Laminar Flame Speeds of Premixed Iso-Octane/Air Flames at High Temperatures with CO ₂ Dilution

Abstract

<div class="section abstract"><div class="htmlview paragraph">Spherically expanding flames are employed to measure the laminar flame speed of premixed iso-octane/air mixtures at elevated temperatures through both experiments and numerical simulations. Iso-octane (2,2,4-trimethlypentane) is an important gasoline primary reference fuel (PRF). While most studies on laminar burning velocity of iso-octane focus on low temperatures (less than 400 K), the experiments here were conducted in an optically accessible constant volume combustion chamber between 373 K-473 K, at a pressure of 1 bar, and from ϕ=0.8 to ϕ=1.6. The effect of diluent is investigated through the addition of 15% CO<sub>2</sub> dilution in order to simulate the effect of exhaust gas recirculation. The decreased reactivity with diluent addition reduces mixture reactivity, which can reduce the propensity for knock in spark ignition engines. All laminar flame speeds were calculated using the constant pressure method enabled via schlieren visualization of the spherically propagating flame front. Results show that laminar flame speeds of iso-octane/air mixtures at 1 bar increase by 46-51% with initial temperature increases from 373 K to 473 K. However, the addition of 15% CO<sub>2</sub> dilution to the iso-octane/air mixtures at 1 bar and 473 K results in a 47-51% decrease in the laminar burning velocity. Numerical results obtained with CHEMKIN [<span class="xref">1</span>] using the kinetic mechanism of Chaos et al. [<span class="xref">2</span>] show excellent agreement with experimental data for ϕ=0.8-1.2; however, the kinetic mechanism slightly underestimates the experimentally observed laminar flame speeds between ϕ=1.3-1.6.</div></div>

Experimental and Numerical Investigation of the CO2 Dilution Effect on Laminar Burning Velocities and Burned Gas Markstein Lengths of High/Low RON Gasolines and Isooctane Flames at Elevated Temperatures

“…The chamber has an appropriate temperature and pressure rating of 523 K and 130 bar. A schematic of the vessel and schlieren setup can be seen in Figure …”

“…The rate of radial growth of spherical flames over time was found from the cold flame front radius data provided by an in-house image-processing code. More details about the experimental procedure, ignition system, schlieren setup, and image processing are available in ref .…”

“…The convergence criteria for the mesh independency study was chosen as a change in the laminar burning velocity less than ±0.1 cm/s. Details about the computational framework can be found in ref .…”

“…Thus, the current study examines the CO 2 dilution effect (a major component of exhaust gases) on the S L and L b of high/low RON gasoline/air mixtures at 1 bar and 373–473 K with 0–15% CO 2 dilution. The S L and L b data of isooctane/air mixtures from ref were used as a reference point for comparison of the gasoline results. At the experimental test conditions, numerical analysis was conducted with the CHEMKIN software using the chemical mechanisms of Chaos et al, Kelley et al., and Jerzembeck et al in order to assess the accuracies of the mechanisms for isooctane/air mixtures.…”

Heat Release Analysis of The Scaled and Colliding Sprays Using RANS Approach

“…High spatial and temporal resolution optical diagnostics and numerical simulations are required for further increase in performance and reductions in fuel consumption and emissions [1]. Due to the complexity of the fuel spray and combustion, in both experiment and modeling areas, analysis of involved physical phenomena in simplified geometries such as constant volume combustion vessels [2][3][4][5][6][7][8][9][10] or rapid compression machines [11][12][13][14] are inevitable.…”