A Preliminary Study of the Spark Characteristics for Unconventional Cylinder Charge With Strong Air Movement

Detailed fundamental understanding of spark discharge under strong air movement condition is crucial to optimize the ignition systems for stratified charge engines. In this paper, extensive bench tests of spark discharge under strong air movement condition are conducted by means of both optical and electrical diagnosis. Strong correlations between the physical structures of spark plasma channel and the gas velocity are found in this paper. The spark heat dissipation distance, the plasma stretched distance and the plasma area under various flow velocities are analyzed. The resistance between the electrode gaps is increased with the enhancement of flow velocity. As a result, the discharge voltage is enhanced, while the discharge duration is shortened. When the flow velocity is enhanced substantially, restrikes of spark discharge are observed. The increasing rate of the discharge voltage before the first restrike is found to be a 2-order polynomial relation to the gas velocity. With the enhancement of flow velocity, the delivered discharge energy increases linearly at the velocity below 25m/s, while it tends to be maintained at the higher flow velocities. Both the increase of the electrode gap size and the flow velocity shorten the spark discharge duration.