| The turbine tip clearance flow is very complicated.The tip clearance loss accounts for about one-third of the aerodynamic loss,and the turbine efficiency decreases by 0.8%to 1.2%for each 1%increase in the relative ratio of the tip clearance to the leaf height.Therefore,reducing the tip clearance to reduce the leakage loss is an important means to improve the performance of the turbine.However,due to the mismatch between the thermal response rate and the radial deformation of the components in the transient condition,the friction between the rotor and the casing will collide,thus affecting the safety of the engine.run.Therefore,it is especially important to study the variation law of turbine tip clearance and conduct effective regulation research.Firstly,the existing turbine tip clearance variation prediction model can not effectively predict the tip clearance variation law when considering multiple loads at the same time.In this paper,the sub-models of the tip clearance variation prediction model are modified for the above problems.Then,using ANSYS Workbench to calculate the simulation platform,the gas-heat two-way coupling and the thermo-elastic unidirectional coupling are used to solve the flow field and structure field of each part of the turbine,and the three-dimensional gap numerical calculation model of the leaf,disk and casing is established.The research shows that the improved tip clearance variation prediction model is consistent with the simulation results of the three-dimensional gap numerical calculation model.The error is less than 5%,and the minimum value of the tip clearance is likely to occur near the 1.35 working condition.Secondly,this paper considers the effects of different loads,different gap heights and the actual uneven shape of the tip of the blade under variable working conditions,and studies the change of tip clearance and the thermal characteristics of the tip of the blade.The research shows that the temperature is the main factor causing the radial deformation of the leaves,discs and casings,accounting for 82.5%,77.5%and 99%of the total deformation respectively.The different gap heights of the turbine blades mainly affect the radial direction of the blades and the casing.The deformation has little effect on the deformation of the wheel;in the simplified form of the non-uniform gap,the leakage loss of the gradually expanding gap is the largest.Finally,in view of the transition condition,the variation law of turbine tip clearance is studied,and the characteristics of the disk’s thermal response lag are taken into account.The structural optimization of the disc’s sealing teeth is carried out to regulate the possible "danger points".The results show that under the condition of transient acceleration,the "danger point" appears at the moment when the 1.35 condition point is delayed by 0.35～0.5s.At the moment of 0.45～0.75 s after the deceleration in the transition deceleration condition,the tip clearance change curve shows a maximum point.On the premise of ensuring that the disc strength meets the design requirements,increasing the sealing teeth plays a certain role in reducing the risk of "danger points".In this paper,the results of different dimensions of the tip clearance model,the influence factors of the tip clearance change,the transition state of the transition state,and the regulation of the "danger point" can be used to study the transient state of the marine turbocharger and the aero-engine/gas turbine.Provide reference for the variation law and regulation of the lower tip of the turbine. |
