FORWARD CENTRIFUGAL FAN: made of high quality thick steel plate folding advantages: low cost, low speed, fine shaft and small bearings, wide operating range. DISADVANTAGES: The shape of the performance curve may be parallel to the pipe network resistance curve and the motor may overload when the system static voltage drops. In addition, the blade structure strength is low, can not run at high speed. Backward Tilt Centrifugal Fan: Made: casting advantages: high efficiency, no overload power curve. The power curve is usually maximized at the center of the General Range to avoid overload. Blades and impellers have high structural strength and can be used in high hydrostatic pressure systems. Low Noise, large air volume, wide efficiency area disadvantages: due to the impeller running speed, the need for large shaft and large bearings, balance requirements are also high static pressure fluctuations easily lead to changes in operating conditions. Where to apply: Comparison of ventilation, fire fighting, dust removal, smoke exhaust, backward tilting and forward tilting blades centrifugal fans in terms of efficiency, noise, power consumption and body size. 1. Efficiency 1 since the absolute velocity C transferred from the forward-inclined blade to the air flow is larger than that of the backward-inclined Blade, the kinetic energy of the air flow in the spiral of the frame is also very large due to the loss of the energy converted into pressure, so the proportion of the static presser that overcomes the resistance of the system is very small. Then, because the absolute velocity C of the inclined blade is small and the energy loss of the flow is small, the proportion of the static pressure to overcome the resistance of the system is large. 2 The groove of the backward-inclined Blade Fan is generally wider than that of the forward-inclined Blade, and the hydraulic loss of the air flow in the backward-inclined Blade groove is less than that of the forward-inclined blade because the curvature of the backward-inclined Blade is less than that of the forward-inclined Blade. In a word, the efficiency of the backward-blade blower is higher than that of the forward-blade blower. The common backward-blade and forward-blade blowers are shown in the table below. As can be seen from the table above, the efficiency of backward-blade fans is increased by 20-30% 2. Power Consumption 3. Axial power of fan can be expressed by the following formula 4. N Rqh / 1025. FORMULA: AXIAL POWER OF N 1 Fan 1Q fan capacity 2 h 1 fan pressure head 3 a Fan Efficiency 4 R air volume 5. From the above formula, the efficiency of blower directly affects the electric power of blower shaft. The tilting blade fan has high efficiency, small shaft power and low power consumption. The forward-inclined Blade Fan has low efficiency, large shaft power and large power consumption. 3. Noise 4. Because the absolute velocity C of the forward-inclined Blade to the airflow is larger than that of the backward-inclined blade, the energy loss of the airflow is also larger, and the velocity of the airflow colliding with the frame is also larger. In addition, the backward-sloping Blade groove curved slowly, the airflow is also smooth. As a result, the forward-blade fan is more noisy than the backward-blade fan. We usually use the product of the flow Coefficient q and the pressure coefficient h to measure the size of the fan. The Q * H of a fan with a forward-sloping blade is larger than that of a fan with a backward-sloping blade, so a fan with a forward-sloping blade is smaller than a fan with a backward-sloping blade. Several comments are made by analyzing the forward and backward tilting blades of the fan when selecting the fan. In addition to comparing the size of the main blower, equipment purchase costs, set up area and other initial investment, but also the efficiency of the blower, consumption of electricity and other operating and management costs for a more full understanding. Therefore, the following suggestions are put forward: 1. Type 4-72 Centrifugal fans are recommended for general ventilation and air conditioning systems. The Fan is a backward-inclined hollow airfoil blade with Max & GT; 91% maximum efficiency and low noise. 2. Boiler air supply system and water heater, heating furnace air supply system recommend G4-73 and Y4-73 type Centrifugal Fan, this fan is the fan of the back inclined airfoil blade, the highest efficiency of the Fan Max & GT; 90.5% . 3,3, if there is a need for high wind pressure system, the wind pressure requirement is greater than 800 mm water column, 8-18 Optional 9-27 Type forward-blade high pressure head Centrifugal Fan, although these two fans are inefficient, backward-blade Centrifugal fan still can not meet the high wind pressure requirements. In order to meet the technological requirements, only the forward-leaning blade blower can be selected.

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