The technique of fault tree analysis is commonly used to assess the probability of failure of industrial systems. During the analysis of the fault tree the component failures are assumed to occur independently. When this condition is not satisfied alternative approaches such as the Markov method can be used. Constructing the Markov representation of a system is not such as intuitive process for engineers as fault tree construction since the state-transition diagram does not readily document the failure logic. In addition to this the size of the Markov diagram increases rapidly as the number of components in the system increases. This thesis presents the development of a new model which uses a combination of conventional fault tree methods with those of Markov methods to solve systems containing sequential or standby failures. New gates were developed in order to incorporate the dependent failures on the fault tree structure. The new assessment method was shown to efficiently solve these systems. With theses extended fault tree capabilities in place the technique was embedded within an optimisation framework to obtain the best system performance for systems containing standby failures. Sequential failures can be represented on a fault tree by using the Priority-And gate, however they can also be represented on a Cause-Consequence diagram. As with the fault tree analysis method, the Cause-Consequence Diagram method documents the failure logic of the system. In addition to this the Cause-Consequence Diagram produces the exact failure probability in a very efficient calculation procedure and has significant implications in terms of efficiency for static systems. Construction and analysis rules were devised for a cause-consequence diagram and used on systems containing independent and dependent failures.

'Coke' may be described as the cellular residue from the carbonisation of a coking coal in commercial ovens or-retorts at a temperature of about 9000C; and a 'Coking coal' as a coal which will yield a commercial coke when it is carbonised. Some of the questions arising from these descriptions are:- What are the standards required of a commercial coke; what is the cause of coke-formation; what are the characteristics of coking coals and how may they-be judged; and how can the quality of coke be improved? It is not proposed to discuss these questions in detail but it is important to be aware of them in order to understand the way the coking industry has developed. These questions have been asked since coke has been used on a commercial scale and the answers to them have altered with circumstances as science and technology have changed. The qualities which render a coke most useful, or most readily saleable vary according to the use to which it is to be put. For all combustion processes, which account for most of the coke used, it would be expected that the intrinsic 'combustibility' would be important. The manner in which a ooke burns depends-so much however upon such factors asp for example, the size of the pieces and the rate of supply of air to the fuel-bed, that differences in intrinsic combustibility may be masked. From observation of the various factors upon whioh the usefulness of a coke for particular purposes depends, it is possible to indicate those qualities of a coke which render it most valuable, for all, or most, purposes (Continues...).

This work stems directly from a manufacturing company's need to improve the quality of its product and increase competitiveness in an industry where a physical understanding of its production process, known as centrifugal spinning, is lacking. Centrifugal spinning is the principal method of producing mineral wool; a product that is predominantly used for thermal and acoustic insulation. The production technique generates wool fibres from a molten jet that is directed to impinge onto four rotating wheels. However, it sometimes, and quite often produces mineral wool fibres of poor quality due to the presence of nonfibrous material or shots; a problem that has so far received little attention. This inquiry was undertaken with a VIew to providing insights into the physical mechanisms governing the formation of fibres and shots. Theoretical analyses and an experiment were conducted to investigate the important non-dimensional groups that govern fibre and shot formation, but concentrating mainly on understanding the mechanics of shot formation. It was established that fibres are formed from the break-up of the thin layer around the rotating wheels. It was also established that shots are formed from droplets produced as a result of jet splashing. Jet splashing is temperature independent since it occurs in a short time-scale from jet impingement with little melt cooling; it is largely governed by force balance and geometrical parameters. Such an observation led to an impinging water jet experiment that was conducted at ambient temperature and its image processed by computer software. From this, it was determined that the significant non-dimensional group that governs jet splashing on a rotating wheel or drum was that due to the jet impact position. The least liquid splashing was found to occur when the jet impinged in the forward position (relative to the direction of rotation) because the depth of fluid underneath the impingement position was always at its minimum. The speed of drum rotation affected jet splashing only up to a critical value, beyond which it had little influence.

No description available.

No description available.

This thesis reports upon a second phase of research into the effects of free-stream turbulence quantities on heat transfer to impermeable gas turbine blading. It describes the development of a novel form of turbulence generator, to control separately the turbulence quantities intensity and frequency upstream of a cascade of blades at levels typical of the gas turbine. The turbulence generator was calibrated for these individual quantities, with a hotfilament anemometer system combined with on-line analog and digital signal processing. Blade heat transfer coefficients measured by two independent techniques are compared. A large quantity of data is presented, taken from a first stage high pressure rotor blade and a nozzle guide vane. These were subjected to steady flow and turbulent streams induced by both the novel turbulence generator and by more conventional turbulence grids. Surface pressure measurements have also been made, to predict the heat transfer rates by applying formulae derived from simple geometries. Much of the boundary layer over the two blades was apparently laminar. For the laminar regions, the simple formulae for heat transfer (flat plate for example) multiplied by a turbulence term, will provide as good a correlation as any. The intensity Tu is the most important turbulence quantity, but there is some evidence that the frequency of the perturbations can effect heat transfer. Other evidence presented would s'uggest that profile geometry is an overriding factor, which dictates the development of the turbulence, whatever its origin, as well as controlling its interaction with the boundary layer. None of the correlations available for the prediction of boundary layer transition are applicable. On both blade suction surfaces separation seems to have occurred, and the analysis indicates that transition on the pressure surfaces of modern blades will be inhibited by the high free-stream accelerations. Beyond transition, heat transfer is little affected by turbulence. It is now clear, that measurements of the turbulence as it develops through the cascade must be performed before a successful prediction procedure for all of the boundary layer regions can emerge.

No description available.

No description available.

No description available.

No description available.