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Accelerometer-Based Estimation of Combustion Features for Engine Feedback Control
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on April 14, 2020 by SAE International in United States
An experimental investigation of non-intrusive combustion sensing was performed using a tri-axial accelerometer mounted to a small-bore high-speed 4-cylinder diesel engine. This study investigates potential techniques to extract combustion features from accelerometer signals to be used for cycle-to-cycle engine control. Selection of accelerometer location and vibration axis were performed by analyzing vibration signals for three different locations along the block for all three of the accelerometer axes. A magnitude squared coherence (MSC) statistical analysis was used to select the best location and axis. Based on previous work from the literature, the vibration signal filtering was optimized and the filtered vibration signals were analyzed. It was found that the vibration signals correlate well with the second derivative of pressure during the initial stages of combustion. Two combustion parameters were the focus of this investigation, start of combustion (SOC) and crank angle of fifty-percent heat release (CA50). The results showed that, for a wide range of engine conditions, SOC can be obtained solely from the first derivative of the vibration signal with respect to crank angle. In particular, SOC corresponds to the first peak of the derivative. Several methods for CA50 determination were explored, and results of the different methods are compared. The results demonstrate that an accelerometer can potentially provide sufficient combustion information for cycle-to-cycle combustion control.