Date of Award

August 2019

Degree Type


Degree Name

Doctor of Philosophy (PhD)


Mechanical and Aerospace Engineering


Benjamin Akih-Kumgeh

Second Advisor

Ashok S. Sangani


CFD, Combustion, Flow Simulation, Reactive Flow Modeling, Real Gas Effect, Spray Simulation

Subject Categories



High-efficiencies and low-emissions can be realized in combustion engines that operate at high-pressures and low-temperatures conditions (high densities). The design of such engines relies on accurate models of the physical processes involved. Three areas of concern are multi-phase phenomena, the equation of state for the gas phase and cost-effective chemical kinetic modeling. Fuel injected as liquid must break up into droplets, evaporate, and mix with air before combusting. Models for these processes have been developed and need to be tested against experiments. As for the gas phases, the ideal gas model fails to capture thermodynamic relations at high-density combustion. A real gas model is needed, including a convenient method of implementing it in combustion simulations that involve multiple species. Detailed chemical kinetic models are too expensive for computational analysis. Reduced chemical kinetic models are therefore needed.

This thesis develops a framework for accounting for real gas effects in chemically reacting flow. It verifies the need for this complicated solution by comparing the simulations of standard flows with real gas and ideal gas models. The method draws from existing kinetic model resources and the relation of real gas behavior to intermolecular potentials.

An efficient chemical reduction methodology that considers the species production and consumption rate as a solution to reduce the reacting flow simulation is also developed. Four \textit{n}-dodecane detailed kinetic models are analyzed and compared to experimental data, then the developed method is applied to obtain a preferred skeletal chemical model for simulation of spray ignition.

After choosing and calibrating a spray break-up and evaporation model, the combined models are applied to the simulation of a standard spray from the international Engine Combustion Network. The simulations predict liquid and vapor lengths as well as ignition times and lift-off lengths reasonably well. The thesis advances the computational analysis of high-density combustion, such as found in the spray combustion typical of diesel and rocket engines.


Open Access

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