If recips were made nowadays

swampyankee said:

Just so; an airplane with the capabilities of a 787, or even 757, isn't possible with piston engines.

Piston engines don't scale up well.

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Ignition systems don't like low-pressure environments either, so there's another maintenance head-ache - pressurised ignition systems.

swampyankee said:

Just so; an airplane with the capabilities of a 787, or even 757, isn't possible with piston engines.

Piston engines don't scale up well.

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Heck, and airplane with the capabilities of a Lockheed C-130J may not be possible with piston engines.

PWR4360-59B said:

Just flush your toilet and you will see the fuel consumption of a turbine, Oh and just check out the youtube videos of agent jz flowing the jet fuel nozzle to see the fuel consumption.

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Small turbines struggle with good bsfc, but big ones are very competitive with the very best piston engines (not counting combined cycle or turbocompound - which is, in itself, combined cycle).

And what he big turbines are is immensely powerful.

The Rolls-Royce aero-derivative industrial turbine makes 52MW dry and 64MW at around 42% efficiency.

Also:

The Rolls-Royce Trent XWB is a British series of turbofan jet engines developed from the Rolls-Royce Trent 1000, exclusively powering the Airbus A350 XWB. It passed one-million flight hours in October 2017 without any in-flight disruptions and with a dispatch reliability of 99.4%.[5] By February 2018, it has completed 1.3 million flight hours with a 99.9% dispatch reliability.

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Rolls-Royce Trent XWB - Wikipedia

And with a take-off thrust of 74,000lb to 97,000lb, depending on version.

Assuming 100% propeller efficiency, you would need approximately 21 - 22 R4360s to match the power of one Rolls-Royce Trent XWB-97.

Which would weigh nearly 5 times as much as the XWB-97.

But let's say we can halve the weight for power of the 4360, the installation would still be 2.5 times heavier than the XWB-97.

The XWB's fan size is 3.0m in diameter, or 9.8ft.

The R-4360 is just under half that in diameter, and would have to swing a larger propeller.

Just imagine an A35WB with 22 R-4360s and propellers

F-WZNU // F-HNET Air Caraibes Airbus A350-900 - cn 091 by Flox Papa, on Flickr

This is pretty much state of the art (less than 10 years old) for big Turbo props (11,000hp) in the west.

Trying to hang 44,000hp worth of reciprocating engines on a plane is going to be a little difficult

Something else to reinforce the fact that the Jets were making more power,
The Orenda 14 in the video's powered the Canadair 6

for a yardstick a P-47N using 2800hp needed 4.6 minutes to climb to 15,000ft. and 9 minutes to hit 28,000ft with a take off weight of 13, 962lbs. Top speed was 467mph at 32,000ft.
The Canadair 6 had an initial climb rate of 11,800ft per minute, needed 6 minutes to get to 40,000ft and was good for 670mph at 36,000ft. Normal take-off weight was 16,426 pounds. Please note the Canadair 6 was one of the 3-4 best performing Sabre variants.

Of course it used more fuel. Streamlining (low drag) only goes so far.

The largest piston engine plane built, the Hughes H-4, had a claimed useful load of about 150,000 lb. It probably couldn't get out of ground effect, though. Compare the performance of, say, the C-130 or An-225.

There are some astoundingly large piston engines, but they top out at about 110,000 shp. Of course, that engine is an I-14 with a 96 cm bore and a dry weight of about 2000 tons....

You'll need two for a 777.

A more practical starting point is the Convair XC-99

Now modern aerodynamics and structural materials/knowledge could improve things somewhat
and modern version of the R-4360 could offer much better reliability.
The commercial version (15 ordered, none built) was supposed to fly at 30,000ft which certainly calls for turbo chargers on a piston engine no matter what type.

If 115/145 fuel made a comeback (not going to happen) then a modern R-4360 (or equivalent) could make more more power.

getting more power, more engine life/reduced maintenance and lowering the engine weight by significant amounts (double digit percentages in each catagory) using 100LL or diesel/jet fuel in reciprocating engines is not going to happen.

The engine in the super Lockheed C-130J weighes 1925lbs (about what a R-2600 weighes) gives 4637hp for take-off and burns under 0.50lb/hp/hr at cruise and is good for around 30,000ft or a bit more in cruise.

Piston engines are going to be doing good to break into the the commuter/feeder airline market (6-20 seats) trying to displace the 500-800 hp turbines.
Anything bigger is out of reach.

Shortround6 said:

A more practical starting point is the Convair XC-99
View attachment 508307
Now modern aerodynamics and structural materials/knowledge could improve things somewhat
and modern version of the R-4360 could offer much better reliability.
The commercial version (15 ordered, none built) was supposed to fly at 30,000ft which certainly calls for turbo chargers on a piston engine no matter what type.

If 115/145 fuel made a comeback (not going to happen) then a modern R-4360 (or equivalent) could make more more power.

getting more power, more engine life/reduced maintenance and lowering the engine weight by significant amounts (double digit percentages in each catagory) using 100LL or diesel/jet fuel in reciprocating engines is not going to happen.

The engine in the super Lockheed C-130J weighes 1925lbs (about what a R-2600 weighes) gives 4637hp for take-off and burns under 0.50lb/hp/hr at cruise and is good for around 30,000ft or a bit more in cruise.

Piston engines are going to be doing good to break into the the commuter/feeder airline market (6-20 seats) trying to displace the 500-800 hp turbines.
Anything bigger is out of reach.

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And they're losing out on that market too. A single PT-6 is more reliable than two piston engines (IFSD rate of 1 per 300,000 hrs, approximately the same as a double-engine piston failure), quieter, and simpler to operate.

A related datum: turbine twin-engine helicopters autorotate from transmission failures more often than helis with a single turbine engine autorotate from engine or transmission failures.

ETOPS wouldn't be possible with pistons.

I think its so funny how everyone wants to compare 50 to 60 year old piston engines to now time applications. And constant mentioning of things like ignition systems and the like. Compression ignition needs no system. For once I'd like to hear how it could be done instead of the pooo poooing it.
Brain storm out of the box, its fun.

PWR4360-59B said:

I think its so funny how everyone wants to compare 50 to 60 year old piston engines to now time applications. And constant mentioning of things like ignition systems and the like. Compression ignition needs no system. For once I'd like to hear how it could be done instead of the pooo poooing it.
Brain storm out of the box, its fun.

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Tell us, how many cylinders, how big a capacity, would your Diesel have?

Here's a 370hp Diesel V8.

Capacity 4.2L, weight 379kg/836lb.

Playing devils advocate, IF the piston guys can come up with a 50hp cylinder (and it seems like they have) then you can get a 200hp four, a 300hp six, a 400hp eight or a 600hp twelve.
Gasoline engines with those power levels have existed for decades (in the light engine catagory) and the Diesel guys have been hovering on the verge of production at those levels for a number of years.
If we assume they can get 2000hrs or better from their engines (and they are promising it now or have been) then we are pretty much down to fuel burn and weight.
Given enough interest (money) computer controls and newer ignition systems and modern fuel injection (older type/s were being used in the 50s on Lycomings and Continentals) could be added to those old engines. Modern materials (more money) could be used to make stronger/longer lasting parts (cost/benefit ratio???).

Gasoline engines are in a bind. Running on less than 100 octane they are limited in compression and/or boost. Yes modern combustion chambers can help but lets face a few facts. 1940s aircraft engines were pretty exotic stuff compared to 1940s (or early 50s) car engines. Even Lycoming and Continental engines were pretty hot stuff compared to most American car engines.
General Motors started in 1949 with overhead V-8 engines from Oldsmobile and Cadillac. Studebaker, and Chrysler followed in 1951, Chrysler's Hemispherical combustion engines hit a high water mark. Buick's "nailhead" overhead V-8 debuted in 1953, and then low-priced Ford got its "Y-block" overhead V-8 in 1954.
Chevy and Pontiac took until 1955 and a few of those combustion chambers were a bit underwhelming.
The 1949 Olds Rocket 88 of 303 cu in was rated at 135hp (3600rpm) and weighed something over 600lbs. (and won ten Nascar races that year although hopped up?)
A 1948 Continental C-125 of 282 cu in was rated at 125hp at 2550rpm and weighed 257lbs.
A 1948 Lycoming 0-435 of 435 cu in was rated at 240hp at 3000rpm and weighed 460lbs.

The increase in aircraft engine life and performance using modern knowledge/technology, while still great, are nowhere near as great as the increase in engine and performance in car engines.

adopting some of the car technology also has problems. In small planes you want to see over the nose. large bulky engines are a problem . Sticking cams in the head or getting real fancy with valve angles means larger, bulkier/heavier heads. Or using smaller cylinders with large heads to turn high rpm so you can fit a reduction gear. Is it worth it?

But this is still pretty much light plane territory unless you move to the eight and 12 cylinder configurations. And here you hit the weight problem.
While many people may be willing to trade a 100-150lbs of power plant weight (cargo/passenger) to got to diesel for better fuel burn in a 200hp or under aircraft are the owners/operators of twin engine aircraft going to be willing to trade 300 or more for the diesel option for the under 400hp class engines?
Once you get to the 500hp turboprops in the small business commuter planes the engine weight when switching back to piston engines becomes really significant.

PWR4360-59B said:

I think its so funny how everyone wants to compare 50 to 60 year old piston engines to now time applications. And constant mentioning of things like ignition systems and the like. Compression ignition needs no system. For once I'd like to hear how it could be done instead of the pooo poooing it.
Brain storm out of the box, its fun.

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I think it is funny how some people think you can ignore the laws of physics when designing engines.
Or compare a "new" engine with a complicated/expensive drive system (constant speed prop) to an old engine with a fixed pitch prop (which is a compromise of some sort in most flight regimes)

I happen to think that a modernized gas engine might be viable alternative to the diesel, considering that the diesel engines on offer show little, if any, improvement in power to weight ratios or longevity to old piston engines running on 80-87 gasoline.

WHy don't you do some of your own work and tell us how one or more of these wonder diesels would actually be configured or work.

I gave up on "out of the box" anti-gravity paint, pixie dust and flying reindeer an long time ago.

Continental 4 cylinder air cooled diesel
http://www.continentalmotors.aero/diesel/engines/cd200.aspx

for 435lbs in 1962 you could get a Lycoming VO-540-A1A vertical helicopter engine that would give 310hp for take-off on 80/87 grade fuel.
Granted the overhaul life was bit short but that is a 55 year old engine. It used a single carburetor.

in 1962 you could also get a TVO-435-A1A vertical helicopter engine. 468lbs including the turbo. 260hp for take-off and 260hp for take-off at 15,000ft.
220hp "normal" rating at 20,000ft. Granted in needed 100/130 fuel and overhaul life may have been shorter than the larger unsupercharged Lycoming.

Many of these old engines used fixed ignition timing, perhaps a variable ignition timing could help with either power or economy or both?
Only some used fuel injection and it was mechanical. A modern computer controlled fuel injection system might be able to reduce fuel consumption at cruise.
Modern materials, material handling/finishing and inspection could certainly add life. Since a gas engine has lower peak cylinder pressures than diesel you can either get longer life or a lighter engine or a bit of both.

However once you get past a certain power level the piston engine is as dead as the Dodo. Nobody is going to try to make 40 cylinder 3000-4000lb diesel engines of around 3000hp.

The laws of physics are made to be broken. There have been some broken, or proved not to pertain in certain circumstances.

PWR4360-59B said:

The laws of physics are made to be broken. There have been some broken, or proved not to pertain in certain circumstances.

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So, we're gonna end up with a 'quantum piston engine'?

PWR4360-59B said:

Brain storm out of the box, its fun.

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So are pixie dust, levitation, and "I dream of Genie", if entertainment is all you're after.

PWR4360-59B said:

The laws of physics are made to be broken. There have been some broken, or proved not to pertain in certain circumstances.

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So far we haven't been shown any credible circumstances, and the laws of physics appear to be functioning just fine, not like something broken.
And the Vet has just declared the horse dead, so maybe we can quit flogging the carcass now.
Cheers,
Wes

Some info on the Napier Nomad

nomad | 1953 | 0350 | Flight Archive
1954 | 1222 | Flight Archive

And Napier Nomad and Eland (turbine)
1954 | 2503 | Flight Archive

A single cylinder turbo-compound test engine by SNECMA

napier nomad | 1953 | 0265 | Flight Archive

Compare the Eland and Nomad (data from Wiki):

Power:
Eland: 3500hp
Nomad: 3150hp

Weight:
Eland: 787kg
Nomad: 1,620kg

Dimesnions (L x W x H)
Eland: 3000mm x 910mm x 910mm (ie 910mm diameter)
Nomad: 3000mm x 1429mm x 1000mm