Dual-pump vibrational CARS measurements of temperature and species concentrations in turbulent premixed flames with CO2 addition

Abstract

a b s t r a c tA dual-pump vibrational coherent anti-Stokes Raman scattering (DPVCARS) system was applied for simultaneous temperature and species concentration measurements in jet flames on a newly developed piloted axisymmetric reactor assisted turbulent (PARAT) premixed flame burner. Turbulent lean premixed methane/air round jet flames with varying CO 2 dilution were stabilized using an annular flow of hydrogen at the flame base. Carbon dioxide was injected into the fuel stream to simulate effects of dry exhaust gas recirculation (EGR). The flames were operated at a nearly constant Reynolds number, Lewis number, and adiabatic flame temperature to minimize thermal and transport effects. Velocity boundary conditions at the burner exit were measured using particle image velocimetry. Simultaneous temperature and major species concentrations (O 2 and CO 2 ) were measured along the axial direction at the burner centerline and along the radial direction at representative axial locations above the burner. Progress variables calculated based on the temperatures were used to study the mean flame brush thickness and the turbulent burning velocity. Probability density functions (PDFs) of temperature at various locations are presented and discussed. The DPVCARS measurements provide an experimental database including temperature and turbulent burning velocity for combustion model evaluation and validation and demonstrated a strong potential for flame structure investigation with future improvement on spatial resolution and signal to noise ratio. The merits and limitations of vibrational CARS for diagnostics in turbulent premixed combustion are discussed. The results show that flames with CO 2 addition depart from the universal mean flame brush structure, while their RMS fluctuation values at an identical mean temperature collapse with the undiluted flame. The CO 2 addition increases the combustion intensity with a decrease in turbulent burning velocity when minimizing the thermal and transport effects.

Coherent Anti-Stokes Raman Scattering Measurements of Time and Length Scales of Temperature Fluctuations in a Turbulent Flame

“…23 This configuration provided small dimensions of the probe volumes (≈0.03 × 0.03 × 2 mm 3 ), which were conditioned by the beam overlap in the focal zones. In this case, the upper limit of the scale for the possible effects of spatial averaging during the measurements 24,25 was determined by the length of the beam overlap. All the beams had the same (vertical) polarizations, and the beam paths of the two sets of CARS beams were directed at a small angle ∼3° to each other (with the side view of the beams shown in Fig.…”

Emission characteristics of turbulent premixed propane/air/carbon dioxide and propane/air/ammonia swirl flames through a rich‐lean combustor

“…When using exhaust gas recirculation (EGR), carbon dioxide (CO 2 ) has been identified as an effective gas with a significant influence on flame structure, dynamics, and as a consequence NOx and CO emissions [8][9][10]. Thus, many studies report that when increasing CO 2 dilution ratio, flame lift-off increased, turbulent velocity and flame temperature decreased which consequently reduced the formation rate of CO and NOx [11,12]. Even if this appears to be promising, the constant demands for reducing pollutant emissions led to search for other efficient fuels or energy carriers.…”

Optimization of a two-step CH4/air reaction mechanism in a CO2-enriched environment for high-fidelity combustion simulations

“…Burdet et al (2010) experimentally operated the DLN SEV single-cup burner under gas turbine-relevant conditions with very low residual O 2 in the exhaust gases (2%-5% by volume). Apart from the studies carried out on industrial burners, the effect of CO 2 addition on the flame has also been widely investigated in simplified laboratory burners (Kobayashi et al, 2007;Cohé et al, 2009;Erete et al, 2017;Han et al, 2017;Han et al, 2018). Nevertheless, in the literature, few experimental studies can be found on swirled stabilized flames (De Persis et al, 2013;Jourdaine et al, 2017;Vandel et al, 2020).…”