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dc.rights.licenseRestricted to current Rensselaer faculty, staff and students. Access inquiries may be directed to the Rensselaer Libraries.
dc.contributorOehlschlaeger, Matthew A.
dc.contributorSahni, Onkar
dc.contributorZhang, Lucy T.
dc.contributorPlawsky, Joel L., 1957-
dc.contributor.authorHuang, Mingdi Michael
dc.date.accessioned2021-11-03T08:29:15Z
dc.date.available2021-11-03T08:29:15Z
dc.date.created2015-10-02T13:28:35Z
dc.date.issued2015-08
dc.identifier.urihttps://hdl.handle.net/20.500.13015/1553
dc.descriptionAugust 2015
dc.descriptionSchool of Engineering
dc.description.abstractA light-duty single-cylinder direct-injection diesel engine (Yanmar L100V) was modeled using the developed CFD methods to numerically investigate the influence of fuel variations on in-cylinder spray ignition. Simulations were carried out using an empirical model developed by Gowdagiri and Oehlschlaeger which is based on a series of previous models produced by Halstead et al., Schreiber et al. and Zheng et al., and provides simplified combustion kinetics for any jet or diesel fuel with known DCN and average molecular formula. Simulation results are compared with experimental crank-resolved pressure traces. Simulations predict ignition delay for a variety of loads and fuels within two crank angle degrees or less and very accurately predict the dependence of ignition variability on fuel DCN. It is observed, within the limits of available experimental data, that fuel parameters other than DCN are unimportant in controlling ignition delay in the single-cylinder diesel engine considered.
dc.description.abstractIncreasing environmental and economic concerns have long motivated research into improving engine performance and efficiency. Computational Fluid Dynamics (CFD) simulations containing chemical reactions to describe combustion chemistry are a critical tool in engine development; however, chemical kinetic mechanisms, which describe the essential ignition and combustion processes in an engine, tend toward the complex and detailed as they become more accurate in modeling the elementary chemical interactions. Such complex chemical mechanisms are computationally expensive – implementing them in a realistic applied simulation, such as combustion in a diesel engine, causes that simulation to become computationally prohibitive. Here, CFD simulations of spray ignition and combustion in a constant volume environment and a diesel engine are demonstrated using global and reduced reaction kinetics models. These simulations are shown to be in reasonably good quantitative agreement with experiment and very good agreement for the variation of spray ignition delay with fuel variation.
dc.description.abstractThe simulations are performed within the CONVERGE CFD code. The computational method utilizes various submodels for physical and chemical processes, including the Re-Normalization Group (RNG) k-ε model for turbulence, the Kelvin-Helmholtz and Rayleigh-Taylor models for spray breakup, and the No Time Counter (NTC) model for droplet collisions. Other submodels for these processes are also investigated to determine the sensitivity of global CFD results to submodel choice and the physics that those submodels represent. For chemistry, both global empirical models, including the Shell model and a recent model from Gowdagiri and Oehlschlaeger, and models reduced from detailed kinetics are investigated. It was found that the simulation is not strongly sensitive to the choice of turbulence submodel and is only moderately sensitive to the choice of spray break up submodel; however, all simulations illustrate the strong sensitivity of spray ignition and combustion behavior to the choice of chemical submodel and specific kinetic rate parameters.
dc.description.abstractThe Ignition Quality Tester (IQT) experiment, a constant volume spray combustion device used in the ASTM method for determining the Derived Cetane Number (DCN), is modeled and simulated. Multiple reduced chemical mechanisms are implemented and compared against experimental data. It is found that though all mechanisms make reasonable approximations of the experimental results at standard operating conditions, where DCN is determined, very few mechanisms are predictive at other thermodynamic conditions. The mechanism of Lu et al. is used to further investigate the dependence of the total ignition delay on physical and chemical factors under a range of IQT operating conditions. It is found that for long ignition delay times, typically occurring at low pressures and/or temperatures, the chemical delay is rate-controlling. At short IQT ignition delay times (~1 ms), the chemical and physical delays are of similar magnitude. Because the physical delay shows little variation with operating conditions, the IQT measured DCN is shown to be governed mostly by chemical kinetics.
dc.language.isoENG
dc.publisherRensselaer Polytechnic Institute, Troy, NY
dc.relation.ispartofRensselaer Theses and Dissertations Online Collection
dc.subjectMechanical engineering
dc.titleComputational fluid dynamics studies on the influence of fuel variability on diesel engine operation
dc.typeElectronic thesis
dc.typeThesis
dc.digitool.pid176795
dc.digitool.pid176796
dc.digitool.pid176798
dc.rights.holderThis electronic version is a licensed copy owned by Rensselaer Polytechnic Institute, Troy, NY. Copyright of original work retained by author.
dc.description.degreePhD
dc.relation.departmentDept. of Mechanical, Aerospace, and Nuclear Engineering


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