Bladeless Fluidic Turbopropulsion

[sevenperforce]

So I truly believe this is MY idea and I should definitely get credit for it...I've been doodling extensively on these designs for years now!

https://medium.com/predict/breakthrough-fluidic-propulsion-system-could-power-the-drones-aircraft-of-tomorrow-a6fe60da8f89

A new aerospace startup has developed a propulsion unit which uses a combination of laminar airflow and the Coanda effect to produce dramatic levels of thrust -- enough to enable VTOL -- without exposed fan blades. 

 Just imagining all the ways this could be used to power an air-augmented rocket....

[Wjolcz]

I actually feel similar about Starship's flaps. Was experimenting with the idea of using dihedral wings to stabilise the reentry profile of a spaceplane (and even posted a thread about it way before we saw the current SS design). I imagined it working, I just wasn't sure why it should (now I know it's about moving your centre of pressure behind the centre of mass). Though, the idea of skydiver spacecraft isn't that new (I just didn't know about it back then.

Anyway, this kind of looks like those Dyson vacuum cleaners or 'bladeless' fans. I like anything that could potentially end up in a high efficency electric aircraft.

Edited March 4, 2020 by Wjolcz

[sevenperforce]

4 minutes ago, Wjolcz said:

Anyway, this kind of looks like those Dyson vacuum cleaners or 'bladeless' fans. I like anything that could potentially end up in a high efficency electric aircraft.

The article mentions similarity to the Dyson bladeless fans -- they say that the bladeless fans can't produce meaningful thrust, but theirs can. Dyson fans use a compressor to suck in air, pressurize it, and spit it out in laminar flow, entraining the surrounding air. This system uses a gas generator -- essentially a small jet turbine -- to produce the pressurized exhaust for the same basis, but evidently uses a differently-shaped inlet to make entrainment more thrusty.

I'm already thinking of an old idea I had about four years ago, illustrated here and discussed on the forum here (images dead so go click on the other link to see what I'm talking about). If an aerospike engine is a conventional bell nozzle engine turned inside out, this would be an aerospike engine turned inside out again, but leaving an inlet at the center. In other words, the same design as the Jetoptera propulsion unit, but with tiny linear aerospike nozzles all along the duct rather than just a pressurized air outlet.

[p1t1o]

Meh, just blown flaps wrapped 360 degrees and used as propulsion. This is 1960's tech  

[sevenperforce]

1 hour ago, p1t1o said:

Meh, just blown flaps wrapped 360 degrees and used as propulsion. This is 1960's tech  

Love it.

[mikegarrison]

6 hours ago, Wjolcz said:

I like anything that could potentially end up in a high efficency electric aircraft.

Any analysis will show that what is necessary is better energy storage. Either several orders of magnitude improvement in battery energy density or some non-battery method of energy storage.

Kerosene strikes a very nice balance between energy mass density and energy volume density (with a bonus of not freezing in the stratosphere or being extremely volatile).

The energy density of even the best batteries is about 50-100 times less.

Also, with fuel, once you expend it you expend it. With batteries you need to carry the mass of the battery the entire flight, even if it has lost some (or all) of its stored energy.

Edited March 4, 2020 by mikegarrison

[K^2]

To accelerate air with laminar flow you need a velocity gradient. Velocity gradient is where energy losses happen. This might not be a big deal on model scale, but as you go bigger, you increase gradients to get more thrust, you increase the air flow, and you increase the volume in which these losses are happening. So it's going to be an unpleasant power law from length scale. Even going from their quarter-scale model to full scale is probably going to absolutely kill performance. Until they show a full scale engine with good specific thrust and fuel efficiency, I chose to remain highly skeptical on this.

[benzman]

It may not scale up easily but it makes for beautiful model aircraft.

 

[Zeiss Ikon]

So, this is basically a Dyson bladeless ring-fan, with as much power as the design can handle?

I seem to recall  discussion (somewhere) leading to the conclusion that this is a terrible way to build a fan, in terms of energy efficiency.  Which would imply it's also not a good propulsion system.

[Guest]

It looks like it might be all right for small drones. Considering there are many uses for those, I think it's not a big problem that it's confined to this niche. We have other ways of powering airliners.

[Nuke]

On 3/4/2020 at 5:55 AM, p1t1o said:

Meh, just blown flaps wrapped 360 degrees and used as propulsion. This is 1960's tech  

older, this is the same kind of thing that makes toilets work. 

[mikegarrison]

5 minutes ago, Nuke said:

older, this is the same kind of thing that makes toilets work. 

Not really. Siphon action is pretty different, relying on incompressible fluids and gravity, while airflow is compressible and usually discounts the effect of gravity.

Edited March 6, 2020 by mikegarrison

[Nuke]

1 hour ago, mikegarrison said:

Not really. Siphon action is pretty different, relying on incompressible fluids and gravity, while airflow is compressible and usually discounts the effect of gravity.

it does need fluid inertia to get the siphon action going though. small water jet accelerates the water in the pipes enough to make it over the trap to initiate the siphon.

[mikegarrison]

32 minutes ago, Nuke said:

it does need fluid inertia to get the siphon action going though. small water jet accelerates the water in the pipes enough to make it over the trap to initiate the siphon.

This brings up bad memories of having to learn all this hydrodynamics nonsense for the Fundamentals of Engineering (EIT) test. The first thing we do in aero engineering is drop that gravity term from the equations. The other engineers keep it in there (but they drop all the compressibility terms...). Anyway, while all fluid dynamics is kind of related, this thing really doesn't work like a siphon.

Try taking your standard toilet and just dumping few liters of water into the bowl. It will probably siphon itself (as long as it's not blocked up somewhere).

Edited March 6, 2020 by mikegarrison

[Zeiss Ikon]

On 3/5/2020 at 11:55 PM, Nuke said:

it does need fluid inertia to get the siphon action going though. small water jet accelerates the water in the pipes enough to make it over the trap to initiate the siphon.

This depends on how old the toilet is.

Jet-assisted siphon bowls came along when the effort started to reduce the amount of water used for each flush.  When I was a young fellow, no one cared if you used 19l (5 gallons) of water to flush the bowl, so the simplest design was preferred; the water just poured in from the rim until the level rose enough to start the siphon, then enough additional was included in the cycle to keep the bowl running long enough to remove all the waste.  Next to no momentum involved.  You can spot these older bowls by two marks: first, they'll invariably taller than modern ones, because the height was needed to give enough head inside the bowl to reliably start the siphon; and second, they don't have the small jet hole in the front side of the lead-in to the trap.

Once people started wanting/needing to reduce water consumption, there was a generation of really bad toilets that would clog at the slightest provocation (sometimes on just a few sheets of tissue).  These had been modeled after pressure-flush bowls from public restroom designs, but there wasn't enough head in the tank to reliably start the siphon if there was material in the bowl -- unless you mounted the tank on the wall, a meter or so above the bowl.  This produced very positive flushes, much like the pressure flush type, but eliminated the ability to store items on the tank lid.

Finally, the modern pressure-assisted siphon bowl came along, starting with premium brands and working its way down to the point where the cheapest stool you can buy today flushes better than the best one did back in the 1990s.  These use an improved pressure jet design which, yes, uses momentum to get the siphon started, and will reliably flush even a very heavy load with less than 3.8l (1 gallon) of water -- I've seen bowls that were rated as low as 2.5l in the last couple years.

Hint: if you have one of these modern low-flow toilets, don't try to save even more water by putting bricks or a full jug in the tank -- they will not work if you cut their water use by even as much as 10%.

[Nuke]

5 hours ago, Zeiss Ikon said:

This depends on how old the toilet is.

Jet-assisted siphon bowls came along when the effort started to reduce the amount of water used for each flush.  When I was a young fellow, no one cared if you used 19l (5 gallons) of water to flush the bowl, so the simplest design was preferred; the water just poured in from the rim until the level rose enough to start the siphon, then enough additional was included in the cycle to keep the bowl running long enough to remove all the waste.  Next to no momentum involved.  You can spot these older bowls by two marks: first, they'll invariably taller than modern ones, because the height was needed to give enough head inside the bowl to reliably start the siphon; and second, they don't have the small jet hole in the front side of the lead-in to the trap.

Once people started wanting/needing to reduce water consumption, there was a generation of really bad toilets that would clog at the slightest provocation (sometimes on just a few sheets of tissue).  These had been modeled after pressure-flush bowls from public restroom designs, but there wasn't enough head in the tank to reliably start the siphon if there was material in the bowl -- unless you mounted the tank on the wall, a meter or so above the bowl.  This produced very positive flushes, much like the pressure flush type, but eliminated the ability to store items on the tank lid.

Finally, the modern pressure-assisted siphon bowl came along, starting with premium brands and working its way down to the point where the cheapest stool you can buy today flushes better than the best one did back in the 1990s.  These use an improved pressure jet design which, yes, uses momentum to get the siphon started, and will reliably flush even a very heavy load with less than 3.8l (1 gallon) of water -- I've seen bowls that were rated as low as 2.5l in the last couple years.

Hint: if you have one of these modern low-flow toilets, don't try to save even more water by putting bricks or a full jug in the tank -- they will not work if you cut their water use by even as much as 10%.

mom has a miniature of one of these old timey toilets, i also believe they showed one in the godfather (apparently a good place to hide a pistol). 

Edited March 9, 2020 by Nuke