In-cylinder particulate size distribution measurements in a direct-injection diesel engine.

摘要

Time resolved primary and agglomerate particle size distribution measurements were made on the samples obtained from the cylinder and exhaust of a single-cylinder diesel engine, which was modified version of an Isuzu 2.8 liter displacement, four-cylinder direct-injection diesel engine. Experiments were performed at fuel-air equivalence ratios of 0.4 and 0.6 and a speed of 1500 RPM. A unique total cylinder sampling method was developed and used to sample, quench, and dilute the entire contents of the cylinder in about 1 ms. An electrostatic aerosol sampler was used to collect particles on 3 mm transmission electron microscope (TEM) grids. A TEM was used to determine primary and agglomerate particle size distributions for both in-cylinder and exhaust samples. An electrical aerosol analyzer was also used to determine the agglomerate size distributions for both in-cylinder and exhaust samples. A diffusion battery followed by a condensation nuclei counter was used to characterize the agglomerate size distributions of exhaust samples.; Geometric number mean diameters (NMDp) of primary particles and agglomerates are determined for exhaust samples and as function of crankangle degrees (CAD) for in-cylinder samples. The earliest particles to appear are agglomerates with NMDp in the range of 0.03-0.05 {dollar}mu{dollar}m composed of a few primary particles with NMDp in the range of 0.018-0.019 {dollar}mu{dollar}m. These agglomerates grow by coagulation into larger agglomerates with NMDp in the range of 0.11-0.16 {dollar}mu{dollar}m composed hundreds and thousands of primary particles in the range of 0.028-0.030 {dollar}mu{dollar}m NMDp. The NMDp of the agglomerates in the exhaust are in the range of 0.1-0.16 {dollar}mu{dollar}m and NMDp of the primary particles are in the range of 0.02-0.022 {dollar}mu{dollar}m.; In general, the diameter of agglomerates increases to about the exhaust level by 15-25 CAD due to coagulation. The diameter of the primary particles first increases and then decreases. Thus coagulation, surface growth, and oxidation appear to be taking place simultaneously. This work represents the first systematic and experimental study of the agglomerate and primary particle size distributions in the cylinder and exhaust.