NOx and PM Control from Heavy Duty Diesel Engines Using a Combination of Low Pressure EGR and Continuously Regenerating Diesel Particulate Filter

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.