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Development of Indoor Air Cleaning Method by Electrostatic Atomization and Its Commercialization
The objective of this work is to get a better understanding of the mixture formation and combustion processes of Diesel sprays. The experimental study, focusing on the characteristics of Diesel sprays from micro-hole nozzles under ultra-high injection pressures, was conducted in a high-temperature high-pressure constant volume vessel using the laser absorption-scattering (LAS) technique and combustion diagnostics.
Firstly, the non-evaporating free spray was visualized using a direct photography system. The effects of the nozzle hole diameter, injection pressure, and ambient density on the spray tip penetration length were investigated. The dependence of the penetration on the nozzle hole diameter was clarified. Then, the preliminary experiment was made of the measurements of both liquid and vapor fuel for the evaporating free spray at a constant ambient density using the LAS technique and axisymmetric data processing method. The fundamental influence of injection parameters on the air entrainment, fuel vaporization, and drop size after the end of injection were acquired.
Subsequently, the flat wall impinging sprays were comprehensively investigated. The injection parameters were varied, simulated engine operating conditions were tested, and the measurement of the evaporating spray was carried out from the timing near the start of injection to the timing after the end of the injection. The mixing rate was introduced to analyze the mixing process around the end of injection. The effects of the wall impingement and fuel evaporation were clarified experimentally. And the detailed evolution of the spray plumes was presented. To clarify the theoretical nature of the spray from micro-hole nozzles, a wall-impinging gas jet theory was employed to predict the spray tip penetration length.
To correlate the fundamental findings with some practical applications, 2-D piston cavity shape sprays and 2-hole nozzle sprays were investigated. The difference in the fuel vaporization for different spray types was clarified, which provides some useful information for the application of micro-hole nozzles and ultra-high injection pressures in real engines.
Finally, the auto-ignition and flame structure of the spray combustion were investigated using a high-speed video camera system. The soot luminosity was discussed qualitatively. The OH chemiluminescence was used as a marker of the autoignition and a measure of the flame lift-off length. The discussion was performed on the basis of the correlation between spray characteristics and combustion process. The primary findings of this work may provide useful information for the design of new Diesel fuel injection systems and for the calibration of predicative spray models.
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Graduate School of Engineering