Post by parkland on Mar 15, 2015 21:37:10 GMT -5
Hi guys.
As a person interested in turbines, I have been thinking more and more lately.
I was recently toying with the idea of a turbocharger jet engine / steam powered boat.
I asked the boating crowd about it, and I think they think I'm crazy, but it's probably because I am, lol.
Obviously gas turbines are not known for fuel efficiency. However, I started thinking.
Things are "efficient" at things, yet energy isn't created or destroyed.
If I run a 100w incandescent light bulb, it is considered very inefficient, but what if I'm running electric heat in the house?
The light bulb would take 100w, and a percentage of that gets turned into light, and the rest into heat.
If I'm paying for electric heat already, the waste heat from the bulb should help heat the house.
So looking at a gas turbine engine, specifically a turbocharger based one, I thought, what about running it in a boat,
and using the waste heat to power a steam engine?
As it turns out, most of what I thought about, and any ideas I had, were already done and proven.
Boiler tubes inside the chamber superheat steam, and reduce exhaust temperatures.
And the pressure causes a greater hear transfer rate than at atmospheric pressure.
Basically, the idea was, to run the jet engine as a 'turbo heat source'.
The exhaust stack would have cooler temperatures where the cooler water pumps through coils, and it would
be super-heated in the combustion chamber before running a steam engine.
Then I started reading, and there is such a thing as a "supercharged boiler", where basically the combustion chamber
is massive, and has piles of boiler tube inside. That sort of proves that combustion chamber size could be quite massive, and still run well.
So THEN, I started thinking even more, lol, and though, if the combustion gasses are cooled so much from heating the steam, the turbine engine
system can ingest much hotter air, because the temperature rise in the combustion chamber is much, much lower than just a gas turbine.
So if that's possible, the engine could suck air from a heat exchanger in the stack, and also pre-heat air in there as well, before entering the combustion chamber.
Basically the combustion temperature could be reduced by design, by adding more boiler tubes, or pushing more water through.
So, I know this is already done in power plants, having a gas turbine, then using the heat to run a steam turbine, but was thinking if it could be scaled down
to the degree of using a turbo based gas turbine.
from what expert advice has told me on the boatdesign site, steam turbines are lousy under about 500 hp, at being efficient at all.
So, maybe a gas turbine an piston steam engine would work.
So basically, what I was thinking, is that the turbo based jet engine, would have a rather large combustion chamber.
Inside, the flame tube, as normal. Then there would be a vaporizing coil, to burn any available fuel oil. After that, the steam superheating coils.
After the exhaust leaves the turbine wheel, it would drive a free air turbine, geared and coupled to the drive shaft.
From the free air turbine, it would go up the exhaust funnel, From the bottom to the top, there would be the boiler coils, to use the exhaust to boil water
before the superheater coils in the combustion chamber, then a pre-heat for compressed combustion air, then the intake air heater.
So that by the time the exhaust leaves the stack, minimal heat is lost.
I know lots still will, but as much was recovered as possible.
I know the design sounds like it would melt down a turbo based turbine, but remember the steam coil heat exchanger in the combustion chamber could basically
suck as much heat out as needed.
Basically it would be an efficient heater, with some exhaust power used as a by product.
Just wanted to know if any of you that enjoy thinking of this kind of thing had any ideas or thoughts to add to this.
The end result would probably still not be as efficient as a normal diesel engine, but considering a vaporizing fuel coil in the combustion
chamber could burn damn near anything, a lot of cheap fuels could be had, namely waste oil. It's running about 1/5th the price of diesel fuel.
With the exhaust gasses controlled in temperature, there is no real reason why the system would fail quickly.
It could be a pretty reliable power plant, I think. lol.
And yes, I do realize that by sucking heat out of the combustion chamber, that the energy is being stolen out of the jet engine, but that can be
negated by simply burning more fuel, and running richer, which is exactly the point.
Ideally, the fuel air mix would be around stoic, so maximum heat could be generated, and the exhaust turbine would run mostly on the combustion gasses, with the
steam coils soaking up the majority of the high exhaust temperatures.
Any air going out the exhaust that wasn't used in combustion, would be wasted heat.
A compound setup might really shine here, because the higher combustion chamber pressures will transfer the heat to the steam coils better.
Anyways, thoughts? lol.
As a person interested in turbines, I have been thinking more and more lately.
I was recently toying with the idea of a turbocharger jet engine / steam powered boat.
I asked the boating crowd about it, and I think they think I'm crazy, but it's probably because I am, lol.
Obviously gas turbines are not known for fuel efficiency. However, I started thinking.
Things are "efficient" at things, yet energy isn't created or destroyed.
If I run a 100w incandescent light bulb, it is considered very inefficient, but what if I'm running electric heat in the house?
The light bulb would take 100w, and a percentage of that gets turned into light, and the rest into heat.
If I'm paying for electric heat already, the waste heat from the bulb should help heat the house.
So looking at a gas turbine engine, specifically a turbocharger based one, I thought, what about running it in a boat,
and using the waste heat to power a steam engine?
As it turns out, most of what I thought about, and any ideas I had, were already done and proven.
Boiler tubes inside the chamber superheat steam, and reduce exhaust temperatures.
And the pressure causes a greater hear transfer rate than at atmospheric pressure.
Basically, the idea was, to run the jet engine as a 'turbo heat source'.
The exhaust stack would have cooler temperatures where the cooler water pumps through coils, and it would
be super-heated in the combustion chamber before running a steam engine.
Then I started reading, and there is such a thing as a "supercharged boiler", where basically the combustion chamber
is massive, and has piles of boiler tube inside. That sort of proves that combustion chamber size could be quite massive, and still run well.
So THEN, I started thinking even more, lol, and though, if the combustion gasses are cooled so much from heating the steam, the turbine engine
system can ingest much hotter air, because the temperature rise in the combustion chamber is much, much lower than just a gas turbine.
So if that's possible, the engine could suck air from a heat exchanger in the stack, and also pre-heat air in there as well, before entering the combustion chamber.
Basically the combustion temperature could be reduced by design, by adding more boiler tubes, or pushing more water through.
So, I know this is already done in power plants, having a gas turbine, then using the heat to run a steam turbine, but was thinking if it could be scaled down
to the degree of using a turbo based gas turbine.
from what expert advice has told me on the boatdesign site, steam turbines are lousy under about 500 hp, at being efficient at all.
So, maybe a gas turbine an piston steam engine would work.
So basically, what I was thinking, is that the turbo based jet engine, would have a rather large combustion chamber.
Inside, the flame tube, as normal. Then there would be a vaporizing coil, to burn any available fuel oil. After that, the steam superheating coils.
After the exhaust leaves the turbine wheel, it would drive a free air turbine, geared and coupled to the drive shaft.
From the free air turbine, it would go up the exhaust funnel, From the bottom to the top, there would be the boiler coils, to use the exhaust to boil water
before the superheater coils in the combustion chamber, then a pre-heat for compressed combustion air, then the intake air heater.
So that by the time the exhaust leaves the stack, minimal heat is lost.
I know lots still will, but as much was recovered as possible.
I know the design sounds like it would melt down a turbo based turbine, but remember the steam coil heat exchanger in the combustion chamber could basically
suck as much heat out as needed.
Basically it would be an efficient heater, with some exhaust power used as a by product.
Just wanted to know if any of you that enjoy thinking of this kind of thing had any ideas or thoughts to add to this.
The end result would probably still not be as efficient as a normal diesel engine, but considering a vaporizing fuel coil in the combustion
chamber could burn damn near anything, a lot of cheap fuels could be had, namely waste oil. It's running about 1/5th the price of diesel fuel.
With the exhaust gasses controlled in temperature, there is no real reason why the system would fail quickly.
It could be a pretty reliable power plant, I think. lol.
And yes, I do realize that by sucking heat out of the combustion chamber, that the energy is being stolen out of the jet engine, but that can be
negated by simply burning more fuel, and running richer, which is exactly the point.
Ideally, the fuel air mix would be around stoic, so maximum heat could be generated, and the exhaust turbine would run mostly on the combustion gasses, with the
steam coils soaking up the majority of the high exhaust temperatures.
Any air going out the exhaust that wasn't used in combustion, would be wasted heat.
A compound setup might really shine here, because the higher combustion chamber pressures will transfer the heat to the steam coils better.
Anyways, thoughts? lol.
