Navitron Renewable Energy and Sustainability Forum

CHP (combined heat and power) => Internal Combustion (eg diesel/gas/petrol engine based systems) => Topic started by: bottleveg on May 19, 2010, 10:19:16 PM



Title: Silent Lister exhaust
Post by: bottleveg on May 19, 2010, 10:19:16 PM
In my quest to achieve a completely silent exhaust Im planning to build a breezeblock chimneystack 40 wide, 10 deep and probably 6 or 7 feet tall. The standard 2 Lister pipe would first go through a Lister cast iron damper and then enter the base of the chimney.
So far I can see two possible options: -
 I could construct a series of horizontal corridors that would be 5x 8 sq, so the gasses would travel along one corridor, turn a corner and travel along a second corridor, on the same level, before passing up into the same construction above. A square spiral, if there is such a thing?
The second option is to have a series of chambers, 5x 8x 12, one above another and the gas would pass through a 6 hole from one to another.
My thinking is that the first option would allow the gases to run out of energy before they reach the top. The second option would give continues expansion chambers.
What do you think? Anyone tried this sort of idea?
Digging a large sump in the ground is not really an option due to tree roots. If Im not 100% successful I still have the option of passing the gases several metres from the top of the chimney through soil pipe. But, as always money is limited so, at the moment, thought is cheaper than action.
My ultimate goal would be able to run the engine 24/7 but to do this I need it very quite.


Title: Re: Silent Lister exhaust
Post by: Justme on May 19, 2010, 10:27:06 PM
Make sure you allow for cleaning it.


Title: Re: Silent Lister exhaust
Post by: knighty on May 19, 2010, 10:31:04 PM
what about both ?

your square spiral, but with limited gap joining the 2, (6inch or whatever is recommended)

so the gasses still have to spiral around, but they also double up as expansion chambers ?



tho i think 6' might be a bit big for the joiners.... i'd use something the same size as the exhaust the engine has...


Title: Re: Silent Lister exhaust
Post by: Alan on May 19, 2010, 10:54:24 PM
If you base a typical fuel with 1% sulphur content and you allow any part of the flue system to run at less than 116 Deg C then sulphuric acid will condense in the flue.
The surrounding area will be affected by acid concentrations if the temperature at the exit is close to the dew point.
It will also condense every time you start the engine until the flue system at the flue exit point is hotter than 116 Deg C.

Regards

Alan


Title: Re: Silent Lister exhaust
Post by: welshboy on May 19, 2010, 11:06:50 PM
This is a link to how a gun silencer works- maybe of interest

http://www.google.co.uk/imgres?imgurl=http://www.freeinfosociety.com/science/pictures/Silencer3.gif&imgrefurl=http://www.freeinfosociety.com/science/silencer.html&usg=__oP5Ej2VGSTHobKiDiBulGrqQaro=&h=287&w=697&sz=11&hl=en&start=9&sig2=jMEzlh_8zKgvhu3TTmGjaQ&um=1&itbs=1&tbnid=Jh0bsFH46DeFYM:&tbnh=57&tbnw=139&prev=/images%3Fq%3Dgun%2Bsilencer%2Bdesign%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1&ei=FGD0S_SiJZOf_Aa2l5GADg (http://www.google.co.uk/imgres?imgurl=http://www.freeinfosociety.com/science/pictures/Silencer3.gif&imgrefurl=http://www.freeinfosociety.com/science/silencer.html&usg=__oP5Ej2VGSTHobKiDiBulGrqQaro=&h=287&w=697&sz=11&hl=en&start=9&sig2=jMEzlh_8zKgvhu3TTmGjaQ&um=1&itbs=1&tbnid=Jh0bsFH46DeFYM:&tbnh=57&tbnw=139&prev=/images%3Fq%3Dgun%2Bsilencer%2Bdesign%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1&ei=FGD0S_SiJZOf_Aa2l5GADg)


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 20, 2010, 01:55:15 AM
Guys, thanks for your input, and hello again Knighty.
Its getting late and my mind is shutting down. Ill read again tomorrow and ponder your ideas. Any more comments very welcome.
                   Mark.


Title: Re: Silent Lister exhaust
Post by: stephendv on May 20, 2010, 07:46:18 AM
Some underground versions here: http://www.navitron.org.uk/forum/index.php/topic,9775.0.html

I think you'd need to get more mass in the chimney walls to help with dampening, e.g. fill the breeze blocks with concrete.


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 20, 2010, 01:47:28 PM
Thanks for the ideas. I was thinking of using solid 4 breezeblocks but I could do a double thickness on the first two layers or build the first two layers with concrete blocks. My thinking on breeze is that it will absorb the sound where as it would probably bounce off concrete.


Title: Re: Silent Lister exhaust
Post by: stephendv on May 20, 2010, 02:25:58 PM
My gut feeling is that if the blocks are too light, they won't dampen the heavy bass thud of the lister, so I'd be inclined to use something with more mass, perhaps fill them with builders sand - so you get mass + absorption.  Or if you're going for a double wall, then you could leave a cavity between them and fill that with sand.


Title: Re: Silent Lister exhaust
Post by: noelsquibb on May 20, 2010, 10:29:56 PM
Oddly, one of the most effective silencers Ive come across was on an old WW2 Lister driven sawbench.
It was a just a length of scaffold tube, with nowt on the end.

Ok it wasn't silent but the mechanical noise far outdid it, in the noise stakes.

Conversations with friends regarding ways to quell the pop that big 4 stroke motorcycles make, had us thinking that while mass absorption is clearly a very effective approach, we considered how we might progressively slow the sound pulse by sending it through a set of parallel pipes of different lengths, so some of the sound pulse is slowed by skin drag on the pipe walls. Different lengths to cause differing amounts of drag with the total sound emitting at a more constant rate as a 'fooof' rather than a 'pop'

We have had some success but really need longer pipe options. Use of the bike frame has been considered.

We reckoned the 6m long scaffold tube might be ideal for skin friction and mass but a bit impractical for a bike.

Further confirmation of the effect the pipe has, is the difference in noise from my 1.9 Citroen diesel when the exhaust pipe separates from the silencer, compared to when the pipe separates from the front down pipe.

One is a nuisance and a bit fumy but drivable the other is ear shatteringly noisy.


Title: Re: Silent Lister exhaust
Post by: Amy on May 20, 2010, 10:40:05 PM
Hospital silencers as used on boats are pretty damn amazing. So named because they were first used for hospital generators so the noise didnt drive every one crazy


Title: Re: Silent Lister exhaust
Post by: rogeriko on May 21, 2010, 12:40:59 AM
Any pipe/chimney in the air is going to vibrate and make noise unless its made of tons of concrete the simplest is a shallow trench in the ground and a long pipe with lots of holes along it. The ground is to heavy to vibrate therefore no noise the exhaust gases will escape through the earth but silently just making little bubbles when it rains. The pipe from the engine can be soundproofed but it should run directly down into the ground. Engine mechanical noises can be eliminated by using silent type generator enclosures and then even building a second house around the generator.


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 10:02:18 AM
Hello Roger, thanks for your input. I was trying to avoid the underground situation, it would involve going across my better halfs garden, but I can see your point.
How deep in the ground would you suggest the pipe needs to be run and what size holes drilled in it? Holes just in the bottom and sides to avoid too much soil ingress? How would it terminate? If I head towards the house then I could go up the wall in the standard soil pipe arrangement and terminate just above the gutter line.
I would have about 10m underground, would this be enough? I could build a chamber half way if needed.
I was hoping to do this part of the operation only once. I wont be too popular if I dig up my partners garden and still get noise at the end of it!


Title: Re: Silent Lister exhaust
Post by: KenB on May 21, 2010, 11:18:57 AM
Bottleveg,

You will need a decent expansion chamber.  An old propane bottle, or 2 gallon fire extinguisher fitted with 2" pipe inlet and outlet is a good start.

Causing the exhaust gas to change direction through 180 degrees is a good way of losing some of the energy. This can be done by taking the inlet pipe down to the bottom of the propane bottle and having the outlet drawn from the top - cleverly done you will get 2 complete reversals of direction.

At the end of the day, the Lister 6/1 is only an engine. Get yourself down to Qwikfit and salvage some second hand car exhaust sections.

Next is the exhaust pit.  Dig an irregular shaped pit in the garden (no parallel sides), put some gravel in the bottom and line with high density concrete blocks. Arrange more blocks as baffles and a 2" thick paving slab over the top.  Use a 4" drain pipe to vent the exhaust skyward.  There was a thread a couple of years ago showing how Frotter constructed his "pit of doom".

Make sure that all sections of the exhaust system slope away from the engine to avoid condensation traps - gurgle gurgle is bad news.



Ken



Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 12:15:18 PM
 Hello Ken,
      Thanks for your input. I believe you have a lot of experience with these matters.
 I already have a cast iron Lister damper on the engine and that works quite well. My ultimate goal is to be able to run my 8/1 through the night, so thats why Im looking for extra silencing measures.
My thinking now is to run a buried soil pipe, with holes drilled in, build an exhaust pit, as you describe, and then another pipe from that to connect on to a conventional soil stack. Total underground pipe would be 10m.
How deep do you think my pipe should be and what size for the pit?
Ill do a search and see if I can find this pit of doom
                             Thanks for your help, Mark


Title: Re: Silent Lister exhaust
Post by: KenB on May 21, 2010, 12:42:02 PM
Mark,

If you are going to run any pipe 10m - make sure that it is at least 3" diameter - so as to avoid excessive back pressure. 

If you can dump the heat with an exhaust gas heat exchanger, (water cooled copper tube around the cast iron damper - suitably insulated with fibreglass) you could probably run a length of 76mm black plastic drainpipe down the centre of a length of 110mm soil pipe,  this would give you a reversal, plus additional expansion, plus the benefit of a buried pipe and the sound deadening properties of being underground.

You would probably want to tune the length of the exhaust so that is is not a wavelength multiple of the 850rpm (or whatever rpm) you are running the engine at.

I don't think perforating the outer pipe will help. You don't really want the exhaust byproducts leaching into the soil.

Run it under the vegetable plot and warm the soil!



Ken



Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 01:47:13 PM
Some underground versions here: http://www.navitron.org.uk/forum/index.php/topic,9775.0.html

I think you'd need to get more mass in the chimney walls to help with dampening, e.g. fill the breeze blocks with concrete.

Thanks for that link Stephen.


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 01:59:56 PM
Mark,

If you are going to run any pipe 10m - make sure that it is at least 3" diameter - so as to avoid excessive back pressure. 

If you can dump the heat with an exhaust gas heat exchanger, (water cooled copper tube around the cast iron damper - suitably insulated with fibreglass) you could probably run a length of 76mm black plastic drainpipe down the centre of a length of 110mm soil pipe,  this would give you a reversal, plus additional expansion, plus the benefit of a buried pipe and the sound deadening properties of being underground.

You would probably want to tune the length of the exhaust so that is is not a wavelength multiple of the 850rpm (or whatever rpm) you are running the engine at.

I don't think perforating the outer pipe will help. You don't really want the exhaust byproducts leaching into the soil.

Run it under the vegetable plot and warm the soil!



Ken



 I was thinking 4 underground pipe and then 4 soil up the house wall and a birdcage on top.
Yes max. Revs. Is 850rpm. What do you mean by tuning a length of exhaust?
The cast iron damper only gets warm but the pipe going in and out gets hot. I could run 15mm copper around that and gravity feed into the water tank.


Title: Re: Silent Lister exhaust
Post by: jotec on May 21, 2010, 06:51:59 PM
I like Kens idea.
I might try that myself on my engine. I am sure we could fix up a heat extractor on yours after if goes through the wall so that plastic pipe can be used. If using plastic it is easy to start long and cut bits of to quieten it down, go to far and add a joiner.
D ick


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 07:26:43 PM
Hi D ick, I have tried 4 plastic on the end of the exhaust and it seems ok. I was thinking of wrapping annealed 15mm copper pipe around the exhaust before it goes into the damper.
How about this pipe-
http://www.drainageonline.co.uk/Land-Drainage/100mm-Perforated-Land-Drainage.htm
I was wondering if the corrugations would absorb more energy than smooth solid pipe. I guess it wont be so good with heat?


Title: Re: Silent Lister exhaust
Post by: noelsquibb on May 21, 2010, 08:23:57 PM
I'm using the corrugated perforated underground plastic silencer for my 4.5 kva diesel genny and its not anything like as quiet as Frots pit 'o doom but I reckon his little Kubota twin starts off a whole lot quieter than my Petter single.

The silencer pipe is about 9" deep and covered in gravel and it was already there, pretending to be a land drain.

When I first tried it, the covering gravel jumped up and down and a fair amount of noise was audible from the junction area. I shut it up a bit more with some conveyor belting and more gravel in this area.

Theres a manhole about 30m down the drain line and when I popped the lid and stuck my head in ( like you do ) there was no audible noise from the incoming pipe, even with the genny running.

Having burnt myself on the far end of bits of scaffold tube that Ive stuck over the silencer outlet in the past, I'm not convinced that the perforated corrugated land drain wont melt in the junction area but I have a length of steel pipe at the ready.  I know that BT duct goes soggy at 100c ..........

Then theres the foul sewer drainage system.
Usually nice and deep and any smells would be taken care of, with the mercury and cadmium deposits in the exhaust particulate blending in with the mercury and cadmium deposits of eeerrr ....

And you could watch the water in the bog pan to see if the genny was running.



Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 09:27:39 PM
I'm using the corrugated perforated underground plastic silencer for my 4.5 kva diesel genny and its not anything like as quiet as Frots pit 'o doom but I reckon his little Kubota twin starts off a whole lot quieter than my Petter single.

The silencer pipe is about 9" deep and covered in gravel and it was already there, pretending to be a land drain.

When I first tried it, the covering gravel jumped up and down and a fair amount of noise was audible from the junction area. I shut it up a bit more with some conveyor belting and more gravel in this area.

Theres a manhole about 30m down the drain line and when I popped the lid and stuck my head in ( like you do ) there was no audible noise from the incoming pipe, even with the genny running.

Having burnt myself on the far end of bits of scaffold tube that Ive stuck over the silencer outlet in the past, I'm not convinced that the perforated corrugated land drain wont melt in the junction area but I have a length of steel pipe at the ready.  I know that BT duct goes soggy at 100c ..........

Then theres the foul sewer drainage system.
Usually nice and deep and any smells would be taken care of, with the mercury and cadmium deposits in the exhaust particulate blending in with the mercury and cadmium deposits of eeerrr ....

And you could watch the water in the bog pan to see if the genny was running.



Well, funny you should mention a manhole-
I have manhole right where my exhaust exits the engine house. Ive run the exhaust though a series of breezeblock ducts and then in to the top of the manhole. The result was mega quite. I did get some transmission through the clay pipe to the downstairs loo (4m run), so I could hear the engine in the loo but not when I went outside, and a slight shimmer on the water. I couldnt hear any noise and no fume when I removed the trap on the sink. Water vapour could be seen rising from the top of the soil pipe, like when the shower is running on a cold day.
My concern was that I might send fumes into my neighbours property; I know this shouldnt happen if all is fixed, as it should be. I cant decide if the fume would sink in the sewer or rise. I think the gases are heavier than air.
The manhole is fairly large so I could construct another series of baffles inside and maybe remove the noise transmission. This would be my preferred design, as I know it works.


Title: Re: Silent Lister exhaust
Post by: noelsquibb on May 21, 2010, 10:41:46 PM
Quote
Well, funny you should mention a manhole-

Yeah, ready made 'n gagging to be filled with noise and fume  whistle

I reckon you should be ok, as all houses should have a high level soil vent pipe ( SVP) at the top end of their system and all connections into a foul drainage system will have a waterseal to ensure no stinky gases can enter the dwelling.

Methane is sometimes generated in sewers and is a heavy gas and carbon dioxide is a regular feature too. Hence the need for gas detectors for these gases ( plus oxygen levels ) as a minimum, for working in a foul manhole.

As your local sewage treatment plant gets a fair amount of what you are putting in by way of unburnt fuel and particulates, you are not really creating a new hazard. Dunno how it might effect the bugs in a digester / septic tank if you had a private sewage disposal system though. They like a bit of oxygen .......

I do have a bit of visible fume hanging around the exit of my land drain, a distance of approx 80m away, so the smoke is pushed along rather than venting through the perforations and up through the gravel.

Its going to have to be ever so quiet if you have neighbours though.
Unless they move cos of the strange smells ......


Title: Re: Silent Lister exhaust
Post by: insolare on May 21, 2010, 10:52:24 PM
I just shuddered at the thought of you pushing exhaust fumes down the sewer. This is wrong on so many levels. Think about it. Faulty air admittance valves, dry traps in sinks that haven't been used in awhile, kitchen/bathroom refurbs with the sewer pipe left open, bad DIY ( washing machines plumbed with no trap - seen it), etc,etc.
I'd say it's just not worth a potential manslaughter charge.


Title: Re: Silent Lister exhaust
Post by: noelsquibb on May 21, 2010, 11:36:41 PM
Yup good points insolare.
The cheerful assumption that no one would put up with drain smells is not entirely fail safe.

Also if there is a partial blockage downstream, that causes a water seal, then the heavier gases could build up and vent through any failed seals.

Not having had to share sewers with neighbours for the last 30 years has messed up my thinking.






Title: Re: Silent Lister exhaust
Post by: bottleveg on May 21, 2010, 11:52:00 PM
Mmm. its a difficult one! I know what you mean about open vents and traps.
 It seems a pity to completely abandon the idea because it was so effective; all I had was a very low hum like a small electric motor. This particular manhole services my neighbour and myself and then its into the main sewer. I could fit a vent on the manhole so the fumes wouldnt travel any further.
I think what Ill do is try it with the extra baffles in, remove some traps, and maybe the loo, from my place and next door, and see what comes out. If we get fumes then Ill have to revert to creating my own manhole. Ill give it some thought.


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 23, 2010, 04:16:51 PM
Interesting results! I reinstated my above ground maize and then built a second one inside the manhole, so the fumes/noise leave the steel exhaust, travel along a series of tunnels, with pieces of breezeblock set at odd angles, and then finally exits through a 3 hole into the manhole. Result, slight reverberations along the clay pipe to downstairs loo, fumes in the manhole, but, most surprisingly, absolutely no noise where the fumes came out of the maize.
Im still not happy with the fumes in sewer but, inspired by these results, I will ether
isolate the maize outlet from the sewer and pipe the fumes along to a vertical soil stack or build another maize away from the manhole and pipe into it and then off to a soil stack.
Im unsure on the merits of using dense concrete blocks. My original maize was built solely from breeze but my new one was capped with dense blocks ( at the point the exhaust entered). The original was very quite but the concrete increased the boom from the exhaust.


Title: Re: Silent Lister exhaust
Post by: Alan on May 23, 2010, 10:48:33 PM

Quote This is wrong on so many levels. Think about it. Faulty air admittance valves, dry traps in sinks that haven't been used in awhile, kitchen/bathroom refurbs with the sewer pipe left open, bad DIY ( washing machines plumbed with no trap - seen it), etc,etc.
I'd say it's just not worth a potential manslaughter charge.

I would not leave a boiler with flue carbon monoxide concentrations above
100 parts per million.

Concentration that is immediately dangerous to life and health is 1200 p.p.m.

Old engines use a proportional air damper ( fixed single blade in the air path, below 25% and above 60% very little mixing takes place )  which means it can only be an efficient means of mixing the air to the fuel ratio when the damper is fully open. Typical readings of carbon monoxide would be.

4000 to 7000 parts per million when the engine is cold or the calorific value of the fuel has changed. ( calorific value of waste cooking oil variable depending on lots of factors )
Exposure to these concentrations means Death in 15 20 minutes

Modern engines use a variable orifice to match the required amount of air to the fuel ratio required. The mixing and turn down ratio is much better on this type of design.
With a catalytic converter. The carbon monoxide in the exhaust is converted to water vapour and carbon dioxide.
Even new design of engine with exhaust products down the sewer. ( Not for Me )

Regards

Alan


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 24, 2010, 01:34:23 AM
Thanks for that extra info Alan. Im not happy with the fumes in sewer idea but at least it was a quick way for me to try out an idea. Im going for an underground maze that is eventually vented above the roofline. I just need to decide between 3 or 4 pipe as the carrier after the maze.


Title: Re: Silent Lister exhaust
Post by: bottleveg on May 28, 2010, 09:41:49 AM
Success. My final design has a breezeblock maze on the side of the engine house and another maze directly below but built inside the manhole. The fumes are then piped through the side of the manhole, in 68mm down pipe, up through a conifer hedge and into 110mm soil pipe. They then run 15m along the top of the hedge and exit from a gas cowl. The result is no noise at the end of the pipe.
Ive managed to use the mass of the manhole but the fumes are isolated from the sewer. The only place I still have slight noise is where the exhaust leaves the engine house but I think a second skin of concrete around the breeze can eliminate this.
So far, so good!


Title: Re: Silent Lister exhaust
Post by: Ivan on July 29, 2010, 12:51:32 AM
Can we see some pictures?