| Anti-surge of compressor is one of the key issues for compressor designers.Once the compressor surge occurs,the situation is relatively light,which will lead to a sharp deterioration of gas turbine characteristics.If serious,it will cause the flameout of the gas turbine or even the blade fracture,which will cause the whole gas turbine to suffer serious damage.Therefore,it is particularly important to broaden the stable operating range of compressors,delay the occurrence of unstable flow phenomena and prevent the emergence of compressor surge.By properly adjusting the angle of the adjustable stator blade of the compressor,stall or surge of the compressor can be prevented at off-design speed.Compared with the simple exhaust,the adjustable stator blade anti-surge has the advantages of enlarging the allowable power range of gas turbine,improving the economy of low operating conditions,improving the start-up acceleration performance of gas turbine and improving the working conditions of engine room.The key of anti-surge design of adjustable stator blades is how to find the optimal rotation angle law of multi-row rotatable stator blades with the change of rotational speed.Because of the large number of variables and degrees of freedom of the rotation angle law,the number of schemes arranged and combined is very large.If the method of three-dimensional numerical simulation of compressor or full-scale test is used for full-range search,the time and cost will be enormous.Therefore,it is necessary to develop a one-dimensional fast design method for multi-row rotatable stator blades.Therefore,this paper takes a low-pressure nine-stage axial compressor as the research object.Through the study of the stage-stacking method for calculating the aerodynamic characteristics of compressor rotating angle,the one-dimensional stage-stacking method is used to calculate the variable geometry under variable working conditions,and then several groups of satisfactory angle combinations under different working conditions are screened out,and the results of numerical simulation and one-dimensional calculation are compared.Finally,the combination of rotation angles can be found quickly to make surge margin and efficiency better.The main work is as follows:Firstly,the stage-stacking method for calculating the aerodynamic characteristics of compressor rotating angle is studied,and the relevant parameters,correlation curves and calculation formulas for stage-stacking calculation are determined.Then the stage-stacking calculation program is established by Excel.Secondly,a low-pressure nine-stage axial compressor is meshed by Numeca commercial software Autogrid5,and then the three-dimensional flow field is simulated by CFX commercial software.The data are extracted after post-processing,and then applied to the elementary stage to calculate by velocity triangle.The characteristic models of rotor blade and stator blade are established for the turning stage,and for the non-turning stage,the stage characteristic model is established.In order to improve the accuracy of calculation,the blocking coefficient and the correction of axial velocity,three-dimensional flow field simulation and average median diameter parameters are considered.Finally,the compressor characteristic curves at 6700r/min,6500r/min and 6000r/min rotational speeds are calculated by one-dimensional stage-stacking program.The results are compared with those of three-dimensional calculation,and the rotational angle laws at different rotational speeds with better surge margin and isentropic efficiency are obtained. |
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