With growing concerns about NOx and particulate matter (PM) emissions from diesel engines, stricter regulations are being implemented which require advanced emission control technology. This paper discusses the combination of a diesel particle filter system (DPF) with a low pressure exhaust gas re-circulation (EGR) system to provide four way emission control of NOx, PM, CO and HC from existing heavy duty diesel engines.
The combined EGR-DPF system has been used in Europe over the past 4 years, with over 1200 systems installed on urban buses and other on-road applications. This system has shown 40-60% NOx reduction in addition to >90% CO, HC and PM reductions. Recently, several field trial programs have been initiated to evaluate the performance and durability of this EGR-DPF system under US operational conditions. These include retrofit applications on urban buses and on construction trucks. FTP tests on engine dynamometer have demonstrated 48 - 58% NOx reductions with these systems while chassis dynamometer tests have shown 50-60% NOx reductions. Simultaneously, >90% CO, HC and PM reductions were also observed in these tests.
In this paper, this combined EGR-DPF system is discussed in detail. In addition, the operational and the emissions testing data from the combined EGR-DPF equipped vehicles are also presented.