The study of anti-stall techniques for fans and compressors has never been more significant, since the potential applications were recognised in gas turbines, tunnel ventilation (jet fans) and industrial process where fans/compressors would benefit from the devices. This thesis will discuss the techniques achieving competitiveness by modifying the conventional casing design of the fan and compressor, which is referred to as casing treatments, taking into account the change of maximum efficiency and flow range. An experimental investigation to examine the influence of the vaned recess casing treatment on stall margin, operating efficiency and flow field of a low speed axial flow fan with aerospace type blade loading is presented. Different geometrical designs of the vaned passages were examined and more than 65% of stall margin improvements and over twice pressure rise with insignificant peak efficiency change were obtained. Experiments to examine the effect of casing treatments on the flow field were carried out using the same fan rig with a tip clearance of 1.2% of the blade height. A high frequency data acquisition system including both hardware and software was developed and the 3-D flow measurements with a slanted hot-wire were undertaken. The first detailed results of flow measurements associated with the vaned recess casing treatment are presented, including both time-averaged and ensemble-averaged measurement results. The flow features in both the solid casing and treated casing builds are captured and comparison between the builds presented. The results revealed that the stall margin improvement due to the casing treatment was not achieved by reducing the incidence nor by increasing the total pressure in the tip region. It appeared that the combined functions of elimination of the whirling flow, the removal of the randomness of the inlet flow and modification of the tip clearance flow are salient features associated with the mechanism of the treatment. The steady flow field of the test fan with various tip clearances has also been simulated in the rotating frame with computational fluid dynamics (CFD) to investigate the clearance effect on the end-wall flow development and to elucidate the behaviour of the tip leakage flow, and hopefully shed more light onto the flow phenomena involved.

This study is laid out in 8 self-explanatory sections. The Introduction sets the scene for the thesis by describing the reasoning behind the study, defines terms and introduces the reader to the markets for amphibious aircraft which drive the design requirements. An overall floatplane design methodology is developed. The advantages and disadvantages of the 2 practical float configurations are identified, which result in a basic configuration choice methodology. A method of initially estimating float dimensions and mass for a required displacement is developed from existing references and the aircraft and float databases. Initial float support structure design solutions are proposed based, again, on the information from the databases. A method of positioning the resultant float and structure configuration relative to the existing land-based aircraft centre of gravity is then developed using existing guidance on lateral and longitudinal water-borne static stability and the aircraft database. Guidance on the initial purchase price of floats is gained from a study of commercially available items. The changes in performance due to fitting floats to a conventional aircraft are studied along with a drag comparison study of the main configurations. The work on flyingboats develops an overall flyingboat design methodology which identifies key areas where design methods are required. These methods are developed leading to initial configuration choice methodologies based on a series of generalised mass, configuration and role classifications. Having decided on the overall configuration, tools are developed to choose the method of providing on-water lateral stability and to complete the initial sizing of that choice. A method of estimating initial planing bottom dimensions is developed along with step position and configuration. Tools to estimate the mass of flyingboat-specific items are developed including planing bottom structure and the choice of lateral stability method. Knowing the mass and configuration of the flyingboat allows spray estimation and detailed on-water static stability calculations to be completed to check the acceptability of the initial configuration and dimensions. Performance estimation methods including take-off and landing, aerodynamic drag and on-water dynamic stability are proposed. Logistic support infrastructure, safety and water loading are common to both floatplanes and flyingboats and these are discussed in a separate section, along with a method of allocating values to amphibious aircraft design attributes to measure the success of the design. The methodologies are then used to design 5 floatplanes and 5 flyingboats based on a crosssection of relevant aircraft specification types. This use of the methodologies illustrates that the concept of a linked series of tools to complete the rapid conceptual design of an amphibious aircraft has been successfully achieved. A discussion chapter summarises the key discoveries in each of then former chapters and a conclusion details how the study's aim to develop integrated conceptual design methodologies for waterborne and amphibious aircraft has been successfully achieved. The study's contribution to knowledge, which includes mass, sizing, performance and cost equations for both floatplanes and flyingboats, are also detailed. A list of further work is included which concentrates on the need for further empirical information to increase confidence in the methodologies. A comprehensive bibliography of relevant texts is included.

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