Ultra supercritical boiler super-heat and re-heater heating surface life evaluation method

Abstract

The invention discloses an ultra supercritical boiler super-heater and re-heater heating surface life evaluation method. The method comprises the steps (1) a mathematic relation between a fatigue damage accumulation process and the crack growth rate is determined based on the circulation crack tip fatigue damage continuous accumulation process and the linear damage accumulation theory; (2) a polynomial is adopted for carrying out fitting on a da / dN-a curve, the maximum curvature point is obtained, the crack length a of a fatigue crack growth rate acceleration turning point is obtained, and the crack length a is the critical crack length; (3) after the crack length a of the turning point is determined, the ratio a / (S-a0) of the a to the difference (S-a0) between the heating surface pipeline wall thickness S and the initial crack length a0 is obtained, and then the fatigue crack growth service life loss of the heating surface pipeline on the actual running condition is a / (S-a0); the fatigue crack growth residual service life of the heating surface pipeline on the actual running condition is obtained by carrying out numerical integration between the turning point crack length a and the pipeline wall thickness S. According to the ultra supercritical boiler super-heater and re-heater heating surface life evaluation method, service life losses produced on any load and overload condition can be described, time and materials are saved, and the effective result is obtained.

Description

technical field [0001] The invention relates to a method for predicting the fatigue crack growth life of the super-reheater heating surface of an ultra-supercritical boiler under actual operating conditions. Background technique [0002] Ultra-supercritical boilers have become an inevitable trend in the development of thermal power units. With the improvement of steam parameters, more stringent requirements have been put forward for the heating surface tubes. The load of the power grid is erratic, which requires thermal power units to have greater flexibility. Therefore, in ultra-supercritical parameter units, peak-shaving operation has been widely concerned. During the peak-shaving operation, high parameters and rapid fluctuations of parameters cause great changes in the complex stress on the heating surface tube, which accelerates the crack growth until the heating surface tube leaks or bursts, which seriously affects the use of the heating surface tube life. [0003] Mo...

AI Technical Summary

Problems solved by technology

The disadvantage of these two models is that they cannot describe the complex behavior after overloading, such as acceleration and "delay delay" propagation behavior, and most fatigue crack growth models under variable amplitude loading need to introduce test fitting parameters to consider Influence of factors such as overload peak, stress ratio and loading history

This is not only time-consuming, loss of test equipment, consumption of a large amount of materials, etc., but also may not be able to obtain effective results during the test, such as fracture toughness

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