Drum Muffler Design

[veggie]

Hi All,

Sketching up a drum muffler and thought I would get some input from the group.
Below is a picture of the proposed muffler.

- This would be located approx. 25 ft. from my GM90 listeroid or R190 Changfa.
- Located outdoors
- There will be a 15 ft. run of 2" flexible exhaust hose connecting the muffler to the indoor piping. Rest will be steel pipe.
- Muffler Inlet is 1.5" (exhaust port on the engine is 1.25")
- Muffler Outlet is 1.5"
- Insulation is 4" - 5" thick Roxul fireproof bat (I tested it with a blow torch.)  

Every one or two seasons the insulation can be thrown away.
One concern is condensation. Should I paint the bottom of the drum with something (??) and drill a few tiny holes in it.

Any suggestions or ideas welcome...

cheers,
veggie

PS: Click the picture to enlarge

[Lloyd]

Veg,

You might be better served by taking a section of concrete culvert buried in the ground. Then pour a concrete bottom in it, insulate the outside before back fill, then put about as many turns of copper inside that you can get=hydronic exhaust heat  recovery, and sound quieting.

Build a resonator out of a ss pipe in a pipe, and and exhaust port as your picture shows.

The steal drum will do just that drum the low htz noise, without a resonator. That insulation will have only a minor effect on the low htz noise. And the sulfuric acid from the combustion process, and wet stack will quickly eat the drum as fast as you can replace it.

If you could line the inside of the drum with lead sheet you mitigate the low htz noise.

lloyd

[veggie]

Hi Lloyd,

Trying to keep portability and ease of cleaning in the design.  
I don't have room to bury any concrete at this time. Although I do agreed it would be the best solution.
The flexible exhaust feed hose gives me the freedom to move it around.

Your point about resonation is well taken.
I was hoping that the high density Ruxol insulation would kill a lot of sound being that this insulation is also used for sound control.
Your lead sheet idea is a good one. Put it between the drum wall and the insulation.

Thanks for the comments,

veggie

[Tom Reed]

According to the Lister manual 2" pipe is needed for distances over 10'. I have a buried LP tank for mine with 13' of 2" pipe for the outlet and it is far from silent. Although it does sound nice outside, it is almost in audible inside. Sounds like a steam locomotive pulling a big load up hill. 

My thought is to concrete a drum in the ground, that way it will be a form for a concrete chamber and rust is no problem. Then fill the drum 1/2 way with 1.5" drain rock and just blow the exhaust at it as a baffle. If you're concerned about condensation just remove the bottom from the drum and set it on a bed of drain rock.

[SHIPCHIEF]

It will be quieter if the muffle inlet pipe enters the drum at a tangent so the exhaust swirls around the sides. The outlet pipe should be in the center like you depicted. It's called a cyclonic muffler, and they work very well.

[veggie]

Shipchief,

Thanks for the idea. I am currently building the muffler and will try to incorporate the swirl effect.
So far I have cleaned/painted the drum inside and out with rust inhibiting paint.
The inside surface will not be subjected to high heat because of the insulation, but it will see moisture.
I have also welded the threaded connector through the side wall of the drum.

veggie

[fabricator]

You should incorporate baffles between the inlet and the exhaust so the gasses can't take a direct route from inlet to outlet. If you could put a single baffle tight-ish to the sides to within about two inches of the bottom, it would make a big difference.
That is basically what mine is and it's quieter than a dryer vent outside.

[rbodell]

Hi All,

Sketching up a drum muffler and thought I would get some input from the group.
Below is a picture of the proposed muffler.

That is quite similar to mine except mine is a 30 gallon drum inside a 55 gallon drum surrounded by dirt and partially buried in the ground.

https://www.youtube.com/watch?v=v1ZJ8e3ihZg&list=UU_PjvlnZ0JNaqB73NZ2kiLQ&index=10

I removed the exhaust so you can hear it. It is 10 feet long and you probably couldn't hear it at all with it. The exhaust on the outlet side is PVC so that is how much it cools the exhaust. You can see it laying against the shed. You can see the wall of my house just barely peeking out beyond the shed in the right, The shd is just outside my bedroom and you can't hear it at all.