Patent RU-2721514-C1 (RU)
Inventor: Georgievskaya Evgeniya Viktorovna
IPC: G05B23/00
Filed: 2019-04-17
Granted: 2020-05-19
Abstract: FIELD: physics. 
     SUBSTANCE: in method for evaluation of residual life of hydraulic turbine impeller at beyond design time of operation, which includes obtaining analytical information, construction of design model, remaining life of hydraulic turbine impeller is determined based on individual prediction of development of cracks in actual operation conditions, obtained analytical information includes design documentation data and results of technical inspection of impeller condition during operation, including measurement of geometrical parameters on natural working of hydraulic turbine with account of size and position of detected defects and cavitation damages, thickness of elements of hydraulic turbine, especially impeller blades considering the thickness variation, radii of the glaze passages in the blade transition zone into the flange for the rotary-vane turbines and in the zone of the blade welding to the rim and the hub for radial-axial turbines, angle of installation of blades, distance in light between identical points of blades, as well as changes in geometric dimensions as a result of repair operations, design model is based on obtained analytical information and is digital double of impeller of hydraulic turbine, broken down into finite elements, conditional limit of fatigue of material   is determined with allowance for influence of water medium for N loading cycles in conditions of corrosive active medium by formula  
     
       
     
     where a, b are material characteristics, which depend on the number of loading cycles, for each operating mode, successively determining: - values of static and dynamic components of external loads, - stressed-deformed condition of hydraulic turbine impeller taking into account local stress concentration in zones of fillet junctions, threaded sections, as well as in fracture vertex, size and position of which are detected earlier, - material fatigue strength factors with due allowance for metallurgical defects and coefficients taking into account cycle asymmetry, - based on the found coefficient of fatigue strength of the material, damageability λ σ (i) is determined   as the ratio of the allowable value of the safety factor on fatigue strength of material to the corresponding design value, and total damageability λ σ  is determined as the sum of damages λ σ (i): 
       , 
     where i is the operating mode number, m is the total number of modes, then the limit state criterion is determined, wherein the resource depletion sign is the calculated total defectability value of the   maximum permissible value [λ σ ] = 1, coefficient of stress intensity in fracture vertex is determined by methods of linear fracture mechanics by numerical and analytical methods in conditions of actual operation, dependence of fracture growth rate on stress intensity factor magnitude is determined, wherein crack length calculation is carried out in accordance with known empirical Paris equation, determining lower and upper limits of impeller operation resource, where lower boundary corresponds to threshold value of crack length, which determines possibility of fast growth of cracks under effect of high-frequency loads of low amplitude, and upper - is determined by maximum allowable length of crack, corresponding to resource failure, as a result of remaining life of impeller of hydraulic turbine is determined in terms of length of cracks as difference of maximum permissible crack length and actually detected. 
     EFFECT: invention relates to the field of technical objects condition monitoring on the basis of periodic surveys, in particular, to the actual conditions and residual resource of hydraulic turbines impellers in operation conditions estimation. 
     6 cl, 2 dwg