Author Topic: WW&F No. 9 - Official Work Thread  (Read 536495 times)

Bill Reidy

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Re: WW&F No. 9 - Official Work Thread
« Reply #840 on: November 28, 2023, 08:59:30 PM »
A photo of the new blast pipes as seen on a shop work bench this past Saturday.

What–me worry?

Jeff Schumaker

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Re: WW&F No. 9 - Official Work Thread
« Reply #841 on: November 29, 2023, 02:31:14 PM »
Wow! What do the blast pipes do?

Jeff
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Bill Piche

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Re: WW&F No. 9 - Official Work Thread
« Reply #842 on: November 29, 2023, 03:08:20 PM »
Wow! What do the blast pipes do?

Jeff

They focus the exhaust steam through the smokestack, which creates a vacuum in the smokebox that pulls the hot gasses from the firebox through the boiler.

My guess is that this nozzle design lessens the intensity of the exhaust blasts when working the engine hard. We all recall that 9 used to have a very sharp crack to the exhaust until a couple years ago when Jason and co cleaned out a whole bunch of carbonized oil from the old blast pipe. Even with that work 9 still pulls a very hard draft on the fire, which can cause boiler stresses when the firebed isn't perfect and allows cold air through to hit the tube sheet (the arch helps with keeping cold air off the tubes too).

I'll be interested to see how this work both lessens stress on the boiler and helps with smoke emissions. Smoke is just gas from the coal that didn't ignite on it's way through the boiler. The arch's main purposes are to protect the tubes from direct airflow and give gasses from the fire more time to combust before getting to the tubes.
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Jeff Schumaker

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Re: WW&F No. 9 - Official Work Thread
« Reply #843 on: November 30, 2023, 10:23:09 AM »
So the blasters cause a Venturi Effect?

Jeff
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Bill Piche

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Re: WW&F No. 9 - Official Work Thread
« Reply #844 on: November 30, 2023, 10:51:53 AM »
So the blasters cause a Venturi Effect?

Jeff
The venturi effect is how injectors work. That's a narrowing of a passage under pressure in order to increase the pressure\speed of the traveling fluid. By reducing the size of the pipe the fluid (in this case water) travels in, it increases the pressure to such a degree that it overcomes the resistance of any pressure at the end of it's travel. Think of like putting your thumb on a garden hose. What was originally a a bubbling flow is now a directed high pressure stream.

This is more that it's creating an area of low pressure in the smokebox by forcing the steam out through the stack. That action carries air with it, thus lowering the pressure in the smokebox. This is what's called an induced draft because it's downstream from the fire. Factories with steam boilers would get this draft from having giant smokestacks, the pressure difference from the top of the stack and the bottom would create a natural induced draft. Locomotives create a great deal more draft relative to the size of it's smokestack because of this exhaust.

Since the only source of air to replace that SHOULD be from under the fire (primary air), the induced draft pulls the air through first the fire, then the boiler. Assuming no dead spots or holes in the firebed, this makes the fire burn hotter from the additional oxygen being pulled through it.

Jason can better explain the fluid dynamics that take place between the exhaust nozzles and the stack.
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ALAIN DELASSUS

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Re: WW&F No. 9 - Official Work Thread
« Reply #845 on: November 30, 2023, 01:38:30 PM »
You rock guys.  The two improvements you just made are going to rise the efficiency of  #9 and save up coal . The brick arch will sure improve the combustion of the coal and protect the tube sheet  but it seems to me that it may also  help the occurence of tongues of fire when the throttle is suddenly shut down and the firebox door is open for some reason. As regards the double nozzle blast pipe it will sure improve the production of steam but it will rise the counter pressure on the piston at release time and will limit a bit the gain of efficiency. Without any doubt these  two modifications will change the way to stoke up #9.