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Originally Posted by Zgringo
Saabjohan,
Once again your using theory or unfounded facts to attempt to prove a point.
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Quote: <HR SIZE=1>Basically you are saying that the change in momentum of these particles imparts energy to the turbine blades. The use of the word “particle” indicates to me that you are taking about relatively massive objects with respect to the exhaust gases. Correct?
There are no particles in the gas flow. Or more correctly, there are suppsed to be no particles in the gas flow. Particles in a gas flow, soot, water drops and so on will cause erosion on the turbine. For a long life there must be no paricles in the flow.
May I ask what a atom partical is? And can a atom be split? So what your saying is the exhaust from a engine is nothing. Just hot nothing or so on.
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The engine exhaust is when it leaves the engine still very hot and has a high pressure. This energy can be contered into kinetic energy in a reaction turbine. In the reaction turbine we have a pressure in the inlet which is higher than in the outlet. The pressure difference is known as expansion ratio or turbine pressure ratio just like the pressure ratio on the compressor.
So when the gas goes from the higher pressure to the lower it will expand and lose heat. The more heat it loses the more power will the turbine produce. The heat lost depends on the pressure ratio over the turbine and the turbine inlet temperature. The higher the inlet temperature the more power the turbine will produce.
Let's try this one. Your correct, the exhaust is very hot and at high pressure but also expanding very rapidly. When it reaches it's maximum expansion point what happens? Hold this though. Well come back to it in a minute.
Now lets take a turbine and place 2000F on on side of the blades and dry ice on the other side. What well happen? nothing.
Now let's take a turbine and use a compressor and apply 200# PSI to the inlet side of the turbine and nada to the exhaust side. What well happen? I'll be damn, we just converted air pressure into energy.
Now lets go back to the point where the exhaust gas has expanded to it's max. There is no more, the amount of pressure it has created thru expansion is all there is. This is the energy we have to work with.
The same principal works with a water turbine.
Pressure differential between inlet and outlet. The only difference being, on the engine the hot exhaust gas is expanding creating more pressure.
I suggest you go to STS web site and read as it seems you are wanting to learn and that is good. There site is posted just above your post.
When your finished ask Ben or Rick anything you want.
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1. Usually an particle in this context is defined as a small part at above atomic level. Soot is an example of a particle, CO2, H2O and N2 atoms aren't considered to be particles.
2. I don't think you have understood the difference between heat and temperature. Putting 2000 degF and dry ice on each side of a turbine will give a large temperature difference, there will however not be any larger amounts of heat involved. The heat will however be enough for a peltier element to convert it into electricity which in turn can propel a small electric motor. This technology is used in the uranium/plutonium batteries used by for example NASA in space.
Recommended reading
http://www.grc.nasa.gov/WWW/K-12/airplane/heat.html
http://www.grc.nasa.gov/WWW/K-12/airplane/thermo0.html
3. I have read books about thermodynamics, mechanics, and turbomachines such as "The Radial Turbine" by Werner T. Von Der Nuell plus technical papers about turbocharging from for example NACA, Garrett, Holset and so on. When reading at the STS page it seams that those guys should try reading some of the above mentioned.
Recommended reading
http://www.grc.nasa.gov/WWW/K-12/airplane/powtrbth.html