Re: Horse power in the old steam engines

Posted by buickanddeere on August 22, 2005 at 16:15:43 from (216.183.130.41):

In Reply to: Horse power in the old steam engines posted by Charlie M on August 22, 2005 at 13:38:40:

There is engine HP and boiler HP.
HP is HP. 50 HP from an electric motor, piston steam engine, turbine steam engine, gas turbine, four stroke diesel Cummons, two stroke Detroit or a Deere two cylinder. If they max out at 50HP, then they can all do the same amount of work per hour.
The boiler is usually undersized with relation to the engine. If a good head of steam is built up then there is several seconds of power far beyond the boiler's continuous rated HP. Available to the engine.
There is the matter of engine efficiency. Additional steam per stroke above the normal spurt at TDC can be used. The extra steam still being added to the cylinder from the boiler as the piston is well down the bore. This does increase overall average cylinder pressure per cycle. Unfortunately the efficient use of steam declines. Not unlike over fueling a diesel engine. After a point, 50% more steam or fuel does not make 50% extra power.
When lugged down a piston steam engines torque is max at stall. Of course at that time HP is also zero but drawbar pull is at max. So they can pound along at a crawl hauling a massive overload.
The old steam engines and locomotives suffered very poor fuel efficiency. There is not enough room for a large enough 2nd stage cylinder or even a third stage cylinder or a turbine.
The boiler uses cold water from the storage tank rather than hot condensate. And that hot exhausted steam from the cylinders is just shot up the stack in order to make draft. It ideally would be preheating boiler feed water then condensed and used again.
The single cycle use of boiler water caused much boiler sludging and thermal inefficiency.

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