Performance simulation and diagnosis of faulty states in air-cycle refrigeration systems in civil aircrafts.

• Simulations models for ACS normal and faulty states were developed. • Trained fault diagnosis model achieved a validation accuracy of 99.00%. • A data set of about 50,000 entries can be used to train a satisfactory model. • A reduced proportion of normal state data improves the model sensitivity. In the present study, performance simulation models and diagnosis method of faulty states in air-cycle refrigeration systems in civil aircrafts are developed, and the effects of the training data set on the diagnosis accuracy were analyzed. A base model for normal state simulation of air-cycle refrigeration system (ACS) was established based on the existing method with several modifications to improve accuracy and performance. Dedicated models for faulty states were developed according to the causes of fault. Based on the established models, a data set was generated. Preliminary training of multiple two-layer neural network models is performed with the existing data set, and the trained model achieved a validation accuracy of 99.00 % which confirms the feasibility of using double-layer neural network for fault identification and classification based on simulation data. The effects of the training data set to the model are analyzed, and it was concluded that: a data set of about 50,000 entries can be used to train a satisfactory diagnostic model; the proportion of normal state data needs to be reduced appropriately to improve the sensitivity of the model to faulty states; it is possible to largely reduce the number of sensors with smaller effect to the diagnosis accuracy. [ABSTRACT FROM AUTHOR]