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Chryssakis, Christos A.
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Evaluation of a Narrow Spray Cone Angle, Advanced Injection Timing Strategy to Achieve Partially Premixed Compression Ignition Combustion in a Diesel Engine

GM R&D and Planning-Robert M. Siewert
University of Michigan-Guntram A. Lechner, Timothy J. Jacobs, Christos A. Chryssakis, Dennis N. Assanis
Published 2005-04-11 by SAE International in United States
Simultaneous reduction of nitric oxides (NOx) and particulate matter (PM) emissions is possible in a diesel engine by employing a Partially Premixed Compression Ignition (PPCI) strategy. PPCI combustion is attainable with advanced injection timings and heavy exhaust gas recirculation rates. However, over-advanced injection timing can result in the fuel spray missing the combustion bowl, thus dramatically elevating PM emissions. The present study investigates whether the use of narrow spray cone angle injector nozzles can extend the limits of early injection timings, allowing for PPCI combustion realization. It is shown that a low flow rate, 60-degree spray cone angle injector nozzle, along with optimized EGR rate and split injection strategy, can reduce engine-out NOx by 82% and PM by 39%, at the expense of a modest increase (4.5%) in fuel consumption. This PPCI strategy has the potential for meeting upcoming stringent fuel specific NOx emission levels of less than 1 g/kg-fuel and fuel specific PM levels less than 0.25 g/kg-fuel.
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Fuel Spray Simulation of High-Pressure Swirl-Injector for DISI Engines and Comparison with Laser Diagnostic Measurements

University of Hiroshima-Jee-Kuen Lee, Keiya Nishida
University of Michigan-Christos A. Chryssakis, Dennis N. Assanis
Published 2003-03-03 by SAE International in United States
A comprehensive model for sprays emerging from high-pressure swirl injectors in DISI engines has been developed accounting for both primary and secondary atomization. The model considers the transient behavior of the pre-spray and the steady-state behavior of the main spray. The pre-spray modeling is based on an empirical solid cone approach with varying cone angle. The main spray modeling is based on the Liquid Instability Sheet Atomization (LISA) approach, which is extended here to include the effects of swirl. Mie Scattering, LIF, PIV and Laser Droplet Size Analyzer techniques have been used to produce a set of experimental data for model validation. Both qualitative comparisons of the evolution of the spray structure, as well as quantitative comparisons of spray tip penetration and droplet sizes have been made. It is concluded that the model compares favorably with data under atmospheric conditions. However, discrepancies occur under higher ambient pressures, suggesting that the physics of the breakup mechanism should be further investigated for these conditions.
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