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高于150公厘以上的汽轮机叶片,频率多在400周/秒以下。这些叶片在运行中,由于隔板在制造、安装和其他不可避免的原因,造成叶轮圆周的汽流不均(压力不等)。假如这不均的蒸汽压力有两处,汽机每转一转,对叶片扰动就有二次,如汽机转速为每秒50转时(3000转/分)则叶片扰动频率即100次。如果扰动的次数,与叶片动频率成倍数时,即产生共振而造成材料疲劳,使叶片断裂。为了防止共振,叶片的共振转速(临界转速)与汽机转子的工作转速,在倍数上必须有足够的安全率,这样才能确保叶片的安全,如图1
Turbine blades above 150 mm are frequent at frequencies below 400 wpm. During operation of these blades, due to the partition in the manufacture, installation and other unavoidable reasons, resulting in uneven steam flow around the impeller (pressure range). If this uneven steam pressure has two, the steam turbine rotates one revolution, there is secondary disturbance to the blade. For example, when the turbine speed is 50 revolutions per second (3000 revolutions per minute), the blade disturbance frequency is 100 times. If the number of perturbations, multiples of the dynamic frequency of the blade, that is, resonance and fatigue caused by the material, the blade rupture. In order to prevent resonance, the blade resonance speed (critical speed) and the working speed of the steam turbine rotor, in multiples must have sufficient safety rate, so as to ensure the safety of the blade, as shown in Figure 1