Ph.D. Defense by Nour Atef

Jun 05 2018 03:00 PM - Jun 05 2018 04:00 PM


Numerically investigating the effects of gasoline surrogate physical and chemical properties in a gasoline compression ignition (GCI) engine

By Nour Atef

Date: 5 June 2018  

Time: 3:00 - 4:00 PM

Venue: Building 4, Level 5, Room 5209

Abstract

Gasoline compression ignition (GCI) engines show promise in meeting stringent new environmental regulations, as they are characterized by high efficiency and low emissions. Simulations using chemical kinetic models provide an important platform for investigating the behaviors of the fuels inside these engines. However, because real fuels are complex, simulations require surrogate mixtures of small numbers of species that can replicate the properties of real fuels. For this reason, the development of high fidelity, well-validated kinetic models for surrogates is critical in order to accurately replicate the combustion chemistry of different fuels under engine-related conditions.

The present work focuses on the development of combustion kinetic models to better understand gasoline fuel combustion in GCI engines. An updated iso-octane and a new 2,2,3 trimethyl-butane detailed kinetic model were developed based on new thermodynamic group values and recently evaluated rate coefficients from the literature. The models were extensively validated against a wide range of experimental data and conditions. 

The iso-octane model was further used in 0D simulations for a homogeneous charge compression ignition (HCCI) engine. The results showed that the low-temperature heat release in engines increases with engine boosting when the addition of alky radicals to molecular oxygen is more favored. Ethanol addition was also found to act as a radical sink, where it inhibits the radical pool formation and results in lower reactivity.

HCCI engines are known to be kinetically controlled, while partially premixed compression ignition (PPCI) engines are also controlled by the physical properties of the fuel; therefore the effects of the fuel’s physical properties were numerically investigated using hollow-cone and multi-hole injectors in a PPCI engine. It was concluded that the effects of physical properties are evident in multi-hole injection cases, which is attributable to the differences in mixture stratification. 

Although detailed kinetic models provide clarification of the combustion chemistry, their high computational cost makes it difficult to use them in 3D engine simulations. For this reason, reduced models for toluene primary reference (TPRF) fuels and multi-components surrogates for three full-blend fuels (light naphtha-Haltermann straight-run naphtha and GCI fuels) were developed. The models were validated against ignition delay time experiments from the literature and applied in 3D engine simulations to better understand gasoline fuel properties in GCI applications.

Bio

Nour Atef joined KAUST for Ph.D. in August 2014. She has been conducting research under the guidance Prof. Mani Sarathy since. She completed her masters in Chemical Engineering from Alexandria University in Egypt. So far, she has authored 3 research papers and co-authored 7 research papers. 

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