Internal exhaust gas recirculation via reinduction and negative valve overlap for fuel-efficient aftertreatment thermal management at curb idle in a diesel engine

Abstract

Low air-flow diesel engine strategies are advantageous during low load operation to maintain temperatures of a warmed-up aftertreatment system (ATS) while reducing fuel consumption and engine-out emissions. This paper presents results at curb idle for internal EGR (iEGR) that demonstrate low airflow and reduced engine-out emissions during fuel-efficient ATS temperature maintenance operation. Internal EGR via reinduction and trapping using negative valve overlap (NVO) are compared to each other, conventional operation and to other low airflow approaches including cylinder deactivation (CDA). At 800 RPM/1.3 bar BMEP (curb idle) iEGR via reinduction enables 200°C engine-out temperature combined with 70% lower NO X, 35% lower fuel consumption, and 40% lower exhaust flow rate than conventional thermal management operation. Internal EGR via trapping using NVO resulted in an engine-out temperature of 185°C, with 56% lower NO X and 25% lower fuel consumption than conventional thermal management operation. Both iEGR strategies have lower engine-out temperatures and higher exhaust flow rates than CDA. No external EGR is required for either iEGR strategy. “iEGR via reinduction” outperforms “iEGR via NVO” as a result of higher open cycle efficiency (via less pumping work) and higher closed-cycle efficiency (via higher specific heat ratio).

A Review of Thermal Energy Management of Diesel Exhaust after-Treatment Systems Technology and Efficiency Enhancement Approaches

“…Internal exhaust gas recirculation (IEGR) is achieved with both negative valve overlap (NVO) and reinduction [169]. Joshi et al [170] confirmed that EEVO/NVO increased the exhaust temperature to more than 255 • C and decreased fuel consumption by 5.7%.…”

Variable Valve Actuation for Efficient Exhaust Thermal Management in an Off-Road Diesel Engine

“…In LIVC, Gehrke et al [40] indicated PM up by 234 % and constant NO x , while Guan et al [41] reported NO x decreased by 13.5 % and PM down by 81 %. In secondary exhaust valve opening (2EVO), Joshi et al [45] achieved NO x reduction of 80 %, while Zhang et al [43] reported a constant NO x level.…”

Numerical Evaluation in a Scaled Rotor-Less Nozzle Vaned Radial Turbine Model under Variable Geometry Conditions

“…Today's engines are not in the list of engines to be admitted in the near future. Therefore, to comply with the exhaust emissions limits defined by the European Union (EU), engine manufacturers have approached the situation in two different ways: treating the pollution emission generated during combustion [4][5][6][7][8], which can have some problems, such as urea injection failures which is treated in [9], and trying to reduce these emissions via hybridization and increasing the combustion thermal efficiency. Increased thermal efficiency can be achieved by supercharging [10][11][12][13].…”