Analysis of Ion Current Integral Characteristics for Estimation of Combustion Process Parameters in Internal Combustion Engines

Abstract

An approach of peak pressure position and maximum pressure estimation in the chambers of internal combustion engine (ICE) is proposed in the paper. The approach is based on analysis of integral characteristic of ion current and has potentials due to robustness of estimation results to cycle-by-cycle parameters variations of combustion process and variations of measuring probe parameters. Besides, the use of integral characteristic does not require the knowledge of noise sensitive ion current profile. The proposed idea is validated via experiments and compared with analogous method of peak pressure angle calculation using thermal ionization of ion current. The final result of estimation can be applied in spark ignition or diesel engine control, wherein the proposed estimation mechanism can be applied in feedback instead of the use of expensive high pressure sensors or analog lambda sensors. 

A Virtual Combustion Sensor Based on Ion Current for Lean-Burn Natural Gas Engine

“…As one of the most important factors affecting engine combustion, λ (excess air coefficient) directly affects the number of molecules involved in the combustion reaction and ionization, which has a significant impact on the ion current. To evaluate this effect, the ignition timing was maintained at 37 • CA before top dead center (BTDC) under 50% engine load, and the excess air coefficient was adjusted by changing the injection pulse width and throttle opening [24]. Figure 4 shows the average ionic current signals of 140 cycles with excess air coefficient between 1.3 and 1.6.…”