Vibration Characteristic Analysis And Optimization Design Of S31 Type Roots Blower Casing

As the one of the important components of roots blower,roots blower casing has played a very significant role for stable operation,The casing structure is not only supporting and connecting the roots blower front-backwallboard and inlet-outlet facilities,but also impacting of internal impeller rotor dynamic air disturbance.So the casing need to meet the requirements of strength and stiffness.At the same time it also need a good dynamic characteristics.It is particularly critical to research on roots blower's vibration and noise characteristics for the modern demands of low vibration and low noise.This paper focuses on vibration characteristic analysis and optimization of S31 type roots blower casing structure,producted by changsha blower co.,ltd.The main works and results are as follows:Firstly,the vibration noise disturbance source and mechanism of S31 roots blower were analyzed.The air flow pulsation of roots blower,including theory flow pulsation,inlet flow pulsation and outlet flow pulsation were analyzed.Secondly,the 3d model and finite element model of S31 type roots blower was established through analyzing its structure characteristics.The meshing rationality of casing finite element model was discussed.And numerical simulation experiment was carried out for the grid quality precision.Thirdly,the free modal analysis was carried out on the casing.Modal experiments with modal test software was carried out for verifying the finite element calculation results.To make the analysis more close to the actual working condition,the constraint modal analysis was carried out on the casing.The prestressed modal analysis was carried out on the casing through loading the prestress beforehand.In order to predict the coupling resonance frequency between inherent frequency and pulse frequency,the vibration response analysis of the casing under gas pressure pulse excitation was carried out.Finally,to grasp the overall dynamic characteristics change rule of casing structure,the sensitivity analysis were carried out with casing's elastic modulus,density,poisson's ratio and relevant structural geometry size.With the DOE central composite design principle,the casing parameters was optimized to make the inherent frequency of casing be away from the gas pulsation frequency in the existed conditions.The dynamic performance of the casing was improved after optimization.In conclusion,modal analysis was carried out on the blower casing.The natural frequencies,main modes and related modal parameters of the casing were obtained.And the reliability of simulation was verified through the experimental analysis.The vibration disturbance source of roots blower was analyzed under the working condition.The structural dynamics modification was carried out on the casing structure with the multi-objective optimization method.The operating dynamic characteristics of S31 roots blower was improved through the optimization of casing structure.This process which named "structural modal analysis----modal test----structural model modification----structure parameters optimization" provides a reference method for the optimization of other mechanical structure.