| Twin-screw compressors are widely used in chemical engineering,transportation,pharmaceutical,aviation and other industries owing to the advantages of simple construction,good dynamic balance,easy operation and maintainment.The advantages or disadvantages of rotor profile of twin-screw compressors have a decisive influence on the performance of the compressor,therefore,the research of twin-screw compressor with better performance and independent intellectual property rights and its rotor profile is of vital significance for promoting energy saving,emission reduction and green development in our country.The independent design of rotor profile of twin-screw compressors is taken as the starting point in this paper,the calculation methods of main performance parameters were studied,the number of segments and the types of composition of the third generation rotor profile(Fusheng profile,GHH profile,SRM-D profile,Hitachi profile and N profile)were introduced in detail.For the design of rotor profile with better performance and the convinence of subsequent programming of the design system,the weights of main performance parameters were assigned by combining subjective weighting method and objective weighting method,and the evaluation method of comprehensive performance of twin screw compressor was derived.By analyzing Analytic Hierarchy Process(AHP)and Superiority Chart in the subjective weighting method and Entropy method,CRITIC,Independence Weighting Method and Information Weighting method in the objective weight method,ultimately,the computational formula of single factor comprehensive performance was derived by AHP and Entropy method and the computational formula of multi-factor comprehensive performance was derived by AHP and CRITIC.Together with the computational formula of comprehensive performance derived by the research group in the early stage,through comparative analysis of these formulas,it was found that the accuracy of the computational formula of multi-factor comprehensive performance is higher,and conducive to the realization of programming.The tooth profile normal law was used to determine the computational formula of the rotor profile of each segment of Fusheng profile,and the NURBS curve theory was used in the segmentation fitting of Fusheng profile.Then the least square method was used to solve the control points of rotor profile,which is beneficial to the efficient design of rotor profile.By comparing several common unconstrained optimization methods,and combining the design process of rotor profile,the Univariate search technique was selected to carry out adaptive optimization of the control points of rotor profile combined with the formula of multi-factor comprehensive performance,it was found that the performance parameters of rotor profile were improved,and the superiority of this optimization method was proved.The analysis of computational fluid dynamics of five third generation rotor profiles was carried out,taking the Fusheng profile as an example,the distribution of flow,pressure,velocity and temperature were analyzed emphatically.The advantages and disadvantages of these five profiles were discussed,the influence of rotational speed on flow,pressure and temperature at the outlet of compressor were also explored.The CFD simulation was conducted on the adaptive optimized profile,the results showed that the outlet pressure of the compressor was improved obviously after optimization,which verified the reliability of the adaptive optimization method.The experimental platform was built to collect the pressure changes in real time,finally,the experimental results were in fine agreement with the simulation results obtained from the CFD calculation.At last,the forward design section of the self-developed profile system was optimized,the specific contents are as follows: The preservation of basic parameters of rotor profile(the number of teeth of female rotor and male rotor,torsion angle,center distance,length-diameter ratio,lead,etc.)was added to facilitate the check of basic parameters of rotor profile;The formula of multi-factor comprehensive performance was added,so as to facilitate the realization of adaptive optimization of subsequent control points;The function of modifying,deleting and saving of the coordinate value of the rotor profile control point was added,which is convenient to compare the comprehensive performance index of compressor before and after the modification of the control point.Based on Univariate search technique,the function of adaptive optimization of control points was added,the change trajectories of relevant control points were drawn and their final coordinates were saved in text format,which is convenient for the optimization design of rotor profile. |
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