Effect of Crankcase Oil on the Particle Size Distribution and Total Number Concentration in a Heavy Duty CNG Engine

In this paper, the characteristics of particle size distribution in the exhaust of a turbocharged 5.9 liter Cummins gas engine lubricated by two commonly used oils of different viscometrics (15W-40 and 20W-50) have been investigated. The study also attempts to differentiate the performance of the lubricants on the basis of fuel economy. A test procedure developed in- house was used for the evaluation, wherein the engine was operated at various speeds (1200-2800rpm) and load (25 %, 50% & 75%) conditions. Particle size distribution is measured using Engine Exhaust Particle Sizing Spectrometer (TSI EEPS Model 3090). Results indicate that a majority of the particle emissions are observed in the nucleation region (particle diameter < 50nm) and particle size distribution is found to significantly vary with engine speed. The geometric mean diameter of particles varied between 10-40 nm with maximum diameter observed at medium speed ranges. 15W-40 lubricant was found to have an advantage over 20W-50 with respect to fuel economy, but a clear differentiation in terms of particle emissions could not be established