successfully transmits 1-kHz and 10-kHz laser pulses with energies of ~5.3 mJ and ~2 mJ, respectively, for more than 25 min without any indication of damage. It is experimentally demonstrated that the tapered fiber possesses the high coupling efficiency (~80%) and moderate beam quality for PIV. Additionally, the nearly uniform output-beam profile exiting the fiber is ideal for PIV applications. Comparative PIV measurements are made using a conventionally ( bulk-optic) delivered light sheet, and a similar order of measurement accuracy is obtained with and without fiber coupling. Effective use of fiber-coupled, 10-kHz PIV is demonstrated for instantaneous 2D velocity-field measurements in turbulent reacting flows. We have also developed and implemented a fiber-coupled, high-speed PIV and PLIF system for measuring hydroxyl radical (OH) concentration and velocity in a realistic 4-MW combustion rig.Simultaneous OH-PLIF and PIV imaging at a data-acquisition rate of 10 kHz is demonstrated in turbulent premixed flames behind a bluff body. Our results show significant promise for the performance of fiber-coupled high-speed PIV and OH-PLIF in harsh laser-diagnostic environments such as those encountered in gas-turbine test beds and the cylinder of a combustion engine. Nomenclature DC= direct current DOE = diffractive optical element LIDT = laser-induced damage threshold NA = numerical aperture OH = hydroxyl radicals PIV = particle image velocimetry PLIF = planar LIF PMT = photomultiplier tube SNR = signal-to-noise ratio UV = ultraviolet

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Section: B High-power Tapered-fiber Beam-delivery Systemmentioning

confidence: 98%

Section: B High-power Tapered-fiber Beam-delivery Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Development of fiber-coupled high-speed particle image velocimetry (PIV) for flow fields measurements in gas turbine engine hardware

Hsu

Jiang

Caswell

et al. 2013

51st AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition

Self Cite

View full text Add to dashboard Cite

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“…The choice to use a picosecond system is motivated by several reasons. The use of picosecond CARS allows the possibility of complete suppression of the NRB; enables timeresolved measurements at nanosecond and subnanosecond timescales; lowers necessary pulse energies, reducing the risk of window damage; and allows measurements in harsh environments via fiber coupling [14,20,21]. Figure 4 shows a schematic diagram of the CARS instrument and its interface to the test section.…”

Section: B Picosecond Coherent Anti-stokes Raman Scattering Diagnostmentioning

confidence: 99%

Nitrogen Vibrational Population Measurements in the Plenum of a Hypersonic Wind Tunnel

et al. 2012

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Picosecond coherent anti-Stokes Raman scattering is used for measurement of nitrogen vibrational distribution function in the plenum of a highly nonequilibrium Mach 5 wind-tunnel incorporating a high-pressure pulsersustainer discharge. First-level vibrational temperatures of the order of 2000 K are achieved in the 300 torr non-selfsustained plasma discharge generated by a high E=n (300 Td) nanosecond-pulsed discharge, which provides ionization in combination with an orthogonal low E=n (10 Td) dc sustainer discharge, which efficiently loads the nitrogen vibrational mode. It is also shown that operation with the nanosecond-pulsed plasma alone results in significant vibrational energy loading, with T v N 2 of the order of 1100 K. Downstream injection of CO 2 , NO, and H 2 results in vibrational relaxation, demonstrating the ability to further tailor the vibrational energy content of the flow. N 2 -NO vibration-vibration and N 2 -H 2 vibration-translation rates inferred from these data agree well with previous literature results to within the uncertainty in rotational-translational temperature.

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“…Recently, several fiber‐based CARS experiments have been conducted for the purpose of endoscopy and microscopy in condensed phases and of thermometry in gas phases . In these cases, however, realization of fiber‐based CARS in gas‐phase flows was found to be challenging since the pulse energy required for CARS signal generation is at least four orders of magnitude higher than that required for condensed phases because of the lower molecular densities in gaseous flows—particularly at elevated flame temperatures.…”

Section: Introductionmentioning

confidence: 99%

Single‐shot thermometry using fiber‐based picosecond coherent anti‐stokes Raman scattering (CARS) spectroscopy

Hsu

Kulatilaka

Gord

et al. 2013

J Raman Spectroscopy

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Coherent anti‐Stokes Raman scattering (CARS)‐spectroscopy‐based thermometry techniques developed for laboratory flames face a stiff challenge when implemented in practical combustion environments such as engine test facilities. In addition to limited optical access, the harsh environments associated with these test facilities (i.e. uncontrolled humidity, vibration, and large thermal gradients) often restrict the operation of sensitive laser systems. To circumvent this problem, we have developed a fiber‐based, picosecond (ps) CARS system employing long‐length (up to 6 m), multimode silica fibers that permits the laser system to be isolated from the high heat and vibration of the test hardware. Proof‐of‐principle, single‐laser‐shot temperature measurements using a 3‐m‐long fiber system are demonstrated in atmospheric pressure, near‐adiabatic, laboratory H2–air flames. Limitations that are imposed by long‐length multimode‐fiber beam delivery for CARS thermometry are identified as nonlinear effects during beam propagation along the fiber, depolarization of the laser beam, and degradation of the beam quality at the output of the fiber. These effects are investigated in detail, and potential improvements are suggested. The current study shows promise for implementation of fiber‐based ps‐CARS spectroscopy in harsh environments such as those encountered in combustors and afterburners in practical gas‐turbine‐engine test facilities. Copyright © 2013 John Wiley & Sons, Ltd.

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Investigation of optical fibers for coherent anti-Stokes Raman scattering (CARS) spectroscopy in reacting flows

Cited by 28 publications

References 66 publications

Development of fiber-coupled high-speed particle image velocimetry (PIV) for flow fields measurements in gas turbine engine hardware

Development of fiber-coupled high-speed particle image velocimetry (PIV) for flow fields measurements in gas turbine engine hardware

Nitrogen Vibrational Population Measurements in the Plenum of a Hypersonic Wind Tunnel

Single‐shot thermometry using fiber‐based picosecond coherent anti‐stokes Raman scattering (CARS) spectroscopy

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