Characteristics Of The Casing Is Installed In The Gas Side And Axial Forces Acting

Casing is an important part of an aero engine, it is supported by bearing rotary members, and also be used to fix stator blades and accessories. There are a variety of purposes and designed recesses or cavities on the casing. The structure of casing is more complex. Since high rotational speed rotors have strict demands for concentricity, hard connections between casing installation sides are adopted. During working conditions, the casing not only withstands the internal gas pressures and bolt preloads, but also withstands front and rear axial forces of casings. The forces subjected to the casings are more complex. The design of connection structures of installation sides should consider not only the strength, rigidity and concentricity requirements, but also sealing requirements.Firstly, influences of bolt joint structure parameters and preloads to the concentricity of casings were studied in this paper. Software of finite element and MATLAB were used to research influences of bolt preloads, bolt locations and bolt numbers to casing concentricity based on a least square fitting circle method. A combined method of neural network and Monte-Carlo was used to statistically analyze bolt locations and preloads, and the influence rules of multiple bolt locations and preloads to casing concentricity were obtained. It's shown that the concentricity increases with the increase of bolt numbers and bolt preload, and the influences of bolt positions to casing concentricity does not change regularly.Taking an aero engine compressor casing as a model, the finite element method was used to calculate stresses and deformations of bolts and installation sides under different bolt preloads, internal gas pressures and axial forces. The calculation results shows that the internal gas pressure has a little influences on stresses of bolts, installation sides and casings; axial force has a certain influences on stresses of bolts, installation sides and casings; and bolt preload has greater influences on stresses of bolts, installation sides and casings; The deformation of installation sides doesn't show any regularity with changes in the internal gas pressure, bolt preload and axial forces. The casing deformation increases with the increasing of axial forces, decreases with the increasing of bolt preloads.This paper analyzed leakage of installation sides of half-type casing and segmented casing. Leakage of installation sides for segmented casing was calculated using finite element software, and verified by experiments. It's shown that internal gas pressure affects the gap of installation sides a little. The gap of installation sides decreases with the increase of bolt preloads in the case of axial force remaining the same. The test results proved the correctness of FEM. Through a comprehensive study on strength, rigidity, concentricity and sealing of installation sides, this paper provide a reference for the design of casing.