Will this be more efficient than the Sterling engine?

[Terrysv]

Hello everyone,
I am going to try show the advantage of using liquid vapor phase equilibrium in my design compared to the expansion of a more common diesel engine using Amonton's law. All gases expand at about the same rate when heated (33%) and water expands at about 1600 times when boiled requiring a lot less energy is to produce an equal pressure change in a quantity of saturated water.
If a piston in a typical diesel engine compresses a volume of air to 41 bar at 450°C and then the combustion event brings the pressure up to 70 bar at 1667°C. Therefore using Amonton's law we know that enough fuel needs to be spent to bring the temperature of the volume of compressed gas up 1217°C to get the pressure desired. A liquid to vapor phase change will need an increase of 33.5°C to convert enough saturated water into the same volume and pressure of saturated vapor.
The benefit of using a phase change in a closed cycle engine is that most of the thermal energy is retained in the condensation and this retained energy is able to get out of its own way during the compression part (4) of the cycle.

Description of the cycle and the activity in a sample chamber:
Section 1 (4:30 to 7:30) the chamber path, has a small volume with a low volume change as the chamber moves past in a clockwise direction.
A chamber of compressed air, with a minimal quantity of saturated water present is preheated to 41 bar at 253.3°C. The chamber will accumulate an additional 33.5°C as it passes by the adjacent reverse flow heat exchange, bringing the contents up to 70 bar at 286.8°C, replacing only the quantity of thermal energy that was rejected on the previous cycle. The additional pressure gained is produced by the quantity of saturated water becoming a compressible water vapor.

Section 2 (7:30 to 10:30) of the chamber path, has an increasing volume.
The 70 bar at 287°C of pressure is declining from adiabatic expansion.

Section 3 (10:30 to 1:30) of the chamber path, has a large volume with a low volume change as each chamber moves past in a clockwise direction.
The chamber pressure is dropping as the water vapor is returning to a liquid state as the thermal energy is rejected to the reverse flow heat sink. Without having an exhaust valve all the remaining thermal energy is retained in the condensate.

Section 4 (1:30 to 4:30) of the chamber path, has a declining volume.
The chamber having lost a quantity of thermal energy is now gaining pressure and thermal energy from adiabatic compression arriving at the cycle starting point with 41 bar at 253°C.

 

[berkeman]

Thread locked temporarily for Moderation...

 

[NascentOxygen]

Are the vanes welded to the cylinder wall?

 

[Nidum]

Are the vanes welded to the cylinder wall?

May as well be - it wouldn't make any difference . This engine is not going to function anyway . #13 and #19 .

 

[Terrysv]

Hi NascentOxygen
No the vanes slide driving the rotor with the pressure generated by a liquid to vapor phase change of the working liquid.

Just enough working liquid is installed in the hermetically sealed cylinder. The advantage of this design over a Stirling engine or other hot air engines is first the operating temperature is lower. Second is that after the heat sink event all the remaining energy in each chamber is carried in the form of liquid condensate to the heat exchanger to be expanded into a compressed gas. These compressed gases can easily double the mole content of the product available for adiabatic expansion.

The Wikipedia page titled Charles’s law has an animation and also contains a modern statement referencing a “dry gas”. The phase change of the just enough water in the chamber changes the graph on the right to look more like a steam pressure chart. Since the chambers are closed similar to the combustion chamber in a Wankel engine it will cause the rotor to move.
Cheers.
Below I have pasted a better drawing and here is a link to Charles law. https://en.wikipedia.org/wiki/Charles's_law

 

[NascentOxygen]

It is difficult to see this developing torque. Take anyone of your expansion spaces near the heat source...picture increasing the pressure of the gases in that space...won't this pressure increase equally likely tend to turn the rotor-with-vanes CW as CCW? Hence, no nett torque?

 

[Terrysv]

The fluid delivering the heat will loos energy as it passes though while the chambers receive the energy traveling the other way, therefore each chamber will be hotter and have more pressure at the 7:00 o clock position than the 5:00 o clock spot. Same deal on the sink side. Also if one found that the sink needed to perform better its size could be extended down to 2:00 or 3:00 without harming the production.
All the best.

 

[NascentOxygen]

I have no doubt about the ability of this device to transfer heat from a source to a sink, and I can see you have put some thought into that. But if you want it to develop mechanical power during that process, you need to be able to point to at least one chamber where pressure (or lack of pressure) will produce a net rotation force on the rotor. That seems to be a major sticking point.

 

[Terrysv]

you need to be able to point to at least one chamber where pressure (or lack of pressure) will produce a net rotation force on the rotor.

Thermodynamics is about adiabatic expansion from pressure produced by boiling a liquid like water or burning a fuel. Two common examples are the external combustion steam engine or the internal combustion engine.

When water boiled it becomes saturated vapor and condensation is called saturated water, meaning that it is saturated with thermal energy. The design presented manipulates the equilibrium that the steam and the condensate exist in. As the temperature of a liquid in a confined space is increased the water becomes steam and it is the steam that has nowhere to go, increases the pressure. It is this pressure that is produces the adiabatic expansion, and produces the work. After the work is extracted enough of the thermal energy needs to be extracted at the sink. This thermal extraction makes the equal adiabatic compression much easier. Therefore we can see that if more work is produced by the expansion process than is consumed by the compression process then each and every chamber contributes to the work produced.

A second benefit of the heat sink is that the engine is a closed cycle and therefore doesn’t need to open an exhaust valve and dispose of usable energy.

Another benefit of this design is that if an identical unit is loaded with just enough ammonia in place of the water, a second engine will produce work from the first engine’s rejected heat. At some point I might have to admit that these engines doesn’t use thermal energy as much as it just wears it out.

 

[billy_joule]

Thermodynamics is about adiabatic expansion from pressure produced by boiling a liquid like water or burning a fuel. Two common examples are the external combustion steam engine or the internal combustion engine.

No one is doubting the thermodynamics of your engine - it's the geometry, as post #19 points out, It's symmetric and no net torque is produced:

The problem becomes more apparent if we remove some vanes and make the eccentricity larger:

In your arrangement the top is hot and the bottom is cold, so the top and bottom pairs of chambers are at the same pressures so all forces cancel and there is no net torque about the hub. Adding more vanes makes no difference.

Now, if we move the hot and cold sinks around 90 degrees (we heat the left and cool the right) then the symmetry is gone then there will be a net torque about the hub.

 

[Terrysv]

move the hot and cold sinks around 90 degrees (we heat the left and cool the right) then the symmetry is gone then there will be a net torque about the hub.

If the hot flow was to enter at say 1100 and exit at 700 and the cold enter at 500 and exit at 100 then yes it will function. However if you think it though that practice is like timing the combustion of a IC engine for well after TDC during the power stroke. Much more work is produced if the timing is right.On the bright side the diesel probably won't rattle.

Maybe you are confusing my adiabatic compression with the compression stroke on an IC engine like the Wankel engine.

This design doesn’t have a true compression event it isn’t needed.

My drawing has 4 numbered areas. Think of a steam engine boiler in the first area then the steam engine piston in the second area. The third area of my design has the heat sink this is more like the water spray of the Newcomen atmospheric engine. In the fourth area I have the adiabatic compression this is like what could be considered the power stroke on the Newcomen atmospheric engine.

Because it is a closed cycle (no valves) the trick is to get the chamber to the starting point. That is what the recuperator in the Stirling engine is for. The recuperator drops of some energy and picks it up on the return trip.

 

[Nidum]

There is no confusion . The engine as drawn won't function .

Do you want to discuss the problems and find some solutions or do you not ?

 

[Terrysv]

Do you want to discuss the problems and find some solutions or do you not ?

Physics the "the knowledge of nature", action and reaction, billy-joule said to advance the timing 90 degrees. OK so what happens if I advance the timing on my engine, an IC engine or steam engine?
I believe your questions are answered. I admit I couldn’t see one concern until it was rephrased by billy-joule. Maybe the others could help you with the answers given the way billy-joule did.

Believe it or not I once had a building inspector tell me to build it his way and if it doesn’t work you can do it over. We only talked the one time, never saw him again.

The answer to my original question, “is this is more efficient than the Sterling engine” is that nobody cares. NASA scraped the Stirling engine research in favor of a more reliable and far less efficient option and at least one solar farm using Stirling engines went broke, leaving the Stirling engine for some submarines and the novelty market.

 

[Vanadium 50]

This will not turn, and it will not provide a torque (because angular momentum is conserved). Can the mentors close this thread now?

 

[Terrysv]

it will not provide a torque (because angular momentum is conserved

Are you referring to the angular momentum in the Wankel engine?
Seeing some tail lights is clearly the best option
TTFN

 

[russ_watters]

Why not just rotate the position of the heat exchangers 15 degrees clockwise to break the symmetry? Then it would produce torque.

In any case, I'm not really sure what the point of this thread is. Terrysv, what is the goal of this thread?

 

[billy_joule]

in the Wankel engine

The greatest advantage of the Wankel engine is it's power to weight & volume, poor emissions and efficiency make it basically obsolete otherwise.
Your design shares many of the fundamental flaws of the Wankel: leakage across the engine due to the temperature differential and the resulting thermal expansion differentials, and tip seal leakage and wear.
Another problem (net torque being zero aside) I see is that the evaporation & condensation happens inside the engine - bad news for engine life. Most turboexpanders avoid this altogether by avoiding any water condensing in the engine itself, some accept some blade erosion due to water droplets and use high tech alloys to extend blade life, but even then they are usually limited to around 90% steam quality (that is, only 10% of the water becomes liquid in the turbine), any higher and the erosion becomes too great and maintenance intervals become too short.

As for whether it's more efficient than a sterling engine, well that was answered a while back; as with any heat engine it depends entirely on the hot and cold temperatures. We can make an engine with arbitrarily high efficiency (within the laws of thermodynamics) if we can increase the temperature difference between hot and cold. We're limited by practical means - the temperature limitations of engineering materials and cost (capital & maintenance) mainly.

 

[Vanadium 50]

Are you referring to the angular momentum in the Wankel engine?

No, I am talking about yours.