Abstract
This work investigates a purely thermal control system for HCCI
engines, where thermal energy from exhaust gas recirculation (EGR) and
compression work in the supercharger are either recycled or rejected as needed.
HCCI engine operation is analyzed with a detailed chemical kinetics code, HCT
(Hydrodynamics, Chemistry and Transport), which has been extensively modified
for application to engines. HCT is linked to an optimizer that determines the
operating conditions that result in maximum brake thermal efficiency, while
meeting the restrictions of low NOx
and peak cylinder pressure. The results show the values of the operating
conditions that yield optimum efficiency as a function of torque for a constant
engine speed (1800 rpm). For zero torque (idle), the optimizer determines
operating conditions that result in minimum fuel consumption. The optimizer is
also used for determining the maximum torque that can be obtained within the
operating restrictions of NOx
and peak cylinder pressure. The results show that a thermally controlled HCCI
engine can successfully operate over a wide range of conditions at high
efficiency and low emissions.