ABSTRACT

Majorities of the public transport buses as well as private buses and trucks, which are pre-Bharat Stage I vehicles emitting significantly higher smoke and pollution than the comparatively newer vehicles. Although these vehicles are less than 15 years of age but they already covered several Lakhs of km. individually. They are the most significant contributors of the ambient pollution in urban India today. At Karnataka Road Transport Corporation (KSRTC) an unique experiment and field trials were conducted first time in the country for the last more than two years where such more polluting but major lot of comparatively old buses were targeted to reduce their smoke level further than what is presently prescribed. A modern Diesel Particulate Filter (DPF) was incorporated without the normally associated burden of ultra-low Sulfur fuel or catalytic fuel additives. The DPF is appropriately designed as a low cost solution for higher smoke emitting vehicles PM reduction without going for any major operational changes. A novel system of DPF with simple and viable electrical regeneration method suitable to Indian urban transport was developed and evaluated for durability by field-testing. While developing the DPF, conflicting requirements like low-pressure drop, high trapping efficiency, high thermal durability, high compressive strength and practical regeneration needs are considered. The effect of DPF diameter, length, cell density and wall thickness on the pressure drop in fresh as well as soot laden conditions are evaluated, based on which the final size of DPF is determined. DPF was designed using wall flow filter made from highly thermal shock resistance cordierite honeycombs after optimising the back pressure and engine power loss. The electrical regeneration system was designed with a practical regeneration interval of about a day using stationary power and pressurized air source. The back pressure, smoke density, temperature, fuel consumption were measured at each cycle of field test before and after regeneration to evaluate the thermal durability, filtration efficiency and regeneration performance. The operational success as well as the mechanical durability was validated by running it for several cycles, accumulating with periodic regeneration in 4 buses each for more than 1,00,000 kms. and observed no deterioration of performance. The developed DPF system showed 0.4 g/km collection of particulate matter without any appreciable loss of power and no significant increase in fuel consumption. The results obtained during the field test and, engine performance and emission data collected on engine test bed are discussed.