| Roots pump is a double-rotor positive displacement pump,which possesses the following characteristics.It has a simple structure,less damageable parts,good dynamic balance,high speed operation,high volumetric efficiency,transportation medium oil-free,forced transportation among others.Attributable to its extensive applications,it is widely used in a lot of engineering perspectives such as electric power,smelting,petroleum,chemical industry and other fields of large pumping speed workplace.Also,due to its high speed work rate,it is commonly used as the core of the rescue vehicle suction power equipment.However,the design process of Roots pump presents some engineering challenges such as complicated rotor design and modeling process,large discharge pressure fluctuation and high noise.In view of the aforementioned problems,the main work of this thesis is structured as follows:(1)Firstly,parametric integration of commonly used rotor profiles based on Roots rotor profile equation through the use of MATLAB software is carried out.In order to enhance the speed and accuracy of rotor profile modeling and optimization,the traditional parameter equation is simplified into module calculation and the rotor engagement is analyzed.The output point file can be used in UG and other three-dimensional software for rapid rotor modeling.Based on Workbench platform,the modal analysis and critical speed calculation of Roots rotor are ascertained.(2)Secondly,the effects of rectangular groove and arc groove on the internal flow field of Roots Pump,especially on the outlet pressure fluctuation and flow rate,are investigated by using Pumplinx.The rectangular groove controls the angle and the thickness of the two parameters,whilst the arc groove regulates the coordinates of the key points of the Bézier curve.The findings reveal that the inlet flow pattern is not obviously improved by different reflow grooves,nonetheless,a reduction in the exhaust pressure pulsation,flow pulsation and exhaust swirl is evident.Meanwhile,the effect of rectangular groove on pressure and flow fluctuation is comparatively better relative to arc groove.Remarkably,the rectangular groove registered higher flow losses compared to the arc groove.(3)The advantages and disadvantages of Q Criterion and Omega Criterion in characterizing vortex structure of flow field in Roots pump are compared by Tecplot software.The results of this thesis can provide a basis for the study of Roots pump airflow pulsation,eddy current analysis and shell structure design optimization.In Roots pump,when using Omega criterion,it is better to obtain eddy current at 0.001,and this eddy current primarily emanate at the Rotor Edge and outlet section,where considerable number of large vortices decreases at the outlet side.Meanwhile,the small vortices increase at the recirculation trough,and these vortices are significantly enhanced as a whole.(4)The aerodynamic noise of Roots pump is analyzed by ACTRAN software.The aerodynamic noise of pipeline and the far-field radiation of aerodynamic noise are studied in detail and compared with the optimization model.It is observed that the aerodynamic noise of Roots pump depicts obvious dipole characteristics.The noise peak value is at the fundamental frequency and frequency doubling.The optimization effect of reflux groove on aerodynamic noise is comparatively better at the middle and high frequencies.(5)Finally,an experimental platform is set up to test the external characteristics of the Roots pump.The flow rate,exhaust temperature,intake pressure,shaft power,vibration and noise of the Roots pump are monitored.The numerical simulation of exhaust temperature and shaft power,theoretical calculation and experimental test data are compared and analyzed.It is worth noticing that the error range is relatively marginal,which confirms the accurateness of the numerical simulation.The noise and vibration data are collected and analyzed,and the influence of different vacuum on vibration intensity is compared under different rotational speeds. |
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