Engine Indicators, Power, Tuning

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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fredrosse
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Engine Indicators, Power, Tuning

Post by fredrosse » Fri Aug 31, 2018 12:42 pm

These devices are instruments designed to make a record of engine cylinder pressure vs piston stroke, and that information allows determination of the work performed during the engine's stroke. Multiplying by the rate of strokes occurring over a standard period of time, then you have the rate of doing work per unit of time, in other words, the power, typically "horsepower" back in the day.

The "indicated Horsepower", derived from the instrument is actually more than the actual power, because there is engine friction in the rotating machine. If one applies a "Prony Brake", a device that measures actual power of an engine, one can determine the real engine output, stated as "Brake Horsepower". Hence the two typical abbreviation terms, IHP and BHP. In our typical engines, friction is around 10%, so if you have an indicator showing 10 IHP, you would find the actual engine crankshaft power at about 9 BHP.

Calculating the engine's power is according to the long established PLAN formula: IHP = P x L x A x N /33,000, where:
P is average differential pressure across the piston, Pounds Force per square inch. Should be a fraction of main steam pressure
L is the length of stroke, in feet
A is the area of the cylinder bore, in square inches
N is the number of power strokes per minute, depends on engine RPM, number of cylinders, if engine is single or double acting.
33,000 is the number of ft-LBf work that a draught horse can perform in one minute, according to James Watt

Early Engine indicators are elegant machines with clever mechanisms to record cylinder "Indicator Diagrams". Later versions were designed for typical IC engines, and had to be capable of much faster recordings. Today, virtually all commercial indicators are electronic devices.

Now for LEON to carry on this topic
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Re: Engine Indicators, Power, Tuning

Post by fredrosse » Fri Aug 31, 2018 1:06 pm

This Prony Brake was actually made to find the horsepower of a small uniflow steam engine. It worked very well, but several graduate engineers at a large firm specializing in power plant design, could not find any answer to the stated question!


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Last edited by fredrosse on Sun Sep 02, 2018 12:12 pm, edited 4 times in total.
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Re: Engine Indicators, Power, Tuning

Post by TriangleTom » Fri Aug 31, 2018 5:10 pm

fredrosse wrote:
Fri Aug 31, 2018 1:06 pm
This Prony Brake was actually made to find the horsepower of a small uniflow steam engine. It worked very well, but several graduate engineers at a large firm specializing in power plant design, could not find any answer to the stated question!
Alright, I'm intrigued. What's the question?
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Re: Engine Indicators, Power, Tuning

Post by RGSP » Fri Aug 31, 2018 8:01 pm

TriangleTom wrote:
Fri Aug 31, 2018 5:10 pm
fredrosse wrote:
Fri Aug 31, 2018 1:06 pm
This Prony Brake was actually made to find the horsepower of a small uniflow steam engine. It worked very well, but several graduate engineers at a large firm specializing in power plant design, could not find any answer to the stated question!
Alright, I'm intrigued. What's the question?
"..several graduate engineers at a large firm specializing in power plant design, could not find any answer to the stated question!"
Sounds perfectly normal to me: doesn't matter what the question is or was!
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Re: Engine Indicators, Power, Tuning

Post by TriangleTom » Fri Aug 31, 2018 8:32 pm

RGSP wrote:
Fri Aug 31, 2018 8:01 pm
TriangleTom wrote:
Fri Aug 31, 2018 5:10 pm
fredrosse wrote:
Fri Aug 31, 2018 1:06 pm
This Prony Brake was actually made to find the horsepower of a small uniflow steam engine. It worked very well, but several graduate engineers at a large firm specializing in power plant design, could not find any answer to the stated question!
Alright, I'm intrigued. What's the question?
"..several graduate engineers at a large firm specializing in power plant design, could not find any answer to the stated question!"
Sounds perfectly normal to me: doesn't matter what the question is or was!
A former job of mine involved working in a lab helping the grad students do research. I don't know what it was, but somehow these people were simultaneously very knowledgeable about very complex topics and entirely clueless on subjects that should be common sense, like why they couldn't hone a perfectly flat surface with an extremely rounded V-block.
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Re: Engine Indicators, Power, Tuning

Post by fredrosse » Fri Aug 31, 2018 9:33 pm

I still need to find out how to post a picture here, then the "unanswerable question" will be clear. At the time I was working within the plant staff analysis group of about 60 engineers, and yes, mostly PHDs with education far beyond mine, but many of them had never turned a wrench. I might add that I too could not find the answer here, even though I had made the Prony Brake, and had used it successfully to measure engine power. I would be very pleased if someone here could actually solve the problem.
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Re: Engine Indicators, Power, Tuning

Post by TriangleTom » Fri Aug 31, 2018 9:59 pm

What image hosting service are you using? I had good luck earlier today with Imgur.
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Re: Engine Indicators, Power, Tuning

Post by fredrosse » Fri Aug 31, 2018 10:47 pm

I have never used image hosting. For the last ten?years here I have always just posted a picture directly onto thesteamboatingforum.net
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Re: Engine Indicators, Power, Tuning

Post by fredrosse » Sun Sep 02, 2018 3:04 pm

Finally, I hope

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Re: Engine Indicators, Power, Tuning

Post by Lopez Mike » Sun Sep 02, 2018 3:39 pm

76.6 watts

Probably I made some bone headed error!
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