Internal EGR Systems for NOx Emission Reduction in Heavy-Duty Diesel Engines

Internal exhaust gas recirculation (IEGR) with retarded injection timing can provide a 30% reduction in diesel nitrous oxide (NO_x) emissions and is an attractive solution to meeting NO_x emission levels in the range of 3.4-4.0 g/bkW-hr (2.5-3.0 g/bhp-hr) for heavy-duty diesel engines, especially for off-road and vocational applications. At lower NOx emissions levels, IEGR may be used to supplement cooled EGR or to control HCCI combustion. Alternative valve actuation strategies for IEGR are reviewed. A valve actuation system to provide on-off control of IEGR combined with compression-release braking is presented. System design and simulation results are reviewed. Engine performance predictions and initial test data are discussed, including turbocharger sizing and particulate emission considerations. System reliability is calculated using Weibull data from similar proven components.