Experimental And Numerical Study On CIDI-HCCI Dual Mode Engine

The HCCI (homogenous Charge Compression Ignition) combustion can reduce NOx and soot either by using the fuel dimethyl ether (DME). It can also resolve the increasingly tense situation in the supply of diesel oil. Meanwhile HCCI has the drawback of uncontrollable combustion phase and narrow work range. By the way of using both intake pipe injection and in-cylinder injection, HCCI and CIDI combustion can be implemented in different work point. This paper present the simulation and experiment research for dual-mode engine.The numerical simulations based on the gas phase computation software CHEMKIN. Sensitivity analysis theory was used to get the reduced mechanism for both DME and n-heptane. A three-dimensional model was developed based on the diesel engine. The model use the hexahedral mesh to get the best quality, the movement of piston and valves were implemented. The discrete phase model was used for diesel oil injection, and the reduced mechanisms were coupled to compute the combustion process. The numerical simulation compared two combustion modes in temperature distribution, NOx distribution, the start of combustion and so on.A mean value model was setup for simulation the mode transition strategy. The engine model contains the combustion start time and heat release rate model for HCCI and CIDI. The model uses the dual Vibe curve to compute the diesel oil combustion process, and uses stick formula to compute the ignition delay. A Fuzzy logic control strategy was designed. A PID control strategy was setup to compare Fuzzy Logic control. The results show that Fuzzy logic control strategy gets the better dynamic performance.This research developed intake pipe injection system and motor-accelerator driven system. The ECU was designed for control the mode transition process. The experiment results show that cycle to cycle dependence is smaller than mode transition in gasoline engine, and close-loop control is more adaptive than open-loop control. But the open-loop control is easier to implement, it can also obtain the good transition process in the HCCI-CIDI mode transition.