| CPC F02P 9/002 (2013.01) [F02P 17/12 (2013.01); F02P 2017/121 (2013.01)] | 30 Claims |

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1. A method of controlling the start of combustion in an internal combustion engine, comprising:
providing a prechamber comprising:
an external surface and an internal surface enclosing a prechamber volume;
one or more ejection ports communicating between the external surface and the internal surface for introducing a fuel-air mixture into the prechamber volume;
a spark-gap electrode assembly, comprising:
a primary electrode disposed within the prechamber volume; and
one or more ground electrodes disposed within the prechamber volume and offset from the primary electrode to form one or more electrode gaps;
introducing a spark across at least one of the one or more electrodes gaps to ignite the fuel-air mixture;
measuring the initial trend of spark voltage or spark current of the spark;
determining whether the spark was initiated at the leading edge or trailing edge of the electrode gap;
determining whether the flow at the location of the spark is fast or slow; and
adjusting a power of the spark based on whether the spark was initiated at the leading edge or trailing edge and whether the flow of the spark is fast or slow to control the rate of flame propagation to maintain a substantially constant start of combustion.
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