SANGSUK LEE & Rolf D. REITZ

1. Spray Targeting to Minimize Soot & CO Formation in Premixed Compression Ignition (PCI) Combustion with a HSDI Diesel Engine SANGSUK LEE & Rolf D. REITZ Motivation Single Injection _ Soot & CO Spray Targeting Why Targeting? Soot • Stringent future emission regulations require low emission strategies. • PCI (Premixed Compression Ignition) is a practical way to achieve near zero levels of soot and NOx trade-off even under fairly rich conditions. • Three combustion regimes (MK, Conventional, PCI) were identified with respect to SOI. • MK (SOI > -5°) • Conventional diesel combustion ; Soot & CO increase as SOI retarded. No big difference in levels except 50 °nozzle. • PCI (SOI < -20°) ; No simple rule to describe the emission trends in PCI combustion. • No significant NOx emission difference observed under high levels of EGR. • Spray Targeting at a piston bowl edge gave the minimum emissions both soot and CO. • Soot was minimized when the spray was targeted at the bottom of the piston bowl. • Targeting at the inner surface of the piston gave optimized CO emissions. Soot Optimum Targeting (SOI = - 43o ) Worst Targeting (SOI = - 30o ) 120° Nozzle 120° Nozzle Objectives CO • To investigate key factors which determine the characteristics of PCI and Conventional Diesel Combustion . • To find the best way to realize low emissions. • To understand how the spray targeting affects on emission formation. CO • Fuel can be dispersed more effectively when the spray is targeted at a spot where the interaction between the spray and the squish flow is enhanced. NOx Start of Burn & Burn Duration Spray Targeting _ Squish Flow Conclusions Split Injections Burn Duration • 10–90 % burn durations about 5 degree regardless of SOI and nozzle within the PCI regime. • In Conventional regime, duration increased as SOI was retarded since fuel burnt within the mixing controlled varies with SOI. Start of Burn • The Combustion starts around -11o ATDC in PCI. ; Similar Combustion Characteristics with different soot formation • What makes the difference in soot & CO emissions? • ; Pre-ignition mixing with squish and swirl flow. • Spray Targeting 10-90% Burn Duration • Hard to find an advantage of split injections compared to single injection optimum in PCI. • Results of Pickett (SAE2005-01-0921) explained that soot emission increased when the spray interacted with the burnt gas due to a shortened lift-off length. Soot • Burn durations are good indicator to classify the PCI combustion in diesel engines. • Spray Targeting at the edge of the piston bowl is a key factor to minimize emissions in PCI combustion. • Soot could be optimized when spray was targeted at the bottom of piston which provided the longest spray travel distance. However, CO emission increased. • CO was significantly reduced when spray was targeted at the inner surface of the bowl, with a corresponding increase in soot emission. • Optimum spray targeting near the edge of the piston bowl was observed regardless of spray angles. • Optimum spray targeting moved up piston bowl as spray angle became narrower. Details for 120o Nozzle CO Start of 10% Burn