GM Patents Twin-Charged, Variable Dynamic Compression, Hybrid Engine

[solarite_guy]

GM Patents Twin-Charged, Variable Dynamic Compression, Hybrid Engine

http://www.enginelabs.com/news/gm-pa...-hybrid-engine

The rumor mill from GM drivetrain has been ablaze lately. Just a few weeks ago, we found out that two new powerplants, both of which are dual-overhead cam V8s, were officially on their way, likely destined for the C8 Corvette. While a DOHC V8 wouldn’t be new to the Corvette, the small displacement would be as it’s rumored that the smallest will displace just 4.2 liters while the “larger” will come in at—a very familiar—5.5 liters.

As if the news of two new mills weren’t enough, AutoGuide has uncovered patents filled by the General for a revolutionary new drivetrain that not only employs both a supercharger and turbocharger in a twin-charger configuration, it also uses a variation on the Atkinson cycle to dynamically control the compression ratio—a method that we’ve been saying would be making its appearance for some time now.

According to AutoGuide, “After eighteen months in review by the United States Patent and Trademark Office, documents published on October 24, 2017 reveal GM has been granted a patent for an internal combustion engine with elevated compression ratio and multi-stage boosting.”

While the patent shows a four cylinder engine, it goes on to mention that the technology would likely be employed on engines with even larger cylinder counts. This could be a ploy by GM to disguise its efforts without full tipping its hand. Before we get down to the twin-charge segment of the patent proposal, lets first look at the Atkinson-type arrangement GM is hoping to use to vary compression ratios.

For some time now, especially after the debut of Nissan’s variable compression engine, we’ve said that the crankshaft doesn’t have to move to change the dynamic compression ratio. You could simply use valve timing events to effectively bleed cylinder pressures to what ever you would like them to be, in essence, controlling the dynamic compression ratio, even if the static compression ratio is rather high.



This is exactly what GM’s proposed new powerplant would do. The engine would be built to a static compression ratio of around 16:1, way outside of what is typically acceptable with today’s pump gas. However, the valve timing would allow the intake valve to stay open longer allowing some of the cylinder pressure to bleed off during the compression stroke leading to a reduced dynamic compression ratio under operation.

Then, when you are coming off power or simply maintaining a speed, the computer would ramp the compression ratio up, making the engine as efficient as possible since the higher the compression ratio the more efficient the engine becomes (to a point). To achieve this, the patent proposes two different methods. The first is radical new camshaft design combined with a variable-ratio rocker.

The camshaft would quickly open the intake valve and then hold it open—as you can see by the cam’s flat-nose profile. The timing of the valve event would then be controlled by a phaser and the variable rocker. The second method would be a electro-hydraulic actuator that would simply act as a solenoid to open and close the intake valve.



The second method would give GM near infinite control over the new engine’s compression ratio and power band. The crux of all this is direct injection. Since the injector will only fire once the intake valve is closed, the air being pushed back up into the manifold while the valve is held open on a portion of the compression stroke won’t contain fuel, as it would if it were used with a port injection system.

The patent seems to lean toward the camshaft design as GM says they thing that they could keep the intake valves at peak lift for an additional extra 20 degrees of rotation. However, if the camshaft is given the boot completely and the valve timing is directed by the ECM, peak intake dwell could be achieved for 5-80 degrees of crankshaft rotation.

After the document outlines how GM would dynamically control the compression ratio of the new engine, it outlines a series of power adders that would combine to make the powerplant even more efficient. The system would use a combination of a supercharger and turbocharger to produce boost.



The patent mentions that the supercharger would be driven by either a continuously variable transmission or even an electric motor and would be “low flow.” It would handle power production down low. The turbocharger would come on at around 3,000 rpm and would handle boost duties from there. In fact, you can see in the patent that there is actually a valve designed into the system that would allow the turbo to bypass the supercharger completely at higher RPM.

This system would provide the best of just about every world we can think of and is likely the future of the internal combustion engine as we know it. What’s more, the system would all be pared with an electric motor making it a hybrid system. At this point, it’s unclear if the drivetrain is destined for the Corvette or any other vehicle, but at this point you can rest assured that it is very early on in the development phases.

We probably won’t see anything with the technology for perhaps another five years, but it is definitely on its way. That is, if the internal combustion engine holds out until then. For now, we’ll just have to wait and find out. But either way, we can at very least appreciate the engineering that went into to the ideas outlined in the patent.

[Pedro]

Yeah, I was going to apply that engineering to my side valve Morris Minor, but I got distracted.

[solarite_guy]

This paper proposes a single unit acting as both the mechanically driven supercharger and the exhaust driven turbo charger. It also talks a little about the differences of series vs parallel twincharging systems when 2 units are used.

https://www.ijirset.com/upload/2014/...PSAAUTO005.pdf

In looking at the GM concept, it looks like a series system.



I think only specifics of this system can be considered under GM patent, as some of these things have been used for quite a while now.

[cheap]

This is the devils work. The 11th commandment says GM ‘performance’ engines must use pushrods.

[solarite_guy]

Someone must be dunked in a lake until they confess.

I am a little surprised about only remaining at maximum valve lift for up to 80* of crankshaft rotation.

My favorite drag radial camshaft stays there for 100* now and it is a 15ys old design.

[ivorya]

Love the idea but when will they just remove camshafts all together and utilize the computer to control the valves?

The technology is here..... now. It would give them better control of everything.

Incremental steps i guess....

[solarite_guy]

Originally Posted by ivorya

...when will they just remove camshafts all together and utilize the computer to control the valves?...

You are right, this technology has been around for I while. Some folks were working on this in the 70s and from what I recall, their concept was based on some pre-existing concepts, so it goes back before the time in the 70s I became aware of it.

Fig 7 in the 1st post shows the rendering of this approach using an electro/hydro approach.

This is the one that I specifically wondered why this system can only hang the valves at full open for no more than 80*. I can only consider a duty cycle limitation on the solenoid envisioned as the electro component of the valve actuator

Also, this is one of the aspects of this system that leads me to believe the entire system an not be panted. There are things described in the paper that have been used for tears already. I have to believe only aspects of this proposed system were granted a patent.

[jpd80]

I fail to see how this is much of an advance over what VW showed a few years back
when it used aggressive VCT with higher compression in a turbo and supercharged engine.

[solarite_guy]

Originally Posted by jpd80

I fail to see how this is much of an advance over what VW showed a few years back
when it used aggressive VCT with higher compression in a turbo and supercharged engine.

UPFRONT APOLOGIES: This post is longer than intended. jpd80 got me on an interesting topic regarding the VW Budack cycle engine. Again another Miller cycle engine re-badged, because, well, in modern days that is what "we" do.

Unless I am missing something, the more I think about it, over all this system seems to be a bit of shell game the patent office fell for.

The are a lot of misconceptions surrounding many of the components.

For example the Atkinson cycle used today is nothing but a Miller cycle with a name change. I'll just list a couple reasons:

1. The true Atkinson cycle, though conceived for a different purpose, resulted in a similar outcome as the Miller cycle in that the compression ratio (CR) was less than the expansion ratio (ER) by way of jointed "crankshaft/connecting rod", whatever you want to call it. The result is less power, however greater efficiency of the fuel consumed. This is one way to reduce internal hp loss by way of reducing "pumping losses". The fuel consumed in the intake and combustion strokes spend less effort compressing the next intake charge. So, although the engine produces less power this way, a greater percentage of the available energy from the combustion process is converted to mechanical rotational force of the crankshaft known as torque.

Along comes modern days and a misunderstanding of what the Miller cycle was. Somehow or another along comes this idea that using a conventional crankshaft and connecting rod arrangement in conjunction with the delay in closing of the intake valve long enough to push some of the intake charge back out of the cylinder past the intake valve, thus reducing the intake charge volume relative to the expansion volume (lower CR compared to ER), is now all of a sudden an Atkinson cycle, simply because there is no supercharger/turbocharger involved.

Actually, this misunderstanding is "the devils work".

2. The intent of the Miller cycle was to reduce combustion temperatures at TDC while an engine is under "full load" to prevent pre-ignition and allow a more complete burn of a rich fuel mixture under full power. Which it does. Anyone who has ever spent time testing on an engine dyno will know the ideal air/fuel ratio (AFR) or stoichiometric for petrol in an engine under full load is around ~12.5:1 and not the ~14.7:1 often taught in school (at least in my day). The 14.7:1 is basically for light load conditions.

How did Ralph Miller accomplish this? With variable valve timing, of course. This was patented back in the early-mid 1950s. Two of Miller's patents cover the aspects of the Miller cycle; one in 1954 and the other in 1956. Under these patents, application of the Miller cycle using variable valve timing applies to enhancements of the following engine types:

1. 4 stroke diesel
2. 4 stroke spark ignition (petrol, alcohol, gas, etc)
3. Naturally Aspirated
4. Boosted (supercharged and/or turbocharged)

The Miller cycle in fact does reduce combustion temperatures at TDC. How? This is probably the 3rd time this is mentioned here, please forgive me, by reducing the CR by way of variable valve timing relative to the ER.

It is interesting, Ralph had 2 valve timing methods of doing this.

1. Closing the intake valve very early
2. Clising the intake valve very late

Ralph liked option 1 for heavy use applications. By closing the intake valve early, before the piston reaches BDC, the intake charge now has a window of time to expand as the piston continues to travel downward to BDC. If anyone has seen a compressed gas cylinder, such as a CO2 cartridge, rapidly decompress they will have noticed how cold it became. Even covered in frost. The same principle applies to an internal combustion engine when the intake valve is closed prior to BDC. The expanding intake charge provides what Ralph called "internal cooling".

Option 2 above is exactly what the modern "Atkinson" cycle engines of today do. Remember Millers patents were not limited to boosted applications.

The sum of this Miller cycle vs Atkinson cycle discussion is Miller cycle engines have been used in a lot of applications for many years, so so GM can not put a patent claim on this particular component of the system presented in the article.

This has grown longer than I anticipated. If I have time I will add another comment or so about the myth that twincharging has only been around for 24 years, why flat nosed cams are nothing new, maybe I will think of something else...

Forgot some interesting references:

https://www.dieselnet.com/tech/engine_miller-cycle.php

https://www.dieselnet.com/tech/engine_miller-cycle.php

[Rallye Sport]

Can the mods delete the dribble going on in what is a seriously interesting, well researched thread that some of us are actually learning from.

[solarite_guy]

Sorry, this was supposed to be the second reference regarding Miller cycle engines for post #9. It is mainly a performance comparison to an Otto cycle engine as a home power unit.

http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

[solarite_guy]

Twincharging.

The idea and application of what is now known as twincharging is at least credited to have happened sometime in the 1930s. Unfortunately, I can not name a specific date, location or inventor. I wouldn't be surprised if the idea popped up 15 or more years earlier.

By the late 30s and through WWII it was a standard implementation in many military aircraft. P-38, F4U, F6F, B-17, B-24, 25, 26, 29, etc.

These twincharging systems used a gear driven centrifugal supercharger with the turbocharger (then called turbo superchargers) blowing through it.

Here is a drawing which was snagged from a video I will link to next.



Then here is a video and at 9:00 mins in an overview of the system is given.

NOTE: The vid was made in 1943 during wartime covering what was then considered restricted material. Time and cultural changes since 1943 haven't done the delivery of the video presentation any favours. Depending on your interests and take on history of the time, you may want to skip to 9:00 minutes and continue from there.



Then during the 1940s a 1920s or earlier concept found it's way into the fray of twincharging using a different approach to anything we've discussed so far. It is called Turbo-Compounding. The conventional turbocharger was replaced with a much larger unit which was powered by the exhaust to which added burning was induced with a little extra air and sometimes fuel almost like an after burner. This turbine spun a shaft which was mechanically connected to the engines crankshaft and the supercharger through gearbox arrangements.

Here's a drawing:

< Ooops, got 2 copies >



Here is a picture of an actual engine sans aircraft components, which was intended to be fit into a super-hydroplane race boat:



The Turbo-Compounding turned out the be the ultimate in piston driven aircraft power plants at the time, then the jet aircrafts came on the scene.

Of interest, not only could Turbo-Compounding add 500-600 hp to an aircraft engine, it could do so while dropping Brake Specific Fuel Consumption numbers from the usually rich ~0.6 range to the mid ~0.30 range. This means instead of consuming ~0.6 lbs of fuel/hp/hr the burn rate was now mid ~0.30s lbs of fuel/hp/hr. That's pretty good. Who would guess by looking at it?

The sum of all this is, twincharging has been around a lot longer than 24yrs and there is no way twincharging could be part of the patent in question.

[XByoot]

That’s great work Solarite
The Wright R3350 was probably the most successful version of turbo compounding . I believe they also claimed 1lb per HP per cube, ie 3350 lbs total weight, 3350 HP and 3350 ci. They powered Connie’s, DC7,s , Neptune’s and the B29’s too. Man I would have loved to play with those things. The metallurgy wasn’t quite up to the task I believe , but man they were pretty impressive. I recall doing my apprenticeship and the teachers at tech college telling their stories about working on them, myself and my tragic petrol head mates used to listen like it was some kind of religious recital haha.

[solarite_guy]

Thank you XB. You are right, the R3350 had some great benefits with the addition of turbo compounding. The designers/engineers used 3 turbos mounted at the back of the engine and I think they added less than a foot to the overall length of the engine.

Yes, I agree, metallurgy needed some improvement, but what a fine piece of engineering.

It's funny, when you have a motor head teach, sometimes the days lessons get side tracked.

[solarite_guy]

"Flat nosed cam lobes"

This pic is from the bottom of FIG 4 in post #1 with a few additions:



Let's set up some points of reference.

40A identifies the base circle of the cam
36A identifies a smaller but parallel circle to 40A. I used 36A because it gives more room to show things.
A identifies a reference from the center of the cam to the left edge of the cams flat nose
B identifies a reference from the center of the cam to the right edge of the cams flat nose
C identifies the distance from center of the angle created by A and B and
to a point perpendicular to circle 36A

Using a measuring graphic sw tool, the length of C is ~13 units from a point perpendicular to 36A and the center of the nose
Using the same tool, the lengths of A and B are ~16.5 units from a point perpendicular to 36A and each corner of the nose

As pictured this "flat nosed cam" will produce higher valve lift at the corners of the nose identified by A and B than at the center of the nose.

I can't imagine the engineers want this. The graphic must be poorly rendered.

For a cam lobe to have a "flat nose" the nose must remain parallel to the base circle of the cam. Not a visually straight line.

[Mercury Bullet]

We have Dan.

https://fordforums.com.au/showthread.php?t=11455094

[solarite_guy]

Nice project. Very clean and well thought out.

[Mercury Bullet]

Originally Posted by solarite_guy

Nice project. Very clean and well thought out.

Very talented fella is our Dan.

Anyone in the US compounding coyotes?

[solarite_guy]

Yes, for twincharging. Kits are available too.

Such a combination is not always an option in many racing classes where only 1 power adder is allowed.

The drag radial car I support runs in an organization that has this limitation. He keeps seeing the power numbers of the turbos and I keep telling him, on their own, they don't hook worth a crap. So he stays with his F3R. If 2 power adders were allowed then I would lean toward a turbo and use a nitrous hit to make the launches predictable.

[yearby]

Dave,

The concept of having the expansion volume being greater than the compression volume is imperative to gaining the most power per pound of fuel used, that is lowering the B.S.F.C.

I once did some mathematics/physics calculations on this.

I started by using a unit volume of air (14.7 mol of air) at a chosen under engine bonnet temperature, at atmospheric pressure and compressed it mathematically at a ratio 10:1.

10 to 1 being the compression ratio I chose.

I then used the Boyle's and Charles gas laws to calculate the new pressure and temperature of the compressed gas.

I then added one mol of petrol to the mixture, (to get the stoichiometric ratio or chemically correct ratio)

I then looked up the energy in 1 mol of petrol and then used it in a change in temperature formula to calculate the new temperature of the burnt fuel mixture if the piston did not move from T.D.C

Given that I knew the volume and the new temperature of the burnt mixture at the compression ratio at 10:1 at T.D.C. I was able to again use the Boyle's and Charles gas laws to calculate the final pressure.

Now what I wanted to know was how far would the piston have to travel down the bore (or should I say how much would the volume have to increase) to get to the point that the pressure on top of the piston was at atmospheric pressure again.
I also assumed that no energy (heat) was lost to the surrounding engine components (piston, cylinder wall, head etc,) such as in a ceramic engine.
And there was no frictional loss.

This would mean that all the chemical energy in the burn would have had to be transferred in to rotational mechanical energy in my theoretical internal combustion engine.

Now my calculations indicated an expansion ratio of about 30-33 times the compressed volume.
Unfortunately I have lost my original working so are only going by memory here..

What this implies is a petrol engine would need a compression ratio of about 10:1 and an expansion ratio of about 30:1 ( in theory).

Now to see if this had any credibility I divided the 10:1 by the 33:1 and the answered is about a 1/3 or about 30% which just so happens to be very close to the thermal efficiency on the typical 10:1 petrol/gasoline engine.

( I better put a special little note here to say the above calculations relate to a pre-emissions engine and that injecting an inert gas like burnt exhaust gas via the EGR valve will change the above expansion ratio and make it smaller and is a topic on it's own.)

So how does this relate to the real world........?

From my observations and experience an engine having an expansion volume greater than the compression ratio does not give any great horse power increase, but it does give a massive drop in fuel consumption.

That is, I played with something along these lines and increased the fuel economy of my 63 falcon from 30mpg (imperial gallon) to 40mpg.
Which is about a 30% increase.

Now I did not use any custom made or exotic parts, they where just what I scrounged up at the auto wreckers at the time.
(yes it's been a long time since anyone could buy 63 Falcon parts at your local auto wrecker)

So that makes me think that the ideas and patents present here are overly complicated and overly exotic.

So how did I do it?

I raised the mechanical compression ratio way beyond the octane rating of the fuel, lowered the volumetric efficiency so as the true compression ratio suited the fuel octane. This gave me a low compression volume and a high expansion volume. But having such a low volumetric efficiency loses power, so to compensate I enlarged the cubic capacity of the engine.

In a nut shell I put a 144 inline falcon cylinder head and carburettor on a 170 engine. I did a little more than this but hopefully you get the idea.
The compression ratio went from 8.7:1 to 10.3:1
At first I was using high octane leaded fuel and the engine was prone to over heating, it had a noisy exhaust (very noisy in the cabin), it suffered detonation, and the exhaust manifold was extremely hot. The exhaust manifold is under the clutch pedal and the floor was too hot for my feet. I was getting about 30mpg.

I then experimented with the then new low octane unleaded fuel.
With out any other modification the car when from 30mpg to 40mpg.
The exhaust when cold, there was no detonation, no over heating, and the engine run extremely quiet and smooth. So quiet that one would have to open the bonnet to see if the engine fan was rotating to know if the engine was running. And some times I tried to start the engine only to get excessive noise from the starter because the engine was already running.

The torque curve was a little lower in the rev's, but I just compensated by changing from 4:1 to a 3.5:1 diff ratio.
When doing too much city driving the plugs tended to foul up, but cleared up on long country runs.
It was about as powerful as the 144 engine it replaced and it drove about the same, but got exceptional fuel economy.

Later I played around with the idea of using a vacuum secondary carburettor to control (limit) volumetric efficiency, but today it would be better to let the computer management system control volumetric efficiency so that the engine could not enter detonation.

So in my opinion, the internal combustion engine has still got plenty of developmental life in it and if I can increase fuel efficiency by 30%, it's going to be around for a lot longer yet.

Peter

[solarite_guy]

Originally Posted by solarite_guy

...Here is a picture of an actual engine sans aircraft components, which was intended to be fit into a super-hydroplane race boat...

That should read Unlimited Hydroplane.

[Mercury Bullet]

Originally Posted by solarite_guy

That should read Unlimited Hydroplane.

Off topic, but what is that engine in the hydro?

When I was boat racing the nankervis brothers had one tucked away in a corner that was packing a 3000hp Merlin.

It was a monster lol.

[solarite_guy]

It is a V-1750 Allison

[Mercury Bullet]

Cheers, Australia used a lot of p40s during ww2 in new guinea powered by the 1710 I believe. I'm not sure what the difference to a 1750 is?

My favourite was the sleeve valved Napier sabre. 4500hp in it's ultimate configuration.
Sadly they all disappeared.

With the turbo-supercharger America was using did the supercharger run the 2 speed geared system or did they have to be single speed only?

[XByoot]

Pretty sure the Allison only ran a single speed blower hence the need for the turbo compound system I guess. The later Merlin’s ran a two speed blower for better altitude performance. The Wright 3350 used PRT ( power recovery turbines) that were exhaust driven and coupled back to the power section via some kind of fluid coupling , they didn’t actually provide any form of boost to the intake, they had a two speed blower to take care of that. They also ran a low tension ignition system, which is a coil per plug arrangement. This allowed a shorter run of high tension cables and less prone to failure at high altitude low pressure environments, basically a coil near plug system as we know it today. Another interesting discovery was jet streams, cores of high speed winds at high altitudes. Many planes were lost or had navigational difficulties due to them having super fast or slow ground speeds. Sorry for the ramble...I love this stuff!

[Mercury Bullet]

Originally Posted by XByoot

Sorry for the ramble...I love this stuff!

Don't be sorry, I love it too.
So many advances during this period.

I'd love to see a lot of it re-visited with modern metallurgy and production.
For example the Napier, hand built examples were stunning yet lots of problems with mass manufacturing.

[solarite_guy]

Originally Posted by yearby

Dave,

The concept of having the expansion volume being greater than the compression volume is imperative to gaining the most power per pound of fuel used, that is lowering the B.S.F.C.

I once did some mathematics/physics calculations on this...

Hey Peter,

I wish you still had your calculations, I would like to see how you came to that 30-33% expansion ratio.

Do you have specs on the two cylinder heads (including flow numbers) and induction systems in your test? I would like to look at it from a mechanical perspective.

Cheers

[solarite_guy]

Originally Posted by Mercury Bullet

Cheers, Australia used a lot of p40s during ww2 in new guinea powered by the 1710 I believe. I'm not sure what the difference to a 1750 is?

My favourite was the sleeve valved Napier sabre. 4500hp in it's ultimate configuration.
Sadly they all disappeared.

With the turbo-supercharger America was using did the supercharger run the 2 speed geared system or did they have to be single speed only?

It was a 1710. I had 50 in my head from the 1650 Merlin.

One of the V-1710 series had a 2 stage supercharger. It was for the P63 that went to the Soviets under the Lend Lease deal during the war.

I don't know that much about the Napier Sabre. I understand it made good power for it's displacement.

[solarite_guy]

Originally Posted by XByoot

Pretty sure the Allison only ran a single speed blower hence the need for the turbo compound system I guess.

Just for clarification, the turbo superchargers were not used in turbo compound arrangements.

The PRTs on the 3350s were a more advanced form of turbo compounding than seen on the 1710 in the picture I put up. This arrangement added direct power to the engine crankshaft and supercharger.

BTW the engine I posted was originally meant for Miss Bardhal before the era of the jet turbine powered Hydroplanes.

Before I forget, there were some 2 stage supercharger arrangements where an "auxiliary" supercharger was the second supercharge. Off the top of my head right now, I couldn't say which engine and which aircraft got these.

[solarite_guy]

Originally Posted by Mercury Bullet

Cheers, Australia used a lot of p40s during ww2 in new guinea powered by the 1710 I believe. I'm not sure what the difference to a 1750 is?

My favourite was the sleeve valved Napier sabre. 4500hp in it's ultimate configuration.
Sadly they all disappeared.

With the turbo-supercharger America was using did the supercharger run the 2 speed geared system or did they have to be single speed only?

I think the B-25 radial engines could come with a 2 speed super charger in conjunction with turbo supercharger aka turbocharger. (Edit: Maybe that was also a 2 stage?)

My family flew the B26s in Europe, following rivers, down on the water and either flying under or hoping bridges.