Ducted Fan Pseudo-Jets

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Malish

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The easy answer is that for some people it is speed that brings utility. More speed means more utility.

But if I was to flip your question around, I might ask: If we only need to go 150 MPH or less, then why even bother designing anything new? I mean, there are HUNDREDS of well proven, existing GA airplanes that fit in this category. Electrics, parafoils, motorgliders, biplanes, RV's, ultralights, spamcans, and classics. Virtually any mission and price range under the sun - why spend the time on "just one more"?

If I only want to go 150 MPH, I pick an airplane and write a check; but if I want to take the speed from 200 knots in cruise to 250, my options are very limited and THAT is going to take some inventing.
Flying at airspeed of 150 MPH - I was saying that thousands of GA aircraft are flying at this speed. If someone want to fly faster aircraft - they will find them at higher price and more expenses. Same apply for DF aircraft if someone want to fly them faster - our DF PJ-II "Dreamer" fly at 200 MPH with 388 HP engine, but Cessna 177 uses 200 HP engine to to fly at same speed...
 

henryk

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no seat belts, crumple zones,
-inventors dont sleep=in place of crumple zone=PULS bumpers
(very short break distance)

>500 "g" ! (5000 m/s^2)...

-look at NASA investigations=
 

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BBerson

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OK, send me a video when the "flying car" is registered as a car for highway speeds and is certified as an airplane that actually flies
The Switchblade is three wheel and will be registered as a motorcycle to avoid regulation. I don’t know if a motorcycle license is required, the link said either car or motorcycle license.
 
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BBerson

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Absolutely correct, Bill. But note that they advertise it as a flying sports car.


BJC
Most buyers (if it ever gets to production) would see it as a car, I think. It would be much safer if the regulators just let them go with using four wheels without the additional regulation. But regulations are not always made with logic.
 

sanman

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Feb 24, 2021
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=big deal...?

Thanks for that - looks interesting:







I assume left side is the front of aircraft, and right side is the back?
Anyway, duct seems to be wrapped around fuselage, thus enabling ingestion of exterior boundary layer






3rd diagram reminds me of Celera 500L







Oh, and look -- the plasma actuator stuff still works with boundary layer ingestion by aft propulsor 😁


Recent efforts to reduce commercial transport aircraft drag include embedding an aft-mounted engine into the airframe in order to fill the vehicle wake with engine exhaust, consequently reducing fuel consumption. Embedded engines can provide substantial improvements compared to conventional wing-mounted engines by generating thrust with lower-momentum boundary layer ingestion; however, the propulsion system must be capable of performing effectively in a highly distorted flow field. An active flow control technique for reducing distorted boundary layer flow entering an embedded duct is evaluated. Plasma flow control is proposed to reduce flow field distortion. Plasma actuators have previously demonstrated capability to manipulate boundary layer growth by imparting a body force on the flow near the surface, increasing momentum. Multiple variables were evaluated in this study to determine potential flow field improvement, including actuator location, frequency, and power input. Tests were conducted in a low-speed, open-loop wind tunnel with a traverse-mounted pitot-static probe to determine dynamic pressure at an embedded duct exit plane. A single-dielectric-barrier-discharge plasma actuator was tested over a range of wind tunnel speeds at different locations relative to an embedded duct inlet. The local operating Reynolds number due to ramp surface length ranged from 1 to 3 million. The test article was a notional boundary layer ingestion ramp and contraction duct having a 1.25:1 area contraction ratio and 10-inch circular, exit diameter. The duct geometry was a modified NACA 0012 airfoil, and the plasma actuator consisted of two copper electrodes separated by a 0.024-inch thick Mica dielectric barrier. A non-dimensional distortion intensity coefficient was used to evaluate plasma actuator performance. Furthermore, qualitative assessments of velocity contour plots are presented. Results reveal the effectiveness of plasma flow control to manipulate distortion intensity.
 
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Malish

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The main reason that people often even care about efficiency is due to its effect on cost. We often don't care about efficiency for its own sake, or for the sake of design elegance. Cost is often a overriding factor. Piston engines are cheaper to operate than turbines.
Ducted fan aircraft as a "pseudo jet" not only cheaper to buy, but also much cheaper to operate then real jet aircraft, because they are less complex in construction and maintenance cost. That is why ducted fan aircraft will be attracted to pilots who would like fly aircraft that look and fly like a jet, but no need to spend thousands of $'s per flying hour!
 

sanman

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Ducted fan aircraft as a "pseudo jet" not only cheaper to buy, but also much cheaper to operate then real jet aircraft, because they are less complex in construction and maintenance cost. That is why ducted fan aircraft will be attracted to pilots who would like fly aircraft that look and fly like a jet, but no need to spend thousands of $'s per flying hour!
I agree -- and it could be a way to create a low-end "jet trainer" which has cockpit layout that intentionally mimics the cockpit controls of some real jet aircraft.

Tell me something -- what made you choose the particular jet styling that you chose for PJ-22 Dreamer? I'd really love to know your reasons behind some of your design choices.

Why did you choose twin-jet look, instead of single-jet with single duct?

Also, if you have single duct, can you do contra-rotating fans inside same duct? Can that improve efficiency?

And I know I sound like a pest, I would be very grateful if you would give me your opinion on the idea of using ionized airflow can also help to improve the efficiency & performance of ducted fan pseudo-jets, especially at higher airspeeds. In my opinion, the same duct geometry that causes the drag can make itself useful for ionizing the air flow to reduce the drag.

 

Malish

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Tell me something -- what made you choose the particular jet styling that you chose for PJ-22 Dreamer? I'd really love to know your reasons behind some of your design choices.

Why did you choose twin-jet look, instead of single-jet with single duct?

Also, if you have single duct, can you do contra-rotating fans inside same duct? Can that improve efficiency?
Main reason to make aircraft looking like a twin jet fighter was - that many choices that builder can make it look like(with some cosmetic changes) - F-15, F-18, Su-27 and Mig-29 ;) This was basically marketing choice.
Also main idea was to make this kit-aircraft as simple as possible to build and cheap to operate by average GA pilot.
Many thing can make ducted fan aircraft more efficient, but it also increase complexity and cost of this aircraft..., but kit cost should be competitive with most GA kit-aircraft(Lancair, Glssair and other).
PJ-II "Dreamer" - very easy to fly, maintain and operate and this was main goal in designing this aircraft.
 
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