Research On Rotor Meshing Line Of Twin-screw On NURBS Curve Segmentation Automatic Optimization

Twin-screw compressor is used in the industrial field on a large scale because of its unique performance advantages.It is found that the meshing rotor is its core component.In the design of twin-screw compressor,the excellent rotor directly improves the performance of the compressor,and the rotor design often starts from the profile.As the country puts forward its commitment to"carbon peak"by 2030 and strive to be"carbon neutral"by 2060,The design of compressor has higher requirements on energy consumption.It is very important to design rotor profile with excellent performance to reduce carbon emission.The rotor profile of twin-screw compressor was studied based on meshing line method（reverse design）,and the multi-factor comprehensive performance index was constructed to realize automatic optimization of meshing line and reverse design of rotor profile.First,take the oil injection compressor commonly used in the market as the research object,study its working principle in detail according to its structural characteristics,analyze the parameters that affect the rotor performance,lead the rotor profile design criteria on the basis of the performance parameters.The geometric characteristics of the screw rotor were studied,and the relationship between volumetric efficiency and performance parameters was deduced in detail.Because it is difficult to quantitatively and qualitatively judge the advantages and disadvantages of the designed meshing line in the design process,the fuzzy analytic hierarchy process（FCE-AHP）is proposed to establish the performance evaluation index of twin-screw compressor.The weight coefficient of each performance index is determined by using the analytic hierarchy process（AHP）,and the comprehensive performance evaluation method of multi factor fuzzy hierarchy is established;The comprehensive performance evaluation method of entropy method is established by using dimensionless data processing performance parameters.Taking a Fusheng meshing line fitted with 6 times as an example,the comprehensive scores of two comprehensive performance evaluation methods for each group of performance data are compared.It is found that the comprehensive performance index K obtained by the comprehensive performance evaluation method of multi factor fuzzy hierarchy conforms to the objective data law.At the same time,compared with the existing comprehensive performance index K₁ of the research group,it is found that K and K₁ have basically the same direction and change,but the former has a higher accuracy of weight.Therefore,the multi factor comprehensive performance index K is selected as the evaluation index of twin-screw compressor comprehensive performance.Using the reverse design（meshing line method）,the coordinate mapping relationship between the meshing line and the rotor profile is derived by graphical and analytical methods,and the design principles of the meshing line are summarized based on the typical profile and the meshing line.NURBS is introduced into the design of rotor meshing line.Based on the expression of its rational basis function,the geometric meaning of weight factor is analyzed in detail,and the solution method of NURBS curve guide vector is deduced.Based on interpolation method,the solution NURBS method of meshing line control points is deduced in detail,and the least square method is used to optimize the number of control points.It makes the adjustment of meshing line more convenient and accurate.After the pole is determined,the meshing line is segmented,and the specific meaning of each segment and the corresponding rotor profile are analyzed.Based on the unique advantages of control point area control,the segmented NURBS meshing line is adjusted,and the rules of the influence of each direction of the meshing line on the performance parameters are summarized.Within the scope of the meshing line design criteria,the adjustment limits of the optimal direction of the meshing line are deduced in detail.Taking a 6 times fitting Fusheng NURBS meshing line as an example,the optimization of each segment of the meshing line is adjusted,and the value of each performance parameter and multi factor performance index is calculated.Based on the multi factor comprehensive performance index K,the optimization degree of the meshing line is discussed.A rotor profile design system（TSPD）for automatic optimization of meshing line is developed.The whole system is designed based on the meshing line method.According to the design route,the composition of the typical line meshing line in the system is enriched,and special functions such as multi factor comprehensive performance index K,calculation of weight coefficient,reverse calculation of control points,display of addendum circle and pole in the meshing line design criteria are added;Based on the multi factor comprehensive performance index and the local control mechanism of the control point,the automatic optimization of the meshing line segment is realized to reverse design the rotor profile;Taking a Fusheng meshing line as an example,after the automatic optimization design in TSPD,the rotor profile is derived,a three-dimensional model is established,and the hydrodynamic analysis is carried out to verify the reliability and accuracy of the multi factor comprehensive performance index and the automatic optimization system of the meshing line.