Analysis On The Failure Of Turboprop's Rotor

In view of the failure of a model engine's compressor rotor, this paper carried out a systematic study of the failure by use of the rotor dynamic theory. The failure cause and development process were also analyzed and discussed in detail. At last, available measures on engineering to overcome the failure were given.This model engine has been derived fromАИ-24 aero-engine made by former Soviet Union. This kind of engine has been produced nearly for 550 sets up to now. Since batch production, the engine suffered more than 70 times failure of compressor rotor. Judging from the feathers of the engine rotation speed, rotor failure status, cold start and hot start, new engine and overhaul engines, bench test and field operation, the failure took on obvious regularity, and the regularity is related to dynamic features. So analyzing the failure, the dynamic features should be analyzed first. This paper calculated the critical rotation speed and unbalance response and thermal bending response of the engine's rotor by using transmission matrix method. On this basis, the analysis about the causes and development process of the engine's compressor rotor failure were carried out.The analysis conclusion is as follows: The rotor failure is caused by the compressor rotor reversal moving due to contact-friction between rotor and stator. So any factors causing compressor rotor and stator contact-friction are the reason of this kind of failure and the factors are varied and relative in engineering reality. According to the engine's structure and process feature, this paper analyzed deeply the main factors such as rotor thermal bending, rotor unbalance, noncentricity between rotor and stator, rigidity of resilient supporting set etc. Thermal bending of compressor rotor is regarded as one of main factors. On the basis of theoretical analysis, two engines in test on bench have been actually measured. Temperature difference between upper and lower part of the compressor case has been taken. The test results shown that after the engine stop there was rotor thermal bending caused by cooling rate difference between the upper part and the lower part surfaces of the compressor. After this, this paper has calculated the deformation of rotor thermal bending by using finite element method, obtained the deflection of rotor thermal bending.On the basis of the failure analysis, this paper proposed measures against the failure, such as to prevent rotor from thermal bending, minimize rotor unbalance, assure good centricity between rotor and stator of the compressor while assembling, repair deformed compressor case and improve character of the resilient supporting set etc. These measures are effective and do not need big change on the engine structure, therefore they are feasible on engineering and have very high practical value.