Session: 05-04: Combustion Measurements 1

Submission Number: 178870

Optimization of Planar Laser Diagnostics in a Whirl Combustor 

Rayleigh Thermometry [1, 2] (RT) is a minimally intrusive technique capable of measuring two-dimensional temperature fields employing Rayleigh scattering of a planar laser sheet off a flame. RT can be implemented together with other laser diagnostic techniques, such as Planar Laser Induced Fluorescence (P-LIF) [3], to provide a comprehensive picture of combustion processes and aid in the design of efficient combustors. Despite its relatively low experimental complexity compared to other laser-based thermometry techniques, such as Raman spectroscopy [4], RT has not seen a wide adoption in the industry since its first demonstration in 1981 by Dibble and Hollenbach [5]: this is primarily due to the intrinsically low signal levels offered by Rayleigh scattering compared to stray reflections from solid surfaces in the combustion chamber. Recent advancements through the works of Kristensson and others [6, 7] drastically improved the signal to noise ratio achievable through RT, thanks to the introduction of a collection of techniques known as Structured Laser Illumination Planar Imaging (SLIPI), in which the structuring of the laser sheet allows a more efficient removal of stray reflections and background noise in post processing analysis.

industrial scale Whirl Combustor [8] under various laser illumination conditions and different post-processing techniques, showing temperature and OH fields within the expected range. A square, four-sides windowed, combustion chamber was tangentially fed through two coaxial air and fuel nozzles, located on a pair of opposite corners of the chamber to induce the whirl motion. A swirler was also placed in the air nozzle to provide a burner piloting stage, until the pilot flame transition to Distributed Combustion.

 

 

 

References:

[1] A. C. Eckbreth et al., Laser Diagnostics for Combustion Temperature and Species 2^nd Ed. Taylor & Francis (1996).

[2] K. Kohse-Hӧinghaus and J. B. Jeffries, Applied Combustion Diagnostics. Taylor & Francis (2002).

[3] I. B. Ӧzdemir and N. Peters, Characteristics of the reaction zone in a combustor operating at mild combustion, Experiments in Fluids 30, 683-695 (2001).

[4] N. M. Laurendeau, Temperature measurements by light-scattering methods, Prog. in Energy and Comb. Sci. 14(2), 147-170 (1988).

[5] R. W. Dibble and R. E. Hollenbach, Laser Rayleigh Thermometry in Turbulent Flames, 18^th Symp. on Comb., The Combustion Institute (1981).

[6] N. J. Kempema and M. B. Long, Quantitative Rayleigh thermometry for high background scattering applications with structured laser illumination planar imaging. Appl Opt. 53(29), 6688-97 (2014).

[7] E. Kristensson, A. Ehn, J. Bood and M. Aldén Advancements in Rayleigh Scattering thermometry by means of structured illumination, Proc. of the Comb. Inst. 35 3689-96 (2015).

[8] R. A. Yetter, I. Glassman and H. C. Gabler, Asymmetric whirl combustion: A new low NOx approach, Proc. of the Comb. Inst., 28 (1) 1265-1272 (2000).

Presenting Author: Alessandro Porcelli Co.Svi.G. S.c.r.l. - Sesta Lab

Presenting Author Biography: Alessandro Porcelli earned a Ph.D. in Physics at the University of Pisa in collaboration with Sesta Lab with a thesis focusing on photonics and laser diagnostics for combustion.

Authors:

Alessandro Porcelli Co.Svi.G. S.c.r.l. - Sesta Lab
Stefano Chiocchini Co.Svi.G. S.c.r.l. - Sesta Lab
Donatella Ciampini University of Pisa - Physics Department "E. Fermi"