Start
March 8, 2017 - 12:30 pm
End
March 8, 2017 - 2:00 pm
Address
UOIT - UA3240 View map
Speaker: Dr. Dipal Patel
Affiliation: University of Newcastle
Localised forced ignition (e.g. spark or laser ignition) of inhomogeneous mixtures has a number of important applications ranging from Gasoline Direct Injection (GDI) en- gines, Lean Premixed Prevaporised (LPP) combustors to high-altitude relight in aero-gas turbines. Lean-burn systems are one of the advanced combustion approaches that could improve thermal efficiency while reducing exhaust gas emissions. An improved understand- ing of localised ignition of inhomogeneous mixtures is essential for designing an efficient ignition system and ensuring self-sustained combustion subsequent to the ignition event. To meet this objective, the influences of initial mixture distributions for both globally stoichiometric and fuel-lean mixture on localised forced ignition have been analysed using three-dimensional compressible DNS for different root-mean-square (rms) values of equiva- lence ratio, turbulent velocity fluctuations, and the Taylor micro-scale of equivalence ratio variation. It has been demonstrated that the initial equivalence ratio distribution has sig- nificant effects on the early stages of burning of stratified mixtures following successful localised forced ignition. The results show that the rate of heat transfer increases from hot gas kernel with increasing turbulent intensity leading to a decrease in the extent of burn- ing. The findings based on DNS data demonstrated that favourable conditions in terms of initial mixture distribution, equivalence ratio variation, length scale of mixture inhomo- geneity, and rms turbulent velocity fluctuation are required for self-sustained combustion on following successful ignition of stratified mixtures. Detailed physical explanations have been provided for the effects of the aforementioned parameters on the extent of burning in stratified mixtures.
