Multi-incentive System Vibration Isolation And Noise Reduction Power Flow And Vibration-acoustic Energy Coulping Theory And Application

Multi-incentive systems, such as central air conditioning system and wind turbinesystem, are usually installed in the same space. Since the equipments'vibration energy ishuge and at the same time the structures become increasingly thin and light, vibration andnoise problems have become increasingly prominent. Based on a number of vibrationisolation and noise reduction engineering cases, large-scale heat pump unit systemvibration isolation model on the thin plate structure is chosen as research object. Vibrationtransfer path power flow characteristics of double-deck isolation system, double sourcesexciting and double output double-deck isolation system and single-deck isolation systemwith inertia block are analyzed by comprehensive use of four-end parameter method andmobility method. Vibration-acoustic energy coupling characteristics of sound fieldgenerated by civil thin plate vibration are studied and then analyze multi-incentivesystem's different machines excitation sources'contribution to the sound field. Applyvibration level difference and power flow transmission ratio to evaluate vibration isolationand noise reduction effect.Firstly, based on the vibration power flow isolation theory, mobility method, four-endparameter method and electricity-force analogy method, build vibration equipments'vibration isolation system models. By the heat pump unit's features and the actual situation,build double sources exciting and double output double-deck vibration isolation system,supporting pipe single-deck vibration isolation system,single source exciting and singleoutput double-deck vibration isolation system with middle mass and water pump'ssingle-deck vibration isolation system with middle mass. For the single source exciting andsingle output double-deck isolation system with middle mass, calculate and obtain curvesof the system's imported and transmitted power flow, machine and foundation speedamplitude, and identify the impact on vibration isolation effect when the vibration isolationsystem with little intermediate mass'path parameters change, such as machine mass, upper isolator stiffness, lower isolator damping and intermediate mass weight. Results show thatthe isolator damping has little effect on the vibration isolation efficiency. Second-orderresonance peak frequency can be changed by adjusting the isolator stiffness and theintermediate mass weight, and then avoid machine working frequency and improve thevibration isolation effect.Secondly, by solving the thin plate vibration differential equation and threedimensional rectangular space acoustic wave equation, knows that symmetric acousticmodes in the rectangular space are promoted when the thin plat vibrates with symmetricalmode. Vibration and acoustic are strong coupling. Simulate the vibration-acoustic couplingsound field generated by the thin plat vibration using the actual vibration data. Resultsshow that vibration-acoustic strong or weak coupling are no difference below 400Hzbecause of the damping of the floor structure. Above 400Hz vibration and acoustic arestrong coupling and simulating results are consistent with the actual measured sound fielddata.Thirdly, main equipments in the central air conditioning room as research projects,based on the vibration isolation models, calculate and obtain curves of the system'simported and transmitted power flow, machine and foundation speed amplitude andtransmitted forces to the foundation with the change of the path parameters. For the heatpump unit, increase the weight of the floating raft mass is the most effective method toreduce the transmitted power flow only if the vibration isolation space is enough. Thoughsmall stiffness of the isolator can reach the same result with the increasing weight of themass, it must assure machine's stable running when it starts. Pump mass can adjust theresonance peak position and reduce the transmitted power flow above the resonancefrequency, and lower the machine's gravitational center to ensure safe operation. Increasesurface density is an economic and practical method to reduce transmitted power flow.Fourthly, based on the actual measured vibration data, apply ANSYS finite elementanalysis software and Virtual Lab Acoustics acoustic simulation software to simulate thevibration-acoustic coupling sound field generated by the machines'vibration before andafter vibration isolation. Analyze the contribution of the heat pump vibration, the pumpvibration and the pipe vibration to the vibration-acoustic coupling sound field. Point outthe machines most important vibration isolation band. For heat pump's vibration energy isthe largest and its location is the nearest to the center of the foundation, so its contributionto the sound field is the whole band. Since the pump is installed near to the corner of the foundation and its vibration energy is much smaller than heat pump's, so it is difficult tostimulate low-frequency vibration. Contribution to the noise sound field is mainlyconcentrated above 300Hz. Though having many pipes'isolation fulcrums, the totalvibrational energy is concentrated below 200Hz and it is consistent with the noisespectrum characteristic.Finally, propose a reference of power flow transmission ratio to evaluate vibrationisolation and noise reduction effect. Draw vibration isolation and noise reduction system'scurves of speed vibration level difference and power flow transmission ratio, and comparewith the band noise reduction spectrogram, results show that power flow transmission ratiocurve is more consistent with the band noise reduction spectrogram, it can be used as anevaluation criteria for the judgment of the noise reduction effect.