Increased operations of aircraft, both commercial and military in hostile desert environments have increased the risk of micro-sized particle ingestion into engines. The probability of increased sand and dust ingestion results in increased life cycle costs in addition to increased potential for performance loss. Thus, the ability to accurately assess the amount of inlet debris would be useful for engine diagnostics and prognostic evaluation. Previous engine monitoring studies were based on the particle measurements performed a posteriori. Thus, there exists a need for in situ quantification of ingested particles. This paper describes the initial development of a line-of-sight optical technique to characterize the ingested particles at concentrations similar to those experienced by aircraft in brownout conditions using laser extinction with the end goal of producing an onboard aircraft diagnostic sensor. By measuring the amount of light that is transmitted due to the effects of scattering and absorption in the presence of particles over a range of concentrations, a relationship between particle diameters and the laser light extinction was obtained. This relationship was then used to obtain information on diameters and number densities of ingested particles. The particle size range of interest was chosen to be between 1 and 10 μm and the size distribution function was assumed to be lognormal. Tests were performed on polystyrene latex spheres of sizes 1.32 μm, 3.9 μm, and 5.1 μm in water dispersions to measure diameters and concentrations. Measurements were performed over multiple wavelengths to obtain information on the size distribution and number density of particles. Results of tests presented in this paper establish the validity of the laser extinction technique to provide real time information of ingested particles and will serve as an impetus to carry out further research using this technique to characterize particles.
A Diagnostic Technique for Particle Characterization Using Laser Light Extinction
Contributed by the Controls, Diagnostics and Instrumentation Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received September 28, 2015; final manuscript received April 12, 2016; published online May 17, 2016. Editor: David Wisler.
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Barboza, K., Ma, L., Todd Lowe, K., Ekkad, S., and Ng, W. (May 17, 2016). "A Diagnostic Technique for Particle Characterization Using Laser Light Extinction." ASME. J. Eng. Gas Turbines Power. November 2016; 138(11): 111601. https://doi.org/10.1115/1.4033468
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