The centrifugal fan is to rely on mechanical energy input, increase gas pressure gas side mechanical transmission, it is a slave fluid machine. Centrifugal fans are widely used in factories, ventilating mines, tunnels, cooling towers, vehicles, ships and buildings, dust emission and cooling; boiler and industrial furnace ventilation and the wind; air-conditioning equipment and household appliances and cooling equipment ventilation; grain drying and sending; wind tunnel source and inflatable hovercraft and propulsion. (1) Purpose 4-68 4-68 type centrifugal fan centrifugal fan can be used for general indoor ventilation factories and large buildings. Can be used to input gas, also be used to export gas. Gas transportation should not exceed 80 degrees in the air and the other is not spontaneous combustion, harmless, non-corrosive material for steel gas within the gas must not contain sticky substances contained in the dust and hard particles not more than 150 mg (2) in the form of 4-68 type centrifugal fan motor from one side elevational per cubic meter, the impeller rotates clockwise, called D-fan, to the right, said impeller rotates counterclockwise, then known as L fan, to the left, said. Export position of the fan to the cabinet said outlet angle. Machine number were made when the factory NO.2.8-6.3 a form, and use according to the requirements needed for the installation location of the outlet, without specify when ordering; machine number NO.8-12.5 outlet position adjustment range 0 degrees -225 degrees, the interval is 45 degrees, machine number NO16,20 of the outlet made of 0 degrees, 90 degrees, 180 degrees in three fixed positions, you can not adjust, need to specify when ordering. Fan drive way there are A, B, C, D-type four. NO2.8-5 with A-type transmission, NO6.3-12.5 using C, D type transmission, NO16,20 using B-type transmission. (3) the structural characteristics of the machine No. 4-68 to 4-68 centrifugal fan type fan NO2.8-5 mainly allocated by the impeller, housing, air inlet and other units directly connected electric motor, NO6.3-20 addition to the above There are portions of the outer portion of the transmission group. 1) Pour the impeller by 12 welded to the curved wing blade wheel cover in the middle of the plate-type wheel, steel plates were manufactured, and after static and dynamic balance, good air performance ,, high efficiency, smooth operation. 1) housing is welded with high-quality carbon steel plate snail shape. Enclosure made of two different forms, NO.2.8-12.5 chassis made whole, can not open, NO16,20 made two open chassis, along carve were divided into two halves, bolted. 2) made convergent inlet streamline the overall structure, mounted on the fan side, parallel to the axial cross-section shape of the curve, the gas can smoothly enter the impeller, and minor damage. 3) the transmission part of the spindle, bearing housing, bearings, pulleys or coupling components. (4) 4-68 type centrifugal fan performance and selection of the sample is given only No prototype dimensionless performance tables and performance curves, which can calculate the performance curve and the curve table above No10 fan dimensionless performance parameters. Fan performance generally refers to the performance of air transport in the standard state. When using a non-standard state of the state, it must be converted to the performance of the non-standard state to state performance standards, and then select the fan according to the conversion performance.