Research On Wide-Condition Aerodynamic Design And Optimization Of Variable Geometry Turbines

The operation of conventional naval ship gas turbine under design conditions only accounts for 1.4%of the total operation time of the year.Away from the design conditions,the performance parameters of the gas turbine will change and the fuel consumption rate will rise sharply.Therefore,in order to improve the matching relationship between the various components of the ship’s gas turbine to improve its wide operating conditions,variable geometry turbine technology came into being.At present,the domestic research on variable geometry turbine technology mainly focuses on the control method of flow loss in the end zone or the simulation of the performance of the whole machine,lacking the aerodynamic design method of wide operaing condition to support the variable geometry turbine’s design.Therefore,in order to realize the tactical indicators of the excellent performance of the new generation of naval ship gas turbines,it is of great significance to carry out research on the design and optimization of variable geometry turbines.Firstly,this paper takes the five different operating conditions of the four-stage power turbine as the reference basis.Research and construction of variable geometry turbine design conditions and design parameters in low-dimensional space.And for the variation of the internal flow and inter-stage aerodynamic parameters of the power turbine under multiple operating conditions,exploring the selection rules of flow parameters along the spanwise direction of variable geometry turbines are explored.Then the wide-operating condition modification design of the first stage of the original four-stage power turbine was carried out.The research points out that:When the 50%working condition is selected as the design point,the efficiency value fluctuates stably under multiple operating conditions;The load factor and flow coefficient should be selected as relatively small values,and the reaction degree is reversed;The change of the angle of attack is the main factor for the performance degradation of the turbine under low working conditions.When the working condition is low,the positive angle of the near-leaf root of the inlet of the moving blade is small,and the positive angle of the near-leaf is larger.The single-stage original variable geometry turbine(without clearance)of the modified design has improved the efficiency values under the five working conditions,and the highest efficiency is increased by 0.43%under the condition of 50%.Secondly,the adjustable design of guide vanes is carried out according to the original variable geometry turbine with modified design.The research points out that:Under the design of the large meridian expansion machine,the adjustment of the vanes will cause problems of protrusions and depressions on the suction side and the pressure side of the end of the drive shaft,respectively.For the loss of flow of the end of the adjustable vane drive shaft,the suction side is larger than the pressure side,and the groove is larger than the protrusion.Therefore,an adjustable guide design method for reducing the groove depth of the suction side of the drive shaft is proposed.The results show that compared with the adjustable design of the conventional vane,the efficiency of this method is basically unchanged when the vane is closed,and the efficiency is increased by 0.29%when the vane is opened.Finally,the characteristics of the variable design of the new design variable geometry turbine are analyzed.The flow and loss distribution inside the variable geometry turbine is explored,and then the variation rules of aerodynamic parameters and performance parameters are analyzed.The research points out that:When designing a variable geometry turbine in a wide working condition,attention should be paid to increasing the outlet airflow angle of the vane when the negative corner is rotated to reduce the positive angle when the working condition is low;When making adjustable design of guide vane,we should focus on the groove structure on the suction side of the end when guide vane opening is large and the tip clearance after the guide vane is closed.