Analysis of Diesel Injector Nozzle Flow Number Impact on Emissions and Performance of a Euro5 Automotive Diesel Engine 2012-01-0891

The present paper describes the results of a research project aimed at studying the impact of nozzle flow number on a Euro5 automotive diesel engine, featuring Closed-Loop Combustion Control. In order to optimize the trade-offs between fuel economy, combustion noise, emissions and power density for the next generation diesel engines, general trend among OEMs is lowering nozzle flow number and, as a consequence, nozzle hole size. In this context, three nozzle configurations have been characterized on a 2.0L Euro5 Common Rail Diesel engine, coupling experimental activities performed on multi-cylinder and optical single cylinder engines to analysis on spray bomb and injector test rigs. More in detail, this paper deeply describes the investigation carried out on the multi-cylinder engine, specifically devoted to the combustion evolution and engine performance analysis, varying the injector flow number. To this aim, an experimental campaign has been carried out, testing the engine in three partial load steady state operating points, representative of the European homologation driving cycle, and in full load engine conditions. The engine behaviour has been investigated performing exhaust gas recirculation flow and lambda sweeps, at partial and full load engine conditions, respectively. Results highlight that the implemented Closed-Loop Combustion Control in the electronic control unit adopted in the tested engine, well compensates the impact of flow number variation in terms of engine performance and emissions at partial load, showing, in general, the expected benefits of nozzle reduction as regards smoke emissions and noise. At full load, an ad hoc engine recalibration of the full load conditions has to be performed in order to achieve the required target of specific power within constraints in terms of inlet turbine temperature, smoke emissions and peak firing pressure.