Heat Recovery

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Viv
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Heat Recovery

Post by Viv » Sun May 17, 2009 2:56 pm

Hi Ace

Don't worry its alive and well as a section in my design portfolio, this thread was to bring out some interesting points that are in the public domain already.

Viv
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ace_fedde
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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Sun May 17, 2009 3:24 pm

Hi Viv,
I also have some nice ideas, that I will probably never execute, around regaining temperature losses from piston machines using steam and turbines.

Already done etc, etc, but my ideas don't include an added steam engine/turbine. :?: :!: Thus it can be used in cars with minimun weight and engine space increase.

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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Tue May 19, 2009 8:05 am

Viv,

Kinda following up on your story:

Let’s imagine two four stroke (preferable diesel) piston engines.

For both we replace the first part of the exhaust system with a chamber. For one engine we install at the end of the chamber a nozzle. For the other we install a small turbine, or an adapted turbo, that is connected (with a variable transmission) to the driveshaft of the engine.

Both nozzle (restrictor) on engine 1, and variable transmission on engine 2, we tune thus that under the same running conditions (in theory) of both motors we end up with an overpressure of 2-3 bar in the chambers.

Now, (again in theory) what happens to the exhaust gas temperatures (in the chamber) of both engines compared to an engine with no restriction at all?
What would (again in theory) happen to the performance of engine 1 compared to an engine without restriction? And what for engine(setup) 2?

No prizes to be won… :( :( :(

Fedde
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Re: Two stroke diesel, turbo compound engines

Post by Viv » Sat May 23, 2009 5:55 pm

ace_fedde wrote:Viv,

Kinda following up on your story:

Let’s imagine two four stroke (preferable diesel) piston engines.

For both we replace the first part of the exhaust system with a chamber. For one engine we install at the end of the chamber a nozzle. For the other we install a small turbine, or an adapted turbo, that is connected (with a variable transmission) to the driveshaft of the engine.
If you pop back to the start of this thread and look at the Wright engine you will see this type of energy recovery from exhaust gas being used, and very succesfully too, check the output figures for this engine as it had a notable history in use.
ace_fedde wrote: Both nozzle (restrictor) on engine 1, and variable transmission on engine 2, we tune thus that under the same running conditions (in theory) of both motors we end up with an overpressure of 2-3 bar in the chambers.

Now, (again in theory) what happens to the exhaust gas temperatures (in the chamber) of both engines compared to an engine with no restriction at all?
What would (again in theory) happen to the performance of engine 1 compared to an engine without restriction? And what for engine(setup) 2?

No prizes to be won… :( :( :(

Fedde
Looking at both cases I think you are starting to mix and match a few things that maybe don't want to be mixed and matched, for both engines, as they are diesels the break mean efficiency pressure is critical to their operation see this http://www.epi-eng.com/piston_engine_te ... dstick.htm you are gaining work from the exhaust in the second case and not the first so a BMEP calculation can be applied.

In this case we can use BMEP to see what happens to the identical engines under different operating conditions the same way we can compare wildly different engines, it is possible to apply a calculation to pulse jets to "compare a builders claims to reality" were people have popped on to this forum claiming to have made a 100 pounds of thrust from an engine frame size only suitable for 20 pounds of thrust and then compounded our amusement by claiming to have done it using less than a third of the fuel the original 20 pounder used.

Viv
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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Sun May 24, 2009 12:16 pm

Viv,
Viv wrote: If you pop back to the start of this thread and look at the Wright engine you will see this type of energy recovery from exhaust gas being used, and very succesfully too, check the output figures for this engine as it had a notable history in use.
You’re right. :)
Viv wrote: Looking at both cases I think you are starting to mix and match a few things that maybe don't want to be mixed and matched,…
You’re not right. :shock:
Viv wrote: …, for both engines, as they are diesels the break mean efficiency pressure is critical to their operation see….
……you are gaining work from the exhaust in the second case and not the first so a BMEP calculation can be applied.
You’re right, but…, let’s now first quote you from another thread: :arrow:
Viv wrote:Hi Ace
…… That aside you were on the right track again but did not keep to the simple model ;-)
Viv
You as well didn’t keep to the simple model :evil: and you went left where I want to go right. :lol:
By doing so you didn’t really answer the posted questions: :(
ace_fedde wrote:Viv,
…..Now, (again in theory) what happens to the exhaust gas temperatures (in the chamber) of both engines compared to an engine with no restriction at all?
What would (again in theory) happen to the performance of engine 1 compared to an engine without restriction? And what for engine(setup) 2?
Let’s not spend to much time on this one, so I will give the answers:

For both engine’s 1 and 2 the exhaust gas temperature (in the chamber) will rise compared to the exhaust gasses from an engine without restriction.

For engine 1 the (available) perfomance will decrease while the engine must “work” to push the exhaust gasses out (simple explanation) In terms of BMEP: One could (somehow) also see BMEP as the difference between the average pressure on the piston compared to it’s outside world: the exhaust.
In this case the outside world has a rissen pressure so the BMEP decreases and thus performance.

For engine 2 the story starts the same as above but in a theoreticly ideal (thus not existing) situation, the turbo-nozzle will regain the lost performance and add to the driveshaft.
So we end up where we were with a non restricted engine? :?
Not really because in the real world there will be energy and efficiency losses so we end up with less performance…. :( But higher performance than engine 1! ( :?: yes so? :?: )

To be continued...
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Re: Two stroke diesel, turbo compound engines

Post by Viv » Sun May 24, 2009 4:04 pm

Hi Ace

Well sort of following along in your footsteps with this ;-) I can see you got to the right place in the end but some of the steps you took on that path to get there were a bit hard to follow at times.

So to Summarize, expanding the piston engine exhaust gasses through a turbine and coupling that shaft power back to the main engine crankshaft is better than expanding the gasses through a nozzle (for thrust?) ?

If you think of the piston engine (any piston engine) as only a gas producer at a pressure and flow, then yes, expanding those gasses through a turbine to extract some useful work is better than simply letting those gasses expand across the engines exhaust valve down to ambient pressure.

Again the Wright engineers have shown how thats done with a pretty remarkable engine, I am interested and have been a for a long time with free piston engines as gas producers for turbines.

Viv
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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Sun May 24, 2009 4:49 pm

Viv,

Hehe, no, no, no. You still haven't got a clue where I wanna go, makes this one an exiting thread.

I'm a bit drunk now so I will not post to much now, but I will give you a hint: Heat pump.
If you now understand where I wanno go: don't tell the others and keep this thread exiting :D

Fedde
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Viv
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Re: Two stroke diesel, turbo compound engines

Post by Viv » Sun May 24, 2009 4:55 pm

ace_fedde wrote:Viv,

Hehe, no, no, no. You still haven't got a clue where I wanna go, makes this one an exiting thread.

I'm a bit drunk now so I will not post to much now, but I will give you a hint: Heat pump.
If you now understand where I wanno go: don't tell the others and keep this thread exiting :D

Fedde
Ha! ok but go look at CHP and heat recovery from exhausts to then ;-)

Viv
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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Sun May 24, 2009 4:59 pm

Viv wrote:Ha! ok but go look at CHP and heat recovery from exhausts to then ;-)

Viv
Is that a thread on our forum?
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Re: Two stroke diesel, turbo compound engines

Post by Viv » Sun May 24, 2009 5:12 pm

ace_fedde wrote:
Viv wrote:Ha! ok but go look at CHP and heat recovery from exhausts to then ;-)

Viv
Is that a thread on our forum?
No not yet but we have had a few good discussions on the subject including steam generation, do a google search for CHP and follow heating and cooling driven from the power plans exhausts.

Viv
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Re: Two stroke diesel, turbo compound engines

Post by Viv » Sun May 24, 2009 11:58 pm

This is one of my favorite engines from the past, for a diesel take note of the sound of the exhaust compared to other diesels, lots of fun to drive

http://www.youtube.com/watch?v=QbaUi4A3 ... re=related

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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Mon May 25, 2009 7:48 am

Viv,
Is that a valved 2-stroke, or valveless :lol: (I mean of courese: with ports) or an opposed piston?
I've been looking for smaller 2-stroke diesels, but they are hard to find in Holland. I found and bought though a single cilinder, with ports, air cooled, 500cc. Will be used for experients!
Fedde
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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Mon May 25, 2009 8:40 am

Viv wrote:
ace_fedde wrote:
Viv wrote:Ha! ok but go look at CHP and heat recovery from exhausts to then ;-)

Viv
Is that a thread on our forum?
No not yet but we have had a few good discussions on the subject including steam generation, do a google search for CHP and follow heating and cooling driven from the power plans exhausts.

Viv
Well, I know regaining heat is nothing new, see my first post, but look at the size and weight of these installations!
Mind what I wrote in my first post:
ace_fedde wrote:Hi Viv,
I also have some nice ideas, that I will probably never execute, around regaining temperature losses from piston machines using steam and turbines.

Already done etc, etc, but my ideas don't include an added steam engine/turbine. :?: :!: Thus it can be used in cars with minimun weight and engine space increase.

Fedde (or Ace)
.. I want to do it automotive...

Fedde
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Re: Two stroke diesel, turbo compound engines

Post by Viv » Tue May 26, 2009 7:11 pm

Hi Ace

I understand you want to do an automotive solution, turbo compound engines originally were for a much more demanding situation and set of criteria but it should be packaging problem to use it, my own thoughts are based around the fact that the transmission systems cause most of the design compromises and thats what's held up any real development in using alternative engine types.

Getting waste heat back is nice but there are still higher grade sources of energy being wasted in the overall package to be dealt with first.

Viv
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Re: Two stroke diesel, turbo compound engines

Post by ace_fedde » Tue May 26, 2009 7:17 pm

Viv,
ace_fedde wrote:Viv,
Is that a valved 2-stroke, or valveless :lol: (I mean of courese: with ports) or an opposed piston?
I've been looking for smaller 2-stroke diesels, but they are hard to find in Holland. I found and bought though a single cilinder, with ports, air cooled, 500cc. Will be used for experients!
Fedde
Couldn't wait for an answer, had to find out :wink: . Man, opposed piston, would love to have a motor like that!!
Unfortunatly we hardly have any in Holland... :(

Back to the project, let's make a little side step:

Imagine a piramide shaped chamber with an open basis and an open, cut off, top.
Now place a radiator (connected to the motor's cooling system) on the base of the piramide and a compressor (turbo, roots, driven by the main shaft) on the top of that piramide.
After the compressor we'll make another chamber which has at the other end again (like the exhaust chamber) a turbine This turbine (or air-motor) will also drive the main shaft and will be set and sized to work as a nozzle again.

So what we have now is a radiator placed on a funnel, a compressor sucking in fresh air through that radiator and creating an (significant) overpressure in the folowing chamber because that chamber is nozzled by the little turbine/air-motor.

Seems silly so far...will only cause performance loss... :( But, the performance loss caused by the compressor will be partly regained by the turbine/air motor. :roll:

Now let's say that the air that's sucked through the radiator is warmed up to 70 celsius. Then again the temperature in the pressurized chamber (like our exhaust example) will be higher, depending on the pressure.
If we would somehow cool down the temperature of the air in the pressurized chamber back to 70 celsius (or colder), what would happen to the temperature of the air coming out of the turbine/air-motor? Could it become (even more) colder?

Fedde
Your scepticism is fuel for my brain.

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