Energy Enhanced Adaptive Spark Ignition for Lean Combustion Initiation 2020-01-0841

For internal combustion engine systems, lean and diluted combustion is an important technology applied for fuel efficiency improvement. Because of the thermodynamic boundary conditions and the presence of in-cylinder flow, the development of a well-sustained flame kernel for lean combustion is a challenging task. Reliable spark discharge with the addition of enhanced delivered energy is thus needed at certain time durations to achieve successful combustion initiation of the lean air-fuel mixture. For a conventional transistor coil ignition system, only limited amount of energy is stored in the ignition coil. Therefore, both the energy of the spark discharge and the duration of the spark discharge are bounded.

To break through the energy limit of the conventional transistor coil ignition system, in this work, an adaptive spark ignition system is introduced. The system has the ability to reconstruct the conductive ion channels whenever it is interrupted during the spark discharge. Furthermore, thanks to the addition of a spark energy management module, the amplitude and the duration of the discharge current are both controllable. As a result, the amplitude of the discharge current can be maintained at a relatively high level within the duration of the spark discharge. Whenever the system detects the interruption of the spark current by external disturbances, such as strong air-motion, the embedded control algorithm in the proposed ignition system would command the generation of multiple consecutive spark breakdowns to reconstruct the conductive ion-channels. With the reestablishment of the conductive ion channels, spark discharge reforms inside the air-fuel mixture. This technique has the potential to improve the flame kernel development in lean air-fuel mixtures. Preliminary ignition tests are conducted in a constant volume optical vessel to demonstrate the performance of the proposed ignition system.