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Post by stealthmanbob on Mar 1, 2016 18:02:50 GMT 1
No, hence I said 'slightly larger'. I believe SFC could drop about 1%. What is SFC ? Should it be added to the abbreviations thread ? |
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philidor
in service - 6 years
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Post by philidor on Mar 1, 2016 20:29:59 GMT 1
What is SFC ? Should it be added to the abbreviations thread ? SFC = specific fuel consumption. Of course, this acronym belongs in the abbreviations thread. |
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Taliesin
Final Assembly Line stage 1
In Thrust we trust
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Post by Taliesin on Mar 2, 2016 0:14:59 GMT 1
This might be nitpicking, but the correct abbreviation is Thrust Specific Fuel Consumption, TSFC.
"Specific" only means that it's referenced to or in relation to something, but doesn't specify exactly what. Referencing fuel consumption to thrust makes the most sense, but it could also be mass flow specific, or speed specific, or something else entirely.
Civilian engines are typically optimised for fuel efficiency, whereas military engines are optimised for most thrust per air flow through the engine. This drives up TFSC, but makes for a smaller, lighter and more damage tolerant engine. If one looks at compression ratios of civilian engines, they are well over 40, closing in on 50 now, wheras the EJ200 for the Eurofighter has a compression ratio of about 25, that's not because it's not technologically feasible, but because the engine was designed for lower pressure ratios from the start.
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Post by stealthmanbob on Mar 2, 2016 1:49:06 GMT 1
This might be nitpicking, but the correct abbreviation is Thrust Specific Fuel Consumption, TSFC. "Specific" only means that it's referenced to or in relation to something, but doesn't specify exactly what. Referencing fuel consumption to thrust makes the most sense, but it could also be mass flow specific, or speed specific, or something else entirely. Civilian engines are typically optimised for fuel efficiency, whereas military engines are optimised for most thrust per air flow through the engine. This drives up TFSC, but makes for a smaller, lighter and more damage tolerant engine. If one looks at compression ratios of civilian engines, they are well over 40, closing in on 50 now, wheras the EJ200 for the Eurofighter has a compression ratio of about 25, that's not because it's not technologically feasible, but because the engine was designed for lower pressure ratios from the start. Is it TSFC or TFSC ? I am now more confused  Re the EJ200, the engine has a much much smaller diameter first stage fan than an airliner engine so it can't produce the airflow to produce a CRAF of 40. If in doubt turn on the burners, that should do it  |
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Post by Jkkw on Mar 2, 2016 3:02:51 GMT 1
That reminds me, I was talking to someone from Rolls Royce at the SG Airshow and on the subject of future growth of the TrentXWB he said (something along the lines of); If Airbus or Boeing wanted a larger engine we could probably push the -97 around 5% [1.05 x 97 = 101.85], anymore and we'd offer a new engine. One a side note, he also said they'll probably do a 'glory run' of the engine and run it up to 120 pounds of thrust to see how much thrust the engine could actually produce but at those thrust levels, the engine would not be economical to run. Some nice bit of exclusive info there. I like the 'glory run' experiment, but I'd like to see how far they can push the engine till it all comes apart!  As for the 5% more thrust, is he saying that it can be done with the existing engine as it is? And what does he mean by 'new engine'? A completely new one or can they just use the same basic core and grow the fan size along with some other adjustments? I'd presume the 5% is for the existing engine as is and I don't actually know what he means by a new engine (larger TXWB or completely new). |
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Baroque
in service - 2 years
Posts: 3,991
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Post by Baroque on Mar 2, 2016 5:39:19 GMT 1
From the other A380 thread... Is that Leahy dropping a hint as to who they are talking with regarding the A350-1100 prospects? Good to see that they've moved on from the ME3 requirements and are looking to bring out something that will work efficiently enough for others. |
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XWB
in service - 11 years
Posts: 16,115
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Post by XWB on Mar 2, 2016 9:30:46 GMT 1
This might be nitpicking, but the correct abbreviation is Thrust Specific Fuel Consumption, TSFC. "Specific" only means that it's referenced to or in relation to something, but doesn't specify exactly what. Referencing fuel consumption to thrust makes the most sense, but it could also be mass flow specific, or speed specific, or something else entirely. Civilian engines are typically optimised for fuel efficiency, whereas military engines are optimised for most thrust per air flow through the engine. This drives up TFSC, but makes for a smaller, lighter and more damage tolerant engine. If one looks at compression ratios of civilian engines, they are well over 40, closing in on 50 now, wheras the EJ200 for the Eurofighter has a compression ratio of about 25, that's not because it's not technologically feasible, but because the engine was designed for lower pressure ratios from the start. Is it TSFC or TFSC ? I am now more confused It's TSFC. |
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Post by airboche on Mar 2, 2016 11:24:44 GMT 1
The 777-9 might in fact be a bit "over-featured", with both extreme range and capacity for ME3 needs to go to the US-westcoast. So they carry quite a bit of structure and weight with them. Being smaller and lighter will certainly be a good point for any upscaled A350 derivatives. I wonder what range will remain for the next stretch without changing too much of the given basic design.
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philidor
in service - 6 years
Posts: 8,950
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Post by philidor on Mar 2, 2016 11:45:15 GMT 1
I wonder what range will remain for the next stretch without changing too much of the given basic design. Apart from the engine improvement issue, which we already have been discussing, any answer depends on whatever wing tweaks Airbus may use to partly offset the additional weight. |
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Baroque
in service - 2 years
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Post by Baroque on Mar 3, 2016 2:16:58 GMT 1
It is possible that Airbus already has a pretty good idea of what needs to be done for the stretch as time and again they've been saying that they were studying it since the 777X launch. But their ambiguous position on the launch is probably due to them waiting to secure suitable launch customers. It obviously won't look good if they launched a product with no customer backing. And if there are customers ready to make a decision on the 777X soon, now is a good time to talk to them about signing up for your alternative instead, and this is probably what Leahy is working on. If not, the launch decision does not need to happen this year.
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