Fredrik Ree Westlye from DTU Mechanical Engineering defends his PhD, Experimental study of liquid fuel spray combustion, Friday, 10th March at 13:00. The defence takes place in Building 421, Auditorium 71 at DTU. Associate Professor Anders Ivarsson is principal supervisor and Professor Jesper Schramm is co-supervisor.
The continuing stringency of emission regulations for marine diesel engines forces a deeper understanding of the complex physical processes occurring inside the engine cylinder. A deeper understanding can lead to higher accuracy of predictive numerical models, thereby enabling evaluation of multiple engine design parameter variations which would otherwise be extremely costly and difficult to evaluate experimentally. The aim of this work is to provide a wide range of experimental data of which to validate current Computational Fluid Dynamic models employing complex physics such as reaction kinetics, soot formation and radiant heat transfer. Models involving spray combustion need also to accurately predict the fuel spray characteristics. These computational models are based on true physics and empirical data. Complex experimental design is needed in order to accurately measure specific physical quantities used in CFD validation of these types of flames.
This PhD thesis is an extensive study of optical combustion diagnostics applied to complex transient spray flames in a high temperature and pressure environment. Firstly, familiarization of the physiochemical properties and electromagnetic interactions in flames of which various optical combustion diagnostics was gained. Key diagnostics were reviewed and tested, providing motivation for the selection of diagnostics to apply to the complex spray flame. A large part of this project was the development of an extinction imaging technique applicable in the harsh ambient environments into which the sprays are injected. The optical setup is able to achieve high temporal resolution, by optimization of the light throughput, while removing artifacts caused by steep gradients in the refractive index through the line of sight. The flow characteristics and combustion process of fuel sprays was reviewed.
A comprehensive experimental campaign of fuel spray and combustion characteristics from cavitating and non-cavitating large bore injectors. Experiments were carried out in an optically accessible constant volume combustion vessel, generating a controlled ambient environment into which the fuel spray is injected with a high degree of reproducibility. Measurements of liquid and vapor boundaries are made using extinction and schlieren imaging respectively, in determining spray characteristics. Flame lift-off, ignition delay and soot volume fraction is measured via 𝑂𝑂𝐻𝐻∗ chemiluminescence, natural flame luminosity and extinction imaging respectively, in determining combustion characteristics. Results have been compared with CFD modelling of the sprays in question. Further, the results were studied to identify the effect of in-nozzle cavitation on spray and combustion characteristics.
This PhD dissertation was carried out at the Technical University of Denmark in the Department of Mechanical Engineering and has been supervised by Associate Professor Ander Ivarsson and Professor Jesper Schramm. The project has been a part of the RADIADE project funded by the Danish Council for Strategic Research. Other supporters of the project have been MAN Diesel & Turbo A/S, DTU Mechanical Engineering, DTU Chemical Engineering, Sandia National Laboratories USA, Norwegian University of Science & Technology (NTNU) and University of Nottingham, Malaysia Campus.