Research On The Influence Of Multi-Dimensional Aerodynamic Design Parameters On The Performance Of Wide-Operating-Range Turbines

Marine gas turbines are in off-design conditions for most of their life,and low conditions can lead to changes in turbine blade impulse angle,Mach number and other parameters,which in turn can cause flow separation and lead to a decrease in the efficiency of the whole machine.The existing research is mainly carried out by adjusting the two-dimensional blade design of the dynamic blades,and there is a lack of research on multi-dimensional turbine design and design laws at the overall level.Therefore,in order to achieve efficient operation of marine gas turbines at full operating conditions,research on turbine design methods for a wide range of operating conditions needs to be conducted from multiple dimensions.This paper firstly analyses the influence of one-dimensional design parameters on the performance of a wide operating range turbine in a more systematic way,starting from two onedimensional design parameters with turbine load factors of 1.4-1.7 and flow coefficients of0.55-0.75.The flow field and loss characteristics of the turbine at design and low operating conditions are analysed,revealing the intrinsic correlation between the load factor,flow coefficient and turbine efficiency,and proposing the selection and design guidelines for the load factor and flow coefficient in the one-dimensional design of a wide operating turbine.At the same time,based on the study of the performance of 2-4 stage turbines in wide working conditions,the results show that the variation of the angle of attack of the rear grille decreases after the rectification of the front grille,the variation law of turbine flow loss under different stages is obtained,and the principle of selecting the number of turbine stages is clarified.The turbine stage with higher load capacity is placed in the middle and rear section of the turbine to ensure efficient flow and stable efficiency of the turbine stage,which is responsible for the main power output at low operating conditions.Following this,the two-dimensional blade design parameters such as the static blade outlet geometry,static blade trailing edge wedge angle,dynamic blade inlet geometry and dynamic blade leading edge wedge angle are selected to match the turbine’s dynamic and static blades at wide operating conditions,and a comparative study of the turbine’s flow characteristics at design and low operating conditions with different design parameters is carried out.The influence of the change of static and dynamic blade parameters on the downstream blade row is clarified,and the selection and design guidelines of the two-dimensional blade parameters in the design of the wide working condition blade type are proposed.For the static blade twodimensional parameters,the blade folding angle increases,the dynamic blade flow separation point moves towards the suction side,the blade load-bearing maximum position moves towards the trailing edge,reducing the suction surface flow separation,and under 30% working conditions,the small trailing edge wedge angle static blade makes the next row of dynamic blade separation vortex amplitude reduced.For the two-dimensional parameters of the moving vane,at 30% operating conditions,an increase in the inlet airflow angle of the moving vane increases the separation vortex on the suction side of the moving vane and increases the entropy gain region at the back of the second stage static vane,resulting in increased losses.A large leading edge wedge angle will result in a slight increase in work capacity at the root and tip of the blade,but will result in a small increase in losses in the middle part of the blade.Finally,based on the analysis of the flow field of the design condition and the low condition three-stage turbine,and based on the obtained rules for the selection of turbine design parameters for a wide range of conditions,the optimized reshaping of the three-stage turbine’s column surface and cone surface was carried out,with emphasis on the influence of different ways of blade shaping on the turbine’s flow field characteristics.It was found that the angle of the axial projection of the tapered face adaptation makes the actual variation of the axial angle smaller than that of the cylindrical face adaptation,and it was concluded that the effect of the cylindrical face adaptation is better when the angle variation is the same.The multidimensional design methods for wide service turbines obtained in this study can provide relevant ideas and solutions for the basic aerodynamic design parameters selection and blade shape design optimization required for wide service operation of marine gas turbines.