【Mechanical Equipment Technology Exchange Edition】Mechanical Equipment 【Daily Question】20191111
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Question: What factors determine the magnitude of fan loss? There are no answers provided for this series of posts; fellow netizens are free to share their own opinions – just reply with what you understand. Replies earn rewards ranging from 5 to 15 points; all forum members are welcome to participate actively and support the development of the forum! ! ! It’s Double 11 today – double rewards for replies on chemical equipment and machinery topics
1. The higher the blade, the greater the variation. 2. The average diameter cross-section exhibits the optimal value, whereas the parameters of other cross-sections along the blade height incur additional losses due to deviating from this optimal value.
The magnitude of the fan loss is inversely proportional to the square of the radius-to-height ratio (θ); the smaller θ is, the greater the fan loss.
The ratio to the radial height ratio θ is inversely proportional to the square of l, b
The magnitude of the fan loss is inversely proportional to the square of the radius-to-height ratio; the smaller this value (the longer the blade), the greater the fan loss.
Fan loss refers to the fact that, due to the blades being arranged in a circular pattern along the rim, the flow channel cross-section takes on a fan shape. Therefore, the pitch, circumferential velocity, and inlet angle vary at different positions along the leaf height, which causes the steam flow to strike the blades and result in energy loss. The steam flow also generates radial flow, further consuming its energy.
The magnitude of the radial flow loss and fan loss present in the axial clearance of a straight-blade stage, which results from a pressure gradient that increases from the inner diameter to the outer diameter due to deviations from optimal values such as pitch, circumferential speed, and inlet angle at sections other than the average diameter, is closely related to the radius-to-height ratio θ (and is inversely proportional to θ²). The smaller it is, the greater the fan loss. Generally, fan losses occur when θ is large (e.g., >8–12) and straight blades with a constant cross-section are used. Although using twisted blades is more difficult to manufacture, it eliminates fan losses.
Fan loss is related to the radius-to-height ratio. It is short; the larger it is, the greater the value. For example, when = l0, the value is 0.007, and when = 3, it is 0.078 – a difference of about 11 times. Generally, when >8~12, straight blades with a constant cross-section are used; although there is fan loss, they are easy to manufacture ； When
The magnitude of the fan loss is inversely proportional to the square of the radius-to-height ratio; the smaller the radius-to-height ratio, the greater the fan loss.
Fan-shaped loss refers to the phenomenon where, due to the radial arrangement of blades around the rim, the flow channel cross-section takes on a fan shape. As a result, the pitch, circumferential speed, and inlet angle vary throughout the height of the blade, which causes the steam flow to strike the blades and result in energy loss. Additionally, the steam flow generates radial movements that further consume its energy