Abstract
The target of this work was to evaluate the potential of retrofit by diesel particle filter (DPF) in reduction of particulate emissions, and to collect experiences for large-scale introduction of retrofit DPF in Hungary especially in low emission zones.
Partial flow and wall flow type, continuously regenerating traps (CRT) from different manufacturers were investigated on the articulated city buses type 280.40, manufactured by IKARUS and its six-cylinder, direct injection, 160 kW engine which complies with Euro-II. emission limits and produced by RÁBA-factory, as well as on the articulated city buses type VOLVO 7700A having a six cylinder, direct injection, 202 kW engine complying the Euro-III. emission level. The filter material was ceramic and sintered metal in case of the tested wall flow filters and metal/ceramic fibers of the partial flow filters. The emissions were measured on engine test bench according to the ECE-R-49.02 Regulation, beside the gravimetric method the particulate number and size distribution were measured too. In real life bus operation the smoke emission, the noise level, the acceleration was tested and continuously the backpressure and exhaust gas temperature before the DPF were monitored to evaluate the auto-regeneration.
In case of the city buses significant reduction of the particulate emissions (90-99%) was achieved by the wall-flow-type DPFs. The degrees of reduction were the same in case of gravimetric and particle number measurements. Due to the oxidation catalyst used for preparation of regeneration the CO and HC emissions were also effectively (by 85-95%) reduced in case of both type of DPFs (wall flow and partial flow). This means that due to the retrofitting of the wall-flow-type DPFs the PM, CO, HC emissions of a Euro-II/III level engine will be reduced to the Euro-IV/V level. The partial flow filters reduced the PMemissions by 40-60%.
The tested passenger car was a EURO-4 level Opel-Astra, in this case only partial flow, CRT were investigated according to the ECE-R-83.04 Regulation. The reduction of the particulate emissions was between 20-40%.
The noise level measured outside of the test vehicles remained unchanged. The reliable operation of wall flow type DPF can be controlled by the continuous measurement of the backpressure. No remarkable increase of the fuel consumption and decrease of the power were recognized after the retrofitting. Follow up field tests are going on city buses to evaluate the durability and lifetime expectations of the DPFs being in question.
Keywords: diesel vehicle, particulate-emissions, particulate filters, retrofitting, emission measurements,