Research Of Surge And Stall For Aero Engine Based On Entropy

Axial-flow compressor is one of the key components of aircraft engines and its steady work plays an important role for the safe operation of aircraft engines. However, in flight,the various effects such as the changes of the operating environment and the engines' structure will cause unsteady air flow inside the compressor, causing stall and surge which may make the engines' components damaged or even failure. This condition may seriously affect the flight safety of the aircraft. Therefore, the early completion of stall and surge with an alarm signal to trigger the anti-surge mechanism, which can prevent the damage to engine components and effectively ensure the flight safety, is of great significance.The mechanism of stall and surge is analyzed and the entropy theory is studied in this paper. It is found that entropy is suitable for the research of stall and surge. So the stall and surge of compressor is researched in this paper, focusing on the transition from steady work state to stall and surge state. The NASA Rotor37 is used for the simulation model in this paper. The software ANSYS BladeGen is used to establish the three-dimensional model of Rotor37 and the software ANSYS TurboGrid is used for meshing. For flow simulation, the software CFX is used by setting different conditions to make the compressor's work state change gradually from stabilization to stall and surge. Based on the theory of thermodynamics entropy, two thermodynamic entropy parameters, the average value of specific and the isentropic efficiency, are selected as study objects. During the simulation, the relevant parameters at each state are extracted to calculate the value of these two thermodynamic entropy parameters and then observe their changes. Based on the theory of information entropy, three types of generalized information entropy, approximate entropy, fuzzy entropy and sample entropy, are selected as study subjects. According to their calculation process and related parameters extracted, the values of these three types of entropy at each state are calculated with the help of MATLAB programming. Then observe the changes of these values. Through analysis, it is found that the average value of specific and the isentropic efficiency change abnormally in the event of stall. The changes of the three types of information entropy's values obtained by calculating using the static pressure sequence signal at the receiver can well reflect the working state of the compressor. But bycomparison, the sample entropy is of more practical value. Thereby the fault diagnosis of the compressor stall and surge can be achieved by using the correspondence relation between the working state and the changes of the parameters and entropy's values.