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Sykes, Dan
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Visual Analyses of End of Injection Liquid Structures and the Behaviour of Nozzle Surface-Bound Fuel in a Direct Injection Diesel Engine

BP International Ltd.-Martin Gold, Richard Pearson
University of Brighton-Dan Sykes, Guillaume de Sercey, Cyril Crua
Published 2019-01-15 by SAE International in United States
For efficiency, the majority of modern diesel engines implement multiple injection strategies, increasing the frequency of transient injection phases and thus, end of injection (EOI) events. Recent advances in diagnostic techniques have identified several EOI phenomena pertinent to nozzle surface wetting as a precursor for deposit formation and a potential contributor towards pollutant emissions. To investigate the underlying processes, highspeed optical measurements at the microscopic scale were performed inside a motored diesel engine under low load/idling conditions. Visualisation of the injector nozzle surface and near nozzle region permitted an indepth analysis of the post-injection phenomena and the behaviour of fuel films on the nozzle surface when the engine is not fired. Inspection of the high-speed video data enabled an interpretation of the fluid dynamics leading to surface wetting, elucidating the mechanisms of deposition and spreading. As the needle re-seated, the abrupt pressure drop inhibited atomisation. Large, slow moving, liquid structures were released into the cylinder with the capability of impinging on nearby surfaces, creating localised fuel rich regions, or escaping through the exhaust and contributing…
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Simulation and Measurement of Transient Fluid Phenomena within Diesel Injection

SAE International Journal of Advances and Current Practices in Mobility

BP International Ltd.-Martin Gold, Richard Pearson
City University London-Mithun Murali-Girija, Foivos Koukouvinis, Manolis Gavaises
  • Journal Article
  • 2019-01-0066
Published 2019-01-15 by SAE International in United States
Rail pressures of modern diesel fuel injection systems have increased significantly over recent years, greatly improving atomisation of the main fuel injection event and air utilisation of the combustion process. Continued improvement in controlling the process of introducing fuel into the cylinder has led to focussing on fluid phenomena related to transient response. High-speed microscopy has been employed to visualise the detailed fluid dynamics around the near nozzle region of an automotive diesel fuel injector, during the opening, closing and post injection events. Complementary computational fluid dynamic (CFD) simulations have been undertaken to elucidate the interaction of the liquid and gas phases during these highly transient events, including an assessment of close-coupled injections.Microscopic imaging shows the development of a plug flow in the initial stages of injection, with rapid transition into a primary breakup regime, transitioning to a finely atomised spray and subsequent vaporisation of the fuel. During closuring of the injector the spray collapses, with evidence of swirling breakup structures together with unstable ligaments of fuel breaking into large slow-moving droplets. This leads to…
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