The Research On Flow Characteristics And Aerodynamic Optimization Of Marine Reversible Turbine

The gas turbine cannot be reversed directly,and the reversing operation of a ship requires additional power transfer equipment which is matched with the power turbine to achieve reversal of the shaft.The installation of power transmission equipment increases the size and weight of the power system and navigation resistance.In addition,power transmission equipment has the upper limit of power transmission,with taking a huge cost exceeding the upper limit.In order to make up for this defect,integrational double bypass reversible power turbine(including forward turbine in inner bypass and reversible turbine in outer bypass)came into being,which can reverse the rotation axis directly,reduce the astern radius and improve the maneuverability of ship.In the existing researches on the reversible turbine,the flow field of the reversible turbine stage is complex,with flow separation,and the turbine power and efficiency are low.In this paper,the flow field analysis and aerodynamic optimization design of marine reversible turbine are carried out.Firstly,structural parameters of the reversible turbine are studied in this paper.In view of its physical structure and aerodynamic parameters,flow characteristics and loss distribution are studied,and the main loss sources and loss distribution of turbine are obtained.The flow field and performance changes of reversible turbine with different cascade solidity are proved for the main losses.The results show that the cause of low power and efficiency of the reversible turbine is the very low solidity rotors,the ability to restrain airflow of cascade is weak;the flow separation occurs at the back of blade where the thickness is maximum;the development of the passage vortex and leakage vortex at the blade tip is promoted with the flow separation,which increases flow loss of the blade tip region and the downstream.Secondly,because of the large scale flow separation of rotor blades of the reversible turbine,the influence of changes in the thickness at the back of blades,blade bending angle and the stacking law on the performance of reversible turbine is studied.It is found that the backward movement of the maximum thickness location,the reduction of the maximum thickness and the increase of blade bend angle can improve turbine power and efficiency.Increasing the bend angle can reduce separation,which is the most effective for power improvement.On the basis of increasing the bend angle,optimizing the stacking rule of the blade can obviously inhibit the separation flow at the tip of the blade,and the power can be increased by 6.56%.At the same time,the application of large and small blades in rotor blade cascades is studied.The application of small blade can effectively increase the confining ability of cascades to airflow,make the separation which is not reattached weak;and the power and efficiency of the reversible turbine are significantly increased.On the basis of optimizing rotor blades,the influence of static blade space structure on the optimization of reversible turbine stage is studied.Based on the comparison and analysis,the influence of three stacking laws of stator blade inclination,bowed and swept on turbine performance is obtained.On this basis,the appropriate stator stacking scheme is selected to match the optimized rotor blade,and the optimal rotor and stator structure is obtained.The result shows that: influenced by the stator blade channel structure,the change of the total pressure loss and turbine performance is different when the same stacking law of stator blade is applied in the original turbine and optimized turbine;composite bowed and swept stator blade is suitable for the rotor blade with violent separation of the original turbine.The optimized turbine can reduce the total pressure loss of stator cascade and improve the efficiency of turbine without a large amount of bending adjustment of stator blades.The flow characteristics of the reversible turbine and the influence of blade structure on the performance of the reversible turbine stage are obtained in this paper,which can provide certain reference for the later research of marine reversible power turbine.