某型燃气轮机压气机叶顶间隙优化设计

Optimization Design of Compressor Blade Tip Clearance of a Certain Type of Gas Turbine

减小燃气轮机基本负荷稳态下的叶顶间隙是提高机组效率的有效途径,然而过小的稳态设计间隙有可能导致瞬态过程叶顶与气缸之间发生碰磨,因此需要对瞬态工况间隙进行分析。对某型号小F燃气轮机整机进行了二维轴对称建模,获取瞬态过程金属温度,进而获得转子及缸体变形量。由于压气机叶片并非轴对称结构,其变形受结构三维特征影响,因此单独对压气机叶片变形量进行了三维计算,并在瞬态工况下对叶片变形量进行了模化。在二维坐标中对各部件瞬态变形量进行集成,获得压气机各级动叶叶顶瞬态间隙。分别对冷态启停工况、热态启停工况进行了计算分析,并与原型机组间隙数据进行对比分析,结果显示前2级最小间隙发生在降负荷阶段,后面级最小间隙则发生在热态启动工况。以恶劣工况下最小间隙不小于原型机为原则,得到了升级机组的冷态间隙优化设计结果。通过该瞬态间隙分析方法,可以对间隙的恶劣工况进行评估,优化机组间隙,保证机组安全性。

An effective way to improve the overall efficiency is to decrease the blade tip clearance of gas turbine under design condition.However,excessive small clearance may lead to friction between blade tip and the casing,so transient clearance analysis is necessary.Taking a certain small F class gas turbine as the research objective,the 2D whole engine symmetric model is established to get the transient metal temperature and the deformation of casing and rotor.Because the structure of compressor blade is not symmetric and the deformation is affected by 3D characteristics,the 3D deformation calculation of compressor blade is independently carried out,and the blade transient deformation is scaled.Furthermore,the deformation value is integrated in 2D coordinates,and the transient clearances of compressor blades in every stage are obtained.The conditions of cold startup-shutdown and hot restart are analyzed,and compared with the data of original unit,the results show that the smallest clearances of the first two stages are found under de-loading condition,while for the rear stages,the smallest clearance are found under the hot startup condition.With the principle that the smallest clearance should not be smaller than the original unit,the optimization design of the clearance under cold condition is obtained.With this analysis method of transient clearance,the assessment and optimization of clearance in bad condition can be carried out so as to ensure the unit safety.