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Title: Measurements and interpretation of shock tube ignition delay times in highly CO 2 diluted mixtures using multiple diagnostics

Common definitions for ignition delay time are often hard to determine due to the issue of bifurcation and other non-idealities that result from high levels of CO 2 addition. Using high-speed camera imagery in comparison with more standard methods (e.g., pressure, emission, and laser absorption spectroscopy) to measure the ignition delay time, the effect of bifurcation has been examined in this study. Experiments were performed at pressures between 0.6 and 1.2 atm for temperatures between 1650 and 2040 K. The equivalence ratio for all experiments was kept at a constant value of 1 with methane as the fuel. The CO 2 mole fraction was varied between a value of X CO2 = 0.00 to 0.895. The ignition delay time was determined from three different measurements at the sidewall: broadband chemiluminescent emission captured via a photodetector, CH 4 concentrations determined using a distributed feedback interband cascade laser centered at 3403.4 nm, and pressure recorded via a dynamic Kistler type transducer. All methods for the ignition delay time were compared to high-speed camera images taken of the axial cross-section during combustion. Methane time-histories and the methane decay times were also measured using the laser. It was determined that the flame could bemore » correlated to the ignition delay time measured at the side wall but that the flame as captured by the camera was not homogeneous as assumed in typical shock tube experiments. The bifurcation of the shock wave resulted in smaller flames with large boundary layers and that the flame could be as small as 30% of the cross-sectional area of the shock tube at the highest levels of CO 2 dilution. Here, comparisons between the camera images and the different ignition delay time methods show that care must be taken in interpreting traditional ignition delay data for experiments with large bifurcation effects as different methods in measuring the ignition delay time could result in different interpretations of kinetic mechanisms and impede the development of future mechanisms.« less
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Univ. of Central Florida, Orlando, FL (United States)
  2. Univ. of Central Florida, Orlando, FL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-707839
Journal ID: ISSN 0010-2180
Grant/Contract Number:
FE0025260; AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Combustion and Flame
Additional Journal Information:
Journal Volume: 180; Journal ID: ISSN 0010-2180
Publisher:
Elsevier
Research Org:
Univ. of Central Florida, Orlando, FL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; CO2; shock tube; bifurcation; ignition delay time; chemical kinetics; 42 ENGINEERING; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1353154
Alternate Identifier(s):
OSTI ID: 1343790; OSTI ID: 1419137