Determination of critical speed of bypass turbojet engine with integrated starter-generator high-pressure rotor

Today, the development of aircraft within the electric aircraft concept framework is relevant. In this case, the key technology is the integrated starter-generator, which makes it possible to refuse the mechanical, pneumatic, and hydraulic power take-off from the aircraft engine. In the well-known scientific articles, integrated starter-generators are designed without considering the features due to their location inside the aircraft engines. This study starts a set of projects devoted to the design of integrated starter-generator for a bypass turbojet engine, considering the features of this technical decision. The purpose of this study is to develop approaches to determine critical rotation frequency of high-pressure rotor considering starter-generator integration. Models to determine the critical rotation frequency of a high-pressure rotor with an integrated starter-generator rotor are developed based on non-traditional models of rotor dynamics by mathematical modeling. An area for the integrated starter-generator location has been determined and a constructive method for its implementation is proposed for a bypass turbojet engine. In this study, mathematical expressions are obtained to determine high-pressure rotor critical speed in case of a detailed study of dynamics and in case of an integrated starter-generator preliminary calculations. Based on the value of the critical speed of the high-pressure rotor calculated from the obtained expressions, firstly, it is possible to check the correctness of the choice of the air gap of the integrated starter-generator and strength calculations of the integrated starter-generator in the most difficult operating mode. Secondly, it is possible to determine safe operation area of the bypass turbojet engine with an integrated starter-generator. The results of the study enhance the theoretical foundations of the design of the integrated starter-generators and make it possible to avoid errors in their design and further operation.