Fracture Fault Analysis of Low Pressure Last Stage Blade of Combined Cycle Steam Turbine Unit under Deep Peaking Regulation
Aiming at the fracture fault problem of low pressure last stage blade of a combined cycle tur-bine unit under deep peaking regulation,this paper analyzed the causes of blade fracture deeply through physical and chemical inspection and test analysis of blade material and crack fracture,combined with the characteristics of deep peaking operation of the unit,and gave relevant improvement suggestions.A-nalysis shows that because the deep peaking gas unit is in the special working condition of turning gear for a long time,the high turning speed setting causes the loose-fitting blade of the low pressure last stage to wear out at the root of the blade,causing the blade to loose.In the process of high-speed turning gear,the blades violently collide with each other,causing damage to the blade tip shroud and blade;the frac-ture occurs under the action of centrifugal force during the steam turbine startup,and the fracture debris falls between the last stage rotor blade and the stator blade,causing serious damage to the last stage blade of the whole circle.After the turning gear speed of the unit reduces from 50 r/min to 3 r/min,the last stage blade of the unit is in good condition,and no accidents of similar blade loosening or blade root wear have occurred.
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