With the increase in complexity of modern electricity grids, the implementation of state-estimators has become a vital aspect of stability and contingency analyses for stable and secure power system operation. Transmission line reactance is an important component in the computation of state-estimators. Two models utilizing real-time synchrophasor data and ERCOT load information are proposed to compute Thevenin equivalent reactance. This thesis presents the results of implementing these methods to estimate the equivalent reactance of a transmission network between The University of Texas at Austin and The University of Texas, PanAm. / text

The work was concerned with experimental study of the turbulent flame development process of alcohol fuels, namely ethanol and butanol, in an optically accessed spark ignition research engine. The fuels were evaluated in a single cylinder engine equipped with full-bore overhead optical access operated at typical stoichiometric part-load conditions with images captured using high-speed natural light imaging techniques (or chemiluminescence). The differences in flame development between the fuels was analysed to understand better the impact of high and low alcohol content fuels on combustion. Advanced image analysis, in conjunction with Ricardo WAVE simulation, allowed for the conclusion that the faster burning exhibited by ethanol was the result of the marginally higher laminar burning velocity providing a faster laminar burn phase and accelerating the flame into the turbulent spectrum thus reducing bulk flame distortion and better in-cylinder pressure development. Such physical reactions are often over-looked in the face of chemical differences between fuels. A further study into the variation of maximum in-cylinder pressure values was conducted focussing on iso-octane and ethanol. This study identified two phenomena, namely “saw-toothing” and “creep” in which cluster of cycles feed into one another. From this it became clear that the presence of high pressure during the exhaust process had a large influence on the following cycles. This is another often overlooked phenomenon of direct cycle-to-cycle variation whereby incylinder pressures during blowdown can dictate the duration, load or stability output of the following cycle. Finally the work investigated the impact on flame development of alcohol fuels when the overlap duration was altered. While the engine produced counterintuitive figures of residual gas, ethanol was confirmed as having greater synergy with EGR by displaying less impacted combustion durations c.f. iso-octane. Care should be taken however when analysing these results due to the unique valve configuration of the engine.

Currently environmental concerns are driving internal combustion engine manufacturers to seek greater fuel efficiency, more refinement and lower emissions. Cyclic variation is a known obstacle to achieving the greatest potential against these goals and therefore an understanding of how to reduce these is sought. It is widely accepted that cyclic variation in in-cylinder flow motions is a key contributor to overall cyclic variation and therefore the characterisation of factors affecting these is an important step in the process of achieving a better understanding and ultimately control of cyclic variation. This thesis reports the development of a novel optical engine research facility in which high speed digital particle image velocimetry (HSDPIV) has been applied to the study of flow field behaviour within a direct injection spark ignition (DISI) engine. This study investigates the spatial and temporal development of flow structures over and within many engine cycles. Flow field PIV measurements have been captured with a high spatial resolution and temporal frequencies up to 5 kHz from a number of measurement locations at a large range of crank angles. The major contributions from this work have included the use of the novel measurement technique to investigate spatial and temporal flow field development in the intake runner, valve jet, in-cylinder tumble and swirl planes and the pent roof. The gathered data have been used to investigate cycle by cycle variations in both high and low frequency flow structures. Major findings of this work have included the observation of highly varying flow fields throughout the engine cycle. Frequency analysis of these flows has allowed the low frequency bulk motions and higher frequency turbulent components to be studied. The low frequency flow field components are shown to create varying flow field interactions within the cylinder that also affect the manner in which the flow develops over the course of the cycle. The intensity of the turbulence fluctuations, u , has been calculated based upon the high frequency components within the flow and variations within this are shown to correlate with pressure related combustion parameters.