Copyright © 2012 by
"Neil Warbrick"
All Rights reserved
"Neil Warbrick"
All Rights reserved
ENTINEL
TEAM
AGGON
No. 5676
Built 1924
S
S
W
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Last updated.20/05/12
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Blast Nozzles
Spring 2008
Next to the design of the boiler and engine, the blast nozzle is one of the most important items that determine the efficient operation of the plant as a whole. A natural draught fire is one which will draw in the amount of air it requires to burn at its natural rate. If extra air is forced through the fire, forced draught, extra fuel can be made to burn more quickly, producing a fire that produces more heat. This is the same principle as a black-smith’s forge, with air being blown through the burning coals to make the fire burn more fiercely. A smaller fire can therefore be used to provide the same energy output compared with a natural draught fire. The blast nozzle is the device which turns our boiler from a natural to forced draught. It is mounted at the base of the chimney, in the combustion gas flow from the coal fire. Exhaust steam from the engine is passed through a narrowing pipe called a convergent nozzle or blast nozzle, and is directed up the chimney. The act of passing the steam through the blast nozzle increases its pressure and velocity. As it exits the nozzle the pressure and velocity drop. As the pressure falls, it creates a vacuum, drawing air through the fire to aid combustion.
The size of nozzle is critical to the efficient operation of both the boiler and engine. Too large a nozzle causes minimal exhaust back pressure on the engine, allowing full power to be produced, but does not create a large enough draught to make the fire burn fiercely, resulting in poor steam production. Conversely, too small a nozzle will create a large exhaust back pressure on the engine, reducing the power available, and can cause the fire to ‘lift’ off the grate, in extreme cases un-burnt coal can be ejected out the top of the chimney, a highly inefficient use of the stuff!
The old blast nozzle assembly had been repaired numerous times; life in the hot exhaust gas flow is not a happy one! It was adapted to test different nozzle sizes, prior to replacement. Different sizes between 1 ¼” and 7/8” have been tried. The most suitable for our operation has been found to be 1". This gives a maximum exhaust steam pressure of around 8PSI, similar to the quoted manufacturers figure. A new nozzle assembly, nozzles and tools for remote removal were made by Abercorn Engineering. This allows changing of the blast nozzle from the chimney top, without removal of the remainder of the assembly.
Spring 2008
Next to the design of the boiler and engine, the blast nozzle is one of the most important items that determine the efficient operation of the plant as a whole. A natural draught fire is one which will draw in the amount of air it requires to burn at its natural rate. If extra air is forced through the fire, forced draught, extra fuel can be made to burn more quickly, producing a fire that produces more heat. This is the same principle as a black-smith’s forge, with air being blown through the burning coals to make the fire burn more fiercely. A smaller fire can therefore be used to provide the same energy output compared with a natural draught fire. The blast nozzle is the device which turns our boiler from a natural to forced draught. It is mounted at the base of the chimney, in the combustion gas flow from the coal fire. Exhaust steam from the engine is passed through a narrowing pipe called a convergent nozzle or blast nozzle, and is directed up the chimney. The act of passing the steam through the blast nozzle increases its pressure and velocity. As it exits the nozzle the pressure and velocity drop. As the pressure falls, it creates a vacuum, drawing air through the fire to aid combustion.
The size of nozzle is critical to the efficient operation of both the boiler and engine. Too large a nozzle causes minimal exhaust back pressure on the engine, allowing full power to be produced, but does not create a large enough draught to make the fire burn fiercely, resulting in poor steam production. Conversely, too small a nozzle will create a large exhaust back pressure on the engine, reducing the power available, and can cause the fire to ‘lift’ off the grate, in extreme cases un-burnt coal can be ejected out the top of the chimney, a highly inefficient use of the stuff!
The old blast nozzle assembly had been repaired numerous times; life in the hot exhaust gas flow is not a happy one! It was adapted to test different nozzle sizes, prior to replacement. Different sizes between 1 ¼” and 7/8” have been tried. The most suitable for our operation has been found to be 1". This gives a maximum exhaust steam pressure of around 8PSI, similar to the quoted manufacturers figure. A new nozzle assembly, nozzles and tools for remote removal were made by Abercorn Engineering. This allows changing of the blast nozzle from the chimney top, without removal of the remainder of the assembly.
