A.E. Elwardany

Numerical Simulations of Hollow-Cone Injection and Gasoline Compression Ignition Combustion With Naphtha Fuels

We acknowledge the help and support from Saurav Mitra and Sarangarajan Vijayraghavan from Convergent Science, Inc. (CSI). This work was sponsored by the Fuel Technology Division at Saudi Aramco R&DC. The work at King Abdullah University of Science and Technology (KAUST) was funded by KAUST and Saudi Aramco under the FUELCOM program.

Effects of In-Cylinder Mixing on Low Octane Gasoline Compression Ignition Combustion

This work was sponsored by the Fuel Technology Division at Saudi Aramco R&DC. The surrogate formulation work at King Abdullah University of Science and Technology (KAUST) was supported by KAUST and Saudi Aramco under the FUELCOM program. We also acknowledge the helpful discussions with Janardhan Kodavasal from Argonne National Laboratory.

Spray Modeling for Outwardly-Opening Hollow-Cone Injector

This work was sponsored by the Fuel Technology Division at Saudi Aramco R&DC. The work at King Abdullah University of Science and Technology (KAUST) was funded by KAUST and Saudi Aramco under the FUELCOM program. We also acknowledge the help and support from Convergent Science Inc. (CSI).

Fuel droplet heating and evaporation: new hydrodynamic and kinetic models

Recently developed approaches to the hydrodynamic and kinetic modelling of fuel droplet heating and evaporation are reviewed. Two new solutions to the heat conduction equation, taking into account the effect of the moving boundary during transient heating of an evaporating droplet, are discussed. The first solution is the explicit analytical solution to this equation, while the second one reduces the solution of the differential transient heat conduction equation to the solution of the Volterra integral equation of the second kind. It has been pointed out that the new approach predicts lower droplet surface temperatures and slower evaporation rates compared with the traditional approach. A simplified model for multi-component droplet heating and evaporation, based on the analytical solution of the species diffusion equation inside droplets, is discussed. A new algorithm, based on simple approximations of the kinetic results for droplet radii and temperatures, suitable for engineering applications, is discussed.© 2010 ASME

New approaches to the modelling of multi-component fuel droplet heating and evaporation

The previously suggested quasi-discrete model for heating and evaporation of complex multi-component hydrocarbon fuel droplets is described. The dependence of density, viscosity, heat capacity and thermal conductivity of liquid components on carbon numbers n and temperatures is taken into account. The effects of temperature gradient and quasi-component diffusion inside droplets are taken into account. The analysis is based on the Effective Thermal Conductivity/Effective Diffusivity (ETC/ED) model. This model is applied to the analysis of Diesel and gasoline fuel droplet heating and evaporation. The components with relatively close n are replaced by quasi-components with properties calculated as average properties of the a priori defined groups of actual components. Thus the analysis of the heating and evaporation of droplets consisting of many components is replaced with the analysis of the heating and evaporation of droplets consisting of relatively few quasi-components. It is demonstrated that for Diesel and gasoline fuel droplets the predictions of the model based on five quasi-components are almost indistinguishable from the predictions of the model based on twenty quasi-components for Diesel fuel droplets and are very close to the predictions of the model based on thirteen quasi-components for gasoline fuel droplets. It is recommended that in the cases of both Diesel and gasoline spray combustion modelling, the analysis of droplet heating and evaporation is based on as little as five quasi-components.

Modelling of droplet heating and evaporation: recent results and unsolved problems

The most recent results referring to the hydrodynamic and kinetic modelling of droplet heating and evaporation are briefly summarised. Two new solutions to the heat conduction equation, taking into account the effect of the moving boundary during transient heating of an evaporating droplet, are discussed. The first solution is the explicit analytical solution to this equation, while the second one reduces the solution of the differential transient heat conduction equation to the solution of the Volterra integral equation of the second kind. It has been pointed out that the new approach predicts lower droplet surface temperatures and slower evaporation rates compared with the traditional approach. A simplified model for multi-component droplet heating and evaporation, based on the analytical solution of the species diffusion equation inside droplets, is reviewed. A new algorithm, based on simple approximations of the kinetic results for droplet radii and temperatures, suitable for engineering applications, is discussed.

Rate Coefficients of the Reaction of OH with Allene and Propyne at High Temperatures.

Allene (H2C═C═CH2; a-C3H4) and propyne (CH3C≡CH; p-C3H4) are important species in various chemical environments. In combustion processes, the reactions of hydroxyl radicals with a-C3H4 and p-C3H4 are critical in the overall fuel oxidation system. In this work, rate coefficients of OH radicals with allene (OH + H2C═C═CH2 → products) and propyne (OH + CH3C≡CH → products) were measured behind reflected shock waves over the temperature range of 843-1352 K and pressures near 1.5 atm. Hydroxyl radicals were generated by rapid thermal decomposition of tert-butyl hydroperoxide ((CH3)3-CO-OH), and monitored by narrow line width laser absorption of the well-characterized R1(5) electronic transition of the OH A-X (0,0) electronic system near 306.7 nm. Results show that allene reacts faster with OH radicals than propyne over the temperature range of this study. Measured rate coefficients can be expressed in Arrhenius form as follows: kallene+OH(T) = 8.51(±0.03) × 10-22T3.05 exp(2215(±3)/T), T = 843-1352 K; kpropyne+OH(T) = 1.30(±0.07) × 10-21T3.01 exp(1140(±6)/T), T = 846-1335 K.

A model for mono- and multi-component droplet heating and evaporation and its implementation into ANSYS Fluent

A model for heating and evaporation of mono- and multi-component droplets, based on analytical solutions to the heat transfer and species diffusion equations in the liquid phase, is summarised. The implementation of the model into ANSYS Fluent via User-Defined Functions (UDF) is described. The model is applied to the analysis of pure acetone, ethanol, and mixtures of acetone/ethanol droplet heating/cooling and evaporation. The predictions of the customised version of ANSYS Fluent with the newly implemented UDF model are verified against the results predicted by the previously developed in house, one-dimensional code. DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4759

Numerical Simulations of Hollow Cone Injection and Gasoline Compression Ignition Combustion With Naphtha Fuels

Gasoline compression ignition (GCI), also known as partially premixed compression ignition (PPCI) and gasoline direct injection compression ignition (GDICI), engines have been considered an attractive alternative to traditional spark ignition engines. Lean burn combustion with the direct injection of fuel eliminates throttle losses for higher thermodynamic efficiencies, and the precise control of the mixture compositions allows better emission performance such as NOx and particulate matter (PM). Recently, low octane gasoline fuel has been identified as a viable option for the GCI engine applications due to its longer ignition delay characteristics compared to diesel and lighter evaporation compared to gasoline fuel [1]. The feasibility of such a concept has been demonstrated by experimental investigations at Saudi Aramco [1, 2]. The present study aims to develop predictive capabilities for low octane gasoline fuel compression ignition engines with accurate characterization of the spray dynamics and combustion processes. Full three-dimensional simulations were conducted using CONVERGE as a basic modeling framework, using Reynolds-averaged Navier-Stokes (RANS) turbulent mixing models. An outwardly opening hollow-cone spray injector was characterized and validated against existing and new experimental data. An emphasis was made on the spray penetration characteristics. Various spray breakup and collision models have been tested and compared with the experimental data. An optimum combination has been identified and applied in the combusting GCI simulations. Linear instability sheet atomization (LISA) breakup model and modified Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) break models proved to work the best for the investigated injector. Comparisons between various existing spray models and a parametric study have been carried out to study the effects of various spray parameters. The fuel effects have been tested by using three different primary reference fuel (PRF) and toluene primary reference fuel (TPRF) surrogates. The effects of fuel temperature and chemical kinetic mechanisms have also been studied. The heating and evaporative characteristics of the low octane gasoline fuel and its PRF and TPRF surrogates were examined.Copyright