Determination of the Evolving Morphological Characteristics of Combustion Generated Nanoparticle and Their Aggregates from a Tailpipe Diesel Generator

The diluted exhaust emitted by a small direct injection diesel engine in an electrical generator is the source of the nanoscale particle emission which has not been studied in the literature. This experimental study investigates the morphology of tailpipe nanoparticles emitted from the combustion of diesel fuel from a small generator using a methodology to directly capture the nanoparticles from the engine tailpipe and then measures and examines their nanoparticle morphology with the high-resolution scanning transmission electron microscope (STEM). This paper presents a new understanding about the pathway of the evolution of morphological characteristics of nanoscale particles emitted at the tailpipe of the small stationary diesel engines. Results revealed that, during no load operating conditions, the particles take the form of spherical- and spheroidal-shaped singlet particles ranging within sizes of 5 nm to 100 nm along with large PAH-containing small aggregates, which then forms agglomerates of carbonaceous aggregates. At medium load conditions, a number of different particle morphologies are observed: carbonaceous aggregates, irregular-shaped particles, electron-opaque spheres, and volatile liquid spheres with irregular solid inclusion. High load conditions formed particle morphologies of large agglomerates of sizes greater than 5000 nm to 10,000 nm from large aggregates of sizes 1000 nm to 3000 nm, flakes formed from coalesced particles, single and aggregate particles inside ash particles, carbonaceous spherules inside the volatile gaseous/liquid phase, and ceno-spheres coated or compacted agglomerate particles. The increasing load caused the exhaust temperature to rise, resulting in the gradual disappearance of round and irregular primary particle droplets due to volatile substance loss and nonvolatile substance oxidation and formation of very large aggregates. The impact of the study will result in a more cleaner development of a smaller, more stationary diesel generator.