Study On Thermal Parameters Model And Its Application In Scale And Erosion Fault Diagnosis Of Steam Turbine Blade

Flow path, through which steam passes and in which thermal energy in steam canbe converted into mechanical work, is one of the key parts of steam turbine, and is alsoone of the important and difficult points on condition monitoring and fault diagnosis ofthermal power plant. Compared with the traditional diagnosis method of vibration, thediagnosis method of thermal parameters has more advantages in diagnosing the faultsof flow path of steam turbine.Based on Flügel Formula, characteristic flow area(CFA), as an importantperformance index which represents flow capability of steam turbine stage group,whose definition, computational method and its application are studied in this paper.By calculating the parameters from different types of sets, it is found that CFA is aconstant for the same stage group when its geometric sizes remain unchangeable, andthis index can represent flow capability of steam turbine stage group. This articleanalyzes the causes of calculation result deviation of CFA which raise in HP stagegroups and the last stage group, and the compressibility factor and statistic regressivemethod are used to correct the calculation deviation of above stage groups respectively,the results of which can satisfy the demand for diagnosis.Ascertaining the basic value of diagnosis index is an important foundation workwhen CFA is used to diagnoses the faults of flow path of steam turbine. According tothe change regularity of CFA in every stage group, flow path of steam turbine isdevided into regulating stage,intermediate stage group and final stage, which areanalyzed by different methods to determine the exact basic value.On the basis of studying on causes and mechanism of blade scale and erosionfaults of steam turbine, the relationship between thickness of blade scale(deepness oferosion) and CFA is analyzed and the fault diagnosis model based on CFA for flowpath of steam turbine is built up. 600MW steam turbine set is chosen as applicationobject in this paper, whose data of two tests are analyzed.Through calculation data,thethird stage group is judged to scale, and diagnostic result is concordant with the actualsituation found in minor repair, which proves the correctness of diagnosis model.Finally, in order to monitor and diagnose running state of flow path of steamturbine promptly and accurately, 600MW fault diagnosis system on blade scale anderosion of steam turbine is developed based on Matlab development platform. This system can count out CFA and relative efficiency and analyze deviation in differentconditions automatically. Thereby, the actual running state of flow path can beevaluated , and which has guiding significance for production practice.