Abstract
This paper presents a dynamic similarity design method to design a scale dynamic similarity model (DSM) for a dual-rotor test rig of an aero-engine. Such a test rig is usually used to investigate the major dynamic characteristics of the full-size model (FSM) and to reduce the testing cost and time for experiments on practical aero engine structures. Firstly, the dynamic equivalent model (DEM) of a dual-rotor system is modelled based on its FSM using parametric modelling, and the first 10 frequencies and mode shapes of the DEM are updated to agree with the FSM by modifying the geometrical shapes of the DEM. Then, the scaling laws for the relative parameters (such as geometry sizes of the rotors, stiffness of the supports, inherent properties) between the DEM and its scale DSM were derived from their equations of motion, and the scaling factors of the above-mentioned parameters are determined by the theory of dimensional analyses. After that, the corresponding parameters of the scale DSM of the dual-rotor test rig can be determined by using the scaling factors. In addition, the scale DSM is further updated by considering the coupling effect between the disks and shafts. Finally, critical speed and unbalance response analysis of the FSM and the updated scale DSM are performed to validate the proposed method.
Highlights
The rotor system is one of the most important parts of an aero-engine, and the rotor dynamic characteristics have great influence on the durability, reliability and safety of the whole engine
The dynamic equivalent model (DEM) was obtained by dynamic equivalent principles and dynamic optimization
The scaled dynamic similarity model (DSM) was modelled using the scaling factors derived by the dynamic similarity method for the rotor-bearing system
Summary
The rotor system is one of the most important parts of an aero-engine, and the rotor dynamic characteristics have great influence on the durability, reliability and safety of the whole engine. Young [13] established dynamic similarity relationships for self-adaptive composite marine rotors, and numerical simulation using a fully coupled, three-dimensional, boundary element method-finite element methods were performed to validate the theoretical scaling relationships and to investigate scaling effects. From the review of the existing literature about the similarity modeling of the prototype, it is seen that most scaling problems have been solved by using both similitude theory and dimensional analysis theory. Similitude theory is used to establish the similarity conditions between the full-size model and the scale model, while dimensional analysis theory is used to determine the scaling factors. The dynamic similitude theory of the rotor system is derived by equations of motion and dimensional analyses, and the scale DSM is obtained based on setting the scaling factor of the frequency equal to 1. Because the literature concerning the dynamic similarity design of a scale dual-rotor system is very scarce, this paper provides a feasible method for dynamic similarity design for a dual-rotor test rig of a realistic engine
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