A Blade Development

Development of the final stage moving blade of 38MW high temperature and high pressure steam turbine

The development of the final stage moving blade of 38MW high temperature and high pressure steam turbine includes blade design, flow field aerodynamic efficiency calculation and strength vibration calculation check. Through this solution, Beijing Steel Flow Electromagnetic Co., Ltd. designed 38MW final-length long-twisted blades to meet the thermal performance requirements and strength and vibration requirements based on the existing 30MW steam turbine final blades, thus expanding technology and experience of the development of customers' long-torsion blades. By applying the above-mentioned blades to the actual engineering project, the customer has fully realized the independent design, manufacture and service of the 38MW high temperature and high pressure steam turbine products.

Figure 1 Blade strength calibration by finite element model

 

Figure 2 Leaf radial projection of stationary and moving leaves

A blade profile refers to a 2D closed profile curve at a particular height. A key technique for the blade profile design approach is the development of the inscribed circle technique. The structure of the 2D leaf-shaped inscribed circle is shown in the figure below. After finding the inscribed circle of a closed curve, (i) the center line composed of the inscribed center and the distribution of the inscribed circle radius (thickness) along the center line are obtained. The inverse of the inscribed circle is to find the 2D closed line based on the known centerline and thickness distribution. It is worth noting that the way in which the inscribed circular decomposition line is not generally versatile is that the leaf thickness variation is sufficiently gentle. However, the inscribed circle technique is applicable to the leaf shape studied in this project.

Figure 3 Inscribed circle of moving leaf type Vibration characteristics

The figure below shows the vibration pattern of the 1600-step of the 38MW final stage moving blade. As shown in the figure, the first-order mode is a bending vibration, the second-order mode is a bending vibration with a first pitch line, and the third-order mode is a torsional vibration.

                                                   

 1-order mode                     2-order mode               3-order mode

                                           

4-order mode                              5-order mode                          6-order mode

Figure 4 Moving blade No. 1-6 mode

The figure below shows the blade Campbell diagram with the frequency avoidance zone. It can be seen from the figure that the V3 blade avoids the excitation zone region at the first three dynamic frequencies of 5000r/min and 5200r/min. As far as the calculation results are concerned, the frequency of the designed V4 blade is acceptable.