|
|
大家好，我是新来的。
叶片通过频率本质是压力脉动，就是流体的压缩与膨胀（就像弹簧的压缩与拉伸），传递方向就是流体运动的方向，就是流到哪里就传到哪里。
叶轮叶片与泵体导叶（或隔舌）之间的间隙是影响叶片通过频率幅值最重要的参数"gap B"。
下面一段摘自某离心泵外文资料
“The distance between the impeller blade trailing edges and the diffuser vane leading edges or the volute cutwater (“gap B”) is one of the most important design parameters for limiting the pressure pulsations generated at high circumferential speeds to an acceptable level and for avoiding fatigue fractures of diffusers, impellers, or other components. According to investigations in [10.1], pressure pulsations and unsteady stresses in the diffuser vanes are proportional to (d3/d2-1)^-0.77. Doubling gap B consequently reduces excitation forces by about 40%. Yet this is strictly true only if a given impeller is combined with different diffusers having different inlet diameters. Trimming the impeller for increasing gap B, increases the blade loading to the effect that the benefits of an enlarged gap B can be less than stipulated above. As a rule however, it can be justly assumed that impeller trimming will reduce pressure pulsations, especially in diffuser pumps. In rare cases an increase of gap B can even lead to higher pulsations, as demonstrated by measurements taken on a volute pump, [10.7]. This finding is explained by a more nonuniform flow distribution at the impeller outlet caused by higher vane loading and possibly by thicker blade trailing edges. Volute pumps are more prone to such abnormal behavior than diffuser pumps (since gap B is large, the relative gain through trimming in terms of (d3/d2-1)^-0.77 is small and the effect of increased blade loading may prevail).”
|
|
发表于 2014-7-1 09:08
提升卡
变色卡
显身卡
发表于 2014-7-1 14:36
楼主