Evaluation of the impact of continuously regenerating trap on volatile organic compounds emitted from turbocharged diesel engine

Abstract

In this study a continuously regenerating trap (CRT) was evaluated on the basis of its performance to control the volatile organic compounds (VOCs) emitted from the diesel engine exhaust. The engine was operated on a test bench by coupling it through an AC electrical dynamometer under the auspices of an 8-mode steady-state cycle. VOCs in their gaseous phase were trapped in Tenax TA® cartridge, and then extracted by thermal desorber (TD) for the subsequent analysis through gas chromatograph-mass spectrometer (GC/MS). According to the results, VOCs were preponderant during both maximum as well as minimum load modes owing to the incomplete combustion. Benzene and toluene were in abundance with respective maximum relative contribution (RC) of 40.3 and 34.7% in upstream of CRT, while toluene and ethyl benzene were the dominant species with respective maximum RC of 38.2 and 30.8% in downstream of CRT. Styrene and butyl acetate were the least contributors to total VOCs in both upstream as well as downstream of CRT. The CRT unit revealed a good control on VOCs with maximum reduction rate (RR) of 45%. The RR of VOCs was decreased with the decrease in NO2/NOx ratio, while the RR of benzene was reduced with the reduction in downstream temperature leading to strong correlations between them. Moreover, the RR trend of both benzene and ethyl benzene led to an important finding that when former was substantially reduced with maximum RR, the latter remained elevated with higher negative RR. Hence, an anti-correlation was found between benzene and ethyl benzene.