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Combustion discussion

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Old 11-26-2007, 05:21 AM
Join Date: Apr 2006
Posts: 841
Default Combustion discussion

When the Howard yard built the Loretta Howard Captain Jim Howard ran into an unusual problem. He had set out to prove that simple high-pressure engines were more efficient, overall, than compounded engines. His claim was that the extra machinery, weight and maintenance cost more than the savings in fuel.
The boat was rigged with every efficiency device available including feedwater heater, condenser and economizer to preheat the combustion air. He set the cut-offs just-so, and made the bucket planks in the wheel with less dip to speed up the engines and thus reduce condensation within the cylinders. (The long, slow strokes of steamboat engines increased both torque AND condensation. They still do.) All steam and feedwater pipes were insulated. Snowden heaters were fitted to deliver the water in the boilers.
He ran paddlewheel tests in his bathtub using a float with several different wheel configurations and measured the energy needed to turn them with a postage scale versus an ammeter.

On the trial trip someone in the pilothouse noticed that the top four feet of the stacks were red-hot.

They hurried back to the yard and everybody aboard had a theory. When Captain Jim went to bed that night he could not sleep, so he mentally set out to examine those boilers from ashpit to stack tops. When he reached the fire doors he saw the problem, rolled over and went to sleep.
What did he see? They were using cannel coal, a very volatile fuel, used for generating household gas, among other things. In the morning he had them remove the fire doors and riddle them with 3/8" diameter holes to allow air to flow over the fire.
Those furnaces were generating hot gas that hadn't enough oxygen to ignite. When it reached the open air at the stack tops it ignited and burned there. The over-fire air consumed it in the furnace and the problem was solved.
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