Prediction of spark kernel development in constant volume combustion

Abstract

Combustion initiation is studied in atmospheric pressure propane-air mixtures in a constant volume bomb with a high speed (10,000 fps) laser schlieren system. The spark current and voltage waveforms are simultaneously recorded for later model input. A phenomenological model for early flame kernel development is presented which accounts for the initial, breakdown generated, spark kernel and its subsequent growth. The kernel growth is initially controlled by the breakdown process and the subsequent electrical power input. A new, spark power induced, mass entrainment term is shown to model this initially rapid volume increase adequately while later growth is mainly dominated by diffusion. Results and model comparisons are presented for the effects of power input, spark energy, and equivalence ratio.

Numerical Simulation of Electric Spark Ignition in Atmospheric Pressure Methane-Air Mixtures

“…A description of the movement of the spark kernel radius with time was obtained based on the condition that the heat evolved in the flame region was greater than the heat lost to the unburned gas, Only qualitative comparisons were made with experimental data; no direct comparisons with experimental spark kernel trajectories were shown. Lim et al (1987) developed an empirical model containing adjustable parameters which included many of the important phenomena in spark ignition. These included a treatment of the initial blast wave, inflow of unburned gas along the electrodes, and expansion of the kernel due to thermal energy transport and combustion.…”

Modelling of early flame kernel growth towards a better understanding of cyclic combustion variability in SI engines

“…In order to enable the physical calculation of the ignition delay period and to enable the simulation of CCV, a new quasi-dimensional ignition model is developed. The burning rate of the spark generated flame kernel largely depends on the energy released by the ignition system, heat losses from flame kernel to the spark plug electrodes, local fluid flow and mixture state [33,34]. Therefore, the developed QDIM, which is based on AKTIM [28], consists of four main sub-models: the electric circuit sub-model, electric spark sub-model and spark plug geometry sub-model and early flame kernel growth sub-model.…”

Temperatures of Spark Kernels Discharging into Quiescent or Crossflow Conditions

“…Figure 2 illustrates how reflected images were used to determine path lengths. Previous works have approximated kernels as a series of cylindrical slices [13,[25][26][27]. However, oval slices were determined to be a better approximation for kernels based on images.…”