Development Of Spark Plug Ion Current Sensing System For Gasoline HCCI Engine

Homogeneous Charge Compression Ignition (HCCI) is a new engine combustion mode, attracting wide attention from home and abroad, due to its high efficiency, economy of energy and low emissions. However, it is still necessary to explore a simple and reliable HCCI combustion sensor in order to realize closed-loop control and find resolutions to the problems such as real time control of combustion rate, start of combustion and HCCI/SI mode transition. Spark plug ion current sensing is a promising technology with spark plug as a combustion detection component instead of other sensors. Therefore, no engine redesign is required and multi-cylinder consistency can be controlled by adopting spark plug detection in multi-cylinders. On the whole, ion current sensing has a high practical application value.First, the spark plug ion current detection mechanism is researched, and the test bench for gasoline HCCI engine ion current detection is built, to detect ion current signal of HCCI combustion process. Experiments have been done based on two work modes, HCCI combustion and spark-assisted HCCI combustion, and the feasibility of spark plug ion current signal detection is validated.The characteristics and influence factors of ion current are researched. Results demonstrate that voltage of biasing power influences the amplitude and end point phase of ion current; the amplitude of ion current is at the peak and the phase is the earliest when lambda is around 1; the load mainly influences the amplitude of ion current.Comparison has been made between the characteristic parameters of ion current at various knock intensity/misfire combustion and those at normal combustion. It is noticed that knock intensity and misfire can be detected by the amplitude of ion current.Relativity between ion current signal and HCCI combustion progress is researched. Results show that significant linear correlations are found between inflexion phase, peak phase of ion current and HCCI combustion phase, and close linear correlations are found between inflexion amplitude, peak, integral value and HCCI combustion rate. Peak phase of ion current is chosen as the indicator of HCCI combustion phase, and peak value of ion current indicates the load and combustion rate. Spark plug ion current sensing is a low-cost, most practical detection method.