Browse Publications Technical Papers 2019-01-0547

Key fuel injection system features for efficiency improvement in future Diesel passenger cars 2019-01-0547

Diesel will continue to be an indispensable energy carrier for the car fleet CO2 emission targets in the short-term. This is particularly relevant not for heavy-duty commercial vehicles only, but also for mid-size passenger cars and SUVs. Looking at the latest technology achievements in terms of after-treatment systems, it can be stated that the issue on the NOx emission gap between homologation test and real road use is practically solved, while the main challenge for diesel survival on the market is to keep its competitiveness in the CO2 vs cost equation in comparison to other propulsion systems. The development of the combustion system design still represents an important leverage for the further improvement of efficiency and emissions while keeping the current excellent performance in terms of power density and low-end torque. The present paper describes the results achieved in developing a new diesel combustion system for passenger car application that, leveraging on the high flexibility of the latest fuel injection technology, combines excellent power and fuel efficiency with low pollutant emissions in ultralight engine characterized by low peak firing pressure. The study has been carried out on a 0.5L single-cylinder research engine, representing the state of the art of diesel technology, on which a high fuel injection pressure of last generation piezo common rail systems (greater than 2500 bar of rail pressure) has been installed. Through an extensive DoE-based test campaign in which all engine and injection operating parameters have been carefully parametrized, including multi-injection patterns, EGR in the whole engine map and nozzle flow number, the capability to achieved high power density and excellent fuel economy with low engine-out pollutant emission has been demonstrated. These results represent only a part of the contribution from the advanced combustion system designs to the competitiveness of the future diesel powertrains, while others typical issues of the diesel combustion would be eligible for improvement by the employed technology, such as the cold start performance, the thermal management of exhaust gas treatment systems etc.


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