An inspirator is a device, similar to a
venturi tube
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section (or choke) of a pipe. The Venturi effect is named after its discoverer, the 18th century Italian physicist, Giovanni Battista ...
and an
orifice plate An orifice plate is a device used for measuring flow rate, for reducing pressure or for restricting flow (in the latter two cases it is often called a ').
Description
An orifice plate is a thin plate with a hole in it, which is usually placed in ...
, which mixes a fuel gas with atmospheric air in a precise ratio to regulate burn characteristics. Only the pressure of the fuel gas is used to draw in and mix the air. They are the most simple and common type of mixing device for gas stoves and furnaces. Burners using an inspirator are considered to be naturally aspirated.
In an inspirator there are two tubes. The first is a fuel gas pipe with an
orifice
An orifice is any opening, mouth, hole or vent, as in a pipe, a plate, or a body
* Body orifice, any opening in the body of a human or animal
*Orifice plate, a restriction used to measure flow or to control pressure or flow, sometimes given specia ...
at the end where the gas comes out. Then in front of this there is another section of tubing with a larger diameter that the gas blows into. Usually (but not always) this second piece of tubing is tapered so that it starts getting narrower downstream from the orifice. Then, at a certain point, it stops getting narrower and either straightens out or starts getting larger again. This gives the fuel and air time to mix. The fuel/air ratio is determined by the ratio of the diameter of the orifice to the diameter of the mixing tube.
The US Government Technological Paper no. 193 describes "inspirators" as "Injecting tubes" when used for "injecting" air into the gas stream for pre-mixing the air and fuel for domestic and industrial gas burners. The experimental evidence provides an optimised "venturi" for developing the low-pressure zone to suck-in the maximum amount of air for a particular gas supply from a jet. The Venturi CSA is optimally 43% of the Burner CSA, and positions and lengths of tubes are described in the document. The "optimum" expansion beyond the venturi is at 2 degrees taper (4 degrees included angle).
This design of "Inspirator" can be seen in many domestic and industrial gas burners in use today.
Heating, ventilation, and air conditioning
Fluid dynamics
{{Unreferenced, date=December 2007