A Comparison of the Particulate Composition Between Turbocharged and Naturally Aspirated DI Diesel Engines

A naturally aspirated Perkins 4-236 engine was compared with a similar turbocharged Perkins engine. The higher pressures and temperature of a turbocharged engine should make the pyrosynthesis of PAH more likely than for a NA engine and this was investigated using the fuel n-alkanes as tracers for the unburnt fuel of the same fuel distillation fraction as the PAH. The results showed that the below C20 the NA and TC survivabilities of fuel n-alkanes onto the particulates were similar at below 0.02%. For higher n-alkanes the turbocharger was much more efficient at burning the fuel, with survivabilities of C24 a factor of 10 below the NA results. The higher operating temperatures of the TC engine reduced the UHC emissions and this reduced the higher boiling fraction unburned fuel. In contrast to these results the fuel PAH apparent survivability's were higher, by approximately a factor of 10, for the turbocharged engine for equivalent boiling point compounds in the range C18-C22. Although for both engines less than 1% of the fuel PAH survived, the results possibly indicate some pyrosynthesis of PAH in the turbocharged engine. For the higher molecular weight PAH the survivabilities were similar between the two engines. For both engines fuel PAH was the dominant source of the particulate PAH.