A 600 mw unit induced draft fan vane crack reason analysis

Induced draft fan vanes of a 600 mw in 2019 - crack reason analysis 05 - 07 li wj ma szu-ts 'ung ( Hangzhou meaning can electric power technology co. , LTD. ) 1 overview of induced draft fan for a 600 mw unit is optimized to improve, but found in the maintenance, induced draft fan shell parts, bearing box of guide vane appear different degree of crack phenomenon, one piece of hollow guide vane ( A type of guide vane) Crack is along the direction of the blade body, as shown in figure 1, the rest of the guide vane crack are in along the flow direction of blade root, as shown in figure 2. For further analysis of crack reason, on the part of an induced draft fan of the different types of guide vane, the rotor static frequency test. The guide vane and dynamic Ye Jingpin test 2. 1 static frequency test on the first level of induced draft fan A part of the guide vane, the second part of the guide vane, the first part of the moving blade, A modal test on bearing box part of the guide vane. The first level of guide vane is divided into three kinds of blade, respectively, hollow short guide vane, guide vane, guide vane long; The second guide vane is divided into two kinds of leaf type, hollow guide vane, respectively, short guide vane; Bearing box type foliage for long guide vane. Guide vane is the first step on the scene graph is shown in figure 1, the second at the scene of the guide vane figure as shown in figure 2, the specific frequency static test data shown in table 1 to table 4. 2. 2 test and analysis through the table 1 and table 2, table 3 shows: the level of the guide vane on the shell length guide blade second-order, third-order static frequency of 145 hz, 221 ~ 228 hz, bearing guide blade second-order static frequency for 153. 8Hz。 After cutting the first level of dynamic Ye Jingpin not near 150 hz. Induced draft fan, driven by a motor speed of 990 r/min, run time, because of the unbalanced rotor will produce 1 x vibration components, namely, 16. The vibration of the 5 hz component; Induced draft fan for two levels of moving blade, all have 14 blades, per level turns there are 14 x vibration component, which is 231 hz. Unstable when the airflow in the fan, the fan vibration increases, the vibration of the fan and guide vane, moving blade, exist in the resonance frequency of the vibration of the component. As a result, the cause of the crack of induced draft fan vanes may: ( 1) Induced draft fan in the process of running on the guide vane under high alternating stress, and produce resonance phenomenon, long running under the crack phenomenon gradually. （ 2) Hollow guide vane due to welding, manufacturing technology, micro cracks exist, gradually expanded in the unit operation, other guide vane also has this problem. Three measures suggested that still need to make the following work: ( 1) According to the induced draft fan vanes Ye Jingpin test data, the first and second class guide vane of the measured natural frequencies and vibration frequency close to the main reason for analysis and calculation, and the flow field, fluid-structure interaction, such as the simulation calculation, and improvement measures are put forward. In view of the long and short vanes optimization scheme, digital analog calculation; （ 2) Support for the gas collecting box and casing on the high side, the divergent tube Angle is larger, etc to make design specification; Put forward to increase frame base ( Counter) , to reduce the chassis supporting height, structure strength calculation and scheme. In addition, in the operation of the various sets of induced draft fan vibration monitoring should be strengthened, when increasing vibration, vibration measurement and spectrum analysis in detail. ( Source: turbine supervision)