The current generation of Airbus long-range civil transport aircraft actively control the centre of gravity of the aircraft by adjusting the fuel distribution between the horizontal tail surface and the forward tanks in order to minimise cruise drag. Here, it is proposed that the current on-off control method could be replaced by a variable flow rate, provided by a variable speed centrifugal pump. The impacts of this at the aircraftlevelintermsof cruisefuelburnreduction,valveoperationcycle reductionand power consumption are investigated here using an extension to an existing fuel system simulationpackage and ageneric aircraftfuel systemdefinition. Itis shownthat using such a control system reduces fuel burn and the number of valve cycles, which could translate into a reduction in operating costs. The benefit of changing the controller to use tailplane trim angle directly rather than inferred centre of gravity position is assessed, and is shown to further reduce the fuel burn. It is suggested that such centre of gravity could provide significant benefits over the existing method. Steady-state anddynamic models ofcentrifugalpumps,ACinductiondrives andtypical aircraft fuel system pipework components are developed. These are validated against experimentaldatafrom a test rig of a representative system. Test rig simulation results areshowntoagreewell with thosefromexperimentation. Anewsecondary noisesource is developed for the dynamic analysis of the centrifugal pump, and a new acoustic experimental method is developed for the prediction of fluid inductance in pipework components. The results are compared against an existing CFD based method and showgood agreement. Thenewmethod representsamuch simplerexperimental means of determining the effects of fluid inertia than the existing secondary source method. Itisdemonstrated thatthedynamicbehaviourof thecentrifugalpumpis, asexpected, insignificant when considering systems containing long pipes, and that steady-state pump models are sufficient for analysing their behaviour. Thepumpmodels aregeneralisedby non-dimensionalisation,in order to maximise their applicability to analysis of aircraftfuel systems. They are applied to ageneric aircraft fuel system simulation, in order to model the behaviour of the system during a trim transfer. Thisisused todemonstratethe application of theproposed variable flowrate trim control system. The results of these simulations agree well with those used to demonstratethebenefitsof thecontrol systemattheaircraftlevel. Conceptsof system health monitoring tools are discussed with reference to the system simulations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:488892 |
| Date | January 2008 |
| Creators | Boyd, Lewis J. |
| Contributors | Edge, Kevin ; Tilley, Derek ; Johnston, David |
| Publisher | University of Bath |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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