Preliminary Design of a High Bypass Ratio Turbofan Engine

Abstract

This paper presents a preliminary design of a high bypass ratio turbofan engine which has been developed through a Masters Degree project at Cranfield University in the UK. It is well known that the design process for a new gas turbine engine requires an understanding of the interrelated requirements of aerodynamics, thermodynamics, heat transfer, materials choice and engine control. Accordingly, the designer’s solution is inevitably the result of compromises involving a large number of mostly conflicting parameters. The preliminary design study in this paper relates to assessment of a suitable engine to satisfy the specification needs of a small airliner. The particular aircraft chosen for the design is one designed by a group of master’s degree students in the College of Aeronautics at Cranfield University. The paper includes a description of that aircraft specification for which the cruise phase is chosen as a design point for the engine. The overall objective of the design is to achieve the least (practical) specific fuel consumption so as to maximize aircraft range. The paper presents the results of the iterative design study and includes the effects of turbine entry temperature, bypass ratio, overall pressure ratio and fan pressure ratio. Subsequently, a procedure for the selection of the annulus geometry for each of the turbomachinery components and the combustor is illustrated which can deliver an acceptable gas path for the entire engine. Finally, using well established compressor cascade data, an approximate method is illustrated for the prediction of the performance characteristic of the high pressure compressor of the core engine.