Formation and transformation of volatile nanoparticles from a diesel engine during exhaust dilution

Abstract

A classic H 2 SO 4 -H 2 O binary homogeneous nucleation model coupled to an aerosol dynamics model, suitable for studying the formation and transformation of volatile nanoparticles (VNPs) during diesel engine exhaust dilution, has been developed. Using the H 2 SO 4 -H 2 O binary homogeneous nucleation model, the nucleation ratio and molecular cluster size were calculated. The effect of aerosol dynamic processes on VNP number size distributions was studied. The effects of fuel sulfur content (FSC) and sampling conditions in the laboratory on VNP number size distributions were also calculated. Our simulations demonstrated that nucleation increased the cluster number concentration and that FSC, temperature and humidity significantly affected the nucleation ratio and molecular cluster size. Coagulation promoted the evolution of cluster-particle size distributions from monodisperse to polydisperse. Soot present in the exhaust can suppress the formation of VNPs. FSC and sampling conditions, like the primary dilution temperature, the primary dilution relative humidity, residence time and the primary dilution ratio have significant effects on VNP number size distributions. . VNP number size distributions are nonlinear and highly sensitive to the temperature, humidity and dilution ratio during the dilution process. Recently, theoretical studies on VNPs in diesel engine exhaust have been conducted [7,8]. These studies largely focused on the evolution of VNPs in the atmosphere, leaving many questions about the mechanisms driving the formation and transformation of VNPs. Further research in this area is necessary. In this study, a classic H 2 SO 4 -H 2 O binary homogeneous nucleation model coupled to an aerosol dynamics model is presented. The work in this paper includes: (1) the nucleation ratio and molecular cluster size based on binary H 2 SO 4 -H 2 O homogeneous nucleation theory, (2) the effect of the aerosol dynamic processes on VNP number size distributions and (3) the effects of fuel sulfur content (FSC) and sampling conditions in the laboratory on VNP number size distributions. The experimental results were then compared with the modeling results.

Investigation of Adsorption Characteristics and Influencing Factors for Diesel Engine Exhaust Particles

“…Many studies have been conducted by domestic and foreign scholars on the evolution of particle characteristics during the exhaust process. XinLing and Zhen (2012) study argued that the exhaust dilution process of diesel engines causes volatile organic compounds to condense and adsorb on the surface of existing particles, and that temperature is an important factor affecting the gas-particle conversion process. Z.…”

Inversely modeling homogeneous H<sub>2</sub>SO<sub>4</sub> − H<sub>2</sub>O nucleation rate in exhaust-related conditions

“…Particle formation due to H 2 SO 4 in real vehicle exhaust plumes and in laboratory sampling systems has been previously simulated by several authors (Uhrner et al, 2007;Lemmetty et al, 2008;Albriet et al, 2010;Liu et al, 2011;Arnold et al, 2012;Li and Huang, 2012;Wang and Zhang, 2012;Huang et al, 2014), but all of them have modeled nucleation as binary homogeneous nucleation (BHN) of H 2 SO 4 and water. Other possible nucleation mechanisms include activation-type , barrierless kinetic (McMurry and Friedlander, 1979), hydrocarbon-involving (Vaaraslahti et al, 2004;Paasonen et al, 2010), ternary H 2 SO 4 -H 2 O-ammonia (Meyer and Ristovski, 2007), and ion-induced nucleation (Raes et al, 1986) mechanisms.…”