Talk:Propfan

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Contents 1 Article histories 2 X-Plane Experimentation Recipricator-Engine PropFans 2.1 Update 3 Eh? 4 NK-12

[edit] Article histories

The histories of Propfan and Unducted fan have just been merged after a previous content merger. violet/riga (t) 21:26, 27 Apr 2005 (UTC)

[edit] X-Plane Experimentation Recipricator-Engine PropFans

In X-Plane, A consumer priced flight simulator program for PCs that is used in some low-end FAA approved full-motion simulators, I modified 'Austin's Designs\Austins Hi Efficiency-4-seat) to have a 2,480 Rand-Cam Engine (Set original value to 8x its value to reflect Rand-Cam's 8x HP to weight ratio over a normal recip), and altered the prop from 3ft radius to 4.91ft radius and let the plane designer curve the blades for 2,500 RPM and 600 Knots Tip Spped @ 500knots TAS, and then added an identical prop on the same drivetrain as a contra-rotating cousin. I also altered the airfoils and had to enlarge the forward wing (acting as the HSTAB) that has hi lift, low drag, but a sharp stall and a narrow range of angle of attack. With the recipricating (non-piston rotary) at 2500 horsepower with 2.5m diameter (4.91 ft) contra-rotating higly curved 12-bladed propellers on a loaded weight of 5000 pounds (3000 empty) it narrowlly exceeds 500 knots (503-508) on level fight at 50,000 feet. It flies at 0 AoA at 60000 feet on cruise throttle at 450 knots TAS. I think i could get faster if I optimize the wings and props some more.

[edit] Update

I got the contra-rotating propeller-plane to 540 knots (560 before I shrunk from 2480 to 1240 horsepower). It is a modification of austin's high-efficiency 4-seat plane. Only the fusalage is unchanged though. Cruises 540 knots at 20 gallons per hour but it needs full throttle to reach 400 knots (at 120 gallons per hour), which it will reach in about 15 minutes, and needs a very long takeoff run (stalls at 150 knotts, low acceleration at 0-400 knots) with the smaller engine. I increased the base weight to 3000 pounds (was 1800) and payload and fuel were increased to 1000lbs each for a max loaded weight of 5000 lbs. The propeller is 16-bladed, 4 meters diameter, .25 meter chord, and highly curved tips (design rpm 1900, design speed 500 acft / 650 prop knots). The plane needs too much runway currently and I don't want to go back to 2500 horsepower (short takeoff with that), and it has pitch stability problems that has lessened with the smaller engine. Also I am using a custom airfoil that I will modify to make it more realistic by modifying it to match the output of JavaFoil and JavaProp that i found on the web at http://www.mh-aerotools.de/airfoils/index.htm .

[edit] Eh?

There is no mention here of whether or not the engine design is actually in production use by anyone anywhere. Anyone wanna help with that? --StarKruzr 06:47, 28 June 2006 (UTC)

"During the 1990s, Antonov also developed the An-70, powered by four Progress D-27s in a tractor configuration; the Russian Air Force placed an order for 164 aircraft in 2003." - final sentence, and the only 'production' aircraft likely to use a propfan soon. ericg ✈ 07:21, 28 June 2006 (UTC)

[edit] NK-12

It would be nice to include some referance to the NK-12 in this discussion. It does, after all, represent the start point of this technology and has been in use for almost 40 years. It is, arguably a propfan, before the term was ever thought up. Blade solidity aside, as a propfan it conforms due to the usual operating flight mach numbers of 0.68-0.72. Ironically most view it as a turboprop and it so managed to achieved the title of worlds fastest turboprop aircraft for the Tu-114. Interestingly the earliest picture i could find of the 'swept prop' principle was also Soviet in design from 1942 on the front of a Yak-3. Intersting that they did not use it for the NK-12, but then ease of manufacture was the most likely reason.

If there is no disagreement then i will include this. —The preceding unsigned comment was added by 80.0.99.31 (talk) 22:09, 12 May 2007 (UTC).

I assume you have sources which consider it a prop-fan? Otherwise, as you stated, it is normally considered a turbo-prop engine. The NK-12 has 2 four-bladed props. Prop-fans normally have more than 8 blades, the most on a conventionl turboprop is 8. Given the fact that the arcticle has NO sources at it is, we should not be adding in unsourced supposition and speculation. - BillCJ 22:23, 12 May 2007 (UTC)

Blade count is not important in the definition of a propfan (increased count is merely to reduce thrust force per blade allowing thinner sections). It is flight regime. It is this that takes you from turboprop->propfan->turbofan. The NK-12 sits in the 0.7 mach flight number of the propfan. The other consideration is fan pressure rise - for the propfan it needs to be greater than 1.1 (this is 1.3-1.8 for a turbofan). There is some loose definition in the NASA report for the propfan studies conducted during the 80s. I shall dig out the report number and quote section here. I am not claiming that the NK-12 is definitively a propfan, but at least a hybrid and hence a stepping stone to this technology. Blade count is up on modern propfans due to reduced prop diameter (NK-12 has 5.6m blade diameter and adds to the concept of UHB, entrained flow providing a large percentage of thrust) and higher rotational speeds resulting in swept blades to try and keep the tips low transonic for a constant given thrust. The NK-12 makes no attemps just raw power to make up inefficiency of an unswept blade and as a consequence deafening (literally). I think it would be interesting to add it as a point of historic note...this is ground that had been trodden before - in the name of fuel efficiency. It is the NK-12 that gives the Tu-95/142/114 its incredible range - not the wing or the size of the fuel tanks.

As an additional note you pose an interesting problem. As a professional aero-engineer i have access to alot of reports/information within the industry, none of which i can reference here. There is a great deal of conjecture and mis-understanding on this topic in public, published sources. By your definition there is very little that i can offer on this topic regardless of whether it s correct. I can add the NASA data but as aero-manufactures what we aim for is changing all the time and the NASA report represents the understanding at that time. I'm not sure what to do here other than abandon it and leave the community to its own devices.

I agree, overly anal referencing can seriously detract from certain documents that can be just statements or comments (you find this in real encyclopedias) e.g. "combustion" has next to no reference but it is absolutely correct. - James