The use of variable engine geometry to improve the transient performance of a two-spool turbofan engine.

摘要

The prediction of the behaviour of a two-spool turbofan engine (Tay Mk610) under steady-running and during transient performances has been carried out in the present investigation. Four different variable geometry features have been investigated with a view to achieving surge-free acceleration and deceleration of the engine. These are: altering the scheduling of the Inlet Guide Vanes (IGVs) of the High Pressure (H.P.) compressor, altering the Handling Bleed Valve schedule in the H.P. compressor, bleeding some air from the I.P. compressor delivery into the Bypass Duct of the engine, and finally altering the throat area of the Final Nozzle of the engine. The method of the Inter Component Volumes has been adopted for the performance prediction. The simulation prediction, for the 'Design' engine, has been based upon the real characteristics of the engine components and engine data provided by the manufacturer, thus the simulation prediction is realistic. These characteristics used for this 'Design' engine are the characteristics used by the manufacturer in the original design of the engine - thus the H.P. compressor IGVs and Handling Bleed Valve move in accordance with the 'Design' schedules. With regard to the effects on steady-running and transient performances of heat transfer, for simplicity these have been ignored, i.e. the systems are regarded as being adiabatic. The predicted transient trajectories, for reasonable thrust response rates, are satisfactory in all compressors with the comments that (a) in the acceleration there is a condition in the H.P. compressor near to surge at (NH/T26) of about 548, (b) in the deceleration there is an approach towards surge in the I.P. compressor over the band (NL/T26) 433 to 340. Characteristics of the H.P. compressor (of 12 stages) are required for the situations with modified IGV and Handling Bleed schedules. Little information on this was available from the manufacturer. An existing programme, of the row by row type, for predicting axial flow compressor characteristics has been developed and used, along with the sparse engine manufacturer's data, to predict the changes in characteristics resulting from altered IGV and Handling Bleed schedules. (Abstract shortened by ProQuest.).