What does load variation affect?
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Why does the control valve for fan operation need to be adjusted when the load increases by several dozen cubic meters, and why does it need to be adjusted in the opposite direction when the load decreases? ? How can I not figure it out? ? With the load remaining unchanged and the induced draft air flow stationary, by increasing the blast air flow by 0.25, does this add more oxygen and thereby improve thermal efficiency?
When the control valve is opened wider, the pressure drop across the entire system decreases, the air volume delivered by the fan increases, and the total air pressure drops.
As the load increases, it is necessary to raise the temperature and increase the amount of fuel gas supplied. To ensure proper and complete combustion, it is also required to increase the air supply, that is, to activate the blower. With the load and induced draft unchanged, increasing the blower speed slows down the flow rate of flue gas accordingly, while the heat generated increases as well. However, strong ventilation increases the oxygen level in the furnace, which can lead to dew point corrosion.
The purpose of increasing the blast air and exhaust air flow is to maintain a certain oxygen level and negative pressure in the furnace. As the load increases, more gas is required; failing to increase the exhaust and blast air flow will result in too low an oxygen level in the furnace, causing the burners to go out. At the same time, the negative pressure in the furnace will decrease, and in severe cases, positive pressure may occur in the furnace. Therefore, it is necessary to increase the capacity of the blast and exhaust fans when the load rises. I hope this can help you
What does that mean? Does increasing the load not increase the gas content? Increasing the gas content necessarily requires using a blower to raise the oxygen level, but when the blower capacity is increased, the negative pressure is definitely affected; therefore, the exhaust fan needs to be adjusted. Of course, when the opening of the exhaust fans and blowers is large, the negative pressure may not necessarily change, but heat transfer is faster, and so is heat loss.