Energy flow model-based safety analysis method for complex mechanical system

Predicting and identifying critical components of complex mechanical systems during the design phase is important for safety. However, traditional empirically based safety analysis is gradually inadequate due to the complexity of physical domains and requires model based and quantitative guidance. Therefore, an innovative method including nominal system and fault injection models based on energy flow and quantitative safety analysis is pro-posed in this paper. Specifically, the nominal model with multiple physical domains is generated based on energy flow between and within components, which could effectively reflect system characteristics and correlate with the design. Simultaneously, the fault injection model could deal with fault information and reflect to energy variation with directly injecting fault into the nominal model. Moreover, Logarithmic Safety Index (LSI) with physical meaning is proposed as the quantitative evaluation. Lower the LSI, the lower the safety. Eventually, the method is illustrated by aviation piston engine. Results show that the simulation and experimental error of the system model based on energy is less than 2.5%, which could effectively characterize the performance after fault injection. Furthermore, a total of 656 possible evolution paths for each component are automatically generated based on the model, and a total of 37 shortest evolution paths are determined based on LSI quantization. Based on the frequency of the evolution path nodes, the critical evolution components could be identified including the intercooler, turbo-charger, intake and exhaust pipes. Therefore, corresponding improvement strategies could be proposed for critical components, and the results show that the proposed method proposed could quantitatively evaluate the degree of safety improvement.