Development of an HCCI index

Abstract: New models of combustion engines have gained a great interest within research in the last decade. This interest has arisen due to the possibility to achieve a higher degree of efficiency and lower emissions, which will impact the environment positively. A higher degree of efficiency implicates an economical benefit in terms of fuel. The HCCI engine has been thoroughly researched due to its combined advantages of the CI and SI engine. As always, there are disadvantages with this type of engine. The main problems are that the combustion is too quick and that the engine is difficult to control. A good way to compare combustion of fuels in different engines is to develop a fuel index. In a fuel index data for mixtures are accounted for in a table, with which the index of an unknown fuel can be determined. In this master thesis only a limited number of fuels are tested, which means that a fully developed fuel index is not able to be accomplished without further research. In this master thesis a fuel index for the HCCI engine has been partly determined by executing experimental and simulated studies. The fuels tested were Primary Reference Fuels 0 to 100. The engine has been run with inlet temperatures between 293 K and 423 K, in intervals of 10 K, and with a compression ratio that give 50 % burn at TDC. The HCCI engine was modeled and the simulations were performed in DARS, which is a chemical kinetics program. The results from the simulations seem to be reasonable. The compression ratios and the ignition temperatures with the corresponding pressures are in the right magnitude. The results from the experiments, on the other hand, are not as reliable as the results from the simulations. The model created in this master thesis may be used with an engine that has the same conditions as the simulations, if a more accurate chemical model is used and the indicator for the inlet temperature is placed at the correct location. Further research concerning the reason why the simulations and the experiments deviated is needed in order to be able to use this base for an index.