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Fully Rotational Internal Combustion Engine

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ColdWontRise

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Over the past year (as a cure for sporadic boredom) I designed an internal combustion engine that runs entirely off of rotational motion. A metaphor on the principles on how it works: Imagine how a gun works, gun fires, bullet comes out going very fast, gun kicks back. Now imagine anchoring the bullet (as in a barrel plug) to a wall, and pulling the trigger. Aside from shattering your wrist, the gun would fly backwards. Now rig that gun to an axis, and let its motion fling it around in a circle. Now imagine a mechanism that, when the gun rotated full circle, the bullet would enter the back of the gun, then fire again, repeating the cycle. Thats the basic idea. If anyone understood my awful analogy and would like to learn more, see drawings, or point out potential issues in the design, feel free. =)

(Fixed minor typo in title - sNerd)

Edited by softwareNerd
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Well, my first thoughts are that, as compared to the linear-displacement intenral combustion engine, the space required for one full cycle of piston motion is larger in your engine. That is, a piston in a linear-displacement IC traces back its motion, while a piston in your design must traverse an entire circle. Some questions (in no particular order):

-How does piston size compare to the LD IC?

-How does energy output of one of your pistons compare to the LD IC?

-What is the power/weight ratio of your engine, and what is it for a comporable LD IC?

-How does the complexity of the mechamism converting the piston motion to shaft-power (fed to a transmission) compare to that of a LD IC?

-What plane does the circular motion of your piston reside in?

I'm sure I'll think of more questions.

Edited by Felipe
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Over the past year (as a cure for sporadic boredom) I designed an internal combustion engine that runs entirely off of rotational motion.

This is an idea that has been tried with great success.

Have you ever heard of a Wankel rotary engine? A well known car, The Mazda RX-7, had one.

The idea, I believe, was that it would put less stress on the piston mechanism.

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Well, my first thoughts are that, as compared to the linear-displacement intenral combustion engine, the space required for one full cycle of piston motion is larger in your engine. That is, a piston in a linear-displacement IC traces back its motion, while a piston in your design must traverse an entire circle. Some questions (in no particular order):

-How does piston size compare to the LD IC?

-How does energy output of one of your pistons compare to the LD IC?

-What is the power/weight ratio of your engine, and what is it for a comporable LD IC?

-How does the complexity of the mechamism converting the piston motion to shaft-power (fed to a transmission) compare to that of a LD IC?

-What plane does the circular motion of your piston reside in?

I'm sure I'll think of more questions.

Well, the first thing is that there arent pistons per say. However, the chambers resemble pistons in their fuction. Imagine plastic box, with an open end on the top, filled with water. If you put a board in the center, effectively sealing off both sides so that its air tight, you can move the board back and forth, and the water level will rise and shrink on either side. Each side is like a piston. You move the board from one side to the other, and the air pressure gets lower on one side (intake, combustion cycle) and higher on the other side (exaust, presure cycle). The obvious issue is, what happens to the board when it reaches the other end of the box. Basically, the board is a wheel, which when it gets to the end of the box, has a section cut away from it, so when it rotates past the wall of the box, it lets it slide by. After that, it rotates back into the box to repeat the cycle. The rotating chamber separator cuts the chamber and half, while the chamber can move in one direction past it.

This is a rather old drawing, but still relevant.

?action=view&current=Wheel.jpg

Much of the design has changed, but the same basic concept remains.

Edited by ColdWontRise
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This is an idea that has been tried with great success.

Have you ever heard of a Wankel rotary engine? A well known car, The Mazda RX-7, had one.

The idea, I believe, was that it would put less stress on the piston mechanism.

Yes, I am familiar, but mine actually works very differently to the Wankel. Mine has a few more moving parts, but its potentially much more powerful.

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Hopefully this image works..

Engine3.JPG

Ok so, the main wheel with the 'chambers' is the big grey one. the red/orange/yellow part is where the separator wheel cuts the chamber in half, the colors matching up with where they intersect. The image to the left of the main wheel is looking at the wheel from the front, with the rounded edges shown where the separator wheel spins through. The one further to the left is looking down at the main wheel (though the surface is flattened out for clarity) and again reveals where the separator wheel cuts in.

Edited by ColdWontRise
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Sounds like you could benefit from an engineering book or two. I can recommend Design of Machinery by Robert Norton that covers basic kinematics (motion) design and analysis. Since yours is a combustion engine, you might also want to find a book on thermodynamics as applied to mechanics. Avoid thermodynamics applied to chemistry or to black holes or stuff like that.

Edited by xavier
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Sounds like you could benefit from an engineering book or two. I can recommend Design of Machinery by Robert Norton that covers basic kinematics (motion) design and analysis. Since yours is a combustion engine, you might also want to find a book on thermodynamics as applied to mechanics. Avoid thermodynamics applied to chemistry or to black holes or stuff like that.

Yeah, I have little knowledge of engineering, which is why this design will never leave the concept stage unless I educate myself. As far as I can tell, the concept works. If certain aspects of piston engines work, this one should work also. Thanks though, Ill check those out =D

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Thanks though, Ill check those out =D

A couple of recommendations:

Internal Combustion Engine Fundamentals by John B. Heywood - mainly about reciprocating engines

Mechanical Engineering Design by Shigley and Mitchell

Engineering Thermodynamics, Work and Heat Transfer by Rogers and Mayhew

Be warned though. You need a basic high school physics and vector calculus background for these books though the latter is not that essential in concept design unless you are designing bearings, performing stress analysis or something.

PS

How is compression generated in your design?. If you need help, you might also want to check out physicsforums.com. Quite a few good engineers and scientists post over there.

Edited by tommyedison
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How does this design generate intake vaccuum to fill the chambers?

Essentially, each chamber that is pressurizing the air moves it to a separate tank. Say the tank has a volume of 1 liter, and say there are 3 chambers pressurizing air, each 1 liter. When they finish a cycle, they move the air to the tank, which will then contain 4 liters of air (4:1 pressure ratio) Then, a valve opens and lets that high pressure air into the combustion chamber, also 1 liter in size. It essentially increases the volume of the tank by a small ammount (allowing air to move freely between the combustion chamber and the tank) so the pressure decreases a small ammount, but is still fairly high. Then the tank gets cut off from the combustion chamber (combustion occurs) and there is about a 3-3.5:1 ratio in the tank now. The next cycle, 3 more liters get stuffed into the tank, raising the ratio yet again (to about 6:1) This cycle continues until the tank maintains a consistent ratio. Sort of acts like a turbo charger, inserting already pressurized air into the combustion chamber.

So the wheel oscillates then?

All the wheels spin. The primary wheel continues to spin in one direction. When the walls of the chamber (they look like gear teeth on the primary wheel in the drawing) come near the alternator/separator (small) wheels, the small wheels allow the walls too pass by, due to their shape. When the wall passes, they move back into the chamber, again sealing off each notch in the primary wheel into two compartments: one contracting, one expanding.

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I don't understand how this thing draws in air. A traditional ICE draws air in via several factors:

1) The piston moving downwards creates a vaccuum as it increases the size of the cylander, thus drawing air in through the intake valve. This works the same way that your lungs do, by increasing the size of the air chamber.

2) After combustion, the exhaust valve opens and lets the spent gasses out. If both the intake and exhaust valves are open, the force of exhaust gasses leaving the chamber will pull air in.

3) Pressure wave dynamics and the force of air as the vehicle moves ("ram air") can be taken advantage of to create greater than atmospheric pressure.

4) The forces produced by a motor can be harnessed to drive an air compressor that will increase air intake. (this is called supercharging) If you attach a turbine to the exhaust system, it can drive a compressor and this is called turbosupercharging or "turbo" charging.

This whole process is reliant on (1), the changing of size/shape of the cylinder. If your cylinders don't change shape, then I don't see how you will be able to generate intake vaccuum.

Even a wankel rotary engine changes the size and shape of it's chambers to draw air in.

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If your cylinders don't change shape, then I don't see how you will be able to generate intake vaccuum.

They do chance shape. Heres another drawing that shows the outside of the Primary wheel, and what happens on each side of the chamber.

Cycle.JPG

The thin grey rectangles are the wheels that cut the chambers in half on the primary wheel. The long bars represent the outer surface of the primary wheel. Each side of the separator wheels cuts each chamber in half as it moves to the right. Notice that the walls (thin black lines cutting up the long rectangles) pass under the separator wheels and continue to the next side. Intake, as you mentioned, occurs when the size of the blue chamber expands, causing a vacuum, drawing in air.

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So the wheel, which spins in one direction, compresses air so as to allow combustion, then what allows the wheel to continue in the same direction after combustion happens?

With the wheel moving, and thus the "walls" attached to the wheel moving also, they would normally crash into a stationary barrier, much like the top wall of a piston chamber in a normal car engine, so it has to turn back around, occilating. However, if it is a temporary wall, the piston could keep going up past it. Basically, the top wall (the separator wheel) moves out of the way of the "piston" wall. After it passes, the separator wheel spins back down into the chamber, again cutting the chamber in half.

WheelInside.JPG

The combustion keeps pushing the wheel forward with each burn, like a hand pushing a wheel chair. The two separator wheels (look like rectangles, as viewed from the side) spin in a way that allows the wall to move under them, via the notch in the wheel (hopeflly the vaguely 3d drawing shows this =D).

The compression occurs in the green section. The air in the chamber gets moved into a pressure tank near the engine, instead of remaning in a highly compressed state inside the engine. After the air is compressed in the tank, it dumps it into the combustion chamber, then is sealed off, allowing the combustion to occur.

Heres an older 3d model I rendered. The only real difference is the orientation of the separator wheels in relation to the primary wheel. It would technically work both ways, but orienting the separator wheels in the middle would be more effient (less gears, less bulky engine) This may make mentally picturing the design easier, as the 2d drawings can be a bit fuzzy.

wheeeeel.JPG

Edited by ColdWontRise
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So there are two wheels spinning here and the combustion chamber spans spaces between the two?

Wouldn't they have to be rubbing up against each other to form a tight seal? Wouldn't this necessarily be enough friction to nix the whole thing? (Maybe calculate the surface area vs a piston engine)

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So there are two wheels spinning here and the combustion chamber spans spaces between the two?

Wouldn't they have to be rubbing up against each other to form a tight seal? Wouldn't this necessarily be enough friction to nix the whole thing? (Maybe calculate the surface area vs a piston engine)

Yes, theyd be spinning perpendicular to eachother, so it would have to be a tight seal but also have minimum friction. As long as the parts were made with enough precision (which is undoubtably possible *cough* Bugatti Veyron) and had well enough lubrication, then it should make each chamber air tight.

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