Hydrous ethanol vs. gasoline-ethanol blend: Engine performance and emissions

Compression ratio effects on an ethanol/gasoline fuelled engine performance

https://biblio.ugent.be/publication/818313/file/818401.pdf

Multi-zone thermodynamic modelling of spark-ignition engine combustion -An overview

Amplified Pressure Waves During Autoignition: Relevance to CAI Engines

Engine Hot Spots: Modes of Auto-ignition and Reaction Propagation

Modeling of Cyclic Variations in Spark-Ignition Engines

Lean mixture combustion might be an important feature in the next generation of SI engines, while diluents have already played a key role in the reductions of emissions and fuel consumption. Lean burning modeling is even more important for engine modeling tools which are sometimes used for new engine development. The effect of flame strain on flame speed is believed to be significant, especially under lean mixture conditions. Current quasi-dimensional engine models usually do not include flame strain effects and tend to predict burn rate which is too high under lean burn conditions. An attempt was made to model flame strain effects in quasi-dimensional SI engine models. The Ford model GESIM was used as the platform. A new strain rate model was developed with the Lewis number effect included. A 2.5L V6 4-valve engine and 4.6L V8 2-valve modular engine were used to validate the modified turbulent entrainment combustion model in GESIM. Results showed that the current GESIM can differ by as much as 10 crank angle degrees compared with test data. The modified GESIM can predict burn duration to within 1--2 CA of experimental data, which is considered very good for engine models.

Diluents and Lean Mixture Combustion Modeling for SI Engines with a Quasi-Dimensional Model

In premixed turbulent combustion models, two mechanisms have been used to explain the increase in the flame speed due to the turbulence. The newer explanation considers the full range of turbulence scales which wrinkle the flame front so as to increase the flame front area and, thus, the flame propagation speed. The fractal combustion model is an example of this concept. The older mechanism assumes that turbulence enables the penetration of unburned mixtures across the flame front via entrainment into the burned mixture zone. The entrainment combustion or eddy burning model is an example of this mechanism. The results of experimental studies of combustion regimes and the flame structures in SI engines has confirmed that most combustion takes place at the wrinkled flame front with additional combustion taking place in the form of flame fingers or peninsulas. As the ratio of the turbulence intensity to the laminar flame speed increases, the importance of the flame peninsulas should become increasingly important. While it has been shown that fractal geometry can be used to account for flame wrinkling, it may be difficult to extend this concept to account for the additional surface area resulting from the flame peninsulas. However, the flame frontmore » convolution that results in flame peninsulas can be envisioned as entrainment combustion. In the present research an effort was made to combine the fractal combustion model and the entrainment combustion model to generate the peninsula-fractal combustion model, so as to improve burn rate predictions of SI engine codes.« less

Combustion modeling in si engines with a peninsula-fractal combustion model

Predictions of In-Cylinder Tumble Flow and Combustion in SI Engines with a Quasi-Dimensional Model

Hydrocarbon (HC) emissions from direct injection gasoline (DIG) engines are significantly higher than those from comparable port fuel injected engines, especially when late direct injection (injection during the compression stroke) is used to produce a fuel economy benefit via unthrottled lean operation The sources of engine-out hydrocarbon emissions for late direct injection are bulk flame quench, low temperatures for postcombustion oxidation, and fuel impingement on in-cylinder walls An experimental technique has been developed that isolates the wall impingement source from the other sources of HC emissions from DIG engines A series of steady-state and transient experiments is reported for which the HC emissions due to operation with a premixed charge using a gaseous fuel are compared to those when a small amount of liquid fuel is injected onto an in-cylinder surface and the gaseous fuel flow rate is decreased correspondingly The steady-state experiments show that wetting any in-cylinder surface dramatically increases HC emissions compared to homogeneous charge operation with a gaseous fuel The results of the transient fuel injection interrupt tests indicate that liquid-phase gasoline can survive within the cylinder of a fully warmed-up firing engine and that liquid fuel vaporization is slower than current computational models predict This work supports the argument that HC emissions from DIG engines can be decreased by reducing the amount of liquid fuel that impinges on the cylinder liner and piston, and by improving the vaporization rate of the fuel that is deposited on these surfaces

Wen Dai

Papers

Modeling of Cyclic Variations in Spark-Ignition Engines

Diluents and Lean Mixture Combustion Modeling for SI Engines with a Quasi-Dimensional Model

Combustion modeling in si engines with a peninsula-fractal combustion model

Predictions of In-Cylinder Tumble Flow and Combustion in SI Engines with a Quasi-Dimensional Model

Liquid Fuel Impingement on In-Cylinder Surfaces as a Source of Hydrocarbon Emissions From Direct Injection Gasoline Engines