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High-frequency measurement of concentration in an isothermal methane-air gas mixture using spontaneous Raman spectroscopy.

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Rodrigues, Jocelino 
Weller, Lee 
De Domenico, Francesca 
Hochgreb, Simone 


A high-frequency (1.5 kHz) spontaneous Raman spectroscopy measurement technique is developed and applied to measure external fluctuations generated in the local concentration of an isothermal binary gas mixture of methane and air. Raman excitation is provided by a high-frequency laser at 527 nm in dual-pulsed mode. The Stokes Raman signal is collected using an EMCCD camera coupled to a high-frequency intensifier as a shutter. The emitted signal is collected over the 596-627 nm wavelength range, which allows for the simultaneous tracking of methane and nitrogen Stokes Q-branch mode signals. Calibration curves are initially obtained for each species ([Formula: see text] and [Formula: see text]) based on steady-state concentrations, and further corrected during use to detect local unsteady mixture fluctuations at gas pulsation frequencies up to 250 Hz. The main novelty is the demonstration of Raman spectroscopy for the simultaneous multispecies measurement of unsteady concentrations of gas-phase methane and air mixtures using a laser beam with a high-repetition rate, low energy per pulse, combined with a high-frequency intensifier and a single camera.


Acknowledgements: The authors thank Dr. Pedro M. de Oliveira (University of Cambridge) for the discussions on Raman calibration procedures, Dr. Alicia Benhidjeb-Carayon (NASA Jet Propulsion Laboratory) for reading and commenting on the manuscript, Mark J. Riches (Invisible Vision Ltd.) for clarifying details regarding the camera intensifier, and Mark Garner (University of Cambridge) for designing and making the energy-saving circuit used to control the injection valve.

Funder: Rolls-Royce; doi:


51 Physical Sciences, 40 Engineering, 4017 Mechanical Engineering, 4002 Automotive Engineering

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Springer Science and Business Media LLC
Engineering and Physical Sciences Research Council (EP/K02924X/1)
Engineering and Physical Sciences Research Council (EP/K035282/1)
Engineering and Physical Sciences Research Council (EP/M015211/1)
This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) grant EP/K02924X/1 and EPSRC EP/K035282/1. Jocelino Rodrigues was supported by the Qualcomm European Research Studentship and the EPSRC DTA Studentship (1754253 – University of Cambridge). Additional support from Rolls-Royce plc is also acknowledged. Lee Weller was funded under the EPSRC UK Award EP/M015211/1 within the ANAM Initiative. Francesca De Domenico was supported by a Junior Research Fellowship (Gonville and Caius College).