25-08-2012, 11:49 AM
Diesel Particulate Matter
Diesel Particulate.pptx (Size: 263.45 KB / Downloads: 45)
Topic selection objective:
Diesel engines emit large quantities of fine particles to the atmosphere.
Air pollution caused by the automotive exhaust emissions has become a serious social problem.
Stringent norms have been rolled out.
All new vehicles manufactured after the implementation of the norms have to be compliant with the regulations.
To increase the efficiency of the ICE.
Introduction
One important challenge for diesel engines is reducing Particulate Matter (PM).
PM mainly includes soot and soluble organic fractions (SOF) adsorbed to the soot.
Particulate matter emitted in diesel exhaust is a complex mixture of carbon particles of soot, unburned fuel and lubricants.
These make up the soluble organic fraction (SOF).
Particulate Matter (PM) is one of the six criteria pollutants, and the most important in terms of adverse effects on human health.
Definition: Particulate matter (PM) is the term used for a mixture of solid particles and liquid droplets suspended in the air.
Particulate matter is composed of both coarse and fine particles.
Coarse particles (PM10) have a diameter between 2.5mm and 10mm.
PM Composition
DPM consists a large number of organic compounds.
Polycyclic aromatic hydrocarbons (PAHs) are prominent.
PAHs are suspected human carcinogens.
Approximately 90% of the DPM mass is within the inhalable range (<1 μm).
FACTORS AFFECTING HYDROCARBON DISTRIBUTION IN DIESEL EMISSIONS:
Effect of Engine Load:
Engine load has effects on DPM mass concentration, size distribution, organic carbon and elemental carbon (OC/EC) distribution, morphology and microstructure.
The particulate emission factor (g particles/kg fuel) has been shown to increase linearly with engine load.
The fractions of EC over DPM increase with increasing load from 21% at 0 kW to 84% at 75 kW.
Effect of Fuel Sulphur Content:
The amount of adsorbed sulphates affects the mass of hydrocarbons in the PM composition.
Sulphuric acid adsorb with organic compounds in the exhaust.
7-12% particulate reduction can be obtained with a reduction of fuel sulphur content from 0.2% to 0.05%.
Fuel sulphur content was reduced from 500 ppm to 15 ppm in June 1, 2006, due to the above reasons.
TWC
Simultaneous conversion of the three criteria pollutants, HC, CO, and NOx, produced during the combustion of fuel.
The active catalytic materials are present as a thin coating of precious metal (e.g., Pt, Pd, Rh),on the internal walls of the honeycomb substrate.
The substrate provides a large number of parallel flow channels.