Conceptual Modelling of Civil and Military Aero-Engines

Abstract

Statistical research has been performed on available turbofan engine configurations up to 1995 and documented by Grieb. A mathematical model is developed as a part of this thesis work to utilize the research data into predicting the parameters for 2015 and 2020 engines. This thesis work mainly focuses on modelling the polytropic efficiencies of the various components that constitute a 3-spool turbofan engine: fan, intermediate pressure compressor, high pressure compressor, high pressure turbine, intermediate pressure turbine and the low pressure turbine. An optimizer code is developed in the C programming language as a second part of this project to feed the modelled values as input to the gas turbine analysis software EVA. It then varies the design parameters like inlet mass flow, velocity ratio, pressure ratios and turbine inlet temperature continuously between two arbitrary fixed points. The specific fuel consumption at mid-cruise conditions is read from the output of EVA. Installed SFC is then calculated by taking nacelle inputs from Weico (a program to calculate engine dimensions) to get the minimal value. Design parameters at this value of installed SFC are returned into the input of EVA. Successive iterations are performed to get a global minimum value of installed SFC.