The Predicted Performance of a Two-Spool Turbofan Engine in Rainstorms

Baki, Tarik (1993) The Predicted Performance of a Two-Spool Turbofan Engine in Rainstorms. MSc(R) thesis, University of Glasgow.

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The present work makes an attempt at predicting the performance of a gas turbine under the ingestion effects of rainwater. Such study was achieved with the aid of appropriate mathematical models which have been devised to enable the forecasting of a gas turbine engine performance during steady running behaviour. The models can also be used to forecast transient performance, although they were not used for this purpose in the present work. This research was based on the simulation of two conditions. The first simulation was of an engine test carried out by Rolls-Royce. The engine was a twin spool turbofan with mixed exhaust called the Tay MK- 650. The engine test involved water injection into the engine core only, ie the water was introduced after the fan and only into the air entering the Intermediate pressure (IP) Compressor. The second simulation accounted for the ingestion of water through the whole frontal area of the engine. The conditions of flight corresponded to an altitude of 6,000 m, Mach Number 0.8 and the water mass flow was 2.3% of the total inlet mass flow - this corresponding to the heaviest rainfall conditions that have been measured. The lay out of this research would therefore be presented as follows: Chapter (1): General background and recent development of gas turbines, with a brief introduction to the problem and definition of the contribution of the present work are exposed in this chapter. Chapter (11): This chapter deals with a briefing about previously studied ways of aircraft simulation and defining the appropriate methods undertaken to tackle this problem for engines under normal conditions (no water ingestion). Chapter (III): Scaling of the main components for the TAY MK-650 engine, from the TAY MK-610 and description of performance prediction programs set for the two-spool turbofan engine during steady running state are presented here. Chapter (IV): This deals with water thermodynamics introduction into the simulation program for the Tay MK-650 engine. A study is made of possible evaporation and drag locations in the engine. Mathematical models are introduced into the engine prediction program to describe these effects of evaporation and drag. A derivation of baseline was necessary in order to establish a link and a comparison between test observations obtained from Rolls-Royce and the simulated results produced in this research. Chapter (V): The complete engine prediction program developed in Chapter (IV) is applied to the conditions of the core ingestion tests carried out by Rolls-Royce. From the comparison between the predictions and the test results it was concluded that the major (90%) location for evaporation of the core flow water was at the plane after the High Pressure (HP) Compressor ie at entry to the combustors. The first 10% of evaporation was regarded as taking place at entry to or within the HP Compressor. This evaporation distribution coupled with drag due to water impingement on all three blade rows in the IP Compressor then gave the best match between predicted and obseved shaft speed and turbine temperature changes. At the water injection rate of 2% by mass of the core air flow, it was predicted that there would be a 40% reduction in surge margin in the HP Compressor. This agreed reasonably with the engine test results where a 3.5% water injection rate caused the HP compressor to surge. Chapter (VI): The aim of this chapter was to give the best indication of the appropriate combination of models which would represent water ingestion through the whole frontal area of the engine. Different methods based on different models are investigated to allow for the comparison of results from the clean engine and its counter-part the water injected engine. General discussions of all results obtained from different simulations, and various assumptions at conditions of 6,000 m altitude, Mach Number 0.8 are presented here as well. For a more realistic high rainfall situation, 2.3% by mass of the engine inlet flow was considered as water. That quantity of water was divided after the fan as 90% into the bypass duct and 10% into the core. Evaporation then took place at corresponding planes and it was found that the steady running line for the HP Compressor had risen by 20% of the initial surge margin at lower fuel flows and as much as 75% at higher fuel flows. It could be said that the main reason for this behaviour was once more due to the evaporation at plane between IIP Compressor and Combustion Chambers with other evaporation planes having little to no effects on the HP Compressor surge margin. Chapter (VII): This Chapter displays a brief conclusion drawn from all assumptions and investigations as well as suggestions for further study. Finally, it was realised that this issue needs dedicated and continuous efforts in order to accomplish positive and highly accurate results in the future.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Additional Information: Adviser: N R L Maccallum
Keywords: Mechanical engineering
Date of Award: 1993
Depositing User: Enlighten Team
Unique ID: glathesis:1993-74815
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 27 Sep 2019 16:01
Last Modified: 27 Sep 2019 16:01

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