TAILIEUCHUNG - Wind Energy Management Part 6

Tham khảo tài liệu 'wind energy management part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 56 Wind Energy Management Aa I a Ị I Ap a9 Pl 9 ì AỚ L m 2sb J K L 9 1 - v ì 16 Herein am a9 dm PL9 E9 v Ap and A0 denote for mechanical and thermal correction factors for stress super-elevation at branches mean diameter mean wall thickness linear expansion coefficient Young s modulus Poisson s ratio and the range of pressure and temperature difference during load change respectively. Fig. 17 shows qualitatively the evaluation of the working stress during load change. The maximum number of load changes comparable to the actual one is generated from the Wohler-curve. The percentile fatigue of the actual load change is then 1 e 4-100 N 17 Fig. 17. Principle of evaluation of component stress for cyclic loading Levin et. al 1990 . This estimation leads to conservative results in order to handle the numerous uncertainties in calculation of working stresses at complex components and material properties. This method allows to benchmark different and possible future operation modes in terms of their level of deterioration to different components. In Fig. 18 is the fatigue of a warm start and several load changes plotted for the in- and outlet headers of the super- and reheaters. It should be stated that currently normal operation is between 50 and 100 load with a ramping rate of 2 per minute so the shown load change of higher then 60 as well as the load gradients of 4 per minute could be considered as an unconventional operation. These load changes corresponds to a possible future operation with a lowered minimum load of for instance 35 and a doubled load gradient. 57 Technical Framework Conditions to Integrate High Intermittent Renewable Energy Feed-in in Germany Fig. 18. Fatigue of heating surface in- and outlet headers for different base stress situations It could be obtained that the outlet header of super heater three and four are affected the most whereas the headers of the reheaters are not or low stressed. Furthermore it could be derived that conventional load .

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