Search

This is the author s version of a work that was accepted for publication in International Journal of Engine Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published as https://doi.org/10.1177/1468087418819250, [EN] This article describes the main results of an investigation about counter-bore injector nozzle impact on the combustion process in a modern Euro 6 diesel engine. First, hydraulic and spray visualization tests have been performed, showing a potential advantage of such nozzle design in fuel-air mixing efficiency. Then, combustion performance has been assessed on a GM-designed 1.6-L four-cylinder engine. The engine has been installed on a dynamometric test bench and instrumented with an AVL cylinder pressure transducer for heat release rate analysis, as well as HORIBA MEXA gas analyzer for exhaust emissions and AVL 415 Smoke Meter. Engine efficiency and emissions have been analyzed on four different part-load steady-state points, representative of New European Driving Cycle and Worldwide harmonized Light duty Test Cycle certification cycles, and covering engine speeds from 1250 to 2000 r/min and brake mean effective pressure between 0.2 and 1.4 MPa. Results of indicated analysis show that counter-bore nozzles have significant differences in terms of pilot injection combustion at low load points, which in turn lead to a better ignition and shorter combustion of the main injection. In addition, an improvement of diffusive combustion is observed as load increases. Because of both, fuel consumption is reduced by approximately 1% with respect to a standard nozzle. Finally, an appreciable decrease in engine exhaust emissions has been recorded, especially in terms of particulate matter and hydrocarbon emissions. This reduction has been linked to the improvement of fuel-air mixing promoted by the counter-bore nozzle previously observed.

[EN] This work investigates the load limits of reactivity controlled compression ignition combustion, a dual-fuel concept which combines port fuel injection of low-reactivity fuels with direct injection of diesel fuel, in a medium-duty diesel engine. The experiments were conducted in a single-cylinder diesel engine derived from the multi-cylinder production engine. In this sense, the stock turbocharger and exhaust gas recirculation systems were replaced by an external compressor and dedicated low-pressure exhaust gas recirculation loop, respectively. Additionally, a port fuel injector was installed in the intake manifold to allow gasoline injection. First, this article presents some results highlighting the effect of the exhaust gas recirculation rate, gasoline fraction, diesel start of injection, diesel injection strategy and intake temperature on the emissions, performance and combustion development in a representative operating condition: 1200r/min and 6.5bar indicated mean effective pressure (25% load). Later, with the aim of showing the reactivity controlled compression ignition potential, the best results in terms of performance and emissions at 25% load are compared against the multi-cylinder diesel engine from 950 to 2200r/min. Reactivity controlled compression ignition engine tests were developed taking into account limitations in nitrogen oxides (NOx) and soot emissions, in-cylinder pressure and maximum pressure rise rate. Finally, keeping the same constraints for testing, the load limits of reactivity controlled compression ignition concept are evaluated for all the engine speeds. Results suggest that reactivity controlled compression ignition allows fulfilling EURO VI limits for NOx and soot emissions without using selective catalytic reduction and diesel particulate filter aftertreatment systems at 25% load at all the engines speeds, providing better indicated efficiency than conventional diesel operation in most operating points. In addition, the maxim