The evolution of species concentrations in turbulent premixed flames crossing the soot inception limit

Particle size distributions in turbulent premixed ethylene flames crossing the soot inception limit

“…with flames stabilised against hot combustion products (HCPs) [37]. The HCPs were generated by stabilising nitrogen diluted hydrogen flames on a perforated plate (PP) located 100 mm upstream of the lower nozzle (LN) exit to provide a well-defined burnt gas state [38,39]. The temperature at the lower nozzle exit (T HCP = 1500 K) was measured using an R-type thermocouple [40] with combustion products generated using a nitrogen diluted stoichiometric H 2 /air flame with a mole fraction ratio x H2 /x N 2 = 0.51.…”

“…The total rate of strain (a T = a b + a t ) was estimated using the approach of Kostiuk et al [41] with a t = (ε r /ν r ) 1/2 , where ε r is the rate of dissipation in the reactants, determined using the method of George and Hussein [42] as applied by Goh et al [43], and ν r the corresponding fluid viscosity. The bulk rate of strain is The conditions correspond to recent investigation of soot compositions [38,39] and gaseous species concentrations [39]. The flame conditions were chosen to determine the evolution of PSDs spanning lightly to the heavily sooting flames at different rates of strain.…”

“…The flame conditions were chosen to determine the evolution of PSDs spanning lightly to the heavily sooting flames at different rates of strain. The impact of the variations in conditions on gaseous species concentrations and soot particle compositions was previously analysed using GC-MS (PAH sampling experiment) and laser diagnostic techniques using ELS and PAH-PLIF [38,39]. Results show that soot formation is exceptionally sensitive to the rate of strain (a T ) and, by implication, to the local flow field with soot expected to grow rapidly in regions of low rates of strain.…”

“…Gas sampling is performed via a versatile quartz glass probe featuring aerodynamic quenching and dual-port dilution at the probe tip and in the transfer-line [38,39] as shown in Fig. 2.…”

“…A pressure transducer (UNIK 5000; GE Measurement and Control) is placed downstream of the probe to control the static pressure in the sampling system. A vacuum regulator and a metering valve are used to set a pressure differential of 20 mbar between the sampling line and the flame to minimise flame disturbances and PAH losses [38,39]. This results in a constant sample…”