29 Mar 2024, 07:23 [ UTC - 5; DST ]
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Post subject: Re: Small Turbines Posted: 27 Apr 2017, 20:51 |
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Joined: 11/22/08 Posts: 2914 Post Likes: +922 Company: USAF Propulsion Laboratory Location: Dayton, OH
Aircraft: PA24, AEST 680, 421
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Fuel cooling of the turbine blades is not a new concept, but never successfully implemented. The fuel has a max temp capability. Uncooled turbine blades are more likely for small engines. There are some materials that can go higher than metals.
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Post subject: Re: Small Turbines Posted: 28 Apr 2017, 08:50 |
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Joined: 11/06/10 Posts: 11885 Post Likes: +2848 Company: Looking Location: Outside Boston, or some hotel somewhere
Aircraft: None
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Username Protected wrote: Has anyone successfully implemented ceramic blades? (Or Blisk?) GE does it for some engines, I recall the press on it. Know, for which engines... I am pretty sure PWC and RR have also demonstrated it. No idea if in production. Tim
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Post subject: Re: Small Turbines Posted: 29 Apr 2017, 00:30 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23615 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: They claim it will make 100hp on 8 gph, which is 12.5hp/gph, which is what a 7:1 compression avgas engine makes LOP.
Not sure I find that credible. Seems reasonably credible to me. 8 GPH, 100 HP is 0.536 lbs/hp/hr SFC. TPE331 are about 0.51 lbs/hp/hr, about 0.47 ESFC when jet thrust is taken into account. PT6 are in the high 50s to mid 60s depending on model. So, with careful design, a high pressure ratio, 0.536 seems plausible, not that far out from current examples despite its small size. An Avgas engine operating LOP is about 0.37 lbs/hp/hr, so this engine is still quite a ways from that efficiency. The effective SFC number is higher when you consider engine weight and cooling drag, so you don't have to reach piston SFC for a turboprop to be "as good". A better metric might be $fuel/hp/hr, in which case a 0.536 turbine is WAY ahead of a 0.37 piston engine due to low cost of JetA (just bought some in Denver for $2.38/gallon). Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: Small Turbines Posted: 29 Apr 2017, 12:58 |
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Joined: 12/03/14 Posts: 19252 Post Likes: +23615 Company: Ciholas, Inc Location: KEHR
Aircraft: C560V
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Username Protected wrote: Interesting thought about weight/cooling drag effects. What do you think engine/fuel weight savings plus cooling drag would do to effective bsfc. Airframe dependent, but the approach would be to compute the extra power the engine needs to carry its extra weight and to overcome its cooling drag, subtract that from the output, then compute the ESFC. For a typical piston air cooled engine, probably in the range of 5-10%. Mike C.
_________________ Email mikec (at) ciholas.com
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Post subject: Re: Small Turbines Posted: 29 Apr 2017, 16:38 |
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Joined: 12/09/13 Posts: 244 Post Likes: +150 Location: KICT/KFFZ/KLAS
Aircraft: CE25B+/CE25C/DA40
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Does it need to be axial flow? Seems like a centrifugal compressor would make for a simpler design and build.
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