Modeling Analysis of Fuel Sprays

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Courtesy of HORIBA Europe GmbH

Current engine development processes in which computations play an important role have sought for numerical models which can accurately represent phenomena in spray combustion. The authors have developed original sub-models taking into account the effects of extensive spray combustion phenomena including nozzle cavitation, droplet breakup behavior, multi-component evaporation process, spray-wall interaction, soot formation and so on. This paper describes authors’ models while accompanied by phenomenological descriptions and focusing on how to model the phenomena. In addition, the authors’ current work on model development for a model based calibration method is also introduced.

Infomations

Electronic control technology in engine development has advanced dramatically in the recent years, enabling clean and high-efficiency combustion by finding the optimal combination of many control variables of various electronic devices. However, the control variables continue to grow in number as they need to comply with the f uel consumption regulations and exhaust gas regulations which are ever stricter. Of these variables, many development man-hours are required for common rail-type fuel injection systems with high freedom in injection pressure, injection count and timing as well as for diesel engines equipped with Exhaust Gas Recirculation (EGR), superchargers and so forth, making it difficult to experimentally determine all the optimal settings for control variables within the limited time and resources the engine manufacturers have.

Meanwhile, engine development utilizing model-based methods has gained popularity these days, and the manufacturers are adopting various different measures in order to improve the efficiency in engine development which continues to be more complicated and increase in scale[1-3]. However, in the combustion chamber of an engine whose trunk power source is nonsteady spray c ombu st ion (s uch a s t h at of a d ie s el e ng i ne for automobiles), liquid or air-liquid multiphase flow running faster than 500 m/s passes through a nozzle with hole diameter around 0.1 mm to be injected, atomized, mixed w it h ai r, evapor ate, ig n ite a nd combust throug hinterference with the wall boundary within only several milliseconds. Numerical modeling of such small-scale, high-speed phenomena which are complex both physically and chemically is still being developed, and construction of a model that can capture the phenomena precisely as

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