Date of Award
Open Access Dissertation
Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)
Administrative Home Department
Department of Mechanical Engineering-Engineering Mechanics
Committee Member 1
Committee Member 2
Committee Member 3
Pradeep K. Agrawal
Ever-changing regulations aimed at improving efficiency and reducing harmful emissions have resulted in many power-generation device (engine) manufacturers to adopt new strategies. Computer simulation of these new strategies of power generation requires more accurate and higher fidelity modelling tools. In the present study, two such models are developed. The first model deals with pre-ignition phenomena driven by lubricant (lube) oil in natural gas engines and the second model is relevant to prediction of wallfilm evaporation by employing analytical solutions to transport governing equations for boundary layers.
Pre-ignition in engines has been the subject of current research with the advent of boosted engines for reduced fuel consumption and emissions. It can be caused by lube-oil drops or carbon deposits within the engine. A computational study of pre-ignition by lube-oil drops in a constant volume chamber and a production natural gas marine engine was done. For CFD simulations, an in-house version of KIVA4 code was used. Oil throw-off into the combustion chamber was modeled with an oil stripping model, in which the criteria for lube-oil drops to be stripped from the piston rings/crevice regions and enter the combustion chamber are calculated. To capture the timing of ignition caused by lube-oil drops precisely, single particle ignition cell (SPIC) model that utilizes grid refinement for drop containing cells was used. For modelling chemical kinetics, a reduced reaction mechanism for lube oil vapor oxidation was developed. Factors affecting lube-oil stripping and subsequent ignition processes were studied and discussed. Based on these studies recommendations for possible mitigation strategies of pre-ignition in the marine engines are given.
For the new wallfilm model, an analytical expression for the external heat flux from ambient gases to the wallfilm-gas interface and the phase change rates at the interface are derived from first principles of transport phenomena. The model was coded into a computer program and applied to simulate transient evaporation of liquid wallfilms placed on the bottom wall of a square channel. Normal and flash boiling evaporation conditions were considered for various composition of the wallfilms. Simulation results are presented and the characteristics of phase change behavior are discussed.
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Ullal, Ankith, "DEVELOPMENT OF ADVANCED MODELS FOR PRE-IGNITION PREDICTION IN GAS ENGINES AND ANALYTICAL MODEL FOR WALLFILM EVAPORATION", Open Access Dissertation, Michigan Technological University, 2022.