Transient RCCI Operation in a Light-Duty Multi-Cylinder Engine

Abstract

Reactivity Controlled Compression Ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NO x and PM emissions, while maintaining high thermal efficiency. Previous RCCI steady-state performance studies provided a fundamental understanding of the RCCI combustion process in steady-state, singlecylinder and multi-cylinder engine tests. The current study investigates RCCI and conventional diesel combustion (CDC) operation in a light-duty multi-cylinder engine over transient operating conditions. In this study, a high-bandwidth, transient-capable engine test cell was used and multi-cylinder engine RCCI combustion is compared to CDC over a step load change from 1 to 4 bar BMEP at 1,500 rev/min. The engine experiments consisted of in-cylinder fuel blending using port fuel-injection (PFI) of gasoline and early-cycle, direct-injection (DI) of ultra-low sulfur diesel (ULSD) for the RCCI tests and used the same ULSD for the CDC tests. Over the step load change, both combustion modes were compared for combustion performance and emissions using fast response HC, NO and PM instrumentation. Similar intake pressures were used for both combustion modes to explore the robustness of the RCCI combustion strategy using real-world operating conditions with production viable hardware. It was found that the engine was able to operate with RCCI combustion with lower engine-out PM and NO but increased HC and CO emissions than CDC over the specified transient engine operating conditions using either open-or closed-loop feedback control of the combustion phasing.

Experimental Investigation of Engine Speed Transient Operation in a Light Duty RCCI Engine

“…A direct comparison is not possible as the OEM results are proprietary and modifications for the Drivven system do not allow the use of the OEM controller. However, these values were found to give similar steady-state emissions results as those from the OEM controller [26]. For RCCI operation, additional tables to control the gasoline PFI system were added.…”

“…First, it is interesting to see how RCCI responds to engine speed changes, but as Glewen showed, an engine speed transient acts similarly to a step-up and then a step-down load transient [26]. Future work should look at load transients as a more fundamental test of transient engine performance.…”

An investigation on the particulate number and size distributions over the whole engine map from an optimized combustion strategy combining RCCI and dual-fuel diesel-gasoline

“…The reactivity controlled compression ignition (RCCI) combustion, initially proposed by Inagaki et al [6] and later developed by Kokjohn et al [7], has been demonstrated to be more promising than previous LTC strategies such us the homogeneous charge compression ignition (HCCI) [8], diesel partially premixed combustion (PPC) [9], gasoline PPC [10] and gasoline PPC spark assisted [11] [12]. The RCCI concept has been extensively studied in different single cylinder engine (SCE) platforms: light- [13], medium- [14] and heavy-duty [15], as well as in multi-cylinder engines [16]. Different strategies have been developed to increase the thermal efficiency of RCCI, such as engine settings optimization: injection settings [17] [18], air management conditions [19]; fuel properties modification: fuel variation [20], use of additives [21], use of biofuels [22]; and hardware optimization: piston bowl geometry modification [23], compression ratio optimization [24] or engine cooling reduction [25].…”

Design of Real-Time Combustion Feedback System and Experimental Study of an Rcci Engine for Control

“…RCCI combustion is also affected by factors like the wall and the residual gas temperatures [52]. So while going from a lower load to a higher load or vice-versa, these conditions will be different [53].…”

“…The main reasons attributed to this were, fuel dynamics [52] and air dynamics [49]. Air dynamics is one of the main factors that caused misfires.…”