Experimental Analysis of Combustion Processes and Emissions in a 2.0L Multi-Cylinder Diesel Engine Featuring a New Generation Piezo-Driven Injector

In this paper, the potential of new generation piezo-driven indirect acting injectors on high feature diesel engine performance and emissions was assessed by combining experimental tests (carried out at both hydraulic and engine test beds) with the diagnostics of combustion and emissions. This latter was performed by means of a refined multizone combustion diagnostic tool previously developed at Politecnico di Torino. More in detail, a complete hydraulic characterization of the injection system has been carried out and injector performance, in terms of robustness and repeatability of the injection process, has been also evaluated. Injectors were then installed on 4-cylinder 2.0L Diesel engine and tests were performed in seven key-points, which were specifically selected so as to reproduce the engine operations over NEDC in terms of emissions and fuel consumption. For each key-point, different injection-train strategies were tested and the corresponding engine calibrations were optimized by Design of Experiment (DoE) methodology. In-cylinder pressure time-histories measured on the firing engine and injection rates evaluated at hydraulic test rig were then processed by the multizone diagnostic tool so as to obtain Φ-T time-histories of each zone. Finally, the injection strategy showing the best compromise in terms of pollutant emissions, fuel consumption and combustion noise was selected for each key-point and the cause-effect relationships between injection rate and combustion process were analyzed.