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Old Jan 23, 2006, 02:24 PM
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Quote:
Originally Posted by winmodels
.....................
Part three (well about a third of it) was published two years ago in Q+EFI, but the interest was so low that I lost interest to finish it............

Klaus
Interest may have been low from a great % of the Q&EFI readers, however I for one was facinated and read/kept all the articles. Some of the math was pretty well above my level of application but gave me a much better understanding of EDF.

Heck, I'd buy a book of all your work if you had one.

-Mike
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Old Jan 23, 2006, 04:19 PM
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Quote:
Originally Posted by Speed is Life
Interest may have been low from a great % of the Q&EFI readers, however I for one was facinated and read/kept all the articles. Some of the math was pretty well above my level of application but gave me a much better understanding of EDF. Heck, I'd buy a book of all your work if you had one.-Mike
Hi Mike

there will be one, but I don't know when.

Have fun with fans

Klaus
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Old Jan 24, 2006, 06:09 AM
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Klaus
[you have to try to be logical. If the outlet velocity of the air (in the static case) is only 37m/s you can not expect to fly at 40m/s, because the delta v will be zero before you reach that (and therefore zero thrust) ]
OK that was stupid of me.
[In your case the possible flying velocity will be nearer 25m/s]
We are still talking about a TwinJet powered by a MidiFan giving a (measured) thrust of 860gr and a (calculated) mass flow of 219gr at (Wemotec data) 37m/sec, all static. Now the plane was actually measured at about 115km/h (33m/sec) in level flight. So delta v is 4. How do we calculate (in full terms) mass flow and then thrust at that flying speed of 115km/h ? And possibly exit flow speed ?

(Incidently, I also fail to correlate 219gr mass flow and 860gr thrust at 37m/sec all static)

Thanks for your patience.
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Old Jan 24, 2006, 06:44 AM
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Klaus,

I found part I to be anything but boring. As an mech.engineer by profession, I found your derivations to be good reading.

Over the last few years I have developed my own EXCEL based EDF flight performance spread sheet and now I'm in the process of integrating your part I with mine.

Any chance of seeing part II?
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Old Jan 24, 2006, 07:13 AM
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I just got to follow this thread ...
THis math is interesting :-)
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Old Jan 24, 2006, 08:25 AM
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Ciao Klaus,

I did also read the .pdf files you did attach in this thread and it looks that the performance depend only from the in/out duct diameters, the lip shape, the ejected speed and the advancement speed.

Iím wondering: In your design methodology, do you consider the number and shape of blades? Does it is important the shape of the nozzle? And how much does the pitch of the blades impact on the efficiency?

Regards,

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Old Jan 25, 2006, 05:02 PM
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Originally Posted by Stekka76
Ciao Klaus,
I did also read the .pdf files you did attach in this thread and it looks that the performance depend only from the in/out duct diameters, the lip shape, the ejected speed and the advancement speed.
Iím wondering: In your design methodology, do you consider the number and shape of blades? Does it is important the shape of the nozzle? And how much does the pitch of the blades impact on the efficiency? Regards, Pí
Hi Paolo

if you read it again you will find that it (thrust, performance) also depends on the efficiency of the fan, which for want of a better description could be termed internal efficiency. This is dealt with in the next installment, which I will upload shortly.

Have fun with fans

Klaus
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Old Jan 25, 2006, 05:10 PM
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I was also thinking. You could also put your documents in your user gallery, since it looks like you still have some free space there and post a link in one of these threads.
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Old Jan 25, 2006, 05:15 PM
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Quote:
Originally Posted by Scramble
Klaus
We are still talking about a TwinJet powered by a MidiFan giving a (measured) thrust of 860gr and a (calculated) mass flow of 219gr at (Wemotec data) 37m/sec, all static. Now the plane was actually measured at about 115km/h (33m/sec) in level flight. So delta v is 4. How do we calculate (in full terms) mass flow and then thrust at that flying speed of 115km/h ? And possibly exit flow speed ?(Incidently, I also fail to correlate 219gr mass flow and 860gr thrust at 37m/sec all static) Thanks for your patience.
The mathematics to do all these calculations are in the article. You probably have to read it a few times before it "clicks". If the real world values do not tally with the physics it's probably a measuring error somewhere, or the published values are not properly or differently defined. And if the results are within around plus/minus 5%, that's the way engineering works (at least at this level). I forgot to mention: the mass flow increases with flying velocity as outlined in the article - so you didn't read it?

Nevertheless, have fun with fans

Klaus
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Old Jan 25, 2006, 05:17 PM
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Quote:
Originally Posted by Larry Dudeck
Klaus, Any chance of seeing part II?
Hi Larry

no, not likely at the moment (I still have to translate it from German), but I will upload part 3 shortly.

Klaus
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Old Jan 26, 2006, 04:41 AM
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Quote:
Originally Posted by winmodels
Hi Paolo

if you read it again you will find that it (thrust, performance) also depends on the efficiency of the fan, which for want of a better description could be termed internal efficiency. This is dealt with in the next installment, which I will upload shortly.

Have fun with fans

Klaus

Ciao Klaus,

Yes, I saw that the (thrust, performance) depends from the efficiency and from the external diameter. I like the simple equation (14.1) because it can determinate also the static efficiency knowing experimental data.

But I was wondering how do you get the efficiency value out from your blading design. It looks you use experimental diagram concerning solidity, distance between blading, gap...and that you do not use directly the kind of airfoils, the shape of the blades, the reynolds, the pitch, the boundary layer...

But first of all the more important is that your designing approch does work.

I will wait to read more about you.

All the best,

P'
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Old Jan 26, 2006, 05:03 AM
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Ejected airspeed

Ciao Scramble,

Concerning message 54,

yes, the ejected airspeed depends from the flight speed.

Consider that if you run statically a fan (i.e. with 100 W) you have your static ejected airspeed.
This last depends from the number of turn of the fan (remember that a fan is a volumetric machine, each turn moves a capacity of air).
And the number of turn depends from the power/torque.
When you increase the flight speed (giving always 100 W) the number of turns increase. Indeed the power depends from the difference of the square airspeed (Ejected-Flight). Thus if the flight airspeed increase, the ejected has also to increase to absorb always the same power...

But to estimate in a 5 min your question it's quite difficult. Even if adopting simplified model, you should at least consider that the aerodynamics within the fan change with the number of turn and thus also the efficiency.

All the best,

P'
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Old Jan 26, 2006, 05:34 AM
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Quote:
Originally Posted by Stekka76
Ciao Klaus,... But I was wondering how do you get the efficiency value out from your blading design. It looks you use experimental diagram concerning solidity, distance between blading, gap...and that you do not use directly the kind of airfoils, the shape of the blades, the reynolds, the pitch, the boundary layer...P'
Hi Paolo

all these factors are taken into consideration when I design a fan. There are some proven mathematical models available which I have employed, and the results have so far confirmed that approach. When calculations and reality show the same results they should be right. One of the major aspects is the L/D ratio of the blade in a bent airflow.

Have fun with fans

Klaus
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Old Jan 26, 2006, 06:18 AM
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Klaus
I read your article but as you said it still has to click. In my example I thought I might neglect the mass flow increase with flying velocity, for simplicity (which is why I was also trying to omit RPM increase - Stekka76). Fact is, your article is quite elaborate, a teacher standing by my side to guide me through it would help me no end ! So I'll be good and read it again and again until it penetrates my mathless brain
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Old Jan 26, 2006, 02:12 PM
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Hi Klaus

Quote:
no, not likely at the moment (I still have to translate it from German), but I will upload part 3 shortly.
Does this mean, that the original script is available in german? If yes, is there a possibility to get the the german version. This would help me a lot because I have to translate it from english to german

Regards - Norbert
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