20-liter Combustion Sphere

Hazards Laboratory
Michigan Tech University
Room 209 Chemical Sciences

The 20-liter sphere shown in the walk-in hood. The two vacuum pumps at the bottom are used to evacuate the unit. The sphere opens in clam-shell fashion to enable cleaning. The solenoids to mix the gases, pressure transducers, and other equipment are also shown.
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The 20-liter sphere is used to characterize the flammable nature of gases. The gases are mixed in the chamber and then an igniter is activated. The pressure is recoreded as a function of time. The ignitor (shown below) consists of a 1-cm 40-gauge fuse wire igniter delivering about 10 J of energy.


The data from the 20-liter sphere includes the following:

These data can be used to determine flammability limits, flame speeds, and to size combustion vents.

The 20-liter sphere with the clam shell open. Not shown is a stirrer inside the chamber which mixes the gases prior to the test. Also not shown is the igniter assembly.
The igniter assembly. The assembly to the left includes a spark plug (to connect the igniter electrically with the outside world) and a quick disconnect fitting. The disconnect is a full through fitting enabling the igniter assembly to be removed and a new fuse wire installed quickly. The insert picture is a close up of the fuse wire.
The control panel for the apparatus. This provides manual override to the computer control functions. Under normal operation, the flammability sphere is under computer control. This includes vessel prep, gas mixing, and data collection / analysis.
This is a typical pressure-time plot obtained from the 20-liter sphere. This is used to determine the maximum pressure of combustion and the maximum rate of pressure rise. These are important parameters used to characterize the combustion.