Finite Element Analysis Of Dynamic Characteristics Of Large Welding Casing

With the quick development of diversity and small batch of products, the substitute of traditional cast casing by the welding casing for large compressors is the requirement due to shortening the period of making, reducing production cost and winning the market. In this thesis, a certain large axial compressor welding casing was analyzed by transient finite element analysis, the dynamic characteristics was researched for the design and optimization of the cast casing.On the basis of research on structural characteristics on the welding casing of large axial compressors and the static finite element analysis, load variation of the compressor under operation condition analyzed to establish welding casing model for the dynamic finite element analysis.By the modal analysis of welding casing, natural frequencies and vibration modeles were gained. Analyzing the vibration mode and stress nephogram of the welding casing, that amplitudes and stress value is bigger, such as the connection sections of supporting and casing, the connection sections of medial cavity and exhaust chamber, the connection sections of air-intake, the connection sections of air-outtake pipes and casing, and the left and right connection plate of midsplit flange and so on. The sections of the connection could be the dangerous regions, which were the key parts to design and optimization for the welding casing.In addition, under some special working conditions, the heat and transient analysis were respectively carried out on the welding casing. The stress, deformation contours at each moment, and transient stress curves of the dangerous points of the casing were obtained. Through analyzing dynamic properties of casing, it was disclosed that biggish concentrated stress was in the area between the casing of medial cavity and left connection plate of exhaust chamber, this stress reach or over the design requirement. Stress concentrated was found in the area between supporting and flange, between air-intake, air-outtake pipes and casing, and the location of flange thickness change were the weakness parts of the welding casing.On the basis of dynamic analysis for the welding casing, this research conclusion and suggestions were given. Main results were as follows:First, by properly increasing the thickness of connection section between medial cavity and exhaust chamber, adopting transition connection, the rapid change of dimension could be alleviated. Second, these measure, which the bearing boxes support of the original design scheme was shifted to two ends to align the outside plate of bearing boxes with two compressor covers, and the axial length of intake and exhaust chambers were properly shortened according to requirement of compressor capacity, greatly improved the flange bending stiffness. Reducing shell thickness of exhaust chamber was necessary to make full use of material properties. Finally, improving scheme is validated combined with dynamic properties on welding casing in the original design scheme and improving scheme...