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TECHNICAL PAPERS

Modeling Mixture Formation in a Gasoline Direct Injection Engine

[+] Author and Article Information
Rossella Rotondi

Dipartimento di Ingegneria Meccanica, Università di Roma “Tor Vergata”, Viale del Politecnico 1, 00133 Roma, Italyrossella.rotondi@uniroma2.it

J. Appl. Mech 73(6), 931-939 (Dec 19, 2005) (9 pages) doi:10.1115/1.2173284 History: Received May 26, 2005; Revised December 19, 2005

Mixture formation and combustion in a gasoline direct injection (GDI) engine were studied. A swirl-type nozzle, with an inwardly opening pintle, was used to inject the fuel directly in a four stroke, four cylinder, four valves per cylinder engine. The atomization of the hollow cone fuel spray was modeled by using a hybrid approach. The most important obstacle in the development of GDI engines is that the control of the stratified-charge combustion over the entire operating range is very difficult. Since the location of the ignition source is fixed in SI engines the mixture cloud must be controlled both temporally and spatially for a wide range of operating conditions. Results show that the volume of the spark must be considered when discretizing the computational domain because it highly influences the flow field in the combustion chamber. This is because the volume occupied by the plug cannot be neglected since it is much bigger than the ones used in port fuel injection engines. The development of a successful combustion system depends on the design of the fuel injection system and the matching with the in-cylinder flow field: the stratification at part load appears to be the most crucial and critical step, and if the air motion is not well coupled with the fuel spray it would lead to an increase of unburned hydrocarbon emission and fuel consumption

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

CAD design of the engine and related computational grid

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Figure 2

Schematic of the whole engine in the 1D approach

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Figure 3

Comparison between numerical (1D and 3D) and experimental pressure (Pascal) in the intake duct. Part load case (top) and full load case (bottom).

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Figure 4

Lambda distribution in the combustion chamber. Homogeneous case.

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Figure 5

Experimental and numerical indicated cycle for nominal crank timing: 21.4deg

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Figure 6

Numerical (dark line) and experimental (lighter lines) indicated cycle for different crank timing: 29, 27, 25, 24, 22, 17, 12, 7, 4, 1, and −2deg

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Figure 7

Lambda distribution at ignition crank angle. Case 3. Grid considering the volume of the plug (left) and grid neglecting it (right).

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Figure 8

Lambda distribution at ignition crank angle. Case 1 (up) and case 2 (down) in two different planes.

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Figure 9

Indicated cycle for cases 1 and 3

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