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The aim of the present work is to provide further guidance into better understanding the production mechanisms of soot emissions in Spark-Ignition SI engines fueled with compressed natural gas. In particular, extensive experimental investigations were designed with the aim to isolate the contribution of the fuel from that of lubricant oil to particle emissions. This because the common thought is that particulate emerging from the engine derives mainly from fuel, otherwise the contribute of lubricant oil cannot be neglected or underestimated, especially when the fuel itself produces low levels of soot emissions, such as in the case of premixed natural gas. The fuel-derived contribution was studied by analyzing the influence that natural gas composition has on soot emitted from a single cylinder Spark-Ignition (SI) engine. To achieve this purpose, methane/propane mixtures were realized and injected into the intake manifold of a Single-Cylinder SI engine.

Since the needle displacement exerts a fundamental influence in the operation of a Common Rail Diesel injection equipment, an accurate measurement of the instantaneous position of the control piston is crucial for a more thorough analysis of the behavior of the injectors, in particular when multiple injections are employed. Moreover, the development of a cheap instrumentation would allow to enlarge the Diesel engine on-board equipment with an instrumentation for the diagnosis of the injector operation. Eddy current sensors have been traditionally used in lab activities to measure the position of the needle inside the injector; apart from its high cost, the scientific literature clearly shows their inadequacy, given the presence of electromagnetic disturbance: the current pulse which controls the opening of the injector nozzles generates electromagnetic fields which strongly affect the acquisition of data.

A simple, cheap and effective way of measuring the pressure inside the cylinders of internal combustion engines is proposed in this paper. It is well known that the in-cylinder pressure is one of the most significant variables describing the combustion status in internal combustion engines; therefore, if the measured value of the actual pressure in the combustion chamber is used as a feedback variable for closed loop monitoring and control techniques, it will be possible both to improve engine performances and to reduce fuel consumptions and emissions. However, to date such a pressure-based control strategy has been limited by costs, reliability and lifetime of commercially available cylinder pressure sensors. To overcome these limitations, the present paper proposes a very simple and low cost experimental device for measuring the pressure inside the combustion chamber, developed for engine control and monitoring applications.

Recent needs of reducing pollutant emissions of internal combustion engines have pushed the development of non-conventional ignition systems. One of the most promising techniques appears to be the so-called pre-chamber turbulent jet ignition combustion system in which a jet of hot combusting gases is employed to initiate the combustion in the main chamber. In the present study, the combustion process related to this ignition system has been experimentally investigated in an optically accessible single cylinder spark-ignition engine. The pre-chamber was composed of a gas injector and a spark-plug, embedded in a small annular chamber connected to the cylinder through a four-hole pipette. A small amount of methane is injected within the pre-chamber for initiating the combustion. The flame reaches the combustion chamber through four narrow orifices and rapidly consumes a homogeneous mixture of port injected methane and air.