Abstract
An efficient combustion depends on many factors, such as injection, turbulence and ignition characteristics. With the improvement of internal combustion engines the turbulence intensity and internal pressure have risen, demanding more efficient and powerful ignition systems. In direct injection engines, the stratified charge resultant from the wall/air-guided or spray-guided system requires even more energy. The Paschen’s law shows that spark plug gap and mixture density are proportional to the dielectric rupture voltage. It is known that larger spark gaps promote higher efficiency in the internal combustion engines, since the mixture reaction rate rises proportionally. However, the ignition system must be adequate to the imposed gap, not only on energy, but also on voltage and spark duration. For the reported study in this work two test benches were built: a standard inductive ignition system and a capacitive discharge high energy ignition system, with variable voltage and capacitance. The influence of the important parameters energy and ignition voltage on the spark duration, as well as the electrode gap and shape were analyzed. It was also investigated the utilization of a coil with lower resistance and inductance values, as well as spark plugs with and without internal resistances.
Highlights
One cause of the efficiency decrease on partial loads in spark ignition engines is the throttle power control
The maximum mixture dilution rate permitted is limited by the tolerated cyclic variation on the engine
Material and methods Typically, on vehicular engines, two ignition system types are usual: inductive and capacitive. These two systems will be compared on the various conditions described previously
Summary
One cause of the efficiency decrease on partial loads in spark ignition engines is the throttle power control. Diluting the admitted mixture with air excess (lean burn) or with burned gases (exhaust gas recirculation) may reduce the pumping losses, improving the fuel consumption. The maximum mixture dilution rate permitted is limited by the tolerated cyclic variation on the engine. A powerful ignition system has influence on the partial load cyclic variations and on maximum dilution rate acceptable. The waveform obtained measuring the primary winding of the ignition system permits good conclusions about its energy and performance. The actual duration and power delivered on spark are influenced by electrical and mechanical parameters not estimated
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