Knowledge-Based Conceptual Design Methods for Geometry and Mass Estimation of Rubber Aero Engines

Kurzfassung

The efficiency but also the dimensions and mass of aero engines have a significant impact on the components, drag and consumed block fuel of the aircraft. The interdependencies between the engine and the aircraft have to be accounted for to find the optimal engine in a multidisciplinary overall aircraft design process. One approach to do this, is the application of a rubber engine model that provides a broad range of different engine designs. However, to create a rubber engine model, the geometry and mass of various engines have to be predicted with sufficient accuracy during conceptual design, when only limited computation time and a small amount of data are available. Therefore, a knowledge-based method for the estimation of engine geometry is developed that utilizes an advanced parameterization of turbo components based on B-splines. The knowledge is extracted from cross-sectional drawings of existing engines that serve as reference. The geometry estimation requires thermodynamic cycle data and is combined with published component-based and part-based procedures to predict the engine mass. This combination of models enables the holistic assessment of interdependencies between thermodynamics, geometry and mass of aero engines on conceptual design level. As a validation case, a generic geared turbofan similar to the PW1100G-JM is modeled and both mass estimation methods are benchmarked. The mass breakdown of the part-based approach is compared to published data. In addition, an analysis of trends is conducted to investigate how the estimates for geometry and mass adapt to design variations. Therefore, the major design variables bypass ratio, thrust, overall pressure ratio and turbine temperature are varied. Their impact on geometry and mass is discussed and the resulting trends are compared to a published correlation-based model.