Performance of straight-run naphtha single-and two-stage combustion modes from low to high load

Double injection strategies with single-stage heat release and two-stage heat release process of straight-run naphtha were investigated on a single-cylinder diesel engine from low to high load. The two-stage combustion strategy is realized by split spray and combustion events around the compression top dead center with a dominant feature of “Combust After Injection End, Inject After Combustion End” to ensure the premixed compression ignition. The single-stage combustion is realized by the “spray–spray–combustion” process with the start of combustion separated from the end of injection. The straight-run naphtha has a research octane number of 58.8, and the compression ratio and displacement of the test engine are 16.7 and 0.5 L. Double injection strategy is used to generate the single- and two-stage combustion modes with different injection timing. NOx and total hydrocarbon emissions of the two-stage combustion mode are lower than that of single heat release mode in this study, and it is much easier to produce two-stage combustion mode at higher engine load. Diesel is also tested under double injection strategy just as the single heat release mode of straight-run naphtha, but the fuel efficiency and emission performance are worse than that of naphtha.