Electrical Ambitious DIY TurboFan Project

[jetsky]

I realize this may sound a little ambitious , but since I’m not going into space I thought I would at least do an initial feasibility study on the following project that a small dedicated group would like to embark on : A compact geared high bypass Turbofan engine with a Static thrust @ Sea Level of about 150Kg (1500N or 330Lbs)
The engine core (@ 100000rpm) is driving a two stage LP spool with a potential output of 60-80 SHP (34-60 KW) which should drive a geared 40cm (16in) diameter Fan stage (8-9cm Hub) @15000rpm (to keep blade tip speeds at or below Mach 1).
The fan stage would be very similar to what can be seen in the PW610F powering the Eclipse:
http://m1.ikiwq.com/img/xl/wK6FwxQhflSqML9VywJ6Xc.jpg
Since regular prop configurations were getting about 4 - 4.5 Lbs of thrust per SHP, I hoped that this would do the trick. Somebody was kind enough to send me a generic spreadsheet that calculates thrust , and it seems that I can only achieve roughly 175Lbs of static thrust in this configuration :(
However in this spreadsheet, wide cord blades, or varying the Fan RPM didn’t seem to change anything (which seems odd ?).
So I am hoping if someone could just confirm roughly if this may still be possible in this configuration in any way, or if I am forced to go the Turbo-Prop route ?

 

[harralk]

I looked into doing a similar project a few years ago and worked out most of the details for a 12 inch fan, modeled after the GE90 engine. But I never had the time or resources to see the project through. If I remember correctly, I expected to achieve about 250lbs of thrust.

Does your spreadsheet include internal pressures/temps/velocities/etc.? My first thought is since your design is very similar to the original PW610F engine which can produce a minimum of 900lbs of thrust, 300lbs should be reasonable. My suspicion is the spreadsheet either has the wrong information about the engine or is assuming a low efficiency output.

When I was doing my research I don't remember the fan chord being as important as it's cross-section. And unless I'm forgetting something, the fan's pitch and overall diameter were the deciding factors in my calculations.

What rpm did you run the fan up to? What is your bypass ratio? And one last question, forgive me if it seems juvenile, but does the spreadsheet include the thrust from the core as well or just the fan?

 

[jetsky]

Hi Haralk,
no such thing as juvenile question, only juvenile answers ;)
Just PM me with you're contact details and I can send you the spread sheets (and yes they take temp into account - but only ambient conditions, but nothing core related ) Only initial core values I can estimate are PR off the centrifugal compressor of about 3.1-4.0, and TIT of 750-800°C. (I'm also incorporating a small heat exchanger)
The rest is only based on an analysis of most commercially available small turbines and their characteristics - to give me an idea of what has already been achieved (as a baseline).
Knowing the theoretical output thrust and the possible extraction of 90% thrust to torque I assumed the probable SHP obtainable to drive the main fan (so core thrust of 40 Kg =88Lbs of which hopefully 80lbs directly extracted to shp)
As mentioned, the fan should run at about 15000 rpm.

 

[AlephZero]

The usual motivation for a geared fan is to reduce the fan speed to reduce noise etc.

I don't understand why you would want to run a geared fan at 15,000 RPM, unless you plan to have the LP shaft running at 30,000 RPM or higher (which would mean the HP shaft speed would be something insane).