Particle emissions from internal combustion engines are increasingly regulated worldwide. With the advent of advanced low temperature combustion (LTC) strategies, while engine-out gravimetric soot emissions have been reduced significantly, there is some concern that LTC strategies may lead to relatively higher nanoparticle and ultrafine particle concentrations whose contributions to measured soot mass can be negligible. However, only a few studies have attempted to quantify engine-out particle number and particle size distributions under dual fuel LTC operating conditions. In this paper, we present particle emissions results from dual fuel partially premixed LTC in a single-cylinder research engine with different primary fuels (methane, propane, gasoline, or E-85 ethanol) and diesel as the secondary fuel (ignition source) over a range of operating conditions. A TSI Engine Exhaust Particle Sizer (EEPS) spectrometer is used in conjunction with a rotating disk thermodiluter to characterize particle number and size distributions with a pre-selected dilution ratio of 1:1870. For comparison purposes, smoke emissions trends (in AVL filter smoke number units) are discussed along with the particle concentration trends. It is shown that the percent energy substituted by the primary fuel, the injection timing of the secondary fuel, the intake boost pressure, and the rail pressure affect both particle number concentrations and particle size distributions to varying degrees in dual fuel LTC.
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