Application of accelerometers for sensing combustion phasing of an advanced combustion engine

This study evaluates the ability of accelerometers to detect combustion phasing of a single-cylinder air-cooled internal combustion engine undergoing homogeneous charge compression ignition. Metrics derived from the measured surface acceleration waveform, surface velocity, and the surface-specific kinetic energy were compared to the 50 per cent energy release location (CA50) on a cyclic basis for three different experimental test cases. The peak surface velocity location showed a robust ability to detect CA50 on a cyclic basis for short combustion durations. Using a simple single-degree-of-freedom vibration model, it is shown the impulsive nature of the combustion load and the natural frequency of the engine structure governs when the peak velocity location will indeed robustly detect CA50 on a on a per-engine cycle basis.