A method for evaluating the life of the heating surface of an ultra-supercritical boiler over-reheater

Abstract

A method for evaluating the life of the heating surface of an ultra-supercritical boiler over-reheater: (1) Based on the continuous accumulation process of fatigue damage at the tip of a cyclic crack, combined with the linear damage accumulation theory to establish the mathematical relationship between the fatigue damage accumulation process and the crack growth rate ; (2) Fitting the da / dN-a curve with a polynomial to obtain the crack length a at the turning point at which the fatigue crack growth rate is accelerated at the maximum curvature point, i.e. the critical crack length; (3) determining the crack length at the turning point After a, obtain the pipe wall thickness S and initial crack length a 0 Poor (S-a 0 ) ratio a / (S-a 0 ), and then obtain the life loss of the fatigue crack growth of the heating surface tube under the actual operating conditions as a / (S-a 0 ); through numerical integration between the crack length a at the turning point and the tube wall thickness S, the remaining life of the fatigue crack growth of the heating surface tube under actual operating conditions is obtained. The invention can describe life loss under various loads and overload conditions, saves time and materials and can obtain effective results.

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

Images