Abstract
Modifications to the critical parameters, such as the exhaust nozzle area, are sometimes done during maintenance of aircraft engines. These modifications are done either to increase the design thrust or to compensate for the reduction of thrust due to leakage in the variable area jet nozzle. There is a trade-off between several performance parameters when such critical parameters are changed during maintenance. A tuned aerothermodynamic simulation model that agrees well with the experimental data from the original engine is required to study the effect of these changes. In the present work, a multipoint map scaling approach and a parameter estimation method are used to develop a simulation model that agrees well with the experimental data from the original turbojet engine. The design modifications are then incorporated in the model, and the effect of the modification on the various performance parameters is studied. The effect of leakage in the nozzle flaps and the corresponding reduction required in the nozzle throat area are calculated. It is shown that the tuned model developed with experimental testbed data enables the identification of ancillary effects of a change in a design parameter, such as the nozzle throat area.
Highlights
Aerothermodynamic simulation models predict gas path parameters at different stations along the engine.In these models, only a single pressure or temperature value can be calculated at a station on the engine
This paper presents a brief description of the engine for which the model is being developed, followed by the characteristic map tuning process adopted to increase the accuracy of the simulation
Air leakage in the exhaust nozzle flaps of the convergent nozzles is often noticed during the overhaul of legacy turbojets
Summary
Aerothermodynamic simulation models predict gas path parameters at different stations along the engine.In these models, only a single pressure or temperature value can be calculated at a station on the engine. They do not account for the radial or circumferential variation of gas path parameters These models are typically used in the design and development phases of engines,as well as during performance evaluation of legacy engines. An in-house aerothermodynamic simulation model (design point and off-design point) has been modified to simulate a legacy twin spool gas turbine engine These engines are periodically overhauled after being used in the field. Because of the use of a tuned characteristics map in simulation, the simulation model agrees well with the experimental data This model is used to study the effect of a small reduction made in the exhaust area of the nozzle at full reheat rating.
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