2 stroke thread (with occasional F1 relevance!)

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
Pinger
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Re: 2 stroke thread (with occasional F1 relevance!)

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Tommy Cookers wrote:
Thu Jan 30, 2020 6:10 pm
Mr Boretti's paper above seems to be wrong in some basic statements

and another poster has today expressed dissatisfaction with another Boretti paper
The inaccuracy - or contradiction - I noticed was he seems to say early on that F1 engines are throttled and later says they are not.
Unless I misunderstood.

J.A.W.
J.A.W.
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Re: 2 stroke thread (with occasional F1 relevance!)

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Tommy Cookers wrote:
Thu Jan 30, 2020 6:10 pm
Mr Boretti's paper above seems to be wrong in some basic statements

and another poster has today expressed dissatisfaction with another Boretti paper
Come now T-C - surely you can do a bit better - than that?

If you, (or "another poster") have identified any particular bones to pick with Boretti's
published points, then a sound technical critique presenting specific objections would enable
a basis for discussion, but a vague "dissatisfaction" based on "...seems to be wrong", won't.

While academics doing peer-reviews of scientific papers presented to journals for publication
are sometimes out of their depth on the functional practicability of technical proposals, it is
reasonable to expect the SAE to be a bastion of sound rigor in doing so, & have you read any such
objections expressed prior to, or post publication, that you can share with members/readers here?
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all.

Boretti’s “Concept paper” begins with the measured fuel efficiency in the F1 engines:

46% at peak power and
50% at peak efficiency


and ends up with a wise suggestion:

“Reduction of the fuel tank capacity with no opportunity to refuel”.

Image


The above suggestion is like saying:

“Cancel the numerous limitations you have now and leave free the Moto-GP (and Formula 1) teams to focus on making powerful fuel efficient engines”,

or like saying:

If
  • the Two-Stroke engines,
    or the Rotary Valve engines,
    or the VVA engines,
    or the Desmodromic-Valve engines,
    or the Rotary engines,
    or the Diesel engines,
    or the Opposed Piston engines,
    or any single engine design / idea / innovation etc,
    can be faster consuming the same quantity of fuel being (under the same emission limits),

then
  • let them win.





If you apply the same rule in the Personal Flying Devices, the existing JetPacks with their less than poor mileage (and extreme CO2 footprint per mile covered) have a serious problem to solve.
Just look at the flight-duration and range given by the JetPack manufacures:

Image


Let the engines prove themselves.

Thanks
Manolis Pattakos

J.A.W.
J.A.W.
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Re: 2 stroke thread (with occasional F1 relevance!)

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Good call Manolis, perhaps an approach through FAI via Red Bull?

To attach a 'personal flyer' demo race - to the air-race series - they already present?
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

manolis
manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all.

Take a look at this video:



and then notice the number of its views.

Thanks
Manolis Pattakos

Tommy Cookers
Tommy Cookers
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Re: 2 stroke thread (with occasional F1 relevance!)

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presumably the late Wing Commander Ken Wallis
who was best known for the gyrocopter flying in a 'James Bond' film years ago
KW said that people should fly either fixed wing or helicopters or gyrocopters - but not mix them

I wonder, was our once prolific poster Autogyro (who sometimes worked with KW) in the crowd of spectators ?

https://en.wikipedia.org/wiki/Ken_Wallis

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all

In page 182 there is a video (uploaded 19 December 2019) where Yves Rossy (the first JetMan) wearing his Delta-Wing JetPack is taking-off from the ground, is hovering over the Geneva lake Switzerland, and then is landing back to the ground.

Quote from Rossy’s website ( https://yvesrossy.com/about-the-first--jetman.html ) :

"After far too much silence since that magnificent formation flight with the Patrouille de France in October 2016, I would like to give you some news.
At the end of last year, I decided to end my relationship with Jetman Dubai.
. . .
I now have new, more powerful "JETCAT P550" engines that allow amazing flight performance such as climbing vertically at 180 km/h (see video), which is the speed at which a human body falls into free fall...
I feel like in my Mirage III at the time, except I'm just a little guy with a wing on his back who plays plane like a kid with his body movements, imagine!
With such an outpouring of power, vertical takeoffs and landings are within reach!
Thanks to the help of extraordinary people who spontaneously offered their help, we can present to you today what seemed impossible: the stable and precise hover flight of the wing-man assembly allowing autonomous take-off and landing.

Image

. . .
developed an electronic stabilization system that reacts to body movements.”


End of Quote


Two months later (17 February 2020), Rossy’s ex-team in Dubai made two more steps:
control over the yaw at zero / small speeds by displaceabling manually some control-fins (thrust vectoring nozzles)
and
transmission to high speed flight after taking-off vertically from the ground.


Quote from https://www.jetman.com/en/jetman-behind ... ai-takeoff

“They built and adjusted a manually controlled thrust vectoring nozzle that allows the pilot to control rotations around the yaw axis at zero speeds, making human control of the wing possible in all flight phases without the aid of any electronic stabilisation systems.



After becoming airborne . . . Reffet hovered five metres above the waters . . . for 100 seconds. Having demonstrated his full control of the flight by performing stops, turns and backward moves, he landed smoothly . . .
Reffet then took off again and headed south . . .building speed and height. Travelling at an average speed of 240kmh, he climbed 100m in the air in eight seconds, 200m in 12 seconds, 500m in 19 seconds and 1,000m in 30 seconds.
. . .
Shortly after his landing, Vince Reffet said:
“. . . One of the next objectives is to land back on the ground after a flight at altitude, without needing to open a parachute. It’s being worked on.”


End of Quote



For several years now Zapata (Fly-Board-Air JetPack) uses the same system (thrust vectoring nozzles) for yaw control at zero / small speeds.

The same is the case for Mayman JetPack.

Browning’s JetPack needs not thrust vectoring nozzles: with a pair of jet-turbines on each hand / arm, he has full control over the yaw.


In the Portable Flyer the yaw control is different, simple and built-in:

The pilot displacing properly his legs / arms in the downstream of the propellers, is pushed by a pair of eccentric aerodynamic forces that cause the rotation (yaw) of the Portable Flyer about its vertical axis towards any direction:

Image

From hovering to cruising:

The pilot by extending his legs / arms towards a destination, displaces the center of gravity of the Portable Flyer relative to the plain defined by the rotation axes of the propellers, which causes the propeller axes to "lean" towards the destination.

The vertical component of the thrust takes the weight of the Portable Flyer, while the horizontal component of the thrust accelerates the Portable Flyer towards its destination.

As the cruising speed of the Portable Flyer increases, the aerodynamic drag displaces the pilot away from the vertical position, reducing his frontal area.

Thanks
Manolis Pattakos

Rodak
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Re: 2 stroke thread (with occasional F1 relevance!)

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You're expecting to fly 400 miles? And control this thing? Good luck, you are impermeable to input.

Pinger
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Re: 2 stroke thread (with occasional F1 relevance!)

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An aero version of this then....


Image

manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all.

Quote fromYves Rossy’s web site (at https://yvesrossy.com/about-the-first--jetman.html ) :

"I now have new, more powerful "JETCAT P550" engines that allow amazing flight performance such as climbing vertically at 180 km/h (see video), which is the speed at which a human body falls into free fall...
. . .
With such an outpouring of power, vertical takeoffs and landings are within reach!"


Image

End of Quote


Image


Based on the above specifications, let's make a few calculations:

The idling consumption of the four JetCat P550 of Yves Rossy’s DeltaWing is: 4*300ml/min = 1.2lit/min = 72lit/hour.

The full load consumption is 4*1650ml/min = 6.6lt/min = 396lit/hour

The maximum thrust force is 4*550N = 2200N = 220Kp = 480lb

With, say, 30 liters of fuel in his DeltaWing, Rossy can fly at full power for 30lt/6.6lit/min = 4.5 minutes.

With the same 30 liters fuel the four JetCat P550 turbines of Rossy can idle for 30lit / 1.2lit/min = 25 minutes.

The weight of the four turbines is 4*4900g = 196N = 19.6Kp = 43lb; in this weight it is added the DeltaWing weight, the fuel weight and the pilot weight.

With the 480 to 750 degrees Celsius exhaust gas temperature the pilot has to keep his limbs away from the exhaust gas.

The supersonic speed of the exhaust gas (2,129Km/h, Mach 1.7) causes extreme / unaffordable noise.

The cost of four JetCat-P550 turbines is over 50,000 euro; in this amount has to be added the cost of the rest DeltaWing “aircraft”.

Thanks
Manolis Pattakos

manolis
manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello all.

The “JetMan-Dubai” team claims 400Km/h top speed for “their” Rossy’s DeltaWing.


Based on the JetCat P550 specifications, let’s see what the various numbers have to “say” and how they connect with each other:


With 400Km/h (111m/sec) speed and 2,200N total thrust, the power that pushes the DeltaWing forwards is:

P = 111m/sec * 2,200N = 245kW

The energy E provided per hour by this power is: E = 245kWh.

Supposing a specific gravity of 0.8Kg/lit for the fuel,
the 4*1650ml/min = 396lit/h fuel consumption per hour of the four jet turbines at full load gives a “BSFC” (Brake Specific Fuel Consumption), if we can call it so, of:

396lit * 0.8Kg/lit / E = 316Kg / 245kWh = 1280gr/kWh

and the resulting “BTE” (Brake Thermal Efficiency), if we can call it so, is:

80g/kWh / 1280gr/kWh = 6%

Where the 80g/kWh comes from?
80gr/kWh is the BSFC of an ideal engine running at 100% BTE;
When a giant marine low-speed 2-stroke Diesel engine consumes 160gr of fuel per kWh of mechanical energy produced, it operates at 80/160 = 0.5 = 50% BTE.


The total Exhaust Gas Power Output is 4 * 162.6kW = 650kW, while the power that actually pushes the pilot / DeltaWing is, as previously calculated, P = 245kW.

That is, the four jet turbines provide 650kW + 245kW = 895kW of power from which the 27% ( 245 / 895 = 0.27, i.e. about one quarter) pushes the pilot / aircraft forwards, while the rest 73% (nearly the three quarters) is lost in the exhaust gas.

This means that the jet turbines run at 22.5% BTE ( 80gr/kWh / (316Kg/h / 895kWh)= 0.225).

22.5% = 6% + 16.5%

The 6% of the fuel energy pushes the aircraft forwards,
the 16.5% of the fuel energy is lost with the high speed exhaust gas,
while the rest 77.5% of the fuel energy is never transformed into “mechanical” (or “aerodynamic” etc) energy.


In the JetCat P550 specifications the Exhaust Gas Power Output is given as 162.6kW;
Taking the derivatives of both sides of the kinetic energy equation:

E = (1/2)*m*v^2

it results:

dE/dt = (1/2) * dm/dt * v^2.

(the dm/dt is the mass flow; the speed v of the exhaust gas is constant 2129Km/h).

(1/2) * (Mass Flow) * (Exhaust Gas Velocity)^2 = 0.5 *0.93Kg/sec * (2129Km/h)^2 = 0.5 * 0.93Kg/sec * (591.4m/sec)^2 = 162.6kW, which is the Exhaust Gas Power Output given in the specifications.


In the P550 specifications the Specific Fuel Consumption (Kg/Nh) is given as 0.144;
0.144Kg/Nh = 1650ml/min * 60min/h * 0.008Kg/ml / 550N
(0.008Kg/ml is the fuel specific density, 1650ml/min is the fuel consumption at full load).


For the pilot, who is “in the open air”, the 400Km/h speed seems exhausting, if not unaffordable for more than a few seconds.

At lower speeds, say at 200Km/h, a substantially smaller portion of the power provided by the turbines is utilized to propel the aircraft, while the rest power provided by the turbines is lost with the exhaust gas; however the aerodynamic resistance falls more (it falls with speed square).

The lower the speed, the smaller the portion of the power provided by the turbines that is actually used to propel the aircraft, with the rest power being lost in the exhaust gas (in case of zero speed, while the turbines continue to consume fuel, all the energy they provide goes to the exhaust gas).

The higher the speed, the more of the turbine power goes to propel the aircraft, and the less power is lost in the exhaust gas.


Quiz:

Suppose Rossy wants to cross Calais channel (some 22miles / 35Km) with his new DeltaWing.
At which speed the required fuel is minimized?



According the previous,
at normal / affordable speeds, say from 100 to 150mph (160 to 240Km/h), only 3%, or so, of the fuel energy is propelling the Jet-Pack Flying Device; the rest fuel is burnt to accelerate the exhaust gas and to warm the atmosphere.

Even if the CO2 footprint was not an issue, the running cost gets extreme.

Worse even, the weight of the required fuel for a useful (say, 50Km) range becomes too high, and this weight has to be lifted by the JetPack Flying Device (just like heavy batteries have to be lifted by the electric Flying Devices).


In comparison, the Portable Flyer with its internal combustion engines and its propellers is many times more efficient than the JetPacks, it needs many times less fuel for the same range, it has many times longer range with the same quantity of fuel, it has many times smaller CO2 footpinrt, it has many times lower running and ownership cost, etc.

Image

Thanks
Manolis Pattakos

Rodak
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Re: 2 stroke thread (with occasional F1 relevance!)

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Wow. And yet you can't even guide this thing. No way throwing your legs around will steer this, even if there was some sort of moment arm to apply force to alter direction.....which there isn't.

Dr. Acula
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Re: 2 stroke thread (with occasional F1 relevance!)

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Manolis, i hope you realise that the basic formula F*v=P, although physically correct, has some severe limitation in how and when to use it.
Rossi and his colleagues gain speed when they go into a dive, right? So does this mean, the efficiency of these engines depends on the attitude they are in? Get they more efficient when they face to the ground?...yes, it's a rhetorical question...

Also please stop to compare your PF to things like Rossis Jet-Wing. Rossi never claimed it would be the future of personel transport. Rossis Wing is just a fun toy mainly for himself and he build it to be exactly that. It's like F1 cars in that regard. They aren't meant for the average person.

manolis
manolis
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Re: 2 stroke thread (with occasional F1 relevance!)

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Hello Acula

You write:
“Manolis, i hope you realise that the basic formula F*v=P, although physically correct, has some severe limitation in how and when to use it.”

The best thing with the physical laws is that they are correct at all cases, without exceptions and limitations.

So, be more specific explaining where the formula F*v=P was incorrectly used / applied.


You also write:
“Rossi and his colleagues gain speed when they go into a dive, right? So does this mean, the efficiency of these engines depends on the attitude they are in? Get they more efficient when they face to the ground?...yes, it's a rhetorical question…”

People who dive freely (unpowered) can reach speeds well above 400Km/h.



At 3:35 of the video is given the world record as 531Km/h

Quote from Wikipedia:
  • “Speed skydiving is a skydiving competition in which the goal is to achieve and maintain the highest possible terminal velocity. It was developed in the mid 2000s and is the fastest non-motorized sport on Earth. The speed, achieved by the human body in free fall, is a function of several factors; including the body's mass, orientation, and skin area and texture. In stable, belly-to-earth position, terminal velocity is about 200 km/h (120 mph).
    Stable freefall head down position has a terminal speed of 240–290 km/h (around 150–180 mph). Further minimization of drag by streamlining the body allows for speeds in the vicinity of 500 km/h (310 mph).”
End of Quote.



Rossy’s ex-team in Dubai claim they can fly (fly horizontally, not dive) at speeds of up 400Km/h.

Quote from https://newatlas.com/aircraft/jetman-vt ... on-winged/
  • “The winged flight capability sets the Jetman team apart from other jet-powered personal flight devices like jet boards, jetpacks and jet suits, because it allows more efficient flight at very high speeds of up to 400 km/h (250 mph), as well as some pretty awesome aerobatic capabilities.”
End of quote


You also write:
“Rossi never claimed it would be the future of personel transport. Rossis Wing is just a fun toy mainly for himself and he build it to be exactly that. It's like F1 cars in that regard. They aren't meant for the average person.”

I bet Yves Rossy does not agree with you.

But Rossy’s Delta Wing is powered by jet turbines which put several limitations like short range, low mileage, extreme noise, extreme ownership and running cost, etc, etc. These limitations are what makes his Delta Wing an expensive toy, not a useful transportation means for everyone.

Replace the jet turbines of Rossy’s DeltaWing by piston engines driving propellers and you have a small VTOL airplane (say, a scaled down OSPREY V22) which may be the future of personal transportation.

Thanks
Manolis Pattakos

Tommy Cookers
Tommy Cookers
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Re: 2 stroke thread (with occasional F1 relevance!)

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manolis wrote:
Fri Feb 28, 2020 6:30 am
..... however the aerodynamic resistance falls more (it falls with speed square).
for a wing-born aircraft ....
aerodynamic resistance aka drag falls with speed reduction from V max then increases again as speed approaches V min
as L is constant for all speeds but L/D decreases greatly at max Cl needed for V min (and min Cl needed for V max)
thrust at V max = thrust at V min

VTOL lift jets were designed 60 years ago with thrust/weight ratios of 40
jet exhaust velocity was presumably rather lower than the conventional