Research On Fault Simulation Method Of Aircraft Air Conditioning System

As one of the important subsystems of an aircraft,the function of the air conditioning system is to regulate the temperature and pressure in different compartments of the aircraft,so that the passengers and crew can complete the flight in a suitable environment.However,the air conditioning system is prone to failures during operation and the types of failures are complex,so air conditioning system maintenance training is an important part of aircraft maintenance training.Traditional aircraft air conditioning system maintenance training is based on real aircraft materials for hands-on training,although this method can make the trainers more intuitive to understand the structural composition of the air conditioning system and its failure causes,but the expensive material price limits the number of trainers and training time.In order to get rid of the limitation of the high cost of actual materials for training,it is of great significance to propose a fault simulation method for aircraft air conditioning systems.In this paper,the simulation methods for different types of aircraft air conditioning system failures are investigated.The specific work is as follows.First,based on the composition structure of the aircraft air conditioning system and the characteristics of the faults,the faults that are prone to occur in the aircraft air conditioning system are divided into two categories: discrete faults and continuous faults.Based on the characteristics of the two types of faults and the simulation requirements,the fault simulation of the aircraft air conditioning system is divided into a functional simulation module for discrete faults and a performance simulation module for continuous faults,based on which the fault simulation structure of the aircraft air conditioning system is designed.Secondly,the structure analysis is carried out for the air conditioning control system which is prone to discrete faults,and based on this analysis the air conditioning control system simulation structure is divided into power supply,state discrimination,cockpit effect,performance parameter selection and other modules.After that,a discrete fault simulation method based on finite state machine is proposed according to the characteristics of discrete faults,and the simulation models of power supply and state discrimination modules are established based on this simulation method.The implementation method of cockpit effect module based on Opengl graphics library and MFC framework is given.The critical proportionality method is used to rectify the PID parameters of the PACK component controller to realize the performance parameter selection module simulation.Again,since continuous-type failures of the air conditioning system mostly occur in the PACK component,the PACK simulation is performed based on the thermodynamic model of the PACK component.In the PACK simulation,for the problem that the heat exchanger simulation using the lumped parameter method is prone to distortion point errors,the lumped parameter method of meshing is adopted to optimize the heat exchanger simulation,and the relationship between the number of meshes and the simulation accuracy is analyzed,and the mesh division applicable to the air conditioning system fault simulation is given.After that,a continuous type fault injection method is proposed to map continuous type faults to corresponding parameter variations in PACK performance simulation.Finally,the simulation implementation of ACSC P1 controller failure,heat exchanger fouling and ram air flap jamming are taken as examples respectively to verify the effectiveness of the simulation method.