Emissive Behavior of a Heavy-Duty SI Gas Engine During WHTC

In the arduous aim to reduce petroleum fuel consumption and toxic emissions, gaseous fuels can represent an alternative solution for heavy duty applications with respect to conventional liquid fuels. At the same time, the imposition of more stringent emission regulations in the transport sector, is a crucial aspect to be taken into account during the development of future gas engines. Aim of the present paper was to characterize a heavy duty spark ignition engine, under development for Euro VI compliance, with a particular focus on exhaust particulate emissions. In this sense, the engine was installed on a dynamic test bench, accurately instrumented to analyze combustion evolution, performance and exhaust pollutant emissions, along the World Harmonized Transient Cycle (WHTC). The emissions diagnostic devices included a gas analysis system for the measurement of regulated species, a photoacoustic sensor and a fast particulate spectrometer for on-line soot, particle number (PN) and particle size measurements, during the transient engine tests. The system layout comprised also a Thermodenuder to provide information on the volatile species contribution to particles emissions. The results reveal a correlation of soot and PN emissions with some specific phases of the test cycle, providing some clues on the source of particles emissions. The paper improves the literature in this field, at present still limited, providing useful information on soot and PN emissions from a heavy duty gas engine at the state of art technology.