Effects of volume and nozzle area in narrow-throat spark-ignited pre-chamber combustion engines

The pre-chamber combustion concept (PCC) concept shows promises for lean combustion to achieve improved combustion stability and engine efficiency. The KAUST narrow-throat pre-chamber design, which can readily fit into the diesel injector pocket of a heavy-duty engine, has demonstrated an increased lean limit extension compared to conventional pre-chamber designs without a distinct throat. This study examines the effect of pre-chamber volume and nozzle opening area on the PCC concept by employing five different pre-chambers with fixed throat diameter. The engine was fueled with methane, and the combustion characteristics of each pre-chamber were assessed at different operating conditions. A 1-D GT-Power pre-chamber engine model was utilized to estimate the temperature and mixture composition inside the pre-chamber and main chamber. A multi-chamber heat release analysis method was applied to determine the response of the main chamber heat release process with different pre-chamber geometries. Engine-out emissions were also measured to compare the emission performance between the different pre-chambers. It was found that an increased pre-chamber volume promoted earlier ignition in the main chamber, and the throat area was a critical limiting factor in determining the engine performance for the pre-chambers with different nozzle opening areas at a given pre-chamber volume.