Abstract
The proposed article involves an investigation of the processes taking place during the preparation of mixed fuels that are combined directly before combustion. The fuel dose formed in this way must take into account the qualitative and quantitative composition of the fuels and the amount of air in the process. Given that liquid fuels similar to gasoline (e.g. methanol, ethanol, butanol) are characterized by different properties, their comparison would be useful in order to use their ratio to influence the combustion process. The process of fuel preparation plays a decisive role in this issue. The article describes abilities of modelling the injection of various fuels simultaneously to the combustion chamber for creating fuel mixture directly before ignition. First part of the article consists of analysis of light hydrocarbon fuels mixing abilities, supported with present research data. Next part describes the evaluation of execution of the assumed system – two fuel injectors with analysis of spray penetration. The modelling of the injection and spray was performed in the AVL FIRE 2014.2 environment and the results were presented. The injection possibility was proven by injecting the fuel to the combustion chamber model. Local values of air-fuel ratio, density and ambient pressure were presented to better understand the potential in mixing fuels directly before ignition. The conclusion includes description of fuel mixing abilities, influence of various fuels on creation of a stratified mixture and definition of controllability of charge ignition.
Highlights
Combustion processes are considered mainly in terms of a mono-fuelled combustion
The research consisted of performing the direct fuel injection events into the modeled combustion chamber through two separate injectors
The area around the spark plug was subjected to research referred to fuel droplets distribution and air excess ratio of the A/F mixture
Summary
Combustion processes are considered mainly in terms of a mono-fuelled combustion. Processes of preparation and combustion of gasoline-like fuels are widely described in literature. The way of preparing such a mixture causes it to have specific physico-chemical properties (viscosity, surface tension and density closely define specific contents of different hydrocarbon groups) [12, 22] In such a situation, sprays of drops with small, homogeneous dimensions are obtained. Ohnesorge number is convergent with the data contained in the publications [4, 8] and amounts to about 6·10–3 to 1.6·10–2 at the temperature of about 283 K, and decreases to a value of about 6·10–3 for temperature of 463 K Indication of these differences is a basis for the conclusion that the created drops of fuel will have different diameters, which will contribute to their diversified evaporation. It is a good indicator of mixing fuels proposed for tests in the current research
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