Abstract
The fuel efficiency of the low temperature combustion (LTC) cycles is commonly compromised by the high levels of hydrocarbon (HC) and carbon monoxide (CO) emissions. More seriously, the scheduling of fuel delivery in HCCI engines has lesser leverage on the exact timing of auto-ignition that may even occur before the compression stroke completes, which may cause excessive efficiency reduction and combustion roughness. New LTC control strategies have been explored experimentally to achieve ultra low emissions under independently controlled EGR, intake boost, exhaust backpressure, and multi-event fuel injection with up to 12 fuel injection pulses per cycle for conventional diesel and neat bio-diesel fuels. Adaptive control strategies based on cylinder pressure characteristics have been implemented to enable and stabilize the LTC when heavy EGR is applied. The impact of heat release phasing, duration, shaping, and splitting on the thermal efficiency has been analyzed with engine cycle simulations. Oxygen sensors at the intake and exhaust of the engine are devised to comprehend the transient impacts of EGR, boost, and load variations.
