Application of Sub-Modelling Technique for Whole Engine Transient Dynamic Analysis

摘要

The design of a commercial aeroengine needs to satisfy the safety requirements from the aviation authority. Among them, the fan blade out (FBO) load is one of the most critical loads for the safety consideration required by the regulation. The most commonly used tool for the FBO event simulation is the so-called transient dynamic whole-engine finite element analysis (FEA). However, because of the model scale, the running efficiency and the results accuracy cannot be satisfied simultaneously. The whole engine FEA model may provide reasonable results for the component interface loads but not the stress distribution for a particular component with reasonable accuracy. In this paper, we propose a dynamic sub-modelling technique for the whole engine transient dynamic analysis, which adopts a two-steps approach. First, we use a coarse mesh model for the whole engine FBO analysis, and select the proper border for the component of interest as the sub-model region. The corresponding nodal displacement time history file at the boundary of the region is created. Next, we create a fine mesh sub-model, and use the previously created displacement boundary condition as the load applied to the sub-model. We also propose the concept of the extended sub-model, which includes the fine mesh sub-model and the border elements. It takes advantage of the feature of "tied-contact" in LS-Dyna which does the displacement interpolation internally. As such, we have achieved satisfactory stress results for a component of interest without compromising the running efficiency. A test case is provided, which shows that the results of the sub-modelling technique agree well with the results for the model with the locally refined mesh. In addition, we use the fan shaft in a whole engine model as another example to illustrate the effectiveness of the sub-modelling technique.