Nowadays the development of downsized Direct Injection Spark Ignition (DISI) engines for automotive application is the main stream in order to comply with both specific fuel consumption reduction and tail pipe vehicle emissions regulation. Direct Injection in the cylinder, however, promotes fuel spray impingement on the cylinder liner and the piston crown, depending on both the air density (engine load) and velocity (engine speed) and the injector specification and operation. Due to the droplet loss of momentum and the resulting local fuel vaporization, the wall impingement results in formation of rich (λ < 0.5) air-fuel mixture pockets, which might burn according to a diffusive flame resulting in particulate formation. In order to provide useful guidelines to GDI combustion system thermo-fluid design, it is mandatory to investigate the interaction of the fuel droplets with the walls and to predict the liquid film occurrence and its evolution in a wide range of engine-like operating conditions. In the present work, a numerical analysis based on 3D-CFD using the commercial code STAR-CD v.4.28 has been performed. In particular, the Lagrangian spray-wall impingement model, the pool boiling model and the Leidenfrost and Nukiyama temperatures correlations were tested and tuned against experimental data. The aim of the work is to understand the main features and the critical aspects of the wall impingement modelling and to assess the coefficients sensitivity, taking into account the most influencing parameters for the engine application as injection pressure, back-pressure, wall temperature. The final goal is to determine a robust and physically representative methodology.

Fuel droplet-wall impingement under GDI-like conditions: A numerical investigation

Mariani Valerio
;
Bianchi;Cazzoli Giulio;Falfari Stefania
2019

Abstract

Nowadays the development of downsized Direct Injection Spark Ignition (DISI) engines for automotive application is the main stream in order to comply with both specific fuel consumption reduction and tail pipe vehicle emissions regulation. Direct Injection in the cylinder, however, promotes fuel spray impingement on the cylinder liner and the piston crown, depending on both the air density (engine load) and velocity (engine speed) and the injector specification and operation. Due to the droplet loss of momentum and the resulting local fuel vaporization, the wall impingement results in formation of rich (λ < 0.5) air-fuel mixture pockets, which might burn according to a diffusive flame resulting in particulate formation. In order to provide useful guidelines to GDI combustion system thermo-fluid design, it is mandatory to investigate the interaction of the fuel droplets with the walls and to predict the liquid film occurrence and its evolution in a wide range of engine-like operating conditions. In the present work, a numerical analysis based on 3D-CFD using the commercial code STAR-CD v.4.28 has been performed. In particular, the Lagrangian spray-wall impingement model, the pool boiling model and the Leidenfrost and Nukiyama temperatures correlations were tested and tuned against experimental data. The aim of the work is to understand the main features and the critical aspects of the wall impingement modelling and to assess the coefficients sensitivity, taking into account the most influencing parameters for the engine application as injection pressure, back-pressure, wall temperature. The final goal is to determine a robust and physically representative methodology.
74TH ATI NATIONAL CONGRESS: Energy Conversion: Research, Innovation and Development for Industry and Territories
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Mariani Valerio, Bianchi, Cazzoli Giulio, Falfari Stefania
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11585/724545
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