Visualization Study On Spray And Combustion Characteristics Of Emulsified Diesel Blending With Water By A Constant Volume Chamber

With an increasing number of vehicles in the world, the pollutants produced by internal combustion engines become more and more, and is one of the most important pollution sources. The huge consumption of crude oil also brings a serves challenge to energy security. It is mainly through the improvement of internal combustion engine performance and looking for new alternative energy sources to solve the problem of engine exhaust and shortage of crude oil. Emulsified diesel blending with water is a kind of oily emulsion liquid that formed by adding a certain amount of emulsion and emulsifier to pure diesel. Previous studies have shown that the combustion temperature will appropriately decrease, then reduce the emission of NOx because of vaporization latent heat of water. The production of soot in cylinder will be reduced by water gas reaction. In addition, the mirco explosion of emulsified diesel blending with water happen under high temperature will help improve the mixture of diesel and air, reducing the PM emissions. Therefore, do the research on spray and combustion of emulsified diesel blending with water is conducive to further reducing diesel engine emission levels.First, this paper explored spray characteristics of emulsified diesel blending with water by using a newly constructed constant volume chamber system. The schlieren technique and a high speed video camera are used to record the spray process, and MATLAB software is used to process the spray digital images. Of particular focus is the effect of water magnitude in emulsified fuel, as well as ambient pressure and injection pressure on the spray characteristics. Results show that as magnitudes of water increase, the spray tip penetration increases, but the spray cone angel, spray volume and area decreases. When the ambient pressures increases, the spray resistances are greater, and the spray tip penetration will be shorter, the spray penetration velocity will be slower, the spray volume and area will be smaller, but the spray cone angel will be larger. As injection pressure increases, the spray tip penetration will be longer, penetration velocity increases, spray area and volume increase, while cone angel decreases.Then, to do the combustion characteristics experiment of emulsified diesel blending with water, not only compare the combustion characteristics of emulsified and pure diesel, but also study the effects of ambient temperature, ambient density, ambient oxygen content and injection pressure on combustion characteristics of emulsified diesel. Results show that, compared to pure diesel, the combustion duration time of emulsified diesel is shorter, and the lift off length is longer, also the flame area is larger. INFL and soot generated rate is lower. The lift off length will be shorter and the INFL and flame area will be higher as ambient temperature is higher, and the high brightness area is more concentrated. The luminous duration time is longer, and the velocity of flame propagation is faster. The lift off length is longer and the INFL and flame area are both lower while the ambient density is lower, and the velocity of flame propagation is relatively lower. The heat release rate peak will reach earlier as the ambient density is higher, and it will be larger. It will suppress the spray combustion while the ambient oxygen content is lower, then the lift off length is longer. The combustion delay time and duration time will be longer, INFL and flame area are smaller. There are great effects of injection pressure on combustion characteristics of emulsified diesel blending with water. The fuel combustion luminous delay time and duration time will be shorter while injection pressure is higher. The INFL and flame area are also smaller, and it has a longer lift off length. And the velocity of flame propagation is greater. The heat release has a liner relationship with the injection pressure. The fuel combustion heat release is faster, and the heat release rate peak is greater and will reach earlier under higher injection pressure condition.