The aim of this research is to experimentally investigate the effects of combustion parameters [ignition timings, injection timings, excess air ratio (λ)] and lubricating oil on particulate matter (PM) emissions from a 2.0 L turbo-charged gasoline direct injection (T-GDI) engine fueled with gasoline (octane number = 97), methanol/gasoline blends and pure methanol.
The results of this paper show that the PM number concentration mostly presents a typical bimodal distribution in figures. The particle number concentration mainly concentrates in the nucleation mode. With the increase of methanol volume fraction in the blended fuel, the PM emissions decrease significantly. Furthermore, there are few particles when the engine fueled with pure methanol. As advancing ignition timing, the total PM number rises by over about 200%. Under the pre-ignition condition, the higher in-cylinder temperature may also accelerate the formation of the nucleation mode particles. As advancing injection timing, PM emissions decrease first, and then increase. As decreasing λ, the total PM number would be more than doubled due to the rich air-fuel mixture. The lower λ may significantly decelerate the oxidation trend of the PM in the combustion process, so that the PM number increases rapidly. The existence of lubricating oil shows a very great impact on PM emissions of T-GDI engine. As increasing a small volume fraction of lubricating oil in the fuel, the PM number significantly increases by several times, especially for accumulation mode particles.