In China’s power industry system, many high-power units have been running for a long time, and there are deviations between heat consumption, cylinder efficiency and design values. Facing the challenge of new energy and new power plant, the traditional steam turbine technology is constantly developing. The new generation of steam turbine equipment should be reliable, large, efficient and low investment. It is more and more important to update and improve products.
The low pressure inner cylinder is one of the important parts of the steam turbine unit. The design of the low pressure inner cylinder will directly affect the safe and stable operation of the steam turbine unit, and has a very important impact on the efficiency of the steam turbine unit. Generally, the low pressure inner cylinder of high-power steam turbine is welded with steel plate. During the welding process, the LP inner cylinder will deform and cause steam leakage at the split plane. Moreover, the steel plates are welded together and the rigidity is poor. The steam flow in the low pressure steam inlet is from the top to the bottom, and the steam vortex is large and the loss is large; The outlet is not uniform, which is not conducive to the downstream flow. In this paper, the finite element method is used to analyze the strength sealing performance of welded low pressure inner cylinder. On the basis of previous work experience, the low pressure inner cylinder of a Supercritical 600 MW steam turbine unit is taken as the analysis object. The inner cylinder is cast in one piece ° The volute steam inlet structure can reduce the internal leakage loss of the contact surface of each part and sleeve, and improve the flow passage operation efficiency of the unit; At the same time, the self sealing cylinder structure technology is adopted to ensure that the low pressure inner cylinder has good rigidity and sealing performance.
It can be seen that the strain values of all positions meet the assessment requirements. Under the action of pressure, the higher limit pressure load factor leaves a large margin for the sudden situation. The low pressure inner cylinder shows obvious contact clearance on the horizontal split, which is very common in the design of low pressure inner cylinder. In Figure 4, the maximum gap is 1.31mm, which may leak from the steam inlet to the first chamber and from the first chamber to the second chamber. The most important thing is that there is no leakage from the inside to the outside of the low pressure inner cylinder. In order to improve the axial sealing performance of low pressure inner cylinder, the sealing key is installed on the horizontal split.
Calculation and analysis of critical 600 MW unit 360 ° The strength, sealing performance, deformation and displacement of the low pressure inner cylinder with volute inlet, and the limit pressure of the cylinder are analyzed. It is proved that the low pressure inner cylinder has good rigidity, strength and sealing, and can meet the safe and stable operation of the unit.