Numerical Analysis of Fuel Vapor Concentration Fields in a Spark Ignition Engine

During port-fuel–injected (PFI) spark-ignition (SI) engine startup and warm-up fuel accounting continues to be a challenge. Excess fuel must be injected for a near stoichiometric combustion charge. The “extra” fuel that does not contribute to the combustion process may stay in the intake port or as liquid films on the combustion chamber walls. Some of this combustion chamber wall liquid fuel is transported to the engine’s oil sump and some of this liquid fuel escapes combustion and evolves during the expansion and exhaust strokes. Experiments were performed to investigate and quantify this emerging in-cylinder fuel vapor post-combustion cycle by cycle during engine startup. It is believed that this fuel vapor is evaporating from cylinder surfaces and emerging from cylinder crevices. A fast in-cylinder diagnostic, the fast flame ionization detector, was used to measure this behavior. Substantial post-combustion fuel vapor was measured during engine startup. The amount of post-combustion fuel vapor that develops relative to the in-cylinder precombustion fuel charge is on the order of one for cold starting (0 °C) and decreases to ∼13 for hot starting engine cycles. Fuel accounting suggests that the intake port puddle forms quickly, over the first few engine cranking cycles. Analysis suggests that sufficient charge temperature and crevice oxygen exists to at least partially oxidize the majority of this post-combustion fuel vapor such that engine out hydrocarbons are not excessive.

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Numerical analysis of the influence of early fuel injection on charge motion in a direct injection spark ignition engine using scale-resolving simulations

International Journal of Engine Research ◽

10.1177/1468087419860725 ◽

2019 ◽

Vol 21 (4) ◽

pp. 664-682

Author(s):

Martin Theile ◽

Martin Reißig ◽

Egon Hassel ◽

Dominique Thévenin ◽

Martin Hofer ◽

...

Keyword(s):

Numerical Analysis ◽

Flow Field ◽

Fuel Injection ◽

Direct Injection ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Post Processing ◽

Charge Motion ◽

Set Up ◽

Direct Injection Spark Ignition

This work summarizes the numerical analysis of the effect of early fuel injection on the charge motion in a direct injection spark ignition engine concerning cyclic fluctuations of the flow field. The combination of the scale-resolving turbulence model “Scale Adaptive Simulation” and post-processing routines for vortex trajectory visualization allows for a detailed insight into the temporal resolved and cycle-dependent behavior of the charge motion. In the first part, a simplified engine set-up is presented and used as a validation case to ensure correct behavior of the turbulence model and post-processing routines. In the second part, the computational fluid dynamics model of the real engine is introduced. The application of the proposed vortex tracking algorithm is shown, and a short discussion about the transient behavior of the charge motion in this engine set-up is given. The third part describes the analysis of the influence of the fuel injection on the charge motion at different engine speeds from 1000 to 3000 r/min and variations of the intake pressure from 1 to 2 bar. Finally, the impact on different flow field properties at possible ignition timings is discussed. Changes in mean flow field quantities as well as in aerodynamic fluctuations are found as a consequence of fuel injection.

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Numerical Analysis of a Torch-Ignition System for an Internal Combustion Engine

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.798.234 ◽

2015 ◽

Vol 798 ◽

pp. 234-238

Author(s):

Fábio Radicchi ◽

Raphael M. Braga ◽

Raniro A. Coelho ◽

Roberto B.R. Costa ◽

Ramon Molina Valle

Keyword(s):

Fluid Flow ◽

Numerical Analysis ◽

3D Model ◽

Combustion Engine ◽

Spark Ignition ◽

Spark Ignition Engine ◽

Spark Ignition Engines ◽

Flow Investigation ◽

Pollutants Emission ◽

Turbulence Parameters

Torch ignition systems in spark-ignition engines represents an interesting option in the efforts to reduce pollutants emission and specific fuel consumption. Based on this idea, this paper presents a 3D model of a prechamber created for a spark-ignition engine and focuses on the numerical analysis of the fluid flow inside the modified chamber. This kind of analysis is very important once it allowed evaluating aspects like turbulence parameters, pressure inside the chamber and prechamber, fluid recirculation and a possible prechamber’s geometry for the engine. The studies were done in a four valve Single Cylinder Research Engine – SCRE. For the numerical modeling and fluid flow investigation was used STAR-CD software. Results show higher values of tumble ratio and kinetic energy with the prechamber.

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