The air system for the average oil burner is generally composed of the air shutter draft tube, the turbulator, and the fan. The draft tube and turbulator have already been shown
The fan construction consists of a (squirrel cage) series of vanes or blades mounted on the rim of a wheel. These vanes are slanted forward in such a manner as to provide the maximum discharge of air. Figure 1-36 shows the construction of a fan and flexible coupling.
The operating principles of the air system are fairly simple. The fan draws air into the fan housing and forces this air through the draft tube and turbulator and into the combustion chamber. The amount of incoming air can be regulated by adjusting the air shutter. As the air is forced through these vanes, it is given a swirling motion just before it strikes the oil spray. This motion provides a more thorough mixture of the oil and air, resulting in better combustion.
The shape of the turbulator varies in different models, but the purpose is the same: to thoroughly mix the air and oil spray. Figure 1-37 shows a double turbulator consisting of an air impeller and nose piece.