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-   -   Efficiency Improvements for Internal Combustion Engines (https://ecomodder.com/forum/showthread.php/efficiency-improvements-internal-combustion-engines-13847.html)

NeilBlanchard 07-12-2010 09:54 AM

Efficiency Improvements for Internal Combustion Engines
 
There are a lot of improvements possible for internal combustion engines (aka ICE's). It helps to list the areas that are causing losses, to start:

-- The geometry of the physical layout of the piston, connecting rod and the crankshaft is less than ideal. The connecting rod needs to be ~60 degrees past top dead center to get the best leverage on the crankpin; but the pressure from the fuel ignition occurs much earlier than this; when the connecting rod is essentially trying to bend the crankshaft sideways. The motion of the piston is necessarily sinusoidal.

- The power stroke is only 25% of the full cycle, and there is a lot of mass that has to be accelerated, stopped and accelerated again.

- The valvetrain has to physically resist being moved, and it has to work against the air flows.

- The piston tends to scrape the sides of the cylinder, because it would "rather" twist that stay straight. The rings must exert friction on the cylinder.

- The oil must be pumped through little tiny passageways.

- Electricity must be generated.

- An ICE is a self-powered air pump, in essence. Air flow and the pressures generated, and the cyclical nature of them cause resonances, and backpressures, and the gasses become spring-like.

- Small volumes, like the space above the top ring and the top edge of the piston, trap unburned fuel because the flame cannot reach it.

- Everything flexes and springs -- the crankshaft and the camshaft flex torsionally and longitudinally, the piston vibrates and distorts, as do the cylinders. Valves bounce and stretch and distort into potato chip shapes.

The list goes on... The net result is an engine that uses ~20% of the energy in the fuel for output motion at best, and requires a transmission to keep the torque of the engine relatively close to the speed of the vehicle.

So, knowing all this, how can we make incremental or wholesale improvements?

+ Offsetting the crankshaft center away from the power downstroke gives the connecting rod some better mechanical leverage -- but is the compression stroke adversely affected?

+ Variable valve timing allows the torque to be available over a broader range of RPM's.

+ Valves can be electrically/hydraulically moved in both directions (opened and closed) to avoid fighting the springs. This also makes it easier to use subtle or more abrupt adjustments to the valve timing.

+ Use cams rather than the crankshaft, to gain a lot more mechanical leverage, and to allow the piston motion to be controlled by the designer; like the Revetec:

http://www.revetec.com/images/revani.gif

This particular design also reduces piston scrape (but it introduces some tendency to spin the piston within the cylinder). It also avoid big changes in crankcase pressures (in configurations with even numbers of pistons). This design effectively doubles the efficiency.

+ Use the Atkinson valve timing, like the Prius does, which has a lot of overlap of the exhaust valve with the beginning of the intake downstroke (I think?) so that there is built in exhaust gas recirculation (aka EGR). This also effectively doubles the efficiency.

Hmmm, how well would a 2-cylinder Revetec with Atkinson cycle and electrically activated valves work?


+ Use a rotary design that reduces the reciprocal motion.

+ Use a 2-stroke design to cut the parasitic losses in half.

++ Use a continuous burn design to further reduce the cyclical nature of the engine; or at least reduce the time between power cycles.

+ Figure out how to reduce waste heat from being produced, and then try to use the remaining excess heat to produce output.

What are other ideas to improve ICE's?

NeilBlanchard 07-12-2010 04:43 PM

Big Dave wrote:

Quote:

Ditching the torque converter would help a lot.
Yes, a more efficient transmission would help. Maybe we should have a system like racing motorcycles or F1 has? The dual clutch transmissions from VW and others could also work.

user removed 07-12-2010 05:05 PM

You have probably seen this before Neil.

It was originally conceived as an IC engine.

This video is running on 120 PSI shop air, but could easily be configured as an engine.

http://www.youtube.com/user/Ride122609

With variable stroke (not configured on the demo model) it could change compression and go to a no stroke position and use it's own spinning mass as short term storage.

Combined with a conventional CVT transmission it could P&G automatically without any additional driver input.

Notice the elimination of connecting rods, which are a major source of side loads on the pistons and most of the reason they need skirts to spread out the loads on the cylinder walls. Piston rods are the main reason why IV piston engines cylinders wear in a oval pattern on the sides 90 degrees in respect to the center line of the crankshaft.

regards
Mech

user removed 07-12-2010 05:09 PM

working principle

I like this engine for a HH, using the low pressure circuit for compression, and the combustion pressure to create high pressure hydraulic fluid for the accumulator.

I have seen efficiency quotes for this basic configuration as high as 58% in DOE hydraulic hybrid research dating back to 2005.

regards
Mech

dcb 07-12-2010 05:19 PM

Quote:

Originally Posted by Old Mechanic (Post 183471)
...
Combined with a conventional CVT transmission it could P&G automatically without any additional driver input.

dude, you gotta get that thing running on gas or some kind of fuel first. And CVTs are not in the "most efficient transmission" column.

user removed 07-12-2010 06:14 PM

Quote:

Originally Posted by dcb (Post 183476)
dude, you gotta get that thing running on gas or some kind of fuel first. And CVTs are not in the "most efficient transmission" column.

Dude!

I went through all the blarney and preconceived notions with the DOE 4 years ago when they made a blank statement about efficiency of rotary engines. Maybe they were referring to a Wankel, who knows?

I decided to pursue the transmission configuration. Back then Infinitely Variable Transmissions were practically unknown.

After confirmation of the design by Va Tech as well as many other Engineers who looked at the design objectively and found multiple benefits, including a ridiculous simplicity compared to any conventional power train, I was informed by a group of PHD students (all veterans) at George Mason University, west of DC, as to how to progress effectively.

1. Patent-done

2. A Virginia Corporation with a Dunn % Bradstreet number, for applications for Gov't grants-done

3. Functional prototype that passes stage 6 of operation for Military consideration.

#3 should be done by my 60th birthday in November, with a street legal functional vehicle to demonstrate wheel to wheel regenerative efficiencies, that we hope exceed 80%, could reach 90%, which beats electric regeneration by at the very least 100%.

Got any constructive suggestions I am all ears ;)?

regards
Mech

dcb 07-12-2010 07:06 PM

Quote:

Originally Posted by Old Mechanic (Post 183480)
Got any constructive suggestions I am all ears ;)?

Test your theories on a working model? Opinion != fact.

user removed 07-12-2010 08:06 PM

The quote for a working IC model was $70,000.

Got some spare change?

Va Tech calculated the in wheel hydraulic drives at 35 HP per wheel and 380 LB feet of torque. Sufficient for a Dodge Sprinter van. The torque was available at the first revolution of the wheel. They thought efficiency would be in the range of 93-95%.
Higher power levels are accomplished by increasing the piston diameter and reserve capacity.

The facts will be available soon enough, especially considering the process has taken 7 years so far.

In the mean time we are pursuing several avenues of cooperation. The suggestion was to partner with an existing manufacturer, and that is our current focus.

The necessary due diligence has been covered and the prototype is in the works as of this post.

I have learned to be patient, and seen many skeptical responses from folks.

That's fine, it's my baby anyway, and the finish line is getting close.

regards
Mech

user removed 07-12-2010 08:07 PM

Quote:

Originally Posted by dcb (Post 183485)
Test your theories on a working model? Opinion != fact.

The OP requested suggestions?

Do you have any?

regards
Mech

dcb 07-12-2010 08:24 PM

a flywheel and a piston cost 70k? I just wouldn't present theory as fact without testing. While I get the benefits of your proposal, I think you all might have missed a few considerations that could put this engine in the realm of seriously impractical for improving the efficiency of vehicles, i.e.: reliance on an inefficient cvt, large amounts of rotating mass , lots of extra weight, unproven delicacies in the crank area, unknown volumetric efficiency, rotating exhaust seal, articulated stroke has exponentially worse compression ratio in response to changes in displacement (unless the cylinders are made to be moveable too).

If you are going to present CVT as an efficiency improvement, you gotta back it up with real data. Number of patents and PHDs and a flow diagram doesn't mean squat. The real data I've seen has CVTs sucking air.


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