The coming new test procedure world harmonized light-duty test procedures (WLTP) will introduce new more transient and higher load cycles like world harmonized light-duty test cycle (WLTC) and real driving emissions (RDE). Without any countermeasures the engine emissions of diesel engines will be increased drastically to levels that require massive NOx after treatment. To keep the diesel engine system cost in a competitive range it has been investigated how the engine out emissions can be reduced within the new WLTC for different weight classes. Based on a 2.0 Liter diesel engine with 103 kW rated power the option to utilize latest improved solenoid injectors with significant improved hydraulic performance and injection pressures up to 2500 bar in combination with improved air path controls has been investigated. By reducing the nozzle flow rate, reduced injector leakage, and by improved hydraulics with closer pilot intervals and smaller pilot quantities finally in the vehicle a soot reduction of 30% compared to the conventional injector was achieved in the new european driving cycle (NEDC), while at the same time the CO2 emissions could be reduced by 3% compared to the baseline level (which represents a typical EURO V production level w/o start-stop system). Initially within the WLTC the engine out NOx emission has more than doubled. With improved calibration and using NOx based air path control, however, a NOx level of 115 mg/km could be demonstrated in the WLTC with 1700 kg inertia. To meet EURO VI tailpipe emissions this would require less than 60% DeNOx conversion rate, which can be utilized to simplify the DeNOx system and/or reduce fuel draw back needed for thermo management of the after treatment. Additional BSFC improvement potentials can be achieved when introducing model based boost pressure control using as lead parameter the engine differential pressure rather than the boost pressure allowing for demand based EGR with optimum fuel consumption at each flexible demanded EGR rate level.
Combustion improvement and emission control technologies supporting the coming new cycle requirements for passenger car diesel engines
2013
30 Seiten, 23 Bilder, 14 Quellen
Aufsatz (Konferenz)
Englisch
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