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Title:Modeling of biofuel-diesel multi-component fuel effects on vaporization, micro-explosion and combustion
Author(s):Shen, Cai
Director of Research:Lee, Chia-Fon
Doctoral Committee Chair(s):Lee, Chia-Fon
Doctoral Committee Member(s):Hansen, Alan; Wang, Xinlei; Stephani, Kelly
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
wall film
IC engine
Abstract:In the effort to reduce air pollution and fossil fuel dependence in automotive and related sectors, internal combustion engine (ICE) designs are optimized for high efficiency and low pollutant emissions, and alternative biofuels are used in ICE mixing with conventional petroleum based fuels. One factor that can greatly deteriorate engine performance is poor fuel atomization, which is characterized by incomplete fuel vaporization and spray impingement on cylinder walls. Residual fuel in the cylinder causes high levels of unburned hydrocarbons and carbon monoxide emissions while altering engine fuel-oil dilution. Thus, fuel atomization that produces fine droplets is preferred, as it enhances the air-fuel mixing rate that will then reduce pollutant emissions. A major hurdle in modeling fuel atomization is how to properly account for the vaporization of complex fuel mixtures. Therefore, the objectives of this research project include: (1) design and develop a multi-component fuel vaporization model using continuous thermodynamics method; (2) investigate the micro-explosion phenomena, which can to occur for multi-component fuel droplets under high temperature, high pressure engine environment and can improve fuel atomization; (3) develop a comprehensive numerical model to predict the occurrence and outcome for micro-explosion; (4) conduct engine simulations for biodiesel and diesel multi-component fuel and syngas enhanced combustion, and optimize the engine operations with blended mixture fuels. In this project, a detailed micro-explosion model was developed, and the effect of different ambient conditions and fuel droplet properties were investigated. The possible approaches to enhance the occurrence of micro-explosion are proposed, and the radius of the secondary droplets after breakup are also given. A continuous thermodynamics model for multi-component fuel film is developed to calculate the film vaporization process with multi-distributions. This model is as efficient as traditional zero-dimensional models, but it considers the preferential vaporization of a complex fuel mixture without the infinite diffusion assumption. The finite diffusion effect is accounted for by giving the difference of the values of interest (such as mole fraction and temperature) between the film surface and film average mean. Engine performance with multi-component fuels was investigated by using a modified KIVA code to perform the simulations. The biodiesel and diesel blended fuel mixture can be used directly in a traditional diesel engine without any modifications, and by adjusting mixture content, injection strategy, and exhaust gas recirculation (EGR) ratio, the engine combustion can be optimized. For the syngas enhanced combustion, the diesel fuel is converted into syngas using exhaust energy, and the produced syngas is introduced back into the engine and ignited by the pilot diesel injection. The overall engine efficiency is improved by recovering exhaust energy, and the emissions are significantly reduced. This study mainly focuses on modeling the multi-component fuel vaporization, and investigating the multi-component fuel combustion in ICE. The future work includes modeling the micro-explosion using the continuous thermodynamics method, and integrating the proposed continuous thermodynamics film vaporization model into the engine simulation code KIVA, and performing engine simulations.
Issue Date:2016-05-13
Rights Information:Copyright 2016 Cai Shen
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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