Optimization Of The Performance And Numerical Research On Internal Flow Field Of Roots Blower

Roots blowers were important industrial equipment, which have been widely used in each domain of the national economy. With the rapid development of economy, people have put forward higher requirement for the performance of Roots blower because the growing demand of market for Roots blower. Therefore, the study on how to improve further the performance of Roots blower was with an important significance for widening the application area and advancing the development of Roots blower. In order to further improve the performance of Roots blower and gain an intimate knowledge of practical situation of internal flow in Roots blower, some discussions and analyses were carried out on the above-mentioned problems and some analytical methods and practical conclusions were given, the results obtained in this paper have important meaning for increasing the volumetric efficiency, reducing the noise and exhaust temperature of Roots blower.The main research contents of this paper were listed as follow: optimized design for rotor profile and casing structure of Roots blower; analysis of the characteristic of air flow fluctuation in Roots blower; numerical analysis method of internal flow field in Roots blower; influence of rotor profile on the performance of Roots blower; numerical analysis of internal flow field in Roots blower with gradually expanding gap; analysis of performance of Roots blower with countercurrent cooling. Main research results were listed as follow:1. Based on CFD software FLUENT, RNG k-εturbulence model and PISO algorithm were adopted to simulate the inside flow field of Roots blower under the compressible and unsteady condition. The result of numerical simulation was contrasted with computing result of the theoretical analysis to validate the better accuracy and reliability of numerical analysis method. The results showed that the dynamic mesh techniques were used to simulate the flow field in Roots blower could reflect truly the distribution of internal turbulent flow and the characteristic of air flow fluctuation, and the method could provide a scientific basis for the analysis of the characteristic of the inner airflow of the Roots blower.2. By selecting circular arc rotor profile and involute rotor profile with same design parameters of three lobe Roots blower as samples to study the effect of rotor profile on the performance of Roots blower. Comparative analysis in circular arc rotor profile and involute rotor profile by the method of the theoretical analysis and the numerical analysis to study the advantages and shortcomings of two various rotor profiles. The results showed that the design of rotor profile played an important part in improvement of the performance of Roots blower. Compared with the circular arc rotor profile, the involute rotor profile has a higher area coefficient, a higher theoretical flow and a higher volumetric efficiency, but the noise would be increased.3. The numerical simulation on Roots blower with gradually expanding gap was conducted with FLUENT software in order to investigate the inside flow field under the compressible and unsteady condition, and it reflected truly the distribution of internal turbulent flow and the characteristic of air flow fluctuation. The numerical results showed that the optimization of the casing structure could indeed weaken and even avoid effectively the backflow eddy at the discharge outlet and reduce power aerodynamic noise.4. The characteristic of Roots blower with countercurrent cooling was analyzed by the method of the theoretical analysis and the numerical analysis to study the effect of countercurrent cooling technique on the performance of Roots blower. Based on the dynamic mesh techniques, the numerical simulation on three-lobe arc type Roots blower with countercurrent cooling was conducted with FLUENT software in order to investigate the inside flow field under the compressible and unsteady condition. The results showed that the countercurrent cooling technique played an important part in improvement of the performance of Roots blower, it not only reduced discharge temperature and increased exhaust pressure, but also avoided the backflow eddy at the discharge outlet and reduced power aerodynamic noise.