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A requirement for thermophysical property data of diesel fuels at conditions removed from ambient was identified. A series of measurements of the pressure-volume-temperature relations of diesel fuels was undertaken using a Micro-PVT apparatus at pressures to 300MPa in the temperature range 25 to 75°C. A new calibration procedure for this instrument was devised to enable measurements of high accuracy to be made. Viscosity measurements of diesel fuels over a range of temperature and pressure were made using the National Engineering Laboratory high pressure viscometer to pressures of 460MPa in the temperature range 25 to 100°C.Corresponding states theory was applied for compressed liquid density prediction. Improvement in density prediction in this region was found through use of iso-octane and heptadecane as reference fluids. Compressibility factors of these were represented by Tait-style equations. An iterative solution technique was developed to allow the corresponding states method to be applied to diesel fuelsusing limited density measurement and a guess value of boiling point as inputs. Densities predicted from this method agreed well with measurements made using the Micro-PVT apparatus. Hard sphere theory was applied as a method for viscosity prediction. Despite the complexity of the diesel fuel mixture, reasonable estimates of viscosity were made with limited measurement input at higher temperatures. At lower temperatures, an additional simple empirical correction term was required. A method of viscosity estimation of complex hydrocarbon mixtures based upon composition is presented. Further development of this would require additional measurements and greater characterisation of the fuel.

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Detection of leaking gas pipelines is important for safety, economic and environmental reasons. Remote sensing of vegetation offers the potential to identify gas leakage. The research aim was to determine the effects of elevated soil concentrations of natural gas on overlying vegetation. Pot-scale investigations were carried out to determine whether changes in spectral characteristics were specific to natural gas or were a generic response to soil-oxygen displacement. Natural gas, argon, nitrogen and waterlogging were used to displace soil-oxygen. Leaf response to soil oxygen displacement was increased reflectance in the visible wavelengths and changes in the position and shape of the red-edge, which shifted towards longer wavelengths as the control plant matured, while the red-edge of the treated plant remained stationary indicating an inhibition of maturing. The shape of the red-edge differed in bean and barley with bean exhibiting a single peak in the first derivative that moved with plant maturity; barley exhibited a peak at 704 nm with a shoulder at 722 nm that shifted to shorter wavelengths during plant stress. Argon and waterlogging exhibited a greater response than natural gas, which had been administered noncontinuously. These experiments suggest the response to natural gas was generic to soil-oxygen deficiency. Field studies were conducted to determine whether spectral changes in leaves identified in pot trials were observable in crop canopies under field conditions. Reflectance of barley growing above a leaking gas pipeline was increased in the visible wavelengths and the red-edge was at a shorter wavelength. When the majority of the crop was fully developed, the barley above the gas leak was greener, suggesting that development was inhibited by soil-oxygen displacement. It might be possible to detect leaking gas by remote sensing of vegetation in conjunction with pipeline maps, but limitations in the spatial resolution of current satellite sensors and the infrequency of cloud free skies in the UK suggest that further work is needed before an operational system could be available.

Dispersed water drops in oils can cause detrimental effects. For example in refining and cracking of crude oil, poisoning of catalysts and equipment corrosion can be major problems due to the presence of water. Therefore there is a need to develop more efficient and cost-effective separators. The work in this thesis covers an investigation of the underlying electrostatic phenomena (i.e. drop-drop and drop-interface coalescence and drop deformation and break-up) leading to the development of compact electrocoalescer-separators. Using novel two-dimensional electrode systems, it is shown here that coalescence readily occurs when the electric field is applied in the same direction as the line joining the centres of the two drops, in line with the previous theoretical prediction of the maximum attractive force induced in this way. An adaptive Finite Element Method, incorporating automatic error and mesh generator programmes, has been used to quantify the electric-induced forces of charged spheres in an insulating medium, for short distances that are much smaller than the drop radius, where analytical solutions are no longer reliable. Moreover, drop-drop attraction can also occur when the angle is 125.3° from the electric field direction. Previous work suggests that pulsed d.c. fields are effective for low-aqueous-content systems, and this has been further investigated here. The applied electric field and pulse frequency can be optimised to achieve the highest coalescence rate. High electric fields (> 3.5 kV/cm) are shown to deform and break up aqueous drops when the electric field-induced stresses overcome the interfacial tension. A critical electrostatic Weber number, corresponding to the onset of drop break-up, has been evaluated to be about 0.49 for several aqueous-oil systems. For the separation of dispersed aqueous drops from an oil phase, it is advantageous to incorporate an aqueous layer to induce drop-interface coalescence. A suitably applied electric field is shown to give efficient drop-interface coalescence. The above investigations have led to the design and development of two compact electrocoalescer-separators. The first separator combines the effects of electrocoalescence and gravitational settling. The second separator, which utilises the electrocoalescence and centrifugal effects, can handle larger throughputs with reasonable separation efficiency. Both devices significantly enhance the separation and are good examples of how the fundamental understanding gained in this studies can be applied to realistic practical situations.

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Der Stand der Sicherheitstechnik beim Explosionsschutz an Biogasanlagen mit erweiterter Peripherie wurde einer aktualisierten Bewertung unterzogen. Ergänzend zum »Stand der Technik«, basierend auf der DGUV 113-001, wurden Empfehlungen erarbeitet, um den Stand der Sicherheitstechnik zur Gewährleistung des Explosionsschutzes an Biogasanlagen weiter zu erhöhen.