SPARK-IGNITION OF PROPANE AIR MIXTURES NEAR THE MINIMUM IGNITION ENERGY .1. AN EXPERIMENTAL-STUDY

Kernel growth from a spark in propane-air mixtures at atmospheric pressure is studied in a constant volume bomb with a high-speed laser schlieren system. The spark current and voltage waveforms of an inductive ignition source are simultaneously recorded with the photographic recordings. The temporal growth of the measured equivalent radii at conditions near the minimum ignition energy shows the existence of a critical radius and the influence of the critical radius on kernel development. In addition, it is shown that the net spark power for ignition can be estimated using data from minimum ignition energy, electrode fall energy losses, and spark calorimetry experiments. These results are used in Part II to develop a model for kernel growth.