Fan Overview: Fan is one of the factories, Centrifugal Fan enterprises generally use one of the equipment, especially the fan application is more extensive. Boiler blast, smoke and dust, ventilation and cooling are inseparable from the fan, in power plants, mines, chemicals and environmental protection projects, Centrifugal Fan fans are indispensable important equipment, the correct control of the fan design, Centrifugal Fan to ensure the normal economic operation of the fan is very important.
Centrifugal fan design usually given the conditions are: volumetric flow, full pressure, working medium and its density (or working medium temperature), and sometimes structural requirements and special requirements.
The design requirements for centrifugal fans are mostly: to meet the required flow and pressure conditions should be in the vicinity of the highest efficiency point; the highest efficiency value should be as large as the efficiency curve flat; pressure curve stable working range to wide; fan structure is simple Easy to operate and easy to operate, easy to operate, easy to operate, easy to operate, easy to operate, easy to operate, Centrifugal Fan easy to operate, easy to operate, easy to operate, easy to operate, easy to operate , Easy disassembly and transportation.
However, at the same time to meet all the above requirements, it is generally impossible. There is also a contradiction between aerodynamic performance and structure (strength, craftsmanship), Centrifugal Fan usually by grasping the main contradictions. This requires designers to choose a reasonable design to address the main contradiction. E.g:
With the use of different fans, the requirements are not the same, Centrifugal Fan such as public buildings used in the fan is generally used for ventilation, the most important requirement is the low noise, multi-wing centrifugal fan with this feature; and require large flow Of the centrifugal fan is usually double suction type; for some high-pressure centrifugal fan, than the low speed, the relative proportion of its leakage loss is generally larger.
(1) reasonable choice of blade type: common fan at a certain speed, Centrifugal Fan the impeller pressure coefficient Ψt smaller, the impeller diameter larger, and its high efficiency; the opposite is the opposite of the impeller.
(2) fan drive mode selection: If the transmission mode is A, D, F three, the fan speed and motor speed the same; and B, C, E three are variable speed, Centrifugal Fan the design can be flexible to select the fan speed. General small fan widely used with the motor directly connected to the drive A, on the large fan, Centrifugal Fan and sometimes belt drive discomfort, and more to drive D, F drive.
On the high temperature, dusty conditions, the transmission method should also consider the motor, bearing protection and cooling problems.
(3) Spiral case size selection: volute size should be as small as possible. For the high than the number of wind turbines, can be used to shorten the scroll, Centrifugal Fan the lower than the number of wind turbines generally use the standard scroll. Sometimes in order to narrow the volute size, optional volute export speed is greater than the fan inlet speed program, this time using the export diffuser to improve its static pressure value.
(4) leaf exit angle selection: leaf exit angle is the design of the first to select one of the main geometric parameters. In order to facilitate the application, Centrifugal Fan we classified the leaves as follows: strong curved blade (pump type), curved curved blade, curved straight blade, posterior bending wing blade; radial exit blade, Centrifugal Fan radial straight blade; , Strong front curved blade (multi-winged). Table 1 lists the approximate range of the exit angles of the blades of the vane type in the centrifugal fan.
(5) the choice of the number of leaves: In the centrifugal fan, increasing the number of blades of the impeller can increase the theoretical pressure of the impeller, because it can reduce the relative vortex effect (ie, increase the K value). However, the increase in the number of blades will increase the friction loss of the impeller channel, which will reduce the actual pressure of the fan and increase the energy consumption. Thus, for each impeller, there is an optimal number of blades. Determine the number of leaves, sometimes based on the experience of the designer. According to China's current application, in Table 2 recommended the number of leaves the choice of range.
(6) Selection of full pressure coefficient Ψt: When designing a centrifugal fan, the actual pressure is always given in advance. At this time need to select the full pressure coefficient Ψt, Centrifugal Fan full voltage coefficient of the general selection range can refer to Table 3.
(7) Determination of the main geometrical dimensions of the impeller inlet and outlet: The main dimensions of the impeller are shown in Fig. Impeller is the only component of the fan's energy delivered to the gas, Centrifugal Fan so its design has a great influence on the fan; it can correctly determine the main structure of the impeller and play a key role in the performance parameters of the fan. Centrifugal Fan It contains the key technology of centrifugal fan design - the design of the blade. The key part of the design of the blade is how to determine the leaf exit angle β2A.