الفهرس 
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Abstract
This work focuses on the modeling of diesel fuel heating, evaporation and breakup processes. The heating process taking into account temperature distribution inside droplets with the radiation effect based on a new polynomial function of the average absorption
average
N
efficiency factor, where the polynomial function JA,R’ where Rd
d is the droplet radius
and N = 3. Explicit expressions for A0, A,, A2 and A3 are derived in a realistic droplet radii range (2- 200 [irn) and radiation temperature ranges (1000 -3000 K) for all types of the considered fuels (low sulphur ESSO AF1313 diesel, gasoline (BP Pump Grade 95 RON ULG), 2,2,4-trimethylpentan (CH3)2CHCH2c(cH3)3 (iso-octane) and CH3CH2COCH2(CH3) (3-pentanone)). This new approximation is shown to be more accurate, compared with the power function aR6 with the case when a and b are
approximated by quadratic functions or fourth power polynomials of the radiation temperature with the coefficients calculated in the whole range 2 – 200 um, and comparable to the case when a and b are approximated by piecewise quadratic functions of the radiation temperature T,.,,, with the coefficients calculated separately in the ranges 2 – 5 ,um, 5 – 50 pm, 50 – 100 pm and 100 – 200 um for all fuels. This difference in the approximations of the polynomial function and the power function, however, is shown to have little effect on modelling of fuel droplet heating and evaporation in conditions typical for internal combustion engines. Three breakup models are considered to simulate the breakup process. The first one is bag and stripping breakup model and the second one is TAB model which based on Taylor Analogy between an oscillating and distorting droplet and spring- mass system. The third model is wave model based on the jet stability theory at the droplet surface. It is noticed that there is a difference in predicting the evaporation time using different breakup model and this is may be happen due to the values of constants used in each breakup model where it is assumed as the standard value of each one which is evaluated based on different experimental results. This difference in calculating evaporation time and ignition delay time is not significantly large when using TAB and bag and stripping models. For the heating process, two liquids models are considered; one is the uniform temperature model with infinite thermal conductivity of the droplet (ITC or Spalding) and the other model which takes into account temperature gradient inside the droplet and the effect of recirculation inside droplet by using the effective thermal conductivity of the droplet (ETC model). For the evaporation process, two gas phase models are considered. The first one is the so-called MO in which the concentration of vapor is so small that its contribution to the heating process (superheat) can be ignored (simplest one). The second model is the so-called M4 model in which the effect of thermal boundary layer is taken into account. The ETC model and M4 model are implemented into KIVA 3V re12 CFD code while the Spalding model and MO model are the original models on it. The predictions of the new model were validated against available experimental data. Bag and stripping breakup model and wave breakup models were implemented into KIVA 3V rel2 while TAB breakup model is the original breakup model in all of KIVA versions. A comparative analysis between the breakup models is presented. The effect of breakup model on the behavior of liquid phase and gas phase models is also introduced.