Development of an Ignition Model for S.I. Engines Simulation

A comprehensive Lagrangian flame–kernel model to predict ignition in SI engines

“…The temperature threshold used to switch from one regime to the other is, as suggested by Falfari and Bianchi [10] and Shen et al [22], three times the adiabatic flame temperature.…”

“…Their formulation can be found in [9,10]. To compute the second RSH term in Equation (2), representing the flame kernel expansion velocity due to energy transfer from the Downloaded by [University of Bath] at 09:48 04 October 2014 electrical circuit, it is necessary to distinguish between the two different mechanisms governing flame kernel growth:…”

“…where E s is the energy stored during the charge time reduced by the breakdown energy computed as in [10], R s is the equivalent resistance of the secondary circuit, L s the secondary circuit inductance and V ie is the inter-electrode voltage fall, computed as the sum of three terms: voltage in the gas column, cathode and anode voltage falls [13]. The values of L s and R s have to be tuned with experimental data of spark discharge at quiescent conditions.…”

“…Starting from this idea, models with different levels of detail have been proposed: the DPIK model (Discrete Particle Ignition Kernel) [24] and its modifications [10], the AKTIM (Arc and Kernel Tracking Ignition Model) model proposed by Duclos and Colin [8] and the more recent Spark-CIMM model introduced to predict combustion in stratified-charge, direct-injection engines, where mixture distribution, flow field and turbulence play a very important role in the development of the combustion process [6]. Recently, the possibility to massively parallelize CFD computations and to use techniques such as Adaptive Local Mesh Refinement [14] allowed the application of Eulerian ignition models also to engine simulations.…”

“…Specific sub-models estimate the instantaneous amount of energy transferred from the electrical circuit to the kernels and calculate the flame expansion velocity accordingly, taking into account the real properties of the hightemperature gas [4]. At each time step, the flame surface density distribution is reconstructed once Downloaded by [University of Bath] at 09:48 04 October 2014 particle positions and their radius are known [10]. Such quantity is then used by the combustion model to calculate the fuel burning rate.…”