The Leakage Mechanism Of Labyrinth Seal And Endwall Cooling With Combustor-turbine Leakage Gap Flow In Turbomachine

The inlet temperature of the nozzle guide vane in gas turbine is getting higher and higher,with the development of technology.That cause a higher efficiency of the gas turbine,at the same time,it also puts forward higher requirements for the cooling of the high temperature parts in the engine.Thus it’s very necessary to carry out the fine cooling design of the high temperature parts of the gas turbine,especially the nozzle guide vane that confront the high temperature gas from the exit of combustor.In this paper,we have studied the cooling effect of the slot leakage between the combustor and the blade platform.Generally the traditional role of this part of the gas is sealed to prevent the turbine internal structure of high temperature gas intrusion and its cooling effect has been neglected.The key point of this paper is to make full use of the slot leakage,that is to say,we try to maximize the cooling effect of the leakage,at the same time,to ensure the sealing effect.This will give more effective protection to the endwall of the nozzle guide vane.In order to find the effective control method for slot leakage flow,we have firstly analyzed the flow mechanism of the labyrinth seal.Labyrinth seal is a very common type of non-contact seal,and its sealing mechanism can be used as a reference for other non-contact sealing structures.In this paper,the leakage of the seal is measured by experiment,and the internal flow structure of the staggered labyrinth seal is simulated by numerical calculation.After comparing different throttle clearance,pressure ratio and rotational speed,two key factors which affect the sealing leakage performance are presented:effective flow area of the throttling process and pressure drop before and after the sealing clearance.The two factors are fully utilized in the study of the leakage distribution of the slot seal.In this paper,the flow structure of the leakage flow in the combustor-turbine slot is simulated,and the flow characteristics are analyzed.Slot leakage can be analogous to a special labyrinth seal leakage.Therefore it can be controlled on the basis of the flow mechanism of labyrinth seal leakage,and ultimately to improve the cooling effect of the endwall.We have applied thetwo factors mentioned above which affect the sealing leakage performance,and attempt several schemes such as part sealing fin,slot import and export step flow around,slot within the nozzle structure and adjustment of slot wide distribution,finally obtained an optimized slot structure which performs better on the endwall cooling than the original structure.After two times of adjustment to the slot width distribution,the new slot can effectively improve the endwall cooling effect on the front of the guide vane.Meanwhile,the optimized slot can make the leakage decreased by 12%,and saving the leakage of secondary air is conducive to improving the efficiency of the whole machine.