Research on the combustion of alcohol-gasoline blends

Engine cycle simulation using GT-Power and GUEST

GUEST: Ghent University Engine Simulation Tool

Within the research group a two-zone thermodynamic model was constructed for the closed part of the engine cycle (beginning of compression till end of expansion), the GUEST code (Ghent University Engine Simulation Tool). This code was validated for spark-ignition engines running on hydrogen [1] and is currently being adapted to be valid for alcohol fuels (methanol and ethanol). It allows fast computation of the power and efficiency of spark-ignition engines running on these alternative fuels. For this reason GUEST is ideal for parameter and optimization studies (e.g. Figure 2).

In order to calculate trapped conditions (volumetric efficiency and internal residual gases), which serve as a boundary condition for GUEST, the gas dynamics during the breathing cycle are calculated using a commercial engine simulation software (GT-Power). This software can also be used to remedy some important current restrictions of the GUEST code, that is the lack of pollutant emission predictions, knock occurrence predictions and a model for in-cylinder turbulence. An overview of power cycle simulation using GUEST & GT-Power is given in Figure 1.

GUEST and GT-Power

Figure 1: Overview of power cycle simulation using GUEST and GT-Power

Varying ignition timingVarying equivalence ratio

Figure 2: Comparison of measured (symbols) and calculated (lines) cylinder pressure traces inside a hydrogen-fuelled spark-ignition engine for varying ignition timing (left) and equivalence ratio (right). Source: [1]

Gas dynamics simulation using GT-Power and AVL-BOOST

GT-Power is the industry standard engine simulation tool. AVL-BOOST is a very comparable tool from another software manufacturer. These programs are based on 1 dimensional computational fluid dynamics simulation of the gas dynamics during intake and exhaust strokes in combination with multi-zone combustion modeling. It can be used for a wide range of engine design and optimization applications (see for example the GT-Power brochure).

Within the research group, GT-Power is mainly used for calculation of the trapped conditions (volumetric efficiency and amount of internal residuals), which serve as a boundary condition for our in-house power cycle code GUEST. GT-Power and AVL-BOOST have also been used in the development and evaluation of new technologies for medium speed compression ignition engines (in cooperation with Anglo-Belgian Corporation).

GT-Power model

Figure 3: Overview (top) and GT-Power model (bottom) of the CFR test engine

References

1. Verhelst, S., "A study of the combustion in hydrogen-fuelled internal combustion engines. PhD thesis", Department of Flow, heat and combustion mechanics 2005.