In-cylinder pressure-based air-fuel ratio control for lean burn operation mode of SI engines

In this paper, an in-cylinder air-fuel ratio control problem for lean burn mode operation of spark ignition engine is investigated with cycle-based model considering the cycle-to-cycle coupling effects of residual gas compositions. The statistical properties of parameter variation of the cyclic transient model are calibrated based on experiments of lean burn operating modes. With the calibrated model, a model-based predictive control strategy is proposed to improve the preciseness of in-cylinder air-fuel ratio at lean-burn operation including transient operation. To analyze the combustion parameters and its stability, the cycle-based indicators, such as heat transfer, indicated mean effective pressure (IMEP), combustion efficiency, residual gas fraction, peak pressure, crank angle at 50 % heat release (CA50) and NOx emission are adopted. The consecutive cycle co-relation is also addressed to analyze the stochastic behavior at lean combustion. Finally, experimental validation are performed and demonstrated on a full-scaled gasoline engine test bench to show the effectiveness of proposed lean-mode control scheme and combustion stabilities.