Turbulent burning characteristics of FACE-C gasoline and TPRF blend associated with the same RON at elevated pressures

Abstract

FACE-C gasoline/air and TPRF (51.6 vol. % iso-octane, 21.5 vol.% n-heptane and 26.9 vol.% toluene)/air mixtures corresponding to the same RON of 85 were characterized in terms of determining their burning rates in a fan stirred turbulent vessel and filmed using high speed dual Schlieren imaging. Moreover, Mie scattering planar laser tomography was employed to characterize the variations of flame morphology induced by the coincident existence of different turbulent length scales and the susceptibility to develop cellular structures at elevated pressures (through the Darieus-Landau instability). Measurements were performed in a well-controlled environment of initial pressures 0.1, 0.5 and 1.0 MPa at a fixed initial temperature of 358 k. These measurements were conducted at a range of measured turbulence intensities from 0.5 to 2.0 m/s. The enhancement of turbulent flame speed S T as a function of turbulent intensity was sized. The absence of bending regime was accounted for based on the size of the vessel and limited range of turbulent intensities investigated in the present work.

Improvement of Turbulent Burning Velocity Measurements by Schlieren Technique, for High Pressure Isooctane-Air Premixed Flames

“…According to (Bradley et al 2011a) this happens when the flame radius is higher than 8 times (so higher than 27 mm). One possible way to improve the results would be to use the effective rms turbulent velocity ′ which correspond to the turbulence actually seen by the flame front, smaller than ′ (Bradley et al 2011b, Mannaa et al 2018. The discussion is similar for the overestimate of Eq.…”

Turbulent Flame Speed of a Gasoline surrogate in conditions representative of modern downsized Spark-Ignition engine

“…-(i) the turbulent spherical vessel, fully described by Galmiche et al [31] and already used for several premixed turbulent combustion studies [14,16,17,[32][33][34],…”

“…Besides, the interaction between the flame front and the turbulence is not instantaneous. It will take time to the flame to be affected by the full spectrum of the turbulence as highlighted by Mannaa et al [17] and leading to a continuous flame speed increase. In order to directly compare the characteristic turbulent flame propagation speed under all the different investigated condition, it is convenient to extrapolate a univocal value for each .…”

“…Only few studies are for liquid fuel [13][14][15][16][17][18]. Most of these studies used isooctane, like the one of Lawes et al [15] focused on flame propagation in a turbulent vessel from 1 to 10 bar with q' from 0.5 to 6 m/s.…”

“…At low q' = 1 m/s, S T was observed to remain constant while for q' > 4 m/s it increased slightly. Mannaa et al [17] studied flame propagation with more realistic fuels, i.e. FACE-C gasoline and its surrogate,…”