Improvement of SI Engine Operating Range by Residual Gas Sweeping from the Spark Plug Vicinity

This paper follows a former one (Robinet [1]) which underlined the spark kernel hazardous development due to residual gas in the spark plug vicinity.

A new igniter called FSP (Fueled Spark Plug) has been designed and compared to conventional spark plug. Its purpose is to sweep away the residual gas from the spark vicinity. This investigation has been performed in a standard research engine and an optical accesses engine.

A faster heat release development and a more repeatable combustion for low-load operating conditions have been observed when firing with the FSP. The lean operating range is extended. The idle performances (IMEP covariance, ISC) have been improved as well as the emissions (CO and NO_X). Unburned hydrocarbons emissions are raised due to non-optimal feed line design.

Contrary to previous alternative igniter designs, residual gas sweeping can be switched on or off at will: in the latter case the FSP falls back to conventional spark plug operation.