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Web Gallery - Transportation |
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Liquid Fuels |
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Physical and Chemical Characteristics |
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| Liquid fuels
release their stored chemical energy by combustion. However, what
actually combust is the vapors from the fuel not the liquid it self.
A good fuel must ignite easily, burn well and not explosively, yield
a lot of heat, produce low smoke and ash, be inexpensive and easy to
store and transport. How well a liquid fuel meets these criteria is
determined by its physical and chemical characteristics. These include: |
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- flash point: lowest temperature at which a liquid can
vaporize to form an ignitable air-vapor mixture, lowest amount
of vapor necessary to ignite with an ignition source is applied,
useful in defining fire hazards of liquids, defines:
- flammable: flash point below 60.5oC 140.9oF)
or 37.8oC (100.0oF)
- combustible: flash point above 60.5oC 140.9oF)
or 37.8oC (100.0oF)
- fire point: temperature at which a fuel will continue to
burn for at least 5 seconds after ignition by an open flame,
below the fire point, evaporation of the liquid fuel is too slow
to maintain combustive conditions
- cloud point: temperature at which dissolved solids are not
completely soluble, precipitation of these solids gives the fuel
a cloudy appearance, results in clogging of filters and
injectors thereby degrading performance
- pour point: temperature at which a liquid becomes semi-solid
and loses its ability to flow
- viscosity:
measure of the resistance of a fluid to deform under stress,
i.e. its ability to flow, low viscosity fluids flow easily
whereas high viscosity fluids do not flow as freely
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The combination of
these variables determines a particular fuel's suitability for
different applications. For example, a fuel with low cloud and pour
points would be suitable for use in cold conditions. In contrast, a
fuel with a high fire point is inherently more safe to handle than
one with a low fire point. |
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Copyright @ 2010 J.D. Myers |
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