The Effects of Biodiesel on the Performance and the Durability of Diesel Engine Active-DPF 2012-01-1089

Recently, due to the concern on shortage in the supply of energy source as well as the greenhouse effect of engine exhaust, the use of renewable fuel, e.g., biodiesel, in the transportation sector is promoted. However, there are distinctions on both the physical and chemical properties between biodiesel and fossil diesel. These deviations in fuel property would result in different combustion characteristics and affect the performance of exhaust aftertreatment system, including the catalytic converter and the diesel particle filter.

The purpose of this study is to investigate the effect of biodiesel on the performance and the durability of diesel particle filter. The biofuel adopted in this study was obtained by transesterification from methanol and spent edible oils, and fulfills the requirements specified in EN 14214 standard. All the tests were conducted in a heavy diesel engine (ISUZU 4JJ1E4N). Two studies were carried out in this paper. In the first study, B5 was used in a durability test to find out the long term performance of active DPF running on biodiesel. The durability test followed the EU ETC procedure for 1000 consecutive hours. The effectiveness test of DPF was performed every 250 hours. At the end of durability test, a thorough examination on the performance deterioration was carried out, including emission conversion efficiency, deterioration rate, and surface analysis of catalyst.

It was found that after 1000 hours of consecutive running on B5, the catalytic converter still maintained its conversion efficiency higher than 90% for both CO and HC during the EU ESC test procedure with exhaust temperature in the range of 350~460°C. No noticeable deterioration in CO, THC, and PM conversion efficiency was found. An examination on the surface of catalyst with SEM and EDS gave the finding that phosphorous and sulfur contents are lower than 1% by weight. The active regeneration system works well during the durability process, and the conversion efficiency on both PM and PN are higher than 90% in EU ETC test as well as ESC test.

In the second study, different contents of biodiesel (D100, B5, B20, B40, and B60) were used to find out the effect of biodiesel on the balance point temperature (BPT) of soot accumulation in DPF as well as the light-off temperature in DOC. In the balance point temperature test, the engine speed was set at 2000 rpm. The engine load was controlled to suppress exhaust temperature lower than 250°C at first to enhance soot accumulation in DPF. Then the engine load was increased gradually to raise the exhaust temperature until the accumulated soot ceased increasing, which was monitored with the differential pressure drop of DPF. It was found that the balance point temperature for biodiesel is lower than that of fossil diesel. The decrease in balance point temperature is 13°C for B20.

In the DOC light-off temperature test, the engine speed was set at 1200 rpm, and the engine load was increased gradually until 300°C of exhaust temperature was reached. The conversion efficiency of CO was monitored during the process, and the light-off temperature was determined as the conversion efficiency reached 80%. It was found that the DOC light-off temperature drops as biodiesel content increases. The maximum decrease of light-off temperature is 41°C for B60.