No description available.

No description available.

No description available.

No description available.

No description available.

Mass-transport deposits (MTDs) are virtually ubiquitous on the modern seafloor and common in ancient slope successions. Their upper surfaces are often irregular due to surface topography, which may vary significantly in wavelength and geometry. Turbidity currents are highly sensitive to topography, resulting in the modification of their density and velocity profiles during topographic interaction, thus affecting their depositional architecture. It is therefore expected that supra-MTD turbidite systems are also affected so. Previous analysis of the upper surface of MTDs and conformable overlying turbidite systems suggests that the upper surface of MTDs support irregularities that vary in wavelength, from 10 m to greater than 1000 m, by which longer length-scales may compartmentalise turbidite systems. But such studies do not investigate in detail the mechanisms by which topography is generated and the effect of the three-dimensional form of topography on supra-MTD turbidite systems. This study therefore addresses these aspects by the application of spectral analysis methods, synthetic modelling of three-dimensional topography, and architectural and lithofacies relationships of turbidite systems with the upper surface of MTDs, illustrated using an ancient slope succession cropping out at Cerro Bola, Argentina, and a modern deepwater system of the Sabah slope, offshore Brunei. In this thesis, an analytical model is described that characterises the three-dimensional form of the upper surface of MTDs in to two types: isolated topographic highs (termed positive topography) and isolated topographic lows (termed negative topography), which describe topography with a low and high degree of confinement, respectively. The geometry of these 'types' of topography are illustrated to vary significantly depending on the variability in the confinement across the surface in question, the degree of anisotropy and the obliquity of the flow direction to its orientation, which are similarly quantified using the analytical model described. Such topographic variability and anisotropy are demonstrated to relate to horizontal variations in thickness of the underlying MTD, generated by various mechanisms, including: internal structure, basal shear surface topography and post-emplacement creep and compaction. Each mechanism may support a variety of wavelengths that typically vary in length-scale and are generated simultaneously upon syn- and post-MTD emplacement. As a consequence, a turbidity current may interact with multiple length-scales of topography that might be produced contemporaneously with deposition. Topographic interaction may therefore not occur over the same length-scale as topographic ponding and, thus, supra-MTD ponded turbidite systems may have vertical and horizontal facies transitions that occur over similar length and height scales to the underlying topography despite ponding over a longer wavelength. Due to the three-dimensional complexity and variability of MTD topography, facies and architectures of supra-MTD reservoirs cannot be generalised in two-dimensions or extrapolated with ease into the third-dimension from isolated exposures/data.

There is a common requirement in the process, oil and gas turbine industries for high performance axial flow compressors operating over a wide range of mass flow rate and rotational speed at high efficiency. The trends have been for higher blade loadings (greater pressure rise per stage) and higher efficiency which are increasingly achieved through sophisticated Computational Fluid Dynamics designs. These trends, however, tend to mitigate against stable operating flow range (reduced surge margin), which can often lead to performance compromises. The objective of this work is to investigate the possibility of using alternative means to gain ow range by better use of variable geometry, which may permit design objectives to be better achieved. Variable geometry of the type envisaged is already often employed to overcome part-speed operating problems, but it proposed here that there may be additional benefits from their more intelligent control. The operation of axial compressors with a wide operating range is limited by instabilities, which cause a full breakdown of the flow, which is surge. These instabilities, which are caused by high incidence and subsequent stalling of stages occur due to different phenomena at part and full speed operation. The problem at part-speed is that the front stages are often heavily stalled and rear stages choked, whereas at high speeds, the front stages are operating close to choke and the rear stages tend to be stalling. Optimisation of the design to full load conditions can often provide part-speed problems and to achieve the acceptable performance, variable geometry over the front region of the compressor is sometimes used to modify the flow angles and avoid stage stall and subsequent surge. To-date, such variable settings follow some schedule established by analysis and experiment whereas this work presents a methodology of setting blade rows using an optimisation procedure and investigates the likelihood of performance benefits being obtained by a control technique which reacts° to these changing conditions. The construction of the numerical method presented in this thesis was done with an emphasis upon its intended contribution towards a eventual online control application. Therefore, a practical approach has been employed in the development of the compressor modelling techniques used in the work. Specifically, a highly empirical one-dimensional performance prediction code was constructed, employing successful correlations taken from the literature. This was coupled to a surge prediction method that has been shown in the past to function more than satisfactorily in a multistage environment. Finally, the predicted stage and overall performance (including the surge point) characteristics were passed to a optimisation program, which allowed these simulated conditions to be investigated. It is hoped that the work presented has illustrated the potential (from a aerodynamic performance point of view) of such a control technique to offer additional freedom in the operation of a multistage axial flow compressor. Moreover, the numerical modelling techniques have been developed enough to envisage (at least in part) their simple integration within a practical system. Clearly, some further investigations are required to take this work forward and the next logical step would be to improve the empirical rules with which the blade performance is predicted. A experimental programme would also be of great advantage, for example in the study of how the deviation angle for a given blade row varies over time (operating hours) in a real machine due to ageing and fouling. This would allow better estimates of the stage work during long term operation so that the optimiser could adapt to the slowly degrading performance of the blades. Finally, it is important to verify the simulated results with measured data, taken at the same optimal stator vane settings as given by the program. This must be carried out before it can be applied to a real application, although a limited study of this nature is presented in chapter 6.

Call number: LD2668 .T4 1952 C7 / Master of Science

No description available.

A sudden expansion combustor (SUE) is analyzed using computation fluid dynamics (CFD). CO emissions and NOx emissions are computed for various operating conditions of the SUE combustor using a can type and an annular type geometrical configurations. The goal of this thesis is to see if the SUE combustor is a viable alternative to conventional combustors which utilize swirlers. It is found that for the can type combustor the NOx emissions were quite low compared to other combustor types but the CO emissions were fairly high. The annular combustor shows better CO emissions compared to the can type, but the CO emissions are still high compared to other combustors. Emissions can be improved by providing better mixing in the primary combustion zone. The SUE combustor design needs to be further refined in order for it to be a viable alternative to conventional combustors with swirlers. / by Daniel Rodriguez. / Thesis (M.S.C.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.