MEMS Application to Monitor the In-Cylinder Pressure of a Marine Engine

The transport of goods and people by sea, today, must meet the need to reduce the consumption of fuel oil. In addition, it has to ensure operational reliability and vessel availability, to reduce maintenance costs and comply with emission legislation. To this end, it is necessary to apply a marine engine combustion control system already widely used in engines for land transport. This will allow the ship's engines to operate reliably and in compliance with the best performance for which it was designed. The combustion control could also ensure a more balanced operation of the cylinders and reduce the torsional vibrations of the entire engine, as well as the management of the engine according to the adopted fuel: diesel, dual fuel, methanol, ammonia. Generally, the control of combustion in engines is carried out through the use of pressure sensors that face directly into the combustion chamber. These are expensive systems and are affected by the severe operating conditions of the marine engine. The present work shows how the use of MEMS (Micro Electro-Mechanical System) represents a valid solution to replace the pressure transducers in the chamber. In particular, two MEMS-type accelerometers were used on a single-cylinder research engine with a displacement of 4.2 l for naval applications, fueled by diesel. A comparative analysis of MEMS sensors with the pressure signal detected in the combustion chamber was conducted. Excellent correspondences were highlighted regarding the moments of closure of the exhaust and intake valves, the instant of start of injection and the instant of start of combustion. The results are encouraging for the use of low-cost and easy-to-apply MEMS sensors (they can be installed outside the engine and there is no need to create specific accesses to the combustion chamber) for effective combustion control of marine engines.