Exhaust gas recirculation (EGR) in internal combustion engines is an effective method of reducing NOx emissions while improving efficiency. However, insufficient mixing between fresh air and exhaust gas can lead to cycle-to-cycle and cylinder-to-cylinder non-uniform charge gas mixtures of a multi-cylinder engine, which can in turn reduce engine performance and efficiency. A sensor packaged into a compact probe was designed, built and applied to measure spatiotemporal EGR distributions in the intake manifold of an operating engine. The probe promotes the development of more efficient and higher-performance engines by resolving high-speed in situ CO2 concentration at various locations in the intake manifold. The study employed mid-infrared light sources tuned to an absorption band of CO2 near 4.3 μm, an industry standard species for determining EGR fraction. The calibrated probe was used to map spatial EGR distributions in an intake manifold with high accuracy and monitor cycle-resolved cylinder-specific EGR fluctuations at a rate of up to 1 kHz.

The need for more environmentally friendly and efficient energy conversion is of paramount importance in developing and designing next-generation internal combustion (IC) engines for transportation applications. One effective solution to reducing emissions of mono-nitrogen oxides (NOx) is exhaust gas recirculation (EGR), which has been widely implemented in modern vehicles. However, cylinder-to-cylinder and cycle-to-cycle variations in the charge-gas uniformity can be a major barrier to optimum EGR implementation on multi-cylinder engines, and can limit performance, stability, and efficiency. Precise knowledge and fine control over the EGR system is therefore crucial, particularly for optimizing advanced engine concepts such as reactivity controlled compression ignition (RCCI). An absorption-based laser diagnostic was developed to study spatiotemporal charge-gas distributions in an IC engine intake manifold in real-time. The laser was tuned to an absorption band of carbon dioxide (CO2), a standard exhaust-gas marker, near 2.7 µm. The sensor was capable of probing four separate measurement locations simultaneously, and independently analyzing EGR fraction at speeds of 5 kHz (1.2 crank-angle degree (CAD) at 1 k RPM) or faster with high accuracy. The probes were used to study spatiotemporal EGR non-uniformities in the intake manifold and ultimately promote the development of more efficient and higher performance engines.

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This paper includes a detailed description of an optimized E85 concept engine developed for medium duty applications (Class 4-6 trucks) targeting ultra-low carbon emissions while maintaining power and delivering competitive cost of ownership. The engine is a light weight, downsized and boosted in-line 4 cylinder with air handling, fuel, and combustion systems designed specifically for E85 capability, producing high brake mean effective pressure (BMEP) at high thermal efficiency. It is integrated with a 12V start/stop system including a smart alternator for improved energy management. The present work demonstrates that even with the relative difference in the cost per heating value of fuel, using E85 can be upwards of 20% lower in cost while running middle to high loads. Combining high BMEP capability and a highly downsized engine displacement can ensure operation at high specific load where engine thermal efficiency is very good even in pickup-and-delivery type drive cycles. The performance characteristics of this engine were mapped using stoichiometric combustion and a three way catalyst for emissions control. The ability to perform at or close to Maximum Brake Torque (MBT) spark timing throughout the torque curve has been facilitated by an optimized combustion system design along with direct injection. The high engine thermal efficiency and knock tolerance of this combustion system eliminates the need for fuel enrichment anywhere in the engine map.