Browsing by Author "Carver, Stephen"
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Item Open Access Communicating in a crisis(Cranfield University School of Management, 2011-09-01T00:00:00Z) Carver, StephenItem Open Access Gas turbine transient performance : heat soakage modelling(Cranfield University, 2004-09) Naylor, Philip; Pilidis, Pericles; Carver, StephenThe ability to accurately extract steady state performance information from transient engine test data has the potential to significantly reduce test bed time and cost, depending upon the accuracy with which engine phenomena such as heat soakage and transient tip clearance changes can be modelled within the context of a whole engine performance code. This thesis describes improvements to the GTTrans generic Whole engine performance code thermo mechanical heat soakage and tip clearance methods. This thesis describes the streams method in which a collection of definite volumes are used to represent engine component hardware and perform transient heat transfer calculations accounting for both conduction and convection to and from non-trivial engine component geometries. Transient metal and gas temperature profiles are then used to estimate transient blade tip clearances. The streams method has been incorporated into a Rolls-Royce Trent 500 engine performance code. Accounting for heat soakage, tip clearances, and bleed temperature Variations within the engine code affected the predicted steady state operation as well as making spool accelerations more sluggish and raising compressor working lines during transient manoeuvres. Although all three effects were significant, heat soakage appeared to have the largest effect on transient performance, particularly during the hot reslam manoeuvre. Rolls-Royce PLC sponsored this EngD project laying down 5 project requirements that enhanced heat soakage and tip clearance methods should meet, i.e. handle both heat soakage and tip clearances, be physics based, run at or near to real time, meet given accuracy targets, and be capable of being calibrated. The streams method met the first three of these requirements, although with further development it might be possible to meet all five. This thesis also contains analysis and recommendations regarding the process of technology transfer from the Cranfield University Technology Centre in Gas Turbine Performance to within Rolls-Royce.Item Open Access Influence of flight-path variability of conditions upon in-flight icing(Cranfield University, 2008-10) Stanfield, Robin; Hammond, David W.; Carver, Stephen; Spooner, PaulIn design and development of aircraft, standard practice uses `the icing design envelopes' to select atmospheric conditions for modelling icing encounters. Over the duration of these encounters, atmospheric conditions are assumed to be constant and to exhibit no variability. In reality variability exists, to an extent where it may adversely affect the severity of ice accretions beyond that identified by ground-based modelling. Similarly, certain tools and systems employed by industry may sacrifice efficiency & effectiveness in neglecting the variability that exists. This project considered what operational and safety bene ts might be derived from an enhanced knowledge of ice accretion under more realistic, variable conditions; in contrast with a reference case identified to have equivalent constant conditions. In doing so, variable encounters were modelled experimentally in an icing tunnel to compare against a constant-condition reference; aerodynamic penalty was assessed numerically using CFD, allowing a comparison to be made between variable and constant-condition profiles; and desk-research considered variable conditions in the context of existing and emerging technology. Considerable differences were observed between variable profiles themselves and with the reference profile, with aerodynamic penalty being considerably enhanced for 25% of variable cases, and considerably reduced for a further 25%. Desk-research suggests that in understanding variability, to reduce costs asso- iciated with aircraft icing, more realistic ground-based modelling capabilities could reduce the need for natural flight-testing in the long term, though this would require substantial enhancement to current numerical prediction capabilities. Similarly, the power applied to ice protection systems could be tailored more speci cally to demand, enhancing e ciency. On the basis of current instrumentation, this would first require development of more accurate and robust LWC measurement systems. It was therefore recommended that specialists in meteorology, icing physics, ice protection systems and aerodynamics; conduct more extensive research towards understanding variability and assessing its potential to enhance flight-safety, whilst simultaneously reducing cost.