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The purpose of the present study was to model combustion, soot and NOx-emissions of a medium speed diesel engine using the modified KIVA-2 code. Assesment of the droplet vaporization, the soot formation and its oxidation models were also done regarding the medium speed diesel engine. Heavy fuel spray was modeled with the standard KIVA-2 chi-squared model including drag modification during droplet vaporization (the droplet distribution model), droplet vaporization with the high pressure Spalding and Abramzon&Sirignano models, combustion with the Magnussen EDC-model including a two step reaction mechanism, NOx formation with the extended Zeldovich model, soot formation with the modified Tesner&Magnussen model and soot oxidation with the EDC-model and Nagle and Strickland-Constable model (NSC). The RNG k-epsilon turbulence model was also implemented into the code. The Redlich-Kwong real gas equation of state and the formulation of Peng-Robinson fugacity coefficient equation were used.

In this study the effect of spray characteristics such as spray penetration, spray cone angle and Sauter Mean Radius have been shown to influence fuel vapor distribution, vapor mixing in air and combustion chamber gas turbulence. The effect can be seen in the combustion results, i.e. cylinder pressure, heat release, cumulative heat release, fuel vapor concentration, soot and NOx-formation. In KIVA2-CFD code the Magnussen EDC ( Eddy Dissipation Concept ) model were used for the fuel vapor and soot particles combustion, the Tesner & Magnussen model for the soot formation and the extended Zeldovich model for the NO-formation. Mainly the modified TAB-model or alternatively χ-squared droplet distribution method (DDM) were used for the spray. The TAB-model constants and the initial SMR in the DDM-model were varied logically in order to obtain different kinds of spray characteristics and accordingly different spray behavior in combustion and non-combustion cases.

The purpose of this study is to simulate combustion, soot and NOx-emissions in the world's largest medium speed diesel V-engine, the W64V, based on simulation results of in line-engine W64L. The simulation tool was the modified KIVA2-CFD code to which the following submodels were added: The Magnussen EDC ( Eddy Dissipation Concept ) turbulent mixing combustion model, the extended Zeldovich NO model and a simple rebounding model for the droplet wall impingement. Further the Tesner&Magnussen soot formation and combustion model was implemented in the code and the modified TAB model was used for the spray. The simulation results, such as the cylinder pressure, the heat release rate and the cumulative heat release were compared with the results of a thermodynamic two zone model because the V-engine is under design and therefore measured quantities are not available.

The combustion process and NOx emission of the world's largest medium speed diesel engine, the Wärtsilä W64L (W64L), were simulated with the modified Kiva2-CFD code. The following submodels were added to the standard Kiva2 code: The Magnussen EDC (Eddy Dissipation Concept) turbulent mixing combustion model, the extended Zeldovich NO model and a simple rebounding model for the droplet wall impingement. The Tesner&Magnussen soot formation and combustion model was implemented in the code, but it has not yet been used in this stage. The modified TAB model was used for the spray. The simulation results, such as the cylinder pressure, the heat release rate and the cumulative heat release were compared to the measured values of the W64L engine. The spray model correctness was tested by comparing the predicted spray tip penetration with Hiroyasu's correlation at room temperature conditions.

The purpose of the paper is to present injection results of heavy fuel spray at room temperature conditions and combustion predictions in a medium speed diesel engine using the k-ε turbulence model in KIVA2. The work consists of two main parts. In the first, the heavy fuel spray is simulated at cold test chamber conditions in which the density of gas is of the same order of magnitude as in the engine at the end of compression. The predicted spray tip penetration and droplet sizes are compared to the measured values. The second part deals with the combustion simulation using the Magnussen and Hjertager ( M&H ) or Magnussen Eddy Dissipation Concept ( EDC ) turbulent diffusion combustion model. The cylinder pressures and heat release in the simulation are compared to the measured values.