A physics-based modeling approach of a natural gas hcci engine

Homogeneous Charge Compression Ignition (HCCI) Engines hold promises of being the next generation of internal combustion engines due to their ability to produce high thermal efficiencies, in addition to low nitric oxides and particulate matter. HCCI combustion is achieved through the auto-ignition of a compressed homogenous fuel-air mixture, thus making it a "fusion" between spark-ignition and compression-ignition engines. The main challenge in developing HCCI engines is the absence of a combustion trigger hence making the control of combustion timing difficult. To be able to control ignition timing, a physics-based model is developed to model the full HCCI engine cycle while taking into consideration cycle-to-cycle transitions. Exhaust Gas Recirculation is used to control combustion timing while the temperature at intake valve closure will serve as the parameter that represents the desired ignition timing. The Modified Knock Integral model defines the necessary relationship between ignition timing and temperature at intake valve closure. Validation of the developed model is performed by determining the ignition timing under varying conditions. Results are shown to be in accordance with data acquired from a single-cylinder model developed using a sophisticated engine simulation program, GT-Power.