Hiroyuki Oyama

VISUALIZATION OF OH RADICAL DISTRIBUTION IN A METHANE-HYDROGEN MIXTURE FLAME BY ISOTOPE SHIFT/PLANAR LASER INDUCED FLUORESCENCE SPECTROSCOPY

Two types of OH radicals exist in a mixture of CH4–H2 fueled flame, which are produced respectively from CH4-air and H2-air combustion reactions. We have devised a new diagnostics tool for planar laser-induced fluorescence (PLIF) spectroscopy using isotope shift (herein called IS/PLIF spectroscopy). This diagnostics was applied to separately visualize two-dimensional (2-D) distributions of net (not absolute) OH radical fluorescence intensities produced from CH4–O2-air and H2–O2-air combustion reactions in a CH4–H2–O2-air premixed flame. In result, the OH radical produced from H2–O2-air combustion reaction appeared on upstream side of the inner flame as compared to that produced from CH4–O2-air combustion reaction. Since OH radical is one of chain carriers in combustion reactions, this indicates that H2 tends to react at more upstream location than CH4 in the CH4–H2 mixture flame. This tendency is attributable to the fact that H2 differs from CH4 in the high burning velocity and extended flammability limit.

Two-dimensional observation of excited atoms and ions and excitation temperature in inductively coupled plasma using newly developed four channel spectrovideo camera

A four-channel spectrovideo camera was developed and applied to the measurement of spatially and spectrally resolved profiles of atomic and ionic emission in an inductively coupled plasma (ICP). Spatial distributions of argon and chromium atoms and iron ions in ICP were visualized successfully. The excitation temperature profiles of argon, chromium, and iron in ICP were also successfully constructed on the basis of the two-line method. The excitation temperature profiles obtained with a monochromator and the spectrovideo camera were in fairly good agreement.Graphical Abstract

Isotope Shift/Planar Laser Induced Fluorescence Diagnostics for Examining Hydrogen-Methane Flames

The chemical species in a mixture of hydrogen-hydrocarbon flame can be classified into two types according to their origins; one is produced from the hydrogen-air combustion reactions while the other from the hydrocarbon-air combustion reactions. For the separate visualization of the distributions of these two types, we have devised a new diagnostics tool for planar laser-induced fluorescence (PLIF) spectroscopy using isotope shift (herein called IS/PLIF spectroscopy). This diagnostics has been applied for separate visualization of the two-dimensional (2-D) distribution of the fluorescence intensity of the OH radicals produced from the CH4-O2-air combustion reactions and the 2-D distribution from the H2-O2-air combustion reactions in a CH4-H2-O2-air premixed flame. The selectively visualized 2-D distributions of OH radicals showed that the OH radicals produced from the H2-O2-air combustion reactions tend to exist upstream in the flame as compared to the OH radicals produced from the CH4-O2-air combustion reactions. For a quantitative comparison, we calculated the ratio of the 2-D integrated value of the OH fluorescence intensity produced from the CH4-O2-air combustion reactions to the 2-D value of all the OH fluorescence intensity in the CH4-H2-O2-air flame. This ratio is directly proportional to the number of moles of H atoms contained in CH4 in the CH4-H2 mixture.

Two-dimensional Visualization of Premixed Hydrogen-Oxygen High Temperature Flame

We applied new type high–speed CCD camera to obtain the 2D chemical composition distributions in premixed hydrogen–oxygen flame. This camera can obtain set of four spectrograph images simultaneously by four channels with interference filters. As a measuring object, the combustion flame of the pre–mixed hydrogen–oxygen gas generated by electrolysis was selected. This electrolyzer equipment can generate the high–temperature flame easily, and it has the ability to substitute the conventional acetylene–oxygen frame. As a result, we obtained the distributions of temperature, OH radical and hydrogen beta line i nt heflame. The usefulness of this new type camera was verified.

Atomic Emission Spectrometry for Profiling High Temperatures in Combustion System

In this work a simple method was succesfully applied to observe proe les of high temperatures above 2000 K in a combustion e eld by combining a chemical seeding technique and a high-speed shuttering camera e tted with an optical bandpass e lter. Spontaneous atomic emission proe les of chromium triplets from a partially premixed e ame of acetylene-oxygen seeded with potassium chromate were measured to estimate the excitation temperature proe le in the e ame. An asymmetric Abel inversion was also successfully applied to illustrate radial proe le of the excitation temperature. A signie cant difference in the proe le was recognized between the results with and without this process. The lower temperature around the e ame axis and a high-temperature donut in the middle zone were found and discussed in conjunction with mixing of acetylene and oxygen.