In mixing controlled Diesel combustion concept, mixing processes are a key phenomenon which significantly effects power, efficiency and emissions. A consequence of fuel-air-mixing is the fuel phase change, which its nature in Diesel engine fuel sprays is not clear to this date. There are different stances on the question whether fuel or a fuel-rich phase might get supercritical (one-phase mixing) or not (two-phase mixing). In this study, phase change mechanisms of sprays of different n-alkanes at high temperature and pressure conditions are investigated. Mie scattering imaging is utilized to obtain the maximum liquid penetration of Diesel surrogates (dodecane, decane, heptane and hexane) injected into nitrogen atmosphere in a constant volume chamber at fuel supercritical temperature and ambient pressures ranging from sub- to supercritical with regard to fuel critical point. Two theoretical 1D calculations which are based on an air entrainment model derived from momentum conservation, are utilized to determine local mass ratios of ambient gas and fuel which leads to predict the liquid length based on the required enthalpy for full phase change. On the one hand, the assumption is taken that fuel evaporates without boiling or getting supercritical and on the other hand, evaporation is excluded, assuming that fuel is heated up until boiling or getting supercritical. Both models allow the calculation of values for liquid length of different fuel sprays. In following, these theoretical models are validated against experimental data (around 400 points) to identify phase change regimes for different fuels. Fitting the predicted liquid lengths from both models to the experimental data, the point of switching between those two models is the concept of “transition point”. The observed transition points for different fuels and temperatures are utilized to estimate a transition line. A transition line, at which the change from evaporation to boiling\transcritical phase change occurs, is indicator of “ideal phase equilibrium ...
Fuel Sprays Phase Change at Diesel Engine Ambient Conditions: Phase Equilibrium Non-Ideality ; Phasenübergang des Kraftstoff Sprays bei Umgebungsbedingungen des Dieselmotors: Nichtidealität des Phasengleichgewichts
01.01.2021
Hochschulschrift
Elektronische Ressource
Englisch
DDC: | 629 |
Fuel Sprays Phase Change at Diesel Engine Ambient Conditions: Phase Equilibrium Non-Ideality
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