Quantitative hydroxyl concentration time-series measurements in turbulent nonpremixed flames
M W Renfro1, G B King, N M Laurendeau
1School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907-1288, USA. renfro@ecn.purdue.edu
Applied Optics
|March 8, 2008
Summary
Researchers measured hydroxyl concentration in flames using laser-induced fluorescence. Accounting for fluorescence lifetime fluctuations is crucial for accurate concentration data in turbulent flames.
Area of Science:
- Physical Chemistry
- Combustion Science
- Laser Spectroscopy
Background:
- Quantitative time-series measurements of hydroxyl concentration are vital for understanding turbulent flames.
- Accurate recovery of these measurements is challenged by fluorescence lifetime fluctuations.
Purpose of the Study:
- To apply novel instrumentation for simultaneous measurement of fluorescence signal and lifetime in turbulent flames.
- To investigate the impact of hydroxyl lifetime fluctuations on quantitative concentration measurements.
Main Methods:
- Utilized picosecond time-resolved laser-induced fluorescence.
- Employed newly developed instrumentation for simultaneous fluorescence signal and lifetime measurement.
- Applied the technique to methane-air and hydrogen-argon-air nonpremixed turbulent flames.
Main Results:
- Correction for hydroxyl lifetime fluctuations significantly impacts mean concentrations and probability density functions.
- These corrections were found to be negligible for power spectral densities (PSDs).
- Hydroxyl PSDs showed variations with flame location and Reynolds number, but were similar between CH(4)-air and H(2)-Ar-air flames.
Conclusions:
- Simultaneous measurement of fluorescence signal and lifetime is essential for accurate quantitative hydroxyl concentration in turbulent flames.
- Lifetime corrections are critical for mean concentration and PDF analysis but not for PSDs.
- Hydroxyl PSD characteristics are influenced by flame conditions and fuel type.
Related Concept Videos
03:09Measuring Reaction Rates
Polarimetry finds application in chemical kinetics to measure the concentration and reaction kinetics of optically active substances during a chemical reaction. Optically active substances have the capability of rotating the plane of polarization of linearly polarized light passing through them—a feature called optical rotation. Optical activity is attributed to the molecular structure of substances. Normal monochromatic light is unpolarized and possesses oscillations of the electrical field in...
01:16Flame Photometry: Lab
In a flame photometer, when a solution like potassium chloride is aspirated into the flame, the solvent evaporates, leaving behind dehydrated salt. This salt dissociates into free gaseous atoms in their ground state. Some of these atoms absorb energy from the flame, leading to their excitation. The excited atoms return to the ground state, emitting photons at characteristic wavelengths. Because only electronic transitions are involved, the resulting emission lines are very narrow. The intensity...
01:02Flame Photometry: Overview
Flame photometry, also known as flame emission spectrometry, is a technique used for the qualitative and quantitative analysis of elements present in a sample using a flame as the source of excitation energy. The concept of flame photometry was realized in the early 1860s by Kirchhoff and Bunsen, who discovered that specific elements emit characteristic radiation when excited in flames. The first instrument developed for this purpose was used to measure sodium (Na) in plant ash using a Bunsen...
02:14Combustion Energy: A Measure of Stability in Alkanes and Cycloalkanes
The low reactivity in alkanes can be attributed to the non-polar nature of C–C and C–H σ bonds. Alkanes, therefore, were initially termed as “paraffins,” derived from the Latin words: parum, meaning “too little,” and affinis, meaning “affinity.”
Alkanes undergo combustion in the presence of excess oxygen and high-temperature conditions to give carbon dioxide and water. A combustion reaction is the energy source in natural gas, liquified petroleum gas (LPG), fuel oil, gasoline, diesel fuel, and...
Alkanes undergo combustion in the presence of excess oxygen and high-temperature conditions to give carbon dioxide and water. A combustion reaction is the energy source in natural gas, liquified petroleum gas (LPG), fuel oil, gasoline, diesel fuel, and...
01:27Fast Reactions
Fast reactions occurring in times shorter than the time needed to mix reactants pose a unique challenge for investigation. In a liquid-phase continuous-flow system, reactants A and B are swiftly pushed into the mixing chamber, where mixing occurs within 1 ms. The reaction mixture then flows through an observation tube, and one measures light absorption to determine species concentrations at various points of the tube. This method is most appropriate when relatively large volumes of reactants...
01:15Drug Concentration Versus Time Correlation
The plasma drug concentration-time curve is a crucial tool in pharmacokinetics, representing the drug's concentration in plasma at different time intervals post-administration. This curve illustrates the drug's journey from absorption into the systemic circulation, distribution to body tissues, and eventual elimination through excretion or biotransformation.
Two pivotal parameters are the minimum effective concentration (MEC) and the minimum toxic concentration (MTC). The MEC is the lowest drug...
Two pivotal parameters are the minimum effective concentration (MEC) and the minimum toxic concentration (MTC). The MEC is the lowest drug...