猪舍风机为什么要安装喇叭口呢？答案在这里！

当你走进猪场时，通常会看到猪舍外墙挂着一排排的风机，整齐又壮观。仔细观察，你会发现，不同规格尺寸的风机都装有或白色或黑色的风机喇叭口。那么，为什么要给风机安装喇叭口呢？安装喇叭口又是如何影响风机的性能呢？大家一起来通过Hog Slat总部工程师的文章了解一下！

Take a look at any fan performance chart, and you'll notice adding a discharge cone to a fan increases its performance.  While almost everyone accepts this as fact, most of us don't know why it improves performance.

看看风机性能图表就会发现给风机增加一个喇叭口可以改善风机性能。尽管几乎所有人都知道这是个事实，然而大多数人却不知道是为什么。

The reason is air disturbance.

原因就是风机喇叭口可以阻断气流干扰。

The fast-moving air exiting the fan pushes against the static air outside the fan housing, causing it to swirl.The swirling air creates a disturbance at the blade tips, which effectively reduces the diameter of the fan causing it to move less air. Adding a discharge cone directs the exiting air along the cone wall, preventing it from being disrupted by the outside air, and allowing it to flow smoothly out the cone.

风机中快速流出的气流，推动风机外壳外的气流，引起气流旋转。旋转的气流会在叶片顶端造成干扰，缩小了风机叶片输送气流的直径范围，导致输送的气流量降低。给风机增加一个喇叭口让气流沿着喇叭口壁直接流出， 防止气流被外部空气阻断，保证其平稳输出。

Also, using a bell-shaped discharge cone, instead of a straight-wall design, permits the exiting air to expand. The air expansion reduces the backpressure against the fan, allowing for increased air movement. 

此外，采用钟型设计喇叭口而不是直壁设计，增加空气流出。空气扩散可以降低对风机叶片的反压力，改善空气流动。

Numerous references have established 7-degree slope as the most effective cone angle.Wider cone angles allow the airflow to separate from the cone walls resulting in the formation of turbulence. The standard length for a discharge cone is between one to one and a half times the diameter of the fan.  While there is some performance increase by lengthening the cone, this subjects the cones to increased damage from snow or high winds.

现在已有大量的文献表明7°斜率的喇叭口性能最好。喇叭口开口角越大，会导致气流从喇叭口壁分离，形成湍流。喇叭口的标准长度为叶片直径的1到1.5倍。延长喇叭口可以提高某方面的性能，但是这样也会使风机更容易受到雨雪或大风的损坏。

There has been no question on the benefits of adding cones to fans located inside facilities designed with positive pressure systems. The same performance increase occurs if the fans operate in a positive or negative system.

使用正压系统的猪舍，给风机增加喇叭口的好处是毫无疑问的。无论猪舍是使用正压系统或是负压系统，给风机增加喇叭口都能同样改善风机性能。

When selecting smaller fans for winter ventilation, adding a cone is not the best choice.  Instead, add a wind diverter to protect the fan from strong winds that decrease its delivery. 

冬季通风时，通常会选用较小型号的风机，这个时候给风机增加喇叭口并不是最佳选择。相反地，增加一个挡风装置保护风机可以使其不受强风天气的影响。

One downside to using discharge cones is increased maintenance from weather damage. It is not uncommon to see sections missing from multi-piece cones after heavy snowfall or strong winds.  The missing parts will decrease the benefits of using a cone.

使用喇叭口的缺点是因天气损害造成的维护工作增加。喇叭口上的部件在大雪或大风天气过后掉落是很常见的。部件一旦掉落则会降低使用喇叭口的好处。

When installing fans with cones, be sure and allow for the increased center spacing. The flair of the cone doesn’t permit the fans to be mounted as close together.  Also, be aware of the extra bracing required on a building end wall when installing a bank of tunnel fans.  Ice and snow can build up on the cones putting additional stress on the end wall.  Consult your building contractor for details.

当安装带有喇叭口的风机时，一定要考虑适当增加风机间距。钟型的喇叭口设计不适宜将风机安装太近。另外，在安装一排隧道风机时，要注意给山墙增加额外的支撑。冰和雪会堆积在喇叭口上，给山墙增加额外的压力。具体细节，可向您的猪舍建造承包商咨询。

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