Shrinkfast 998, Operatin

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A. Principles Of Operation
The SHRINKFAST 998 introduces a signifi-
cantly improved jet pump based on using a
multiple nozzle orifice (patents pending). The
jet pump is shorter and more efficient with
the benefits of a wider and more powerful
heat pattern. Like the Model 975, it is basi-
cally a simple jet engine, the high energy
exhaust of which is used to pump and heat
the surrounding air and deliver an air blast
of high velocity and moderate temperature.
Its effectiveness is based on the high level
of technical development which has gone
into optimizing each stage of operation:
1. Jet Pump. The propane jet (A) draws the
correct amount of combustion air through
the air inlet (B). They mix together in the
straight section (C).
2. Compression. The conical section (D)
turns speed into pressure.
3. Combustion. The combustion process is
carried out inside the combustor (E). The
flame holder (F) prevents flashback (where
the flame travels back into the jet pump)
and the flame out (where the flame is blown
out of the combustor). Another proprietary
function of the flame holder is to achieve the
unusual effect of maintaining cold combus-
tor walls in spite of the fact that the com-
bustion is substantially completed inside the
combustor. This it does by imparting a swirl
to the mixture. During combustion, the
burned portion of the mixture expands, and
its density diminishes. The swirl centrifuges
the unburned, heavier portion outward and
thereby creating a blanket of cold mixture
along the walls. As combustion proceeds,
the process draws from the protective layer
of unburned mixture, and when combustion
is completed the cooling effect stops. The
size of the combustor ensures that for rated
flow the point of completion coincides with
the outlet. At less than rated flow, the blan-
ket of unburned mixture does not extend all
the way to the outlet and results in a red hot