Aerodynamic Design And Performance Research On The High-loaded Helium Compressor

In the situation of new energy and environment, helium-medium-based Brayton closedcycle heat engine is of great potential of application. It is applicable to high-security hightemperature gas cooled reactor (HTGR), relying on which the fuel thermal efficiency can beimproved significantly, while the system can be simplified greatly as well. HTGR heliumturbine is the key equipment, and the aerodynamic design of helium compressor is one of thedifficulties.Helium compressor as a function of traditional design guidelines reveals many problemssuch as low stage pressure ratios and excessive stages. Technical solutions for these problemsare to adopt the stage concept and method of the so-called high-loaded helium compressorwhich breaks the air conventions and meets the physical property of helium。The design concept of newly velocity triangle was put forward to design heliumcompressor which can fully display the physical properties of helium. In this paper294new-type cascades are simulated by the financial software NUMECA, function relationsamong inlet angle,loss coefficient and lag angle of result data are studied associatedly bycubic spline interpolation function. The results show that the diffusion factor associated withthe pressure loss is no longer applicable for the high-loaded cascade with negative outletangle. It is necessary to use new calculation method summaried from cascades simulation todesign high-loaded helium compressor.In order to increase the performance of the new cascade, optimization design is studiedon the cascade with bigger total pressure loss coefficient in the stage performance calculation.The Artificial Neural Network is used to build the approximate function which is based ondatabase sample space. The Genetic Algorithm is used to search a new design, and theArtificial Neural Network is reused to predict the aerodynamic performance of the new design.The mean camber line and thickness distribution are optimized respectively, and theoptimization results show that the total pressure loss coefficient can be reduced by14.48%than that of the primary.Performance of new stages is calculated with the method of total pressure losscoefficient and lag angle from cascades study. A kind of three-dimension stage was designed and simulated with CFD software based on the better elementary stage and the comparisonstudy on three-dimensional stage of conventional design criteria was also presented. Theresults show that high-loaded elementary stage radial stacking to three-dimensional stage isreasonable. At the same conditions, the stage pressure ratio of design point of high-levelthree-dimensional stage design is1.1388, which is more than twice that of the conventionaldesign and the efficiency still maintains a high level.Focusing on a design concept which frees from the conventional air work mediumdesign principle and aims at significant improvement of helium compressors’ stage loadingcapability, multi-stage aerodynamic design and numerical simulation are performed by usingthe cascade empirical data and incidence formulas and software gained from the preciousdevelopment of this kind of high-loaded helium compressor. Aerodynamic design andnumerical simulation iterative method are adopted here.Through numerical simulation by using CFD, the performance and the result ofthree-stage design are shown here: regarding the index parameters, the total pressure ratio ofthree stage design point reaches up to1.467with an average stage pressure ratio of1.136,wherein the stage pressure rario is more than two times of that of conventional design (usuallyranging1.05-1.06in conventional design). The efficiency of three-stage compressor is up to88.4%, which is equivalent to that of conventional design. The3D flow field of stage1issimilar to that of the single-stage3D flow field studied before, excepting some small vortex atthe tailing edge of blade convexity.3D flow fields of stage2and3perform extraordinary wellwithout any separation vortex or any similar signs even on the limiting streamline figure ofblade convexity adherence. Such far better result compared with stage1is out of theexpectation and can be ascribed to multi-stage design. As for the operation margin, numericalsimulation of three stage flow fields at flux of90%design point is carried out, showing a lightincrease of pressure ratio and a slight drop in efficiency. Moreover, the stability stage2and3remains the same and the overall performance is normal，and showing there is enoughcompressor surge margin--stable operating range.