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Scuderi Group Developing Air-Hybrid Implementation of its Split-Cycle Engine

Scuderi
Cylinder pairs in the Scuderi Split Cycle. Scuderi divides the four strokes of the Otto cycle across two paired cylinders, a compression and a power cylinder.

The Scuderi Group, a company that designed and is developing a new internal combustion engine based on dividing the conventional four-stroke engine cycle across two paired cylinders, is enhancing that basic design with the addition of an air-hybrid capability.

The group, which just announced that it has raised more than $8 million in funding—including a $1.2 million award from the US government—will introduce the new air-hybrid split-cycle engine at the upcoming SAE World Congress exhibition in Detroit.

In the conventional four-stroke engine, a single piston slides up and down in a cylinder through the intake, compression, power and exhaust strokes—each power stroke requires two revolutions of the crankshaft. This basic design has not changed for more than 100 years.

The patented Scuderi Split-Cycle Engine divides the four strokes of the Otto cycle over a paired combination of one compression cylinder and one power cylinder. Intake air is compressed in the compression cylinder and transferred via a gas passge to the power cylinder for combustion.

The gas passage includes a set of uniquely timed valves, which maintain a pre-charged pressure through all four strokes of the cycle. Shortly after the piston in the power cylinder reaches its top dead center position, the gas is quickly transferred to the power cylinder and fired to produce the power stroke.

The design does not imply the doubling of the size of engines. In the four-stroke cycle, the engine fires every other revolution; in the split-cycle design, it fires every revolution. This is similar to a conventional two-stroke engine, but without the corresponding emissions and fuel consumption issues.

In other words, a four-cylinder split-cycle engine (two sets of paired cylinders) will produce the same number of power strokes as a four-cylinder four-stroke engine (four independent cylinders), but with enhanced efficiency, according to Scuderi.

In the Scuderi split-cycle, an intake charge is drawn into the compression cylinder, the piston of which then pressurizes the charge and drives it through a crossover passage, which acts as the intake port for the power cylinder.

A check valve prevents reverse flow from the crossover passage to the compression cylinder, and a crossover valve prevents reverse flow from the power cylinder to the crossover passage. The check valve and crossover valve are timed to maintain pressure in the crossover passage at or above firing conditions during an entire four-stroke cycle.

Combustion occurs (soon after the intake charge enters the power cylinder from the crossover passage and after the power cylinder piston passes through its top dead center position (ATC).

The crossover passage valves are critical to the efficiency of the engine. Although there have been paired-cylinder designs in the past, they were not able to match the thermal efficiency levels of the conventional four-stroke engine.

Part of that inefficiency resulted from the over expansion of the charge in the power cylinder, necessitating re-compression. By maintaining pressure in the crossover passage at combustion pressures, and firing after top dead centre, the Scuderi engine avoids that problem, according to the company.

According to the Scuderi Group, some of the benefits from the non-hybrid split-cycle design would include:

  • Fuel efficiency improvements of 15% to 30% initially with further improvements possible;

  • Potential reduction of NOx emissions of 50% to 80%;

  • Lower average operating engine speed reduces engine wear and tear;

  • High torque at low RPM means higher power at lower engine speeds;

  • Compatibility with existing engine manufacturing processes and tooling;

  • Same total engine size (number of cylinders and displacement) as comparable conventional internal combustion engines.

Because the compression cylinder is only concerned with delivering a pressurized charge to the power cylinder, enlarging the compression cylinder could take the place of a charging system such as a supercharger or turbocharger—the basic role of which to is force more air into the charge.

This specialization of cylinder function also opens the door to the air-hybrid concept to be announced in Detroit.

The Group believes that the Scuderi Air-Hybrid Engine will allow internal combustion engines in a variety of applications (diesel and gasoline, personal and commercial) to be 60% fuel efficient (compared to today’s 33%, almost doubling mileage, in other words) and reduce toxic emissions by 80%, while making it easier and less expensive to incorporate the technology into today’s automobile manufacturing process.

Scuderi identified a number of potential issues with the design during the modeling phase. These include:

  • Sustained elevated temperatures in the power cylinder could lead to thermal-structural failures of components and problems with lube oil retention. Scuderi may need to utilize different materials or techniques for the cylinder walls. Lower temperature coolants may be necessary. Lubrication may also be an issue, although one addressed with advanced synthetic or solid lubricants.

  • Possible valve train durability issues with crossover valve due to high acceleration loads, and possible valve-to-piston interference in the expansion cylinder. Both this and the preceding concern may be addressed by new valve designs.

  • Auto-ignition and/or flame propagation into crossover passage. Scuderi is looking to the placement and timing of fuel injection as well as crossover-valve timing to address these.

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Comments

Lucas

This is an interesting attempt to improve on existing 4-cycle engines by using two pistons and a bunch of valves to do what already can be done in a 2-cycle engine without valves.

In my proposals that I have been trying to give away to automakers worldwide, I suggest a constant speed diesel 2-cycle driving a generator at the most efficient speed to recharge the Lithium-Ion battery pack, only when needed.

It would have no valves. Fewer parts. Much higher efficency, and if done right, you could probably drive from coast to coast on five gallons of BioDiesel lubricated with castor oil.

d

A 2 cycle diesel engine would have some atrocious emissions of PM and HC. No thanks in LA. Now, constant speed 4-stroker with PM trap, ok.

Ash

I am very skeptical of an improvment in efficiency.

It would seem to me that the increase in rotating mass would negitavely impact the efficiency and performance.

I would also worry about reliability and cost with all of those vales.

Engineer-Poet

This concept is a regenerator and cylinder fuel injector away from an Ericsson-cycle engine.

Ray Killorn

Here is an implementation of this idea that was perfected in the early 1990s. It utilizes a 'Scotch yoke' rotary to linear converter which results in a true sine movement of the linear portion of the motor. This allows the crankcase to be sealed away from the piston. The benefit of this is that the back of the piston can serve the same function as the compression piston in this idea.

Although this looks like a conventional 2 stroke engine it has a special direct injector and an electronically controllable exhaust valve. These design features provide part of the flexibility necessary to provide radical improvements in engine efficiency.

A miniature fuel refining system targeted ultimately at this improved engine has been developed which improves efficiency of conventional, production engines. The gains are available in a simply installed, after market system. Funds invested in the venture, All Power Development Inc. (Email: lg@allpower.ws) will hasten the fuel economy savings in this very effective economy device. I have invested, I would recommend that you take a good look at what is going on here.

Rafael Seidl

This ia variation of an old design called a U-Cylinder engine. I beleive the Germans experimented with for diesel designs before the war. Placing a valve into the transfer conduit is mildly novel but it cannot compensate for the fact that this conduit represents a dead volume, which is bad for compression. On the combustion side, the main problem is that you never have cold air entering the chamber, so your temperatures and NOx will be very high and specific power low.

There's a reason why this idea has been gathering dust for decades.

Nick

I also doubt that this will go anywhere. As stated by Rafael, the expansion cylinder never gets cooled, leading to many problems with valves, lubrication, etc., which may only be solved, if solved they can be, by very expensive exotic materials. Gas turbines have some of these same issues. As I recall, the genius of the internal combustion engine is that combustion is not continuous but is part of a cycle of gas flow which includes much cooler temperatures. This allows the mechanism to be made from inexpensive materials (iron, steel alloys, aluminum, etc.) which could not withstand constant exposure to the instantaneous temperatures achieved during the explosion of the fuel mixture.

tom deplume

Looks like the Brayton 2-stroke of the 1890s. It was a part of the notorious Selden patent. There is only one occasion where it powered a car and then for only a few hundred feet before failing.

A.Syme

The proof will be in the building of a proto-type. Let's see it run!

A Vieira

Sorry if this seems basic but in the article it's stated that:

"In the four-stroke cycle, the engine fires every other revolution; in the split-cycle design, it fires every revolution."

If you have two cylinders in the split-cycle to fire once every revolution, doesn't that equal a 2 cylinder 4 stroke engine? Each cylinder fires every revolution, making that a combustion per revolution...Right?

Mike

In the split cycle engine, only half of the cylinders actually fire. So in a four-cylinder split-cycle engine, two cylinders firing every revolution = two combustion events per revolution. In a standard four-cylinder Otto cycle engine, every cylinder fires, but only after two revolutions. Hence four-cylinder Otto = two combustion events per revolution--equivalent to the two combustion events per revolution of the four cylinder split-cycle engine. Looking at it another way, each of the dedicated power cylinders in the split-cycle engine does twice the combustion work of the "multi-purpose" cylinders in a standard Otto engine for the same number of revolutions.

Eric

"In my proposals that I have been trying to give away to automakers worldwide, I suggest a constant speed diesel 2-cycle driving a generator at the most efficient speed to recharge the Lithium-Ion battery pack, only when needed."

E-traction is 4 years ahead of you: http://www.etraction.com

14 MPG bus! wow!

Edward

Very interesting but our concept is a much more improved power source. An introduction to the CAFEC (compressed air, fuel, external combustion) Engine concept. Both the intake and compression strokes are eliminated. All movement of the piston supplies power to the back wheels.

Visit http://www.cafecengine.com and watch the test model MR SCRAP run.

hirosha

i like to know about this environmental fiendly compressed air engine...
how it works.. its smply super..
i like to fix it to a bicycle ..so it wud b a motorcycle-if u succeed just let me know+ 4 ma idea giw atleast 10 dollars per bicycle u make..

using bicycles rather than cars vans or any other vehicle would take less space,excellent 2 eleminate traffic jams..
bicycles are also lighter,.so plz think about it.if u succeed plz send me also 1 bicycle with a compressed air engine.

hirosha

i like to know about this environmental fiendly compressed air engine...
how it works.. its smply super..
i like to fix it to a bicycle ..so it wud b a motorcycle-if u succeed just let me know+ 4 ma idea giw atleast 10 dollars per bicycle u make..

using bicycles rather than cars vans or any other vehicle would take less space,excellent 2 eleminate traffic jams..
bicycles are also lighter,.so plz think about it.if u succeed plz send me also 1 bicycle with an compressed air engine.

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