Micro Turbofan manufacturing feedback

[f112owner]

We are looking for feedback for investors ...what is the level of interest in this experimental engine?  What would one pay for a 500 lbst (potentially much more upwards of 1200# in future developments) fuel efficient micro turbofan engine with a projected SFC of .46lb/lb/hr    Small package of apprx 12” x 30” approx weight of 90 pounds. TBO to be determined.  

Please vote to manufacture or not.  Thank you

[f112owner]

building an updated version of this 40 year old advanced turbofan has been a dream of mine for quite some time as still to date NOTHING has even come close to this engines features and abilities. living life has always been a priority and has, at times, gotten in the way. ..chit happens...so it was sidelined....Flash forward 17+ years....Technology and metallurgy, SPF and 3D printing and scanning has arrived....Reverse Engineering this taxpayer funded (apprx$250 Million 1979 dollars). turbine for the benefit of the general public is absolutely rightt. It’s time. Im finally moving forward on this. Recycling taxpayer funded R&D for the benefit of the general public.

[racket]

Hi

You'd need to increase the fan contribution to thust , a >3:1 bypass ratio , you won't be making a missile engine , you'll be be making a "slower" engine , so greater mass flow at a lower fan pressure ratio

Cheers
John

[f112owner]

John,

Thank you for the input. Currently the two stage fan is made from heavy 17-4 stainless. I was pondering SUperplastic formed (SPF) Titanium to lighten the assembly and go w a slightly larger diameter fan...but using the same LP turbines....feasible? Im also considering Carbon Fiber fans but Im thinking Ti would be a better fit for durability...trying to consider all...

[racket]

Hi

Larger flow at a lower pressure ratio but with the same power requirement , the LP turbine RPM would need different gearing to match the larger fan , things get difficult once we start trying to modify a design , we basically need to redesign the whole stage .

The original engine had a job to do within certain parameters , you want to change "the job" , so a rethink on the entire engine required , a pretty big , and expensive, task especially if you want to get it Certified for GA use

Cheers
John

[f112owner]

I think it be best to stick with basically the original design....improve the materials and tolerances...use 3d printing where advantageous.. I bought up spares when I could find them. i have a few 3rd stage stators...combustion cans .bearing mounts/holders....a few other ods and ends... This engine uses “cold” compressed air (apprx 910*F) to cool the hp turbine nozzle guide vein shroud to keep tolerances tight. This engine has some very cool features.

[racket]

Yep , they were/are a nice little engine with a lot of development put into them over the years .

They're probably a bit too complicated for general aviation , but OK for military use , complication equals cost unfortunately .

It would depend on what you see as their potential end use though

Cheers
John

[f112owner]

If I were to take this into production, i believe its worth is in the experimental and non-people carrying side of aviation....at least at the moment. It is an advanced turbine ...counter-rotating assemblies. I just aquired a GE videoscope so I will be video borescoping this engine and will probably upload a video of it. The counter rotating feature makes this the ONLY design absolutely right for vertical take-offs and flight. I have some ideads...i think they are brilliant but im biased.

[racket]

LOL......lets hope those ideas come to pass :-)

The experimental class has cost constraints , so simple/cheap will have more appeal , as for unmanned usage , its a crowded marketplace already , plenty of research required before spending too much cash .

Cheers
John

[f112owner]

The core of this engine should make around 400lbst and would be much smaller and more powerful than anything on the market and the fan version ..well there is nothing even close..esp the SFC vs size.   I envision a turboprop and shaft version being easier to convert or re-engineer than increasing bypass ratio (from what I gather from your posts).



 The two-stage axial compressor is attached to the free fan shaft.  Im not sure the fan efficiency could be improved to increase mass flow without increasing the diameter...It is a 40yo design..non curved blades...a blisk with updated design might improve it but to 3:1? Doubt it. 

[racket]

Hi

Once you remove the fan and go to a turboprop the engines overall Pressure Ratio will be halved , this will affect your SFC and you'll probably find your combustor/flametube will have troubles burning the required fuel flow at the lower air pressures/densities going through it :-(

As I mentioned in an earlier email , its a lovely little engine that was made for a specific job , it might not be easy to change, increasing the bypass ratio would be possible with a fan only several inches bigger in diameter , remember, half of the fan flow goes through the "engine" , so you only need to multiply that other remaining "half" , an 18" fan would be more than big enough .

Cheers
John

[f112owner]

John,

Well..shoot....an 18” fan would be more than double the diameter what is already there. Were back to “just copy the darn thing”...improve materials and possibly update thefan geometry...a 10 or 12....@ 10” thats only 8.5% larger in diameter..and about 3000 RPM slower (or over speed the fan by 8-1/2% over the current fans 35500 max speed. ...or deal with a faster jet exhaust speed....will still work for prjects like the Xjet (WASP)....and would make a really fast BD5J...with extended range.

[racket]

Hi

The most important question is ...............what is the projected airspeed of the "vehicle" your upgraded engine would operate in ??

This would then influence the pressure ratio for the fan, its specific power requirements and its thrust potential , theres no point having a high pressure ratio fan engine in a relatively "slow vehicle", the SFC suffers .

Theres not a lot of info out there on actual mass flow numbers for the engine , but what I did find was a flow of ~14 lbs/sec , which would mean a fan inlet annulus of ~70 sq inches , assume 35 sq ins for the core engine and 35 for the fan flow , 3 times that is roughly 100 sq ins , so you'd need a fan inlet annulus of ~135 sq ins , lets add on 15 sq ins for the hub for an intake of 150 sq ins .......... ~13.8 inch dia fan

A 5:1 bypass figure which is even more realistic for general aviation would need an ~ 17" fan .

Cheers
John

[f112owner]

You are very close on mass airflow...its min at 18,000rpm idle is 6lb/sec and 14.5 @ max.

[racket]

LOL......standard turbo inlet flow of 12 lbs/min/square inch with a transonic compressor inducer