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Test Cell Exhaust system for large v engine

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oilburner75

oilburner75

Automotive
Mar 4, 2010
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Hi all,

I'm designing an exhaust system for an industrial engine (50 litre) test cell and need a design that covers engines of various sizes and exhaust outlet configurations.

To achieve this I need X2 articulating exhaust systems for each cell ( one for each bank of V 12-16's engines ) - something like a jib crane with a flexible fall tube. This could be swung back to the test cell wall when not in use

Is this possible? - I guess I would need some kind of spherical joint to allow movement that would also be gas tight.

All help or ideas appreciated :), thanks Kenneth
 
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Based on your handle, I'm assuming these are diesel engines. Do you really need a piped exhaust system? The easiest (and probably best) design is a "fume hood"-type exhaust where you have an open collector above where the exhaust outlets are and a large fan to extract the fumes from the test cell. Most of the diesel QC cells I've seen use this setup and there's no hookup parts/labour involved. The fan also provides ventilation for your test cell by drawing in (excess) air. Also, Novaflex (and, presumably, other companies) make an excellent high temperature flexible hose from glass fibre (as long as exhaust "backfires" aren't as issue, 20" diameter is about $500/ft).

Brian Bobyk - Hoerbiger Canada
 
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I have seen dyno bays with flexible steel tubes a bit bigger than the largest likely tail pipe. They are simply pushed on with a big overlap. There was also a hood and exhaust fan over the joint. There were also a few adapters to reduce the gap if say a 3" exhaust was fed into a 6" flexible pipe.


Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &
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I'd suggest some flexible metal hose to a wall, supported by floor stands that you can move around to suit.

Floor stand: heavy base + adjustable pole + loose fitting ring, sort of like the base for an industrial fan. It might even be cheapest to just buy some big floor fans and throw away the fan and motor.





Mike Halloran
Pembroke Pines, FL, USA
 
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The engines are all diesels

Unfortunately I need to measure exhaust back pressure/smoke/temperature in each bank of the engine. To simulate back pressure from mufflers, a flap has to be set in a Y piece where the gases from both banks meet. So I don't think i can use a hood and extractor. Cell temperature also has to be controlled by fans.

I like the idea of using flexible metal pipe to the wall - I have used braided stainless steel tube which has good flexibility. It's complicated by needing a back pressure sensor about 12" from the exhaust outlet and some engines have flat, 45 or 90 degree outlets so quite a bit of movement would be needed.

The method used now is to have many sets of pipes to rig the engine to an A frame mounted on the test cart with outlets in fixed positions. This is time consuming fitting/removing them and storing all the exhaust pipes needed takes a lot of space. What we really need is a single adjustable exhaust system in the test cell to cover everything.

Sorry about the rambling message!

Thanks again, Kenneth Moore


 
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Mike's suggestion is the usual one for an adjustable back pressure system. Some car manufacturers do use spherical joints in their exhausts, which may appeal for articulation, but most people use convoluted pipe for the same job (flex joints/couplings).

Mind you, one might think that 4 joints in a rigid pipe might be less hassle than a flexible articulating system, if you are testing for a week at a time.





Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
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The usual test cycle time is about 2 hours so minimising rigging/de -rigging time is very important.

I like Mike's idea of using flexible hose to the test cell wall or I could hang it down from the roof if sufficient movememnt can be achieved to cover all the outlet locations. It would then need to be secured out of the way when docking the engine in position which presents another problem,

I have found that aluminium convuluted tube becomes almost ridgid when it is heated and contaminated with soot. If it is possible to buy braided stainless steel tube in long lengths at 10" diameter this would be better.

If anyone knows of a spherical/swivel joint of about 10" in diameter that can withstand temperature I would be very interested!,
Many thanks Kenneth
 
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Stainless braid is just a cover over the real tube, typically convoluted metal bellows. I think there may be a limit to the length that can be made in one piece, but even if there weren't, the convolutions add to the pressure drop, a lot, so you'd have to upsize the tube.

Better to use straight tube where you can, and join it with pieces of bellows/braid, acting as flexible elbows. The elbows should be considered consumables, and made easily replaceable. Or rigid elbows and swivel joints.

Frankly, I like the standardized test cart interface better; maybe you just need a better way of keeping the adapters neat and organized.





Mike Halloran
Pembroke Pines, FL, USA
 
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Another thing. For the 48 litre Diesels with which I've worked, 10" tube is a little on the small side for the per-bank tube, so you need to be careful about adding elbows or convolutions.



Mike Halloran
Pembroke Pines, FL, USA
 
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The standardized test cart does work okay. But from a production point of view I'm trying to eliminate work that doesn't add any value. It seems more logical to fit the exhaust once in the test cell directly to the engine if the problems can be overcome.

Ideally I would like some kind of space age fabric that is very flexible and temperature resistant but it seems that no such product exists!

If i could find a company that could flare a 16g 10" steel tube to the right profiles for a spherical joint that could be an option. Something else to investigate.

At the moment what Mike said has got me thinking about having a flexible joint at roof level for each cylinder bank, attached to about 5ft of straight pipe and another flexible section on the end. The exhaust outlet could have a swivel joint with say a 15 or 30 deg. elbow.

It's just getting the drop height correct to the exhaust outlet that concerns me. I guess I would need some kind of sliding gas tight joint but I doubt anything is on the market ready made .

Thanks all help and ideas much appreciated ,Kenneth



 
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You are probably already doing this, but if not consider making up a short adapter for the different engines you deal with so that they all end in the same orientation and diameter. That would make it much easier to use the drop tubes as you wouldn't have so much variation in the length.

If my memory is correct you would need a fabric that is good to ~1200°F. (if I'm wrong - its been a long weekend. ;-) ) I have designed several exhaust covering systems to help prevent fires in forklifts. The problem with these materials is that they become brittle after they heat up. If you leave them undisturbed it is OK, but they will not stand up to handling. We would not stand behind the products if they had been removed even once!

ISZ

 
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After the turbo, Diesels mostly don't get above about 1000F.
But the binders that hold glass fibers together in fabrics and batting will burn off at lower temperatures than that, making insulation basically a one-shot, or one thermal cycle, deal.



Mike Halloran
Pembroke Pines, FL, USA
 
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You could talk to Unique Heated Products in SM Michigan. They supplied the emission lab where I worked. They may have an off the shelf solution. They were also good at custom work.
 
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go to a large resterant supply store and have a look at
their heavy duty stainless mixing bowls

they make them from small to huge,

they all have a flat bottom, and they nest together tightly

one could cut the bottoms out and have stainless pipe tig welded in and you have your ball swivel parts pre-made.

don't laugh till you at least take a look!

bob g


 
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