Ducted fan theory and practice

Whoops I had the feeling an X or L fell off in a paste!
Yes, 1’000W is at the extreme limit of the Kontronik safe operating limit chart **LINK** (click on performance chart) for the 600 / 17 motor.
It seems that Schubeler recommends 1’300 - 1’500 rpm/V on those fans so I guess the extra 200 rpm/V was the straw the broke the camel’s back & confirms your experience.
I read your comments on the Victor thread & agree that matching motor & fan gets very tricky at your >2’000W power levels.
Kind regards
Mark
PS Off to work on a stand at the IFA show in Berlin so will be offline for 7-10 days

Space Ship One as an EDF project!
If you want something really unusual check the video
**LINK**

You can read about it (in French) on
**LINK**

Use “Feuilleter cette revue” & go to pages 54 – 55, EDF unit shape on Page 56.
Hope you enjoy it
Mark

For Mark Powell, the Space One creator mentions the following EDF unit on his site:

4’200 Watts continuous at 100A. Scorpion HK-4035-560, weight 430g, Chinese turbine Haoye 5 inches (127 mm)
**LINK**

Hopefully Google translate can do the rest.

Mark

Here is a nice video of a Harrier by Davylah flying very nicely.
**LINK**
Davy modified the EDF outlet ducts and gave me permission to publish his photos here, thanks Davy.

I adapted Richard’s spreadsheet to calculate how close Davy came to what the “theory” says. He got those dimensions very close. I set up a similar system on my Harrier and it flew fine with plenty of thrust (my club buddy forgot to film it so sorry no video!)

So thanks Richard for a nice tool to help setting up EDF duct sizes for optimum flight characteristics

Mark

Did this conduit method method work and did your planes fly with these custom EDF ducts?

Can someone tell me how to make such ducts like in the picture shown above. I want to make such ducts. What material was used to make such ducts? How was it molded and given a shape like that?

Hi All

This tread is massive !!! so maybe some one can answer my question

The gap from the air intakes ducts and the edf fan does this need to be open or closed

if I close it will it make the fan stall at speed

Thanks in advance

Folks, I'm a newbie here and forgive me for not having followed all the posts so far....but is this just electric DF we are discussing or does I/C feature as well ? It seems to me there are some fundamental differences : The EDF units are working purely on mass-flow effects (although there will be some heat from motors /esc units).

The I/C powered fans have significant heat in the system from cylinder head /muffler temperatures etc,so, unless this 'surplus' heat is ducted elsewhere, it will impinge on the fan unit and modify the mass flow /change the physics of thrust generated.

Also, the pitot measurement method is interesting as a means of measuring model airspeed /duct inflow speeds. I have a model wind-tunnel in construction (10% scale), this is to be used for a Le-Mans style sportscar that I'm currently building. The speed range of the full-size car for aerodynamic effects is about 50-150 mph about the same as a DF model ? I have a Phd student working on calibration methods for the tunnel. He says that pitot placement can be critical (I know this from my full-size gliding days). A suggestion is that we use a 'hot-wire' measurement method to be more accurate. I wonder if this could be adapted for on-board model /telemetry use ?

Thanks for a very interesting thread.

Dave

Forgot to mention in the previous post that I have access to some CFD (Computational Fluid Dynamics) software. The model wind tunnel lap-top is ready but have yet to load the CFD stuff on. The idea is to compare the CFD predictions with the tunnel data.

The relevance to Ducted Fan study is that I may be able to model duct /fan characteristics in both the tunnel and the CFD if anyone is interested ? I would need a CAD file of the duct as input to the CFD and an actual model's duct for the tunnel. (I have 'ram-jet' type ducts on the sportscar which I'm waiting to model).

Shortly, I'm getting a building firm in to level and strengthen my garage floor. This done, I can finish the tunnel and get to work !

Dave

Hello all !

This is one for the aerodynamics engeneers !!

I came at the point of designing the thrust tube for my magister 1 /4.5 EDF.

The parameters in this job wich i can't choose are the exhaust diameters .They should be 62 mm for true scale , but i already enlarged them to 72 mm.

Following the advice of Mr Schubeler himself , this aircraft needs a 128 mm fan to perform well so that's the next fixed measure.

Looking inside my fuselage , the transition from 1x128mm to 2x72 should happen in 30cm.

My question :

Are there rules to follow in designing the thrust tube ?

Should the ''split'' in the middle of the 128mm diameter , start as soon as possible ? Or as far away from the fan as possible ?

I came up with a drawing of a Y tube , that looks natural to me .

Wat do the experts say ????????????????

I think you would find any heat benefit added after the fan from IC would be insignificant compared to the flow losses from directing the airflow around or cooling the engine.

The reduction from 128mm to 2x 72mm is quite a noticable reduction in cross sectional area, I do not know the motor mount diameter but it may be OK at 80%.

Whilst I do not know the exact rules, I would have a minimum gap of 1 fan diameter between the fan outlet and the start of the splitter so minimum of 128mm in you case. Make the reduction in flow area as smooth and as gradual as possible, the more abrupt the increase in air velocity, the higher the pressure loss. Your drawing shows a gradual change so it looks about right.

Thanks for your input Peter !

I'm just at the begin to make this part and will keep your advice in mind !

Hi all !!

For those who do not follow the magister thread :This is an update on the thrust tube.

The plug was drawn up by me and 3D printed by Andy Meade.(Great job !! ).It was sanded ,primered and painted wit 2K automotive paint.

After that it was moulded in two parts.The next step was a try-out as i made the end part on the moulds with the plug still in place :Worked fine !!

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