Study On Knock Control Of A HCCI Gasoline Engine

Homogeneous Charge Compression Ignition (HCCI) is a new technology with advantages of low fue1 consumption and 1ow emissions. But the difficulty of controlling the combustion process and narrow operation range 1imit its uses in automotive industry. Knock detection, identification and control for HCCI engine are of great significance to the practical application of HCCI combustion technology because the high load range of HCCI is limited mainly by knock and fast combustion will lead to knock too.In this paper, a lot of knock sensor signal data of HCCI, SI and the mixed-mode combustion were sampled from single-cylinder HCCI gasoline engine equipped with 4 valves variable system; knock characteristic values were extracted and a curve indicting the relationship of knock threshold and engine speed is fitted for detecting no knock, slight knock, heavy knock in real-time.Based on the hardware computing capacity of a 32-bits micro-controller of Infineon company, Tricore-1766, a knock detecting method using the mixed AAF and FIR-BPF is proposed, For testing and calibrating the knock detecting algorithm a four-stroke gasoline engine knock signal simulator is developed with the TC1766. Based on the development of the knock detector, the HCCI, SI and mixed-mode combustion knock control method is studied.The results show that the knock detection solution can reflect the knock situation precisely. The ability keeping the engine from knock area of the control strategy for different combustion mode in HCCI gasoline engine is proven.