Why Hybridize? There will be no stop-start or regenerative braking so you don't gain the traditional car hybrid advantages. I would have thought the load would have been in a narrow enough range for a helicopter so that you could get away with an ICE and a single-speed gearbox. So why hybridize?

This makes a funky kind of sense. These OPOC engines, on paper, are incredibly efficient gen sets. I agree, I'd like to see them as gensets in medium duty serial PHEVs, but hey, if this gets them more research attention, that's probably good.

This opens up the question of serial hybrid or parallel hybrid?
The serial gas electric hybrid that they are proposing will be way too heavy and inefficient to implement. Having a large electric motor, generator, power controller will take up too much weight.

However, imagine a kind of hybrid like the Toyota HSD, which functions like a CVT using electric motors, in which the weight of electric motor, generator and power electronics will be cut to half.

Why hybridize helicopters? Because the rotor needs to turn faster in high speed flight and can turn slower in hovering or low speed flight to conserve power. Rigid rotor design can allows variable rotor speed without the inherent vibration problem associated with articulated rotors.
The energy stored in the battery will greatly facilitate autorotation in case of engine failure, making the helicopter much safer. This allows single engine helicopter to be just as safe as a twin-engine helicopter at lower cost and higher fuel efficiency.

A more fuel-efficiency aircraft will carry less fuel, permitting more payload.

Toyota HSD would suck in this application. Very low specific power of the ICE (due to the Atkinson cycle), a power split transmission and two electric machines. It sounds very heavy to me. Eventually, a helicopter is probably not the best application for a diesel engine. A long-distance aircraft would be a better application, since the engine weight penalty could be offset by less fuel load. But, to make this happen, we would need a well-developed propfan too that would enable cruising speeds similar to jet planes.

@Peter,
Who is saying anything about Atkinson cycle engine? The engine used here is OPOC, a relatively light-weight two-cycle engine. It's just that the transmission will be electrical CVT to reduce fuel consumption. All helicopters have transmission already, albeit a single-speed transmission (gear reduction unit). A significant part of the helicopter gross weight will be fuel weight. Reduction in fuel weight will allow for higher power propulsion weight.

If you save 30% in fuel, that makes up for the heavier engine/genset. Direct drive the rotor and get rid of the transmission, even more weight saved and safer too. Rotor speeds were quoted backwards, you want slower rotor speeds for high speed forward flight, the tip speed of the advancing rotor blade is a major part of a helicopter speed limitation. With a tilting motor/mast and rotor system, they may be able to get rid of the articulation. No gear box needed for the tail rotor, just a good motor and fly by wire, maybe double windings and inverter boxes for redundancy, helicopters can land without a tailrotor as long as they have forward speed. When I first read the title I thought this was another dumb idea, but with all the flapping bits and gear train on a normal helicopter that are critical to flight safety, a tilting electric motor with a battery backup sounds like it could work...

perhaps an application for a small tilt rotor similar to the V22 Osprey, the electric setup would simplify the transmissions. Something like the helicopters in the movie Avatar. This would give a you the high speed advantages of a tilt rotor without the complexities of dual turbines and transmissions in a small heli.. but electric motors and generators are still heavier than a transmission.

Ben: Correct me if I'm wrong but if you increase the efficiency a vehicle with 25% fuel efficiency by 45% it will only reach 36.24% efficiency (25% x 1.45 = 36.24%. That's a long way from 70%.

Very few ICE vehicles have reached 45% in regular use.

Going to have to brush up on my cyclic and collective.

Ben: I have to agree with you that the newest slow speed very large marine diesel can be 47.6% to 52.6% efficient under ideal conditions. (between 160 to 160 g/Kwh). However, under operational conditions they rarely do more than 45% because it is very difficult to keep them operating at their ideal sweet spot for long periods of time.

Assuming that 45% is possible (occasionally) in a heavy truck, increasing that efficiency by 45% = (45 x 1.45 = 65.25%). That would happen only when the heavy truck is operating at the engine sweet spot, about 30% of the time. However, even 50% to 60% would be much better than the 30% that most diesel trucks are currently getting.

The main advantage of an electric transmission is full power from the engine at any time it is needed at any aircraft speed or propeller speed. Another advantage is operating at maximum engine efficiency at any aircraft speed. The propellers can also operate at the highest design thrust at any engine speed if the power is available and also at the most efficient thrust. There is no reason for any battery in the main power circuit of such an aircraft. Multiple OPOCs even of different sizes or even a turbine generator for very high power low weight are more suited to flight than a battery.

Model aircraft are now using many electric motors, and I have been trying to promote a hybrid electric model for many years. The large IC engines now used in model aircraft would be suited for a tiny emergency range extender for an electric automobile of any size. You would be surprized how much faster one horsepower is than walking even in a large electric car. One horsepower is good enough for a constant five miles an hour or more in an electrically operated PRIUS. The Tesla may do a little better.

The electro-turbo-supercharger gives very high power density to this engine that I have been mentioning for years for use a range extender in electric cars, and it also gives very quick power response. The electric part of it can be used as a generator to put more power into the propellers when available, and conversely power can be robbed from the propeller to accelerate the turbo for more power. There is no limit to the supercharging of a diesel engine except the need for cooling.

The lightest weight motor/generator that can be made is a switched reluctance machine, and it does not use any moving magnets or moving conductors. It has high redundantcy and is already being used where reliable motors are used in aircraft. The switching semiconductor circuits are simple and thus more reliable. and they can be made redundant. Such motors can also continue to operate at lower power with a failure of one or more phases, and a shorted winding will not burn up the motor. ..HG..

Replacing, in the above application, the OPOC engine with the pattakon OPRE engine, everything improves.

The OPRE with two counter-rotating electric generators is not only absolutely rid of inertia vibrations (like a Wankel rotary engine), but it is also absolutely rid of combustion vibrations (torques) on its mounts.
In the case of the OPOC or of the Wankel electric generator set (or range extender), each combustion-expansion creates a strong pair of forces on the engine mounts.

The OPRE has extended piston dwell at the combustion dead center - some 20% as compared to the OPOC - which means higher revs and higher power density. It also means improved fuel efficiency at specific revs because of the additional available time for the injection and the combustion of the fuel at high “compression” conditions.

The multiple modules is applicable to OPRE too.

The lubrication and reliability of the OPRE are better because the thrust loads are taken away from the hot cylinder walls and away from the ports. In comparison, the lubrication of the skirt of the inner exhaust piston of the OPOC is anything but easy or efficient (the piston skirt abuts on the hot cylinder, onto the bridges among the exhaust ports, oil is lost at the exhaust etc).

The synchronizing mechanism between the two crankshafts of the OPRE remains completely unloaded in application of divided load, like the electric generation set.

Yet, in case the two crankshafts of OPRE seem as a disadvantage, the PatOP engine, which is the single crankshaft version of the OPRE, is the next reasonable selection (opposed-piston, single-crankshaft, single-cylinder, full balance of inertia forces and moments, extended piston dwell etc ect).

For more, take a look at www.pattakon.com web site.

Manousos Pattakos