Control Strategies for Steady and Transient Operation of a 4-Stroke Gasoline Engine with CAI Combustion Using a 4-Variable Valve Actuating System (4VVAS)

In the last few years, residual gas trapping has been widely used to achieve CAI combustion operation in the four-stroke gasoline engine by means of the negative valve overlap period. In this paper, a flexible mechanical variable valve actuation system based on the production technologies is described. The 4VVAS system is capable of independent control of intake valve lift and its timing, exhaust valve lift and its timing and it has been incorporated in a specially designed cylinder head for a single cylinder research engine.

In addition, an engine simulation program has been developed to investigate the potential of the 4VVAS system for CAI engine operation and the switch between CAI and SI operations on the same engine. The engine simulation program is written with Matlab Simulink and incorporates an engine block, a newly developed CAI ignition and heat release model, a valve profile generator, and an engine control module for spark ignition and fuelling control. The simulation program is then used to investigate the effect of valve events on CAI combustion operations and the control strategies for steady and transient operation of a 4-Stroke gasoline engine with CAI combustion using the 4VVAS.