The emissions legislation of non-road diesel engines becomes more stringent all the time. In current development work, emissions standards entering into force in the 2010s need to be prepared for. Without question, different exhaust after-treatment systems will be needed but the emissions downstream the engine itself must also be reduced as effectively as possible to improve the operating conditions of after-treatment devices.
In the present study, a turbocharged, intercooled direct-injection non-road diesel engine was developed to comply with future emissions legislation. The engine was equipped with a common-rail injection system and a waste-gate turbocharger. The injector tips were optimized. Relative to standard nozzles, the fuel flow rate was first reduced. The effects of the orifice number were then investigated. Next, the coning angle of the fuel sprays was varied at a constant orifice number. Finally, the effects of the intake valve closing timing were briefly studied.
The emissions were determined based on the eight-mode ISO 8178 C1 test cycle. Additional loading points were, however, also examined since the engine should cope with the demands of the transient test cycles adopted in future emissions measurements.
The reduced fuel flow rate led to a clear decrease of PM emissions but NMHC + NOx slightly increased. NMHC + NOx could be reduced by decreasing the injector orifice number. Nevertheless, keeping the orifice number constant resulted in good low-speed performance which is of importance in transient engine operation. The tips with the highest hole number were therefore selected.
With an increasing coning angle, NMHC + NOx increased but PM emissions and fuel consumption decreased. Outside of the ISO test cycle, the full load performance and smoke proved to be advantageous with the tips of a large coning angle. These tips were therefore selected for further optimization of the engine. Mild Miller timing also brought some benefits.