Ok so does this mean tuning on ICE with ethanol can overcome its weight disadvantages in aircraft applications?
... an aircraft of my design taking flight and choosing fuel sources..
... So does ethanol's benefits outweigh its faults in an aircraft?
So what is it, if you were building an ICE powered aircraft, and influencing your client on critical choices, what would it be.... Keep in mind, your comments influence what actual fuel ends up in the wings of and airplane. Are we building compact turbocharged 4 stroke tuned to extract the maximum from ethanol or sticking with gasoline, or even av gas to keep this bird in the sky the longest on the maximum weight requirements?
ICING and/or VAPOUR LOCKING - ethanol or E85 will kill you in one of these ways
they inherently carry c. 5% water by solution and absorb further water
there was enough trouble with Mogas - and worse Mogas mostly now contains 5% ethanol or 10% ethanol
btw avgas is designed for (eg turbo) supercharged engines - it's 100/130 PN whereas road 100 octane is maybe
100/108
Last edited by Tommy Cookers on 15 Apr 2020, 11:39, edited 1 time in total.
Ok so does this mean tuning on ICE with ethanol can overcome its weight disadvantages in aircraft applications?
... an aircraft of my design taking flight and choosing fuel sources..
... So does ethanol's benefits outweigh its faults in an aircraft?
So what is it, if you were building an ICE powered aircraft, and influencing your client on critical choices, what would it be.... Keep in mind, your comments influence what actual fuel ends up in the wings of and airplane. Are we building compact turbocharged 4 stroke tuned to extract the maximum from ethanol or sticking with gasoline, or even av gas to keep this bird in the sky the longest on the maximum weight requirements?
ICING and/or VAPOUR LOCKING - ethanol or E85 will kill you in one of these ways
there was enough trouble with Mogas - and worse Mogas mostly now contains 5% ethanol or 10% ethanol
btw avgas is designed for (eg turbo) supercharged engines - it's 100/130 PN whereas road 100 octane fuel at best 100/108
Thanks. That is very valuable information that leads me down a rabbit hole, one I should be deep into already. Man this forum is great, filled with honest experts. Thanks.
Hi Guys.
I've been interested in this picture for some years. Perhaps this forum has the knowledge to answer my questions. How does underneath 2-stroke v4 work with regards to port timing, sharing a sump for each 2 cylinders. As you can see the conrods seem to share pin position, but not the actual pin. Does the crank lob in between the pins cause a separate sump per cylinder? It's so much more compact then the 500cc V4's of motor cycles back in the day. http://www.aaenperformance.com/images/snow/V4_Cross.gif
each cylinder needs its own crankcase induction with this combination of V angle and crank design (chosen for even firing)
isn't this the convention for 90 deg or near-90 deg V angles with 2 or 4 cyl 2Ts ?
others eg 'BB' Honda NSRs had very unusual cranks that were a discouragement to crankcase sharing
lavish space for a good porting system may dictate cylinder spacing and so crank/crankcase layout eg for race engines
to have 2 or more cylinders with a 'shared crankcase' would need adjacent cylinders to have simultaneous firing or nearly so
not inconceivable with an inline 4 or a V with many cylinders - also shared induction systems and exhaust systems of course
and so-called 'split singles' used a 'shared crankcase'
the few simultaneous-firing parallel twins (OSSA and Husqvarna) didn't because they were just adaptions of existing designs ?
Last edited by Tommy Cookers on 15 Apr 2020, 14:56, edited 1 time in total.
Ok so does this mean tuning on ICE with ethanol can overcome its weight disadvantages in aircraft applications? Remember, I hinted at my understanding, i.e. lower egts, knock reduction, and higher boost and/or advancing timing, all things which have garnered faster lap times from my peers/customers, but it still doesn't address the Manolis comment. Is ethanol a suitable fuel source for aircraft, assuming all those benefits? This isn't a bait and switch I am honestly curious , and I have some skin in the game (not just commentary but actual risk i.e. an aircraft of my design taking flight and choosing fuel sources)
So does ethanol's benefits outweigh its faults in an aircraft? Sure I could do the math for myself, but yall are pretty keen and more wise than I, by far, by miles, by km, by light years. I am a merely a designer, the butt of well deserved jokes.
So what is it, if you were building an ICE powered aircraft, and influencing your client on critical choices, what would it be.... Keep in mind, your comments influence what actual fuel ends up in the wings of and airplane. Are we building compact turbocharged 4 stroke tuned to extract the maximum from ethanol or sticking with gasoline, or even av gas to keep this bird in the sky the longest on the maximum weight requirements?
That depends. I would think it could be intresting for ultra lights like uniflows gyrocopter, not so much for bigger aircraft for reasons TC already mentioned. Performance wise it's probably not the best choice for an aircraft. But it brings other advantages with it. It's cheap, some people can even produce it by them self, existing engines need little to no modifications to run it and so on. If you want maximum performance, you will go with a jet- or propturbine anyway.
I had simply a problem with what Manolis wrote because it's not that one dimensional in reality. If it would be, we all would use liquid hydrogen because it has the absolut highest energy content per mass value. But we don't use it because it comes with a shitload of problems attached.
If it would be, we all would use liquid hydrogen because it has the absolut highest energy content per mass value. But we don't use it because it comes with a shitload of problems attached.
Yep. Besides the fact it's cryogenic it also takes up a far greater volume. Volumetric energy density of liquid hydrogen at 20°K is about 130 MJ/kg, and volume is about 14 L/kg. Gasoline energy density is about 45 MJ/kg with a volume of about 1.3 L/kg. So the liquid hydrogen equivalent energy to a liter of gasoline would be about 4.5 L ± of cryogenic liquid.
You write: “I had simply a problem with what Manolis wrote because it's not that one dimensional in reality. If it would be, we all would use liquid hydrogen because it has the absolut highest energy content per mass value.”
No.
The necessarily strong / heavy tank required to hold the Hydrogen, reduces several times the actual energy density of it.
Storing 1 kg of hydrogen at 100 kPa and 25°C requires a tank of volume 12.3 m3. Compressing hydrogen to 350 bars decreases the required storage volume by 99.6%. Further pressure increases lower the required storage volume, but increase the compression work input and safety concerns (Hosseini et al., 2012). A key enabler factor to use this route of storage is the public's awareness on safety issues associated with high pressure hydrogen tanks. Compressed hydrogen can be stored in closed tank systems at volumetric densities of around 20–50 kg/m3 and gravimetric densities (kg H2/kg of the tank) of around 5%–10% (Hosseini et al., 2012).
In the case of automotive systems, it was internationally agreed upon a standard pressure for the storage of gaseous hydrogen in the car of 70 MPa (700 bar).
End of quote
The above quote talks for gravimetric densities (Kg H2 / Kg of tank) around 5% to 10%.
Zapata had to carry 40Kg kerosene (in a tank / bag weighing no more than 1Kg) for the crossing (in two steps) of the English channel; this quantity of kerosene has as much energy as 40Kg * 45MJ/Kg / 130MJ/Kg = 14Kg Hydrogen.
The tank required for 14Kg of Hydrogen weighs, according the previous quote, from 140Kg to 280Kg. I.e. Zapata should carry on his back some 200Kg.
When we talk for flying devices the actual (including the tank) energy density of the fuel is crucial.
Another crucial factor is the efficiency of the engine because the quantity of fuel required for a specific task is inversely proportional to the efficiency of the engine that burns the fuel.
A jet turbine running at 3% BTE (Brake Thermal Efficiency) requires ten times more fuel than a reciprocating piston engine running at 30% BTE.
The JetPacks of Zapata, Mayman, Browning and Rossy run on less than3% BTE.
These explain the expected range and flight duration of the Portable Flyer:
At 30,000 ft Ethanol would need well over 30% water content to freeze.
it's induction system icing that is an ever-present factor eg in light aviation
ok the potential (on gasoline) is much less now (with injection) than with carburettors
nevertheless precautionary running on 'alternate' ie heated air pre takeoff and pre landing are still mandatory
injection type induction systems still have venturis and throttles
remember every landing immediately follows a period of heavily-throttled running
compared to terrestrial air aviation air is colder and closer to 100% relative hunidity
replacing gasoline with a fuel having 10 - 20 ?? times the evaporative cooling seems most unwise
replacing gasoline with a fuel of such low BP (so greater vapour locking tendency) seems most unwise
re Mogas Lycoming won't (or wouldn't ?) accept any ethanol and only 1% oxygenates
E5 Mogas applications are only for some engines and within extensive restrictions (no-one seems to accept E10)
eg tank fuel temperature below 20 deg C and altitude below 6000 ft
the LAA requires placards for E5 warning of 'carb' icing, water contamination, and vapour locking
ethanol vapour has a lower specific heat ratio (than gasoline) - though methanol vapour has a higher SHR
butanol is the better-performing alcohol - its mass-specific heating value is quite high and its airmass-specific HV is outstanding
In case of malfunction of the one engine, or in case one propeller hits an obstacle and falls apart, or in case a transmission tooth belt is broken, or . . ., the “healthy” engine-propellers-set is sufficient for a safe landing.
So here is this guy flying along, as you postulate, at 200 kph horizontally, and a belt breaks and disables one of the propeller units. So what happens? Even if, by some weird chance, the pilot was able to control this craft before the malfunction, all of a sudden, in horizontal flight, one of his engines (the propeller) fails. In a light twin there is an immediate tendency for the plane to roll and invert, and this is in a craft with actual wings, rudder, and tail; with your machine I would expect a rapid and fatal roll and spiral into the ground. You really have control issues here that you don't seem able to understand. The pilot who would fly this craft is either very brave or very stupid, and I suspect the latter. Even if you have some sort of ballistic parachutes in the spinners, there would be no way to deploy them. Your engine? Great. Your machine? Deadly.
You write:
“So here is this guy flying along, as you postulate, at 200 kph horizontally, and a belt breaks and disables one of the propeller units. So what happens? Even if, by some weird chance, the pilot was able to control this craft before the malfunction, all of a sudden, in horizontal flight, one of his engines (the propeller) fails. In a light twin there is an immediate tendency for the plane to roll and invert, and this is in a craft with actual wings, rudder, and tail; with your machine I would expect a rapid and fatal roll and spiral into the ground. You really have control issues here that you don't seem able to understand. The pilot who would fly this craft is either very brave or very stupid, and I suspect the latter. Even if you have some sort of ballistic parachute in the spinners, there would be no way to deploy them. Your engine? Great. Your machine? Deadly.”
Moisture condensing into visible water vapor in the low pressure vortices formed by the propellers of an Airbus A400M. Credit: Ramon Jordi
The above airplane has four propellers.
When one of the four engines stalls, or when one of the four propellers falls apart, the pilot switches off the one pair of symmetrical engines and continues the flight with the other pair of healthy engines / propellers.
Here is the complete Portable Flyer propulsion unit:
And here are the functional parts after a stall of the left engine (or after a broken toothed belt of the front propellers, or after one of the front propeller falls apart).
Even after an engine stall, the Portable Flyer has a running engine and two counter-rotating propellers (the one at left, the other at right) which provide a central thrust force without creating any reaction torque.
Excluding the reduction of the maximum thrust force, the Portable Flyer with the one only engine running is as controllable and as stable and symmetrical as with both engines running.
If the maximum thrust force with the one only engine is not adequate for pulling the Portable Flyer / pilot at the speed they had before the engine stall, what will happen is a progressive reduction of the flying speed. Nothing dramatic: the pilot switches off the problematic set of engine / propellers and opens the throttle more widely .
If the above are not persuasive, please be more specific about where you see the control problem when an engine stalls.
When one of the four engines stalls, or when one of the four propellers falls apart, the pilot switches off the one pair of symmetrical engines and continues the flight with the other pair of healthy engines / propellers.
No, really no. That's not the procedure. If one engine fails in an 4 engine aircraft, you simply fly on with 3 engines. The rudder and ailerons of the A400M have more than enough autohority to compensate even for 2 engine failures on the same side. It would be completly idiotic to negate the power of a third engine when you're already short of one engine, especially just after a MTOW takeoff.
Btw, the A400M had that actually happend multiple times because they had gearbox problems for some time which lead to frequent engine shutdowns in flight.
The above airplane has four propellers.
When one of the four engines stalls, or when one of the four propellers falls apart, the pilot switches off the one pair of symmetrical engines and continues the flight with the other pair of healthy engines / propellers.
No, really no. That's not the procedure. If one engine fails in an 4 engine aircraft, you simply fly on with 3 engines. The rudder and ailerons of the A400M have more than enough autohority to compensate even for 2 engine failures on the same side. It would be completly idiotic to negate the power of a third engine when you're already short of one engine, especially just after a MTOW takeoff.
Btw, the A400M had that actually happend multiple times because they had gearbox problems for some time which lead to frequent engine shutdowns in flight.
Thanks DrAcula.
With the Portable Flyer not having rudder and ailerons of such authority, the pilot has to switch off the un-healthy propulsion unit.
So correct my:
"When one of the four engines stalls, or when one of the four propellers falls apart, the pilot switches off the one pair of symmetrical engines and continues the flight with the other pair of healthy engines / propellers."
by
"When one of the four engines stalls, or when one of the four propellers falls apart, the pilot CAN switch off the one pair of symmetrical engines and continue the flight with the other pair of healthy engines / propellers."
Βy the way, did you get what problem /asymmetry Rodak sees in case the one engine of the Portable Flyer stalls?
As he says, it has nothing to do with lack of power, but with controllability.
Βy the way, did you get what problem /asymmetry Rodak sees in case the one engine of the Portable Flyer stalls?
As he says, it has nothing to do with lack of power, but with controllability.
Thanks
Manolis Pattakos
Yes. I would recommend to make a list of all possible failure modes and if and how they are recoverable or what the "Plan B" would be. Just as an example, what if only one belt rips? It would generates asymetrical torque, wouldn't it. What if you hit something which damages both rotors on one side? which is quite likely to happen with such a setup You would have asymetrical lift which you can't recover.
Than an other thing. If i would hover in 5 or 10m hight and one engine seizes, does the other one automatically increase power or would i have to do this myself, in which case it's highly likely that i have not enough time to assess the situation and react to it before i come crushing down, with one pair of rotors still spinning which generates a chance to injure me further or even kill me.
How heavy is somebody allowed to be, that one of your engine can keep him in the air? And i don't wanna know what other engines can achieve, what do you think your engine can do? I'm a a bit on the fat side so i don't think i'm ideal anyway, but remember, an average european male is over 80kg in underpants.
Hanging in a 6 point harness isn't exactly comfortable, especially for men. So i hope you have a solution that wouldn't cut the blood flow to the testicals for your proposed up to 2 hours flight time.
And one more thing. You came up with the "pendulum rocket fallacy". But you didn't seem to notice, that your construction has exactly the same problem. Center of lift is above center of gravity, right? So what if, i can't bring the center gravity excatly under the center of lift for what ever reason?
if you tilt your rotorsystem to compensate for that, you induce a lateral movement. So basically, your personal flyer can't properly hover if the CoG isn't exactly under the CoL. And let me guess, do you plan to store the Fuel in a backpack? What do you think where the CoG goes when you attach a 20kg backpack to the person hanging under your flyer?
Edit: a Good demonstration i think is a shuttle start. If you look closely, you can see that a shuttle moves several meters lateraly in the first few second, just because the center of thrust is not alligned verticaly with its center of gravity.
You can use your mouse curser as a refrence, the camera is on a gimbal, but it doesn't move in the first few seconds.
Just a few points you really should consider.
Last edited by Dr. Acula on 18 Apr 2020, 00:07, edited 1 time in total.
