Detailed Approach for Pre-Chamber Heat Release Analysis for the HSASI Pre-Chamber Spark Plug Using a Pressure Sensor Glow Plug

The hot surface-assisted spark ignition (HSASI) pre-chamber spark plug, which was developed at the Karlsruhe University of Applied Sciences, increases the dilution limit with excess air and the tolerance to residual gas in the pre-chamber compared to a conventional passive pre-chamber spark plug. In this study, the conventional glow plug which is integrated in the pre-chamber of the HSASI pre-chamber spark plug was replaced by a pressure sensor glow plug (PSG) from BERU. This allows for a detailed combustion analysis in the pre-chamber. The signal of the PSG was validated with a piezoelectric cylinder pressure sensor and a method to analyse the pre-chamber heat release was introduced. Experimental investigations were carried out on a single-cylinder gasoline engine. A series of operating points diluted with excess air and a variation in load were conducted. The gas flow rate through the orifices of the pre-chamber was calculated from the pressure difference between the pre-chamber and the main chamber. Furthermore, the momentum and the enthalpy flow of the gas jets leaving the pre-chamber were calculated to determine their influence on the heat release in the main combustion chamber. The HSASI operation was compared with a passive pre-chamber spark plug. It shows a faster heat release inside the pre-chamber which leads to a higher enthalpy and momentum of the gas jets leaving the pre-chamber. This results in a faster flame development in the cylinder and less cycle-to-cycle variations.