Knocking is still one of today’s major limitations regarding efficiency-increasing measures for SI combustion engines. Due to the complex stochastic nature of the phenomenon, not only prediction and consideration within the engine development is of relevance. A further challenge is control of the phenomenon during engine operation, with the aim of maximizing the efficiency while preventing engine damage and maintaining the driver comfort. Conventional knock control is characterized by detecting knock events and subsequently adjusting the spark timing depending on whether knock was detected. This paper proposes a new knock control concept based on the prediction and direct control of the knock frequency, compared to the conventional reactive and indirect control of the knock frequency. For the prediction of the knock frequency, a calculation approach based on three different parameters is utilized. Two parameters contain information about the auto-ignition onset distribution of single working cycles at a respective operating point, while the third parameter contains a calibrated limit for the knock frequency calculation. Thus cycle-to-cycle variations and the state of chemical reactions via the auto-ignition determination are included in the prediction. Two zero-dimensional (0D) models to simulate the new knock frequency-based and conventional knock control are set up to investigate the potential of the new control approach under stationary and transient conditions. Comparison of the two controllers under various operating conditions reveals an efficiency increase of up to 0.8%, realized mainly by reduced variability of the center of combustion over time. Finally, the new concept and the investigation by simulation are discussed with regard to an engine application, highlighting the relevance of the computational performance.
Knock Frequency-Based Knock Control
Sae Technical Papers
Automotive Technical Papers ; 2022
2022-06-07
Conference paper
English
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