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.