M Michael Golombok

Catalysts for producing high octane-blending value olefins for gasoline

New restrictions on gasoline components mean that oxygenates and aromatics must be replaced by other high octane components. The dimerization of linear butene to form high octane gasoline blending components is evaluated under liquid phase reaction conditions over a number of different heterogeneous catalyst systems. These fall mainly into the category of solid acid catalysts as well as metal oxide on support catalysts - with supplementary examination of fluorotantasil and ion exchange systems. The parameters determining performance are the conversion of feed and the blending octane number of the raw product as well as the stability of the catalyst for sustaining these product properties. Subsequent deactivation of the catalysts is measured by the decrease in both these parameters. An amorphous silica alumina catalyst is found to give optimal performance according to these criteria.

SURFACE COMBUSTION IN METAL FIBRE BURNERS

Metal fibre burners exhibit stable radiant surface combustion over a range of thermal inputs. The model outlined in this report explains why stable surface combustion is possible for some values of thermal input but not for others. It also identifies parameters which will affect burner operation and provides temperature profiles through the burner material which cannot be obtained experimentally. The model takes account of heat transfer by conduction, convection and radiation within the burner, combustion near the burner surface and radiation from the surface. The method of activation energy asymplotics is used to simplify the equations which result.

Fuel effects on knock, heat releases and CARS temperatures in a spark ignition engine

Net heat release, knock characteristics and temperature were derived from in-cylinder pressure and end-gas CARS measurements for different fuels in a single-cylinder engine. The maximum net heat release rate resulting from the final phase of autoignition is closely associated with knock intensity. Aromatic fuels have lower maximum heat release rates and lower knock intensities than expected from their octane number when compared to paraffinic fuels ; this is observed even when there is significant heating of the end-gas from pre-flame reactions. Leaner mixtures have lower combustion rates so that pressure development is slowed and hence ignition needs to be more advanced to get knock to occur as frequently as in a richer mixture. However, for a given frequency of knock occurrence, there is no significant difference in peak net heat release rates and hence in knock intensities for different mixture strengths.

Laser flash thermal conductivity studies of porous metal fiber materials

The laser flash method has been used to measure thermal conductivities in a porous metal fiber material at room and elevated temperatures. The anisotropy of heat conduction in this material is reported and a novel technique using a focused laser beam is described to access directly the off‐diagonal components of the conductivity tensor. A simulation study shows the anisotropy to be determined by the layered structure of the material. Enhanced conductivities are reported at elevated temperatures and are shown to be due to radiation heat transfer within the porous structure.

Emissivity of layered fibrous materials

The radiant energy properties of fibrous materials may be described by an effective surface emissivity, which is a function of the material construction. The important parameters are porosity and the emissivity of the solid component. The layered construction leads to a unit cell model determining radiant heat transfer through the material to the environment. Geometric absorption cross sections are used as radiation view factors in a pseudoenclosed configuration. The emissivities are obtained by comparison to a material made from black fibers and are in qualitative agreement with experimental measurements.

Droplet sizing in fuel injections by stimulated Raman scattering

It is often difficult to distinguish between morphology-dependent resonance and Raman intensity features in nonlinear Raman spectra of organic fuel droplets. In theory the morphology-dependent resonances can be deconvoluted from single-shot spectra, but in practice this is difficult because of shot-to-shot parameter variation. Frequency-analysis methods have been applied to spectra obtained from fuel sprays, and correlation analysis is found to be quick and easily interpreted.

Performance of a Novel Rotating Gas-Liquid Separator

A novel gas separation process makes use of a rotating phase separator to separate micron-sized droplets from a gas stream. Based on an industrial scale design, a water/air separator is constructed and tested. The first experiment concerns the drainage of large fractions of separated liquid. During operation, drainage is observed via windows and a descriptive model is formulated. Because of the major influence on overall separation efficiency, liquid drainage is a key issue in the separator design. The second experiment comprises a droplet collection efficiency measurement using micron-sized droplets dispersed within the airstream. The separation efficiency of fine droplet removal is measured. This is an important factor in reducing capital costs. DOI: 10.1115/1.4001008

Suppressing fluid loss in fractures

Injected fluid losses in large subsurface channels can be suppressed with the use of low concentrations of viscoelastic surfactants which selectively retard flow in larger apertures. The effect is demonstrated by pumping viscoelastic surfactants through smooth capillaries. The choice of capillary diameters relate to fractures in oil or geothermal reservoirs as well as induced hydraulic fracturing operations in tight gas reservoirs. Selective retardation is favoured at a lower range pressure drops usually associated with oil recovery. The effective apparent viscosity contrasts between different capillary diameters are not as high as those previously observed in permeable flow because the measured effects in the smooth capillaries are mainly shear driven. We expect an elongation contribution to the apparent viscosity in real non-smooth fractures.

Thermodynamic factors governing centrifugal separation of natural gas

The classical objection to using centrifugal gas separation industrially has arisen from the throughput restrictions associated with uranium isotopes. However the restrictions for lighter gas separations are much less severe. Pressure is no longer limited by desublimation to sub-atmospheric levels. Radial pressure gradients are a factor of 10 4 less so that overall higher throughputs may be obtained for a given sized unit. The wall pressures are further reduced if we allow for the fact that, prior to diffusive separation of components, the mass transfer associated with setting up the radial pressure gradient takes place under thermodynamically adiabatic conditions. This variation from the usual isothermal assumption enables higher throughputs.

Shear induced structure additives and nonlinear pressure drop effects in permeable flow

In classical flow through permeable rock, the pressure drop is linearly distributed through the medium. Shear induced structure materials, surfactant/co-solute pairs, were added to retard flow in higher permeability rock samples. A novel core holder allows the axial pressure distribution along the flow direction to be measured. This enables the pressure drop to be measured as a function of distance along the core. The results show the spatial scale and the effect on pressure distribution associated with varying concentrations of shear induced structure additives. Subsequent flushing with water leads to restoration of the original flow level. The rate of recovery is dependent on the pressure of flushing which determines shear--showing that break up of the shear induced structure materials deposited in the porous rock is also dependent on shear.