Research Of Tuned And Mistuned Characteristics Of Bladed Disk

Turbine machinery is widely used in machinery manufacturing, gas separation, electricity, petrochemical and many other industries. Blade is one of the most important and most core part of the unit.The operating environment of blade is very harsh. As the blade bears alternating load including centrifugao load, air load, temperature load and other load, it can easily produce crack even fracture, so the dynamic characteristics analysis of blade has a great significance.In this paper, the finite element method was used to conduct modal analysis of a long blade in a certain type of industrial steam turbine. The influence of three kinds of boundary conditions, namely fixed support constraint,elastic support constraint and normal displacement constraint, on the frequency and vibration mode of the blade was analyzed. And resonance analysis of the blade was conducted by Campbell diagram. At the same time, the strength analysis of the first self-locking blades of a certain type of steam turbine was carried out. The results showed that the static strength fulfilled requirements.In view of the shortcomings of the Campbell diagram method commonly used in blade resonance analysis, this paper focused on the vibration safety evaluation method of steam turbine blade based on interference diagram. The basic principle and mapping method of interference diagram were introduced,and the vibration safety evaluation of the first stage blade of a certain steam turbine was conducted based on interference diagram.Ideally, the bladed disk is harmonic, but the actual blade structure is often mistuning. In this paper, the effects of stiffness random mistuning (mistuning strength 1%, 3% and 5%) and cracked blades (crack length 1mm, 3mm and 5mm) on the vibration characteristics of the bladed disk were studied. The results showed that stiffness mistuning and cracked blade can both lead to vibration localization; stiffness mistuning lead a large resonance frequency range of the bladed-disk, and the cracked blade had a slight effect on it; the vibration direction of the cracked blade was opposite to its adjacent blades.As the core part of large-scale rotating machinery, it is very important to monitor the vibration state of the blade. This paper introduces the vibration test scheme based on the existing equipment of the laboratory, the test scheme based on blade tip timing (BTT) was used, and the hardware system and the software system that needed for the experiment were introduced respectively. The equipment and the procedure were also described respetively.