Gasoline Compression Ignition: Optimizing Start of Injection Time
Authors: Joseph A. Insley (Argonne National Laboratory), Janardhan Kodavasal (Argonne National Laboratory), Xiaochuan Chai (Convergent Science Incorporated), Kevin Harms (Argonne National Laboratory), Marta Garcia (Argonne National Laboratory), Sibendu Som (Argonne National Laboratory)
Abstract: We present visualization of a high-fidelity internal combustion engine computational fluid dynamics (CFD) simulation. This engine operates in an advanced combustion mode called Gasoline Compression Ignition (GCI), where gasoline is used as a fuel in a diesel engine without the use of a spark plug, to combine the high efficiency of a diesel engine with low soot emissions of gasoline fuel. Further, combustion is a result of sequential autoignition without propagating flames, resulting in low temperature combustion, which in turn significantly reduces nitrogen oxides emissions. Fuel injection timing is a critical parameter determining the ignitability of the gasoline-air mixture, and engine operation stability. Four different start of injection (SOI) timings were evaluated through CFD simulation.
The simulations confirmed experimental findings of a “sweet spot” in SOI timing, where most stable combustion was achieved. The engine experiments were unable to explain the reason for the non-monotonic behavior of stability with relation to SOI timing, since the combustion chamber of the engine is not optically accessible. However, the visualization of these simulations was critical in explaining this behavior. The visualizations showed that earlier SOI timings resulted in fuel being directed into the “squish” region of the engine combustion chamber, resulting in greater heat losses, and lower reactivity and stability. Later SOI timings, however, did not provide enough time for the gasoline to chemically react and ignite in a stable fashion. This insight is critical in terms of determining optimum fuel injection strategies to enable stable operation of gasoline fuel in GCI mode.
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