Is this wishful thinking?

Is this just another bit of wishful thinking or has anyone built one yet?

https://www.aquariusengines.com/technology/

Edited By Breva on 20/01/2023 22:45:58

Just more clickbait flypaper to try and get investors. Nothing new to see here. I imagine it shakes like crazy, reciprocating unbalanced. Just my opinion.

I agree, it is an unbalanced double action pneumatic actuator.

It appears to be a free piston gas generator, no indication of how it produces shaft power. Nothing particularly new, they usually feed into gas turbine expanders, which convert high pressure gas to shaft power. Wikipedia has a good write up on free piston engines.

Edited By duncan webster on 21/01/2023 00:15:48

The video briefly shows two parallel shafts which would help with the balance, but as mentioned, no explanation of how that power is coupled to a generator. Also, there's no mention of fuel consumption per Kw output. It looks like a simple two stroke principal to me.

In another video I saw on this engine they showed a reciprocating generator very briefly. The principle was the same as kids' shake-to-charge flashlight. The coil looked like it surrounded the piston rod extending out of the engine housing. Presumably the piston rod has magnets inside, like the shake charge flashlight, or a special wound armature fed through slip (or in this case slide) rings.

In another video I saw on this engine they showed a reciprocating generator very briefly. The principle was the same as kids' shake-to-charge flashlight. The coil looked like it surrounded the piston rod extending out of the engine housing. Presumably the piston rod has magnets inside, like the shake charge flashlight, or a special wound armature fed through slip (or in this case slide) rings.

It's essentially a double-acting, two-stroke ic. version of a Uniflow steam-engine so not ever so novel.

If the generator is of that linear pattern, like a solenoid running "backwards", I can't imagine it giving a very smoothly sinusoidal output.

It could operate a rotary machine but would need a cross-head, connecting-rod etc at each end so complicating the machine considerably.

I admire the inventors' efforts to make a yet-more-efficient i.c. engine, as I assume they intend; but I am not sure if ones like this are not close to re-inventing wheels.

Doesn't say so in the blurb, but I think the benefit of this type of engine depends on how it's used. The generator, not described, is important too.

Conventional IC engines spin a rotary alternator by wastefully driving a heavy crankshaft with several bearings, and the alternator probably has to be geared up as well - more waste in the transmission. There are circumstances in which a few percent better efficiency is valuable, especially if the power comes in a compact format.

A linear engine like the Aquarius could drive a pair of linear alternators, each perhaps as simple as a supermagnet oscillating to and fro inside a solenoid. It would produce variable frequency AC well above 50Hz. High frequency variable AC doesn't matter if the generator is used to top up a battery powered vehicle, because such AC can be immediately rectified into DC.

A linear arrangement could be quite compact, and being able to run on Hydrogen is a useful bonus. Obviously not a plug-in substitute for the petrol engine in my car, but potentially useful in an EV/Hybrid. This class of vehicle has an important future. All my motoring could easily be done with a pure battery car, but there are plenty of other use-cases where longer legs and more stamina are needed. Hybrids are almost certainly part of the answer, but the IC part need not be based on an 1886 Karl Benz Motorwagen! .

Dave

That depends where the engine and alternator are. The speed is multiplied in a car by the pulley ratios, but industrial generating-sets are directly-coupled. The heavy flywheel helps the machine rotate smoothly.

I doubt if the Aquarius engine would really save much in efficiency over a comparable, conventional reciprocating engine, although it may be more compact and does have fewer moving parts. Notably, their fancy animation did not reveal the cooling and lubricating systems, and it's not obvious how they would work.

As for "based on an 1886..." - the modern car engine if a very far cry from that, but if it's never been replaced in basic form maybe hardly anyone has devised anything genuinely better than a piston, connecting-rod and crank.

The one serious contender, gas-turbines apart, was the Wankel rotary engine but it was a complicated, difficult thing to make and maintain, and did not spread far. I don't know if it offered any efficiency advantage over a contemporary engine of similar shaft HP.

Dunno about the Aquarius engine, but Toyota claim 42% for their free-piston engine, which is rather better than the average reciprocating engine, which are usually less than 30% efficient, even when not idling at traffic lights.

Choosing a motor isn't simply about efficiency though because different motor types suit different operating conditions:

• Turbines are highly efficient,- well over 30%, and reliable but only at constant high rpm, no reverse. They easily outperform reciprocating IC in long-haul aircraft and for generating electricity, but are terrible for variable speed applications like road vehicles.
• Reciprocating IC engines are complicated (more maintenance), don't reverse, and are relatively inefficient, but they have a high power to weight ratio, convenient fuel, and can vary RPM over a reasonable range. Supported by a gearbox, they do well in road vehicles.
• Steam reciprocating engines have high start torque, but low efficiency (<5%), and massive boilers. Main advantage, they aren't fussy about fuel quality. Otherwise, almost entirely obsolete.
• Electric motors are efficient (>60%), high torque over a wide range of RPM, reversible, simple and reliable. Their Achilles heel is the need for a power supply, but whenever mains power is available, they slaughter other types of motor.

Free piston engines look to be a good option for Hybrid EVs. They're compact and don't need a big engine compartment. And their high efficiency is well suited to generating electricity. May only be a niche application, but the type could be important in future.

Dave

Looks like piston cooling and sealing would be a significant challenge on that design. Wankel engines have similar issues and they have more mass behind the seal and oil in the center gears.

Robert G8RPI.

Hi,

2 stroke engines run forwards and backwards.

Maurice

A la Bond minicar

Having owned not one but two Bond Minicars (built by Sharps Commercials who also produced the Bond Bug, I can remember them well!

The engine and gearbox was a modified Villiers motorcycle unit and available in 200cc and a heady 250cc variants. The reverse was effected by the Siba 'Dynastart' motor/dynamo on the end of the crankshaft, opposite the transmission. This could be run in reverse to start the engine in reverse, from a shielded second position on the ignition-switch; but I forget if the engine had two contact-breakers timed on either side of, or a single one on, TDC.

Whether a two-stroke engine is more or less efficient than an equivalent 4-stroke I do not know, but having no valves does mean slightly less power absorbed within the machine itself.

Very large marine Diesel engines are or were built in two-stroke form, as were some 4-stroke ones reversible via the valve-timing.

.

Missing from your list is the Steam Turbine.

As with the reciprocating engine the overall efficiency is let down by the need for a large boiler, hence external combustion; more than the engine itself. Nevertheless, power-station and marine steam-turbine sets achieve significantly better than 5% overall efficiency, thanks to long, steady running against fairly constant loads, full pressure-range through the engine to the condenser, and the heat-recovering economiser and feed-water heater.

Some ships, including the three Titanic class liners, used reciprocating engines followed by exhaust-steam turbines, to gain maximum expansion from HP inlet to the condenser's partial vacuum.

Large coal fired steam turbine stations achieved better than 40% efficiency, but you needed a condenser and very high pressure to get there. Big reciprocating mill engines achieved much better than SOD's 5%, but again using condensers. Not much chance of this in a vehicle. There were I think 2 attempts at condensing locos in UK, one with turbine (Reed Ramsey) and one with reciprocating engine. The first was a complete failure, the second had problems getting the condenser to work in tunnels.

Remember that gas fired CCGT stations have a boiler and steam turbine. They claim 60% efficiency, again not much hope of that in a vehicle.

Two-stroke have a higher power-to-weight ratio than 4-stroke, but 4-stroke are more fuel efficient and the exhaust is cleaner. Being more complicated 4-stroke are more expensive to make. So you tend to get 2-stroke engines when a cheap dirty noisy inefficient light-weight power unit is beneficial: usually open-air stuff like lawn-mowers, chainsaws, ATVs etc. 4-stroke engines win as soon as fuel economy, quiet, or cleanliness matter. Motorbikes are interesting because they straddle the line: sometimes 2-stroke, sometimes 4.

Whilst it's possible to build a reversible reciprocating IC engine, it's rarely done. 2-strokes don't require much modification, basically move the timing and spin it backwards. It's a cheap way of providing vehicles that rarely reverse with the ability. Might ask if it does the engine any harm, and the answer is yes, after a while, but not so it matters for occasional reversing. Did 2-stroke Bubble Cars have reverse? I seem to remember people had to get out and push!

Reversible 4-stroke engines need a complete second set of valve control gear, making them extra complicated. Sometimes done in ships to avoid installing a monster gearbox, but generally avoided. The lengths shipbuilders go to avoid fitting gearboxes is another story!

Dave

Hi,

I presume you consider a Napier Deltic 2 stroke turning out a maximum of 2500 bhp powering various ships and railway locomotives to be a cheap dirty lightweight power unit.

Maurice