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Old 03-15-2017, 07:19 AM   #1 (permalink)
Less waste = better FE
 
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Shock storing conrod arm mod

I have been thinking for a while about a way to change an internal combustion engine to make it more fuel efficient. This mod to the conrod is the simplest/cheapest implementable solution I came up with.

I am now asking for comments why it can or can’t work. As far as I could think everything through it should work. But I probably haven't thought of everything.

The idea, as can be seen on attached "artist" drawing, is to put a spring on a conrod arm, and split the arm in 2 so that it is compressible. The spring can store the energy shock at peak combustion, and give it back to the crank shaft after TDC. This will increase torque and reduce fuel consumption.

It will also solve a few problems associated with internal combustion engines.
1) Reduce/eliminate NOx in diesels as peak combustion temps will be lower.
2) Eliminate detonation (ping) in petrol engines.
3) Probably have a cleaner burn with reduced wasted exhaust gasses.
4) Engine parts can be made smaller/lighter as peak combustion will be lower.
5) Have more torque as there will be more pressure on crankshaft after TDC which was stored temporarily in spring.
6) Timing can be advanced more leading to better combustion and improved fuel consumption without damaging the engine or having bad exhaust gasses.
7) Quieter engine operation with less shock and vibration and wear.
8) Less wasted heat going into cooling fluid as combustion temps are lower.

Disadvantages I can think of.
1) Conrod arm will be heavier. This can be compensated with lighter crankshaft and lighter piston.

A bit about the drawing. It is just a concept for explanation. I am sure it can be improved. I don't have all the knowledge of what type of spring strength is needed, but I am sure someone can work it out.

The conrod arm is made of 2 pieces, which fits into each other. The pieces shouldn't be able to twist in each other, as it will break the swivel point on the piston. A pin through the top conrod will slide in the slot on the side of the bottom conrod. This will stop the spring from pushing the two conrod pieces apart. At the top of the spring there is a piece of metal to hold spring so that it doesn't interfere with the swivel point at the piston.

An oil channel runs from the big end to a hole connecting it to a slot along the top conrod arm. This slot in the top conrod will always be connected to the hole opening in the bottom conrod. So as the top conrod slides into and out of the bottom conrod, there will always be a path through for the oil to the piston. The oil volume will also not change as the compression / expansion happens. This oil will also lubricate the sliding surfaces between the conrods.

If the pin in the top conrod is made better to stop the two pieces twisting in each other, the conrod arms could be made from round metal. I was just concerned about wear on the groove and pin of the top and bottom conrod arms respectively. So I drew it with square pieces fitting into each other.

Please comment on what you think the problems associated with this design is or how it can be improved, I would like to know if it can work. After that we can start messing with lawn mowers, etc. to test it.

Jan


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Last edited by DieselJan; 03-15-2017 at 07:32 AM.. Reason: Try to move it out of aerodynamics
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Old 03-15-2017, 07:54 AM   #2 (permalink)
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Durability and stiffness are just a few issues that I foresee. The bending forces on the conrod will require a significant overlap, adding yet more weight. The spring will also need to be huge to control the mass of the piston.

I cannot see any advantage to the design.

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Old 03-15-2017, 08:30 AM   #3 (permalink)
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I think the biggest flaw in this design is, that a normal rigid conrod, doesn't cause the problems You think it does.
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Old 03-15-2017, 09:30 AM   #4 (permalink)
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Quote:
Originally Posted by jakobnev View Post
I think the biggest flaw in this design is, that a normal rigid conrod, doesn't cause the problems You think it does.
Hi Jakobnev
I know the conrod doesn't cause the problems, but I think it can solve the problems. The problems is caused in the combustion chamber above piston. The problem is caused by sudden combustion causing an impulse, this impulse is the sudden high pressures and temperatures. The conrod mod is to smooth the impulse and convert it into useful work.

See an example here

The resulting waveform with the modification will probably look something like the attached scan. The area of the graph above the spring pressure will be delayed and added where it is more useful to generate output work. Remember that all the pressure and heat at TDC does nothing for usefull work, it only heats combustion chamber walls and cooling fluid. The real work is only transferred to the wheels after TDC.

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Last edited by DieselJan; 03-15-2017 at 09:37 AM.. Reason: Spelling and adding some info.
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Old 03-15-2017, 09:42 AM   #5 (permalink)
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Let me get this straight, you want to take energy going into the rod/conrod and convert it into spring/mechanical energy because you think it can be engineered in a way to delay the energy's transfer to a more opportune moment in time called peak compression?

This sounds like an attempt to mechanically augment the octane of the fuel. That is to say to control/predict the "kick". That little snap in the end of an ankle which gives some double jointed swimmers an advantage.

I do not think you will get your "kick" in this way because you can cannot destroy or create energy, you can only convert it. You are converting energy in this case from motion via fuel combustion into spring compression, there will be energy losses in the conversion (typically heat).

You want to get more mechanical energy out of the engine, heat is lost energy. You do not need more heat.

What your time might be better spent pondering is why fuel energy is spent only on the down-stroke and not the upstroke of the piston. If you ever put toe clips on your bicycle you know what I'm talking about.





There are experimental engine designs which deal with this issue, some are round, some are flat/horizontally opposed, look them up.

I'm curious why this topic is in the Aerodynamic section of the forum. Maybe you can answer that first.

In short, I think you have created more problems than you have answered, making you a better philosopher than an engineer. I'm just an architect, so take it all with a grain of salt.

EDIT: Heat caused from mechanical braking (friction/brake pads) is replaced in electric cars and hybrids with regenerative braking. This is your clue, salvage all the wasted heat in your system. Where there is heat, there is wasted energy - look at the incandescent light bulb for example.

If you had an engine which created no waste heat, it would be 100% fuel efficient.

Maybe make your engine block into a Seebeck generator?

https://en.wikipedia.org/wiki/Thermoelectric_generator
Quote:
A thermoelectric generator (TEG), also called a Seebeck generator, is a solid state device that converts heat (temperature differences) directly into electrical energy through a phenomenon called the Seebeck effect (a form of thermoelectric effect). Thermoelectric generators function like heat engines, but are less bulky and have no moving parts. However, TEGs are typically more expensive and less efficient.[1]

Thermoelectric generators could be used in power plants in order to convert waste heat into additional electrical power and in automobiles as automotive thermoelectric generators (ATGs) to increase fuel efficiency. Another application is radioisotope thermoelectric generators which are used in space probes, which has the same mechanism but use radioisotopes to generate the required heat difference.[1]
https://en.wikipedia.org/wiki/Thermoelectric_generator

I'm guessing you could eliminate your cooling system or at least go air cooled.
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Last edited by kach22i; 03-15-2017 at 09:50 AM..
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Old 03-15-2017, 10:05 AM   #6 (permalink)
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Quote:
Originally Posted by kach22i View Post
I'm curious why this topic is in the Aerodynamic section of the forum. Maybe you can answer that first.

In short, I think you have created more problems than you have answered, making you a better philosopher than an engineer. I'm just an architect, so take it all with a grain of salt.
Hi Kach22i
Yes, check the reason why I edited the first post, to move it out of aerodynamics. It was an mistake as I posted new thread from aerodynamic thread. Didn't know it works like that.

Luckily I am a electronic engineer, not mechanical. That is why I asked comments.

If you look at a bicycle and only peddle at the same angles that an engine applies peak power, you will not get far very fast. Normally one will pedal from about 1-o-clock to 5-o-clock looking at the pedal as a watch. The engine applies most force close to 12-o-clock. If you get on your bike and stand on the pedal at 12-o-clock you will not move, you only start to move as soon as the pedal goes forward to 1-o-clock.

I fully understand heat is waste. The spring will generate very little heat. The energy it absorbs will be converted back to pressure as soon as combustion pressure goes below spring pressure. See the attached graphs I added before.
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Old 03-15-2017, 01:40 PM   #7 (permalink)
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I would also fear it to actually increase the pumping losses.


Quote:
Originally Posted by DieselJan View Post
The spring will generate very little heat. The energy it absorbs will be converted back to pressure as soon as combustion pressure goes below spring pressure.
Even though the heat generated would eventually be almost negligible, it's still not going to be converted back into "pressure", neither control so effectively to which direction it would be applied.
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Old 03-15-2017, 09:07 PM   #8 (permalink)
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Quote:
Originally Posted by cRiPpLe_rOoStEr View Post
I would also fear it to actually increase the pumping losses.

Even though the heat generated would eventually be almost negligible, it's still not going to be converted back into "pressure", neither control so effectively to which direction it would be applied.
What if it were applied to the first gif below?

914World.com > Camless engines


The spring would probably make it go crazy in two directions instead of one.


Well, how about some conventional layouts?


Professional Automotive Repair | Timing Belt Replacement - Professional Automotive Repair Atlanta | Marietta | Car Maintenance


engine - what is difference between DOHC and SOHC? - Motor Vehicle Maintenance & Repair Stack Exchange


https://www.pinterest.com/pin/339810734358256743/


Camshaft VVT

Quote:
Double overhead camshaft (DOHC) - 4 stroke engine with fixed valve timing that the valve train is set by the auto maker for peak efficiency running at a specific point in the engine's operating range, and
These Gif's are a lot closer for discussion purposes than the bicycle diagram/video. The bike one was a "what if" the up stroke was powered. Kind of a side bar distraction, trying to stay focused.

There are a lot of stresses on conrods/rods forces from all directions, just not feeling a spring application in my bones.

https://grassrootsmotorsports.com/fo...r/50017/page1/





https://www.tomeiusa.com/_2003web-ca...60_conrod.html

Quote:
The forging process ensures that the conrod is capable of high stress loads at high RPMs when the tension loads exceed 1 ton.
I'm afraid to think what a one ton spring looks like.
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Old 03-15-2017, 10:00 PM   #9 (permalink)
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What if you sealed the bottom part of the cylinder and had compressed air push the pistons up will fuel continued to power the downstroke??
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Old 03-15-2017, 10:09 PM   #10 (permalink)
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I am trying to understand how effectively reducing the compression ratio of the combustion chamber, you are "increasing efficiency?"

In a conventional engine design, increasing static compression ratio will increase the energy gained...up to the maximum point the fuel you are using will handle..

Perhaps just do what all modern car manufacturers try to achieve..control the flamefront / swirl through the engine with head / piston design, and try to reduce the ignition / expansion of gasses event to be as close to TDC as possible (To prevent the expansion of gasses pushing the piston backwards on its upstroke).
  • Improve head desgin to promote better combustion
  • Improve piston design to promote better combustion
  • Reduce time before TDC
  • reduce friction in the combustion chamber (Short skirts, lighter weight)
  • Use higher quality materials that do not transfer heat (Ceramics etc)
  • use higher quality fuel that allows quicker, more controlled flamefronts

Of course, a standard internal combustion engine (4 stroke especially) is pretty poorly designed interms of efficiency..
Maybe look at the Miller Cycle / Wankel / etc engine designs..many are much more efficient than a typical 4 stroke..of course they have a few other faults that need to be taken into account..(Reliability / emissions / size / weight / serviceability etc)

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