Multi-mode Low Temperature Combustion (LTC) and Mode Switching Control

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Low temperature combustion (LTC) modes offer high thermal efficiency and low engine-out NOx and soot emissions. The common LTC modes include homogeneous charge compression ignition (HCCI), partially premixed charge compression ignition (PPCI), and reactivity-controlled compression ignition (RCCI). To realize these promising LTC modes, optimal combustion control of the engine in each LTC mode is required. This will require precise control of combustion phasing and engine load, while constraining engine variables including peak in-cylinder gas pressure, maximum pressure rise rate, high intensity ringing or knock, and coefficient of variation of indicated mean effective pressure (IMEP) to allow safe and stable combustion. This chapter explains state-of-the-art of LTC engine control, including dynamic modeling, model predictive combustion control, experimentation, and implementation of real-time closed loop combustion controllers. A well-recognized limitation of LTC engines is a constrained optimal operating range. To this end, multi-mode engines are desired. These include (i) multi-mode LTC engines with mode transition among LTC modes, e.g., dual mode HCCI-RCCI engine, or triple mode HCCI-PPCI-RCCI engine, and (ii) multi-mode engines including LTC and conventional combustion modes, e.g., dual mode HCCI-SI (spark ignition) engines or dual mode RCCI-CDC (conventional diesel combustion) engines. These demands for innovative combustion controllers that capture the engine transient dynamics such as in-cylinder air–fuel ratio variations or residual gas temperature variations during mode transitions. This chapter introduces multi-mode LTC engines and explains controller development for these engines.

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Energy, Environment, and Sustainability