Control Oriented Model and Dynamometer Testing for a Single-Cylinder, Heated-Air HCCI Engine

In recent years, HCCI (Homogeneous Charge Compression Ignition) combustion concept has attracted attention due to its potential for high fuel efficiency and low emissions. The essence of HCCI combustion is auto ignition of a very lean, homogeneous air-fuel mixture. However it leads to a major challenge for control engineers – controlling combustion timing to achieve required torque and optimal fuel consumption. There is a need for a simplified HCCI engine model to guide control strategy development. This paper presents such a control oriented model for a “heated intake air” HCCI engine concept that uses two streams of air (cold and hot) to achieve a variable temperature at intake valve closing. The model captures some of the physical engine phenomena such as throttle flow characteristics, cylinder heat exchange, and simplified combustion and simulates important engine outputs, such as start of combustion, cylinder pressure, cylinder temperature, indicated mean effective pressure (IMEP), air to fuel ratio, and mass flow rate. The model can also accommodate different intake and exhaust valve timings and valve profiles. To validate the model, a control mapping plan was developed and test data collected on a single cylinder engine. The paper explains the hardware setup and shows engine behavior from experiments including the fuel consumption and emissions benefit of this HCCI engine concept. Finally, the simulation results were compared with the dynamometer tests.