Compressor Casing Preliminary Design Based on Features

Abstract

Structural parts, such as casings, have a significant share of the overall turbo-machinery mass of modern aero-engines. Therefore preliminary design studies must aim to include the effect of such structures. For this paper compressor casings of commercial aero-engines have been investigated in terms of their design philosophy. It is shown that compressor casings have very similar designs from the preliminary design perspective, even though they appear as very complex structures in reality. The study identified design similarities from which generalized and simplified casing structures have been derived. The casing is divided into geometrically similar basic structures. Such generalized parts are each individually characterized by features. Through simplified physical design algorithms the features are then dimensioned based on blade containment conditions, pressures and temperatures. Finally a generalized form of compressor casing design is derived from the assembly of the individual parts. The derived preliminary design method of casings is no longer dependent on a known representative casing thickness. When increasing compressor characteristics such as blade numbers, diameters or revolution speed the casing design responds directly while still maintaining a characteristic shaping philosophy. Thus a scaling method based on physics rather than only geometrical identity is achieved. The method was integrated into an existing high pressure compressor preliminary design tool. The examination of the developed methodology is carried out against existing compressor designs. Results are presented and discussed.