Date of Thesis

Spring 2018


Automotive engineers typically increase the air-fuel ratio (AFR) of an engine to control the amount of smoke emitted, but it not quite known how this process affects particulate number (PN). In the work presented, AFR was independently varied to study its effects on PN. It was found that increasing the AFR reduced the concentrations of larger particles from 108 #/cm3 to 106 #/cm3 which is an effect observable as a reduction in smoke. However, the same increases in AFR only resulted in an energy specific PN change from 1015 #/kWh to 1014 #/kWh. The study was then extended to examine how different combinations of engine speed, torque and timing affected PN. It was found that variations in timing (17 oBTDC to 4 oBTDC), speed (2000RPM to 3000RPM), and load (0 ft-lb to 12 ft-lb) had negligible effects on the amount of normalized PN produced. A novel study was performed to investigate the contribution of lubricating oil on the PN, and it was found that changing the oil formulation changed the amount of nuclei (sub-20nm) mode particles produced, and running the engine with no oil substantially reduced the nuclei (sub-20nm) mode while leaving the large (over-20nm) particle mode unchanged.


particulate number, lubricating oil particles, diesel, engines, air-fuel ratio, forced induction

Access Type

Masters Thesis

Degree Type

Master of Science in Mechanical Engineering


Mechanical Engineering

First Advisor

Dr. Indranil Brahma