Research On Mechanism And Suppression Of The Gas Flow Noise From The Rotary Compressor

The rotary compressor used in air-conditioner and refrigerator has complicated structure and prominent gas flow noise. It is very important to identify the noise source, analyze the research method and suppress the radiated noise. The current research characteristics about the flow noise at home and abroad are detailedly analyzed, which shows that the important research methods, accurate prediction models and research results are all very few, moreover, the general control methods of the gas flow noise are also absent. The direct analysis for the whole machinery is very difficult so that it is very necessary to separately research on the different parts of the compressor, such as the the discharge valve, the discharge muffler, the discharge passage and the accumulator.Based on the current research conditions, some research methods are further analyzed, some new analytical models and methods are proposed. Combined with the acoustic characteristics of compressors, the noise mechanism and the angular domain of prominent noise level are studied through the theoretical analysis, prediction model and experimental methods. Finally the noise from the compressor is effectively suppressed. The research contents are as follows:Firstly the research meaning and characteristics of the gas flow noise are reviewed. The present advantages and disadvantages are both indicated and some questions needed to be solved are proposed.The computational result of the four-pole parameters is questionable due to the singularity of the point source model. Although the circular surface source model substitutes for the real acoustic source and avoids the singularity, the calculations for the four-pole matrix are complicated and the pressure responses on the sources are not uniform. Based on these problems, a circular line source model is firstly proposed, which avoids the complex computations and singularities of the point source model, moreover, the responses on the line sources are relatively uniform. Therefore this circular line source model could be utilized in engineering problems due to its convenience and practicality.The Ewald’s method, a method generally used in electromagnetism analysis, is introduced in the acoustic problems in order to improve the convergent speed of modal expansion method. The acoustic response formula with absorbent boundary condition is induced. The numerical examples show that the great superiority of Ewald’s method to the modal method. Based on the real compressor, the turbulent pressure pulsations inside the accumulator are computed and analyzed for the first time. The pressure amplitude of turbulence flow is apparently greater than that of the monopole source. The mechanism of the turbulent pressure pulsations is discussed and suppression methods are also put forward, which shows good improvement through computational and experimental results.Since there are obvious suction, compression and discharge process in the rotary compressor, the angular analysis is carried out for the first time, including the analysis of noise, vibration and pressure pulsation signals. From the single pulse and multi- pulse experiment methods, it can be seen that the overall noise mainly comes from the discharge process and further analysis is stated, which provides the theoretical proof for the noise the noise reduction.The pressure pulsation in the discharge cavity is predicted using the combination methods comprised of thermodynamic method, CFD method and experiment data. The differences between the computational and experimental results are analyzed and the pressure amplitude for different observation points is compared, based on which, the improvement method of discharge noise is proposed.The acoustic performance of discharge muffler is improved according to the angular analysis and the prediction of discharge pressure pulsations. The numerical calculations of transmission loss are validated through theoretical formula. One method advancing the transmission loss is concluded and some improvement projects are carried out. The numerical calculations and experimental results both show the good improvement effects.From the analysis above, the research of theoretical methods provides the conditions for the foundation of acoustic models and application of numerical methods. The numerical calculations, experimental analysis and improvement research of the real compressors are useful for the further explanation of mechanism of the gas flow noise, noise control and design of low noise compressor.