Laser-induced plasma; Equivalence ratio; Plasma emission; Spray flame;LASER-INDUCED BREAKDOWN; EQUIVALENCE RATIO MEASUREMENT; TO-AIR RATIO; INDUCED SPARK; GAS-DENSITY; SPECTROSCOPY; METHANE; MIXTURE; PRESSURE; IGNITION

A portable device composed of photodiodes and bandpass filters was developed to measure local fuel concentration in a liquid hydrocarbon-fueled spray flame. The plasma emission spectra in and around the flame were selectively captured using such simplified device or plug instead of using a laboratory standard laser-induced breakdown spectroscopy (LIES) system consisting of an ICCD and a spectrometer. The hydrogen (656 nm) and oxygen (777 nm) atomic lines were selected to determine the fuel concentration in atmospheric pressure. The WO signal intensity ratio was found to be a strong function of the fuel concentration, and thus a calibration curve for the concentration measurements was established and validated using conventional LIES. The proposed scheme to measure the local equivalence ratio of spray flames using a bundled layout of multiple LIES plugs alongside the combustor wall may offer simple and highly robust diagnostics, especially under the harsh combustion conditions within air breathing engines. (C) 2017 Elsevier Ltd. All rights reserved.

Raman; laser-induced breakdown spectroscopy; LIBS; matrix effect; geological samples;QUANTITATIVE-ANALYSIS; SPECTROMETER; MIXTURES

Quantitative Raman analysis was carried out with geologically mixed samples that have various matrices. In order to compensate the matrix effect in Raman shift, laser-induced breakdown spectroscopy (LIBS) analysis was performed. Raman spectroscopy revealed the geological materials contained in the mixed samples. However, the analysis of a mixture containing different matrices was inaccurate due to the weak signal of the Raman shift, interference, and the strong matrix effect. On the other hand, the LIBS quantitative analysis of atomic carbon and calcium in mixed samples showed high accuracy. In the case of the calcite and gypsum mixture, the coefficient of determination of atomic carbon using LIBS was 0.99, while the signal using Raman was less than 0.9. Therefore, the geological composition of the mixed samples is first obtained using Raman and the LIBS-based quantitative analysis is then applied to the Raman outcome in order to construct highly accurate univariate calibration curves. The study also focuses on a method to overcome matrix effects through the two complementary spectroscopic techniques of Raman spectroscopy and LIBS.