Regenerative fans move air without trapping it, using an impeller enclosed in a housing with a gap. They are efficient, compact, reliable, and produce low noise and vibration. They are used in various applications and require little maintenance, but need to be kept free of debris and not over-pressurized.
Regenerative fans are machines used to move air via a non positive displacement method. A positive displacement device would trap an amount of air and force it to move a certain distance in a certain direction. The method by which regenerative fans move air, however, allows air passing over an impeller blade to slip past. This air is moved forward by another blade.
The structure of a regenerative fan is relatively simple. It consists of an impeller with blades radiating from it. This impeller is enclosed in a housing with gap between the blade tips and the housing so that they do not make contact. Air flows into the fan through an inlet port and exits through an exhaust port.
To drive the fan, a motor or motor drives the impeller so that the blades rotate within the housing. The air blower draws air through the inlet and this air contacts a vane on the impeller as it enters. Contact with the moving blade accelerates the air, thereby moving it outward towards the housing. Pressurized air is discharged from the fan through an exhaust port, but not all of the air touched by a given blade leaves immediately.
A circular ring of space between the impeller blades and the housing allows air to flow past the first blade it contacts. Regenerative fans are sometimes referred to as ring compressors or ring blowers for this reason. This air falls to the base of the next blade. Contact with this second blade then re-accelerates this air in the same way as the first.
Many applications make use of regenerative blowers, from heavy industry to chemical and environmental processes. They can be used in operations such as packing, lifting and transporting products in a factory; dust and smoke removal; wastewater aeration; and soil vapor extraction. In general, regenerative fans are best suited for applications involving high air flows at low pressure or where vacuum is required.
Regenerative fans operate at high efficiency and are generally relatively compact in size for the large amount of air they move. They produce lower amounts of acoustic noise than many other types of blowers and generate little vibration as they operate with dynamically balanced impellers. Since the only moving part of each unit is the impeller, regenerative fans are highly reliable and have low wear. As a result, they require little maintenance or downtime.
The minimal clearance between the impeller and housing requires debris to be kept out of the fan for trouble free operation. Filtering the air before it enters the fan is a good way to keep the unit clean and the impeller moving freely. If the impeller and housing become blocked, the unit could be irreparably damaged.
Some regenerative fans rely on the airflow passing through them for cooling purposes. Over pressurizing the unit can cause the airflow to slow or stop, thus preventing necessary cooling. If a fan impeller heats up at a different rate than the housing, it may expand in size faster than the housing. Such a mismatch may result in the impeller being prevented from moving due to contact with the housing. This can also lead to a catastrophic failure.
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