Study On Combustion Performance Of Emulsified Diesel Oil Mixed With Water Under Various Conditions

Under the background of worldwide energy consumption and environmental pollution,our country advocates the development of green energy conservation.As an alternative fuel different from pure diesel,emulsified diesel with water can effectively reduce the emissions of combustion products under the condition of meeting the power demand.Numerical simulation can accurately explore the combustion performance of emulsified diesel under different conditions,which has guiding significance for the combustion of emulsified diesel in cylinder.In this thesis,based on AVL fire software,the L21/31 marine medium speed diesel engine of man company in Germany is selected as the research object,and the cylinder combustion model of diesel engine is established.Firstly,the combustion simulation is carried out under standard fuel injection quantity and standard oil content.On this basis,the simulation is carried out under the condition of fixed water content of 12%and standard injection quantity.The influence of external conditions（engine speed,injection temperature）and internal conditions（injection advance angle,injection duration）on the combustion performance,emission and dynamic performance of emulsified oil in cylinder is studied by changing the external conditions（engine speed,injection temperature）and internal conditions（injection advance angle,injection duration）The system realizes that the emulsified oil is directly connected to the fuel supply system of diesel engine after emulsification,effectively avoiding the problem of long standing separation of emulsified oil.In this thesis,the combustion characteristics and emission characteristics of emulsified diesel oil with 12%water were analyzed on an experimental bench.Through the analysis of simulation and experiment,the following conclusions are drawn1)Under the standard injection quantity,the combustion heat release efficiency,in cylinder temperature and cylinder pressure decrease with the increase of water content.The soot and CO₂emissions from the combustion of emulsified oil decrease with the increase of water content,which also shows the influence of the reduction of diesel content in emulsified oil.2)Under the standard diesel content,the heat release rate,in cylinder temperature and cylinder pressure increase with the increase of water content.With the increase of water proportion,the amount of nitrogen oxides increased,while the soot content decreased.The water proportion had NO_Xeffect on the amount of carbon dioxide.3)When the water content is 12%,the temperature and pressure in cylinder decrease with the decrease of injection advance angle;for the emission characteristics,with the decrease of injection advance angle,the production of NO_Xand soot also decrease.The injection duration angle has a great influence on the combustion and emission characteristics of emulsified oil.The results show that the heat release rate,in cylinder temperature and pressure decrease with the increase of injection duration angle,and the production of NO_Xdecreases with the increase of injection duration angle.When the water content is 12%,only changing the injection temperature or engine speed has NO_Xeffect on the combustion and emission characteristics of emulsified oil.4)An experimental platform was built to verify the combustion characteristics of emulsified oil with 12%water under propulsion and load characteristics.With the increase of engine speed and load,the consumption of diesel oil in emulsified oil decreases.Under load characteristics,with the increase of load,the average fuel consumption rate,soot,nitrogen oxides and so on are reduced.Based on the conclusion of this thesis,we hope to provide theoretical guidance for the application of emulsified diesel,the introduction of emulsified system and the modification optimization of diesel engine.