Dynamic Analysis And Noise Prediction Of The Large-Scale Compressor

Compressor is machinery which is used to increase the gas pressure and transport gas.Along with the development of science and technology in recent years, particularly in thepetrochemical industry, the pressure energy can be more widely applied in the differentsectors of the national economy, then compressors are made one of the indispensable keyequipments. With the continuing rise in the level of modern design, compressorperformance indicators are continuously strengthened, how to reduce compressor noise andvibration has become an important subject. Therefore, for the first time this dissertationconducts, dynamic analysis and noise prediction of reciprocating compressor in the designdomain of compressor, and it aims mainly at dynamic characteristics and acoustic radiationresearch of compressor structure, exploring a suit of theoretical model and analysis method,thus providing reliable theoretical foundation for low noise design of the compressor.Firstly, in this dissertation, the Finite Element Modal Analysis (FEMA) is conductedon the crankshaft and block of K5206NM compressor which are the main bearingcomponents of compressor, modal parameters of the crankshaft and block such as thenatural frequencies and modal shapes are obtained, the foundation is laid for the dynamicanalysis of the crankshaft system and the forced vibration analysis of the block.Based on topological analysis of K5206NM compressor crankshaft system, throughapplying multi-body dynamics theory and Finite Element Method (FEM), rigid multibodymodel and flexible multibody model of the crankshaft system by the consideration offlexible role of the crankshaft are respectively developed. Pistons, connecting rods andcrankshaft loads are respectively acquired through the simulation analysis of the twomodels, relatively accurate analytical results can be provided for the interaction relationsamong rigid parts in the crank and connecting rod mechanism and the interaction relationsbetween connecting rods and the crank pins by two models; however, more reasonable andaccurate computational results can be provided for the interaction relations between themain bearings on the crankshaft and block only by flexible dynamic model. In addition,force boundary conditions and displacement boundary conditions on the crankshaft can besimulated and calculated within the entire work cycle in the compressor by flexibledynamic model, the Finite Element Method is combined, the forced vibration response ofthe crankshaft can be analyzed.Through the dynamic analysis of the flexible crankshaft system, the gas forces in cylinder, piston guide bearings impact and the main impact which are applied on thecompressor block may be acquired. The dynamic response of the block is analyzed inaction of above various loads, and the force and displacement boundary conditions andstructure damping of the block are discussed in detail. Through the dynamic responseanalysis of the block, the displacement and stress distribution of the block can be not onlygrasped, but also displacement, velocity and acceleration history of nodes in the block canbe obtained in the time domain, it provide a baSis for the structural design and improvementof the block. In the mean time, through dynamic response analysis of the block, availablesurface vibration displacement/velocity of the block agrees well with experimental data ofpartial testing nodes.The mean square value of surface vibration velocity of the compressor block is takenfor factor, surface acoustic radiated power of the block is calculated according as theacoustic principle, which is inosculated with the measured results. Based on the structuralacoustic radiation theory, acoustic boundary element model of the block is established, thecombination of FEM and Boundary Element Method (BEM) can adequately bring into playtheir respective advantages in the numerical simulation of low noise block, throughsimulation analysis of acoustic radiation field of the block, the block soured radiationparameters, such as farfield pressure, farfield intensity, acoustic radiated power andradiation efficiency, can be acquired, the foundation is laid for the structural acousticoptimization of the compressor block.