Prediction of off design performance of turbojets and turbofans using gas dynamics.

摘要

The purpose of this thesis is to develop mathematical models which can be used to analyse the design and off-design performance of non-afterburning turbojets and twin or three spool non-afterburning turbofans with separate exhausts. The technique used is essentially based on mass flow and work compatibility between different components, reinforced with generalized turbine characteristic curves. Off design performance has been estimated by using gasdynamic properties of the exhaust nozzle, which regulates the aerothermodynamic behaviour of the upstream components. Approximate overall performance of a turbojet or turbofan at typical cruising conditions can be estimated, making the use of compressor and turbine maps redundant.;The computer program is validated by comparing it with the data available from three turbojets, with the best data available from a Rolls Royce Viper 20F-10. In the case of turbofans, the predicted results are compared with a twin spool Garrett TFE 731-2 and a three spool Rolls Royce RB211-22. To test the veracity of the methods developed, the program was again validated against a preliminary version of the PW300. Finally conclusions are drawn regarding the modelling procedure and what improvements could be made.