Portable In-Cylinder Pressure Measurement and Signal Processing System for Real-Time Combustion Analysis and Engine Control

This paper presents an in-cylinder pressure measurement system for cycle-to-cycle feedback combustion control purposes. Such a system uses off-the-shelf components to measure cylinder pressure and performs user-defined algorithms for heat release analysis. The working principle of the device is discussed as well as the simplifications for heat release analysis required for fast computation. The system is benchmarked against a commercially-available combustion analyzer in order to quantify the accuracy and time response. The results showed that the system is satisfactorily accurate for combustion phasing control. The main advantage, however, comes from the reduction of calculation and communication delays observed in the commercially-available system. This enables the use of cycle-to-cycle cylinder pressure-based feedback control algorithms. The functionality of such a device is demonstrated in a spark-ignition experimental engine fitted with an externally cooled exhaust gas recirculation (EGR) loop. Here, an optimal combustion phasing was the target for a feedback combustion controller that automatically adjusted the spark advance. The favorable results proved the system suitable not only for this particular combustion control problem with EGR but also for many of the modern combustion control strategies in gasoline and diesel engines.