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).

低空气流量柴油发动机策略在低负荷运行期间有利于保持预热后处理系统（ATS）的温度，同时减少燃料消耗和发动机排放物。本文介绍了内部EGR（iEGR）在路缘怠速时的结果，这些结果表明，在节油的ATS温度维持操作过程中，气流低，发动机排出的废气减少。将通过还原和使用负气门重叠（NVO）进行捕集的内部EGR与传统操作以及包括气缸停用（CDA）在内的其他低气流方法进行了比较。在800 RPM / 1.3 bar的BMEP（怠速怠速）下，iEGR通过还原实现了200°C的发动机熄火温度和低70％的NO _X，与传统的热管理操作相比，可降低35％的燃料消耗和40％的排气流量。使用NVO捕集的内部EGR导致发动机熄火温度为185°C，与传统的热管理操作相比，NO _X降低了56％，燃油消耗降低了25％。与CDA相比，这两种iEGR策略均具有较低的发动机熄火温度和较高的排气流速。两种iEGR策略均不需要外部EGR。由于更高的开环效率（通过较少的泵功）和更高的闭环效率（通过更高的比热比），“通过还原的iEGR”优于“通过NVO的iEGR”。