If recips were made nowadays

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wuzak said:
So that performance is at sea level?
Click to expand...

The topic of this thread was "if they were made now" - so you are certainly not going to be using a gear driven
blower, the only advantage of which was packaging and weight (now rendered defunct by the miniaturisation possible
by a fourfold increase in possible turbomachinery shaft speeds, a WW2 turbo is topping out about 28,000rpm -
anything less than 100,000 would be viewed as sluggish now). You`d probably end up with a two-stage turbo
on either cylinder bank if you were talking about fitting it into a sort of size envelope in an original WW2
fighter. I dont think a single rear installation behind the engine would work well, as I dont see a good
exit path for the turbine exhaust. Since such a turbo would be custom made (at least the compressor stages)
it would be an extremely expensive proposition - but entirely possible.

The Cosworth compound turbo design for F1 use (quickly banned...) used
a multi-stage axial turbine. The output was somewhat in excess of 2000bhp
from 1.5litres. Naturally with an extrordinarily short lifespan. But you can
begin to imagine the compression ratio necessary through that compressor to
achieve that.

The balance of sea level boost vs high altitude performance is essentially then balanced by swept volume.
So you would probably need to decide on priorities to decide where that balance was exactly, engine
size vs performance per unit weight vs the expense and complexity of the turbocompressor needed.

Since this is a total for fun hypothetical I`m ignoring finance issues, so I stick to my figures as a pretty good
baseline for whats possible.

An interesting view can be taken by looking at "Raikhlin Aircraft Engine Developments GmbH.", which was formed when my old workplace
shut down their F1 operation. Several of the key engine designers who were made redundant got together and decided
to take the Toyota Formula One engine concepts they had been working on for years and use it as the basis for a brand new aero engine.
Even the camcover looks almost the same as the F1 ! - the biggest new development is the prop-reduction gearbox stuck on,
which is of course nothing like what it looked like in the F1 car. This is being a little unfair perhaps ! - by now it really is a
new engine I`m sure, but the design lineage to the Toyota F1 engine dept means of course it has some resemblance !

It recieved EASA type testing approval 4 years ago. Their larger A06 It is a 6 litre v12, with
turbochargers, but quite conservatively rated at 500bhp (it IS a diesel though !). This is a civilian engine for civilian use, hence
natually well short of what one COULD do if it were some sort of bizzare time-travel back to 1935 but with
modern know-how, tools and materials - for pure ultimate performance military application.

RED A03 - Wikipedia

https://red-aircraft.com/engines/red-a03-v12/?lang=en

 
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And here we hit part of the problem.
From Wiki in the link provided.
368kW (500 HP)Take-off at 2127 propeller rpm ; 338kW (460 HP) maximum continuous at 1995 Propeller RPM
weight is all over the place.
  • Dry weight: 363 kg dry
from the text. " It weights 250kg net, 320 kg (705 lbs.) gross including two alternators, starters, engine and gearbox oil, heat exchanger and propeller governor."

Now just for comparison sake the Hispano-Suiza 12 X engine (the small one) in the very late 30s was good for 740hp take-off at 2600rpm, 690hp/2600rpm at 12,800ft, and cruised at 520hp/2360rpm at 12,800ft for a dry weight (without accessoires ) of 848lbs/385kg. using 87 octane fuel.

two things,
The modern diesel probably has a fuel burn of about 70% of the old Hispano for specific fuel consumption at cruise powers.
The modern diesel probably has an engine life about 20 times better than the old Hispano.

Continental is fooling around with a 3 liter V-6 diesel of just under 300hp.
http://www.continentalmotors.aero/diesel/engines/cd300.aspx

Assuming they could double it into a V-12 and the V-12 would weigh 85% of the weight of the two V-6s you get a 600hp engine that weighs 935lbs(?) with a fuel burn in the 0.35lb per hp hr range and engine life of 1200-2000 hours? Open to correction on the weight as the 85% is a wag.

fortunately for safety but unfortunately for performance a lot of what has been learned about materials and manufacturing techniques would go into much longer overhaul lives, more time between failures and less maintenance rather than pushing the performance envelope.

People claim that the US air cooled engines in small aircraft have made no improvements in the last 70 years but they may have doubled their overhaul life.
I would also note that both the big companies offered certain models with reduction gears and superchargers (both engine driven and Turbo) back in the late 50s and early 60s. Most of these highly stressed engines faded from the catalogs and were replaced by larger displacement but slower revving engines and gear drive superchargers and high boost was also dropped. Turbos were mostly for maintaining power at altitude.

Lycoming for example had the IGSO-480 model that gave 340hp at 3400rpm using 9lb of boost (100/130 fuel) for 497lbs. Max continuous was 320hp/3200rpm at 11,000ft. Book fuel consumption was 0.48lb/hp/hr for 240hp/2750rpm and the power rating could be held to 13,500ft.
They also had an IO-540 (same bore, longer stroke) without the reduction gearbox and supercharger which would give 290hp at take-off at 2,575rpm and only weighed 395lbs. Used 80/87 grade fuel. Fuel burn was claimed to be 0.42lb/hp/hr.

Most of the modern small diesels seem to barely equalling the power to weight ratios of the old gas engines and depend on their lower fuel burn and cheaper fuel for their market appeal. It some cases it may very well be a large advantage and nothing else is needed.
As power goes up and the planes get larger things get a bit more complicated. When you hit 500hp and up you are entering turboprop country.
Most of the currant small turboprops are of rather dated design. They are light however, a 500-750hp turboprop can weigh around 150kg. For long range work a high performance diesel may be an advantage (fuel per gallon cost is now the same so fuel burn is the big advantage) for short range work the extra several hundred KG of payload with the turbines may be an advantage (for the same gross weight aircraft). Helicopters (aside from very small ones) especially would be hard pressed to change to diesels. Going up to 1000-1500hp engines it gets worse for the recips. The turbine engines are around 500-700lbs.
 
Shortround6 said:
People claim that the US air cooled engines in small aircraft have made no improvements in the last 70 years but they may have doubled their overhaul life.
Click to expand...
Even then, the overhaul life is extremely conservative.
A major market for these engines is currently as a replacement for older pistons. as such, something about hte same power and same weight is an advantage, as you don't need extra strengthening to absorb the power, or introduce C of G issues if the engine is too light.
Fuel burn and future availability is the main driver of the move towards diesel engines. Over the life of an engine there is a major savings, both due to the reduced fuel cost and burn. There is a small saving with overhaul/replacement costs too, but not enough to drive it economically.
 
Again to accomplish the task it takes some thought and engineering. Just like the idea now of having supersonic corporate jets that make almost no sonic booms. Here is a thought for a start of a compact engine design that has a small foot print, just look at the HP ratings of small motorcycle engines.
W16 engine - Wikipedia
 
And small motorcycle engines get power how?

By using small cylinders and using high( very high) rpm. This is not exactly new, Frank Halford used the small cylinder/high rpm path in Napier Rapier, Dagger and Sabre back in the 1930s and I doubt if he thought it up himself. Eight cylinder engines of two liters or under being used in auto racing in the 1920s.

Car and motorcycle engines are not built for the same duty cycle as aircraft engines. Piston aircraft engines are going spend most of their life at 55-80% of their rated power. Some small engines cruised at 90%. High performance cars and motorcycles on the street spend most of their time at 20-30% max power (if that).
running your FZR based engine at 95hp per liter for hundreds of hours is going to what to the engine life?
There was a reason that those old foggy Continental and Lycoming 100-115hp engines used 200-235 cu in to make their power and trying to use old Corvair car engines of 145-164cu in isn't going to give a good result even if they were rated at higher power for road use.

Porsche has tried to enter the Aviation market at least twice. In the Early 60s they were offering engines based on the 356 pushrod engine. The 678/4 model offered 75hp at 4600rpm for take-off and 60hp at 4270rpm for cruise. It weighed 218lbs with the reduction gear. The Continental O-200-A weighed 190lbs and offered 100hp for take off and 75hp cruise (2500rpm).

Or see this link: Porsche PFM
For one mans opinion of the Porsche PFM 3200 fiasco.

From Wiki " This was roughly twice the horsepower of a conventional lower-rpm design of the same displacement."
but there are few, if any, constraints on displacement for aircraft engines. No taxes based on engine size and no racing classes with displacement limits (for 99.9% of the aircraft in the world) so it is horsepower per pound/kg that is important, not hp per cu in/liter.

Lets look at the Volkswagen W16 since you provided the link.
8 liters ((487.8 cu in) is very good for making almost 1200hp. Piston speed isn't to bad for this day and age at 3390fpm.
It is compact (short) but it is hardly light. 882lbs in given in the specification sheet.
lets not forget the over 100lbs of coolant in the radiator/intercooling circuits though.

The GE T700-GE-700 shaft turbine used in the first Sikorsky Blackhawk Helicopters in the late 70s could run at 1560hp max. and 1258hp continuous. It weighed 432lbs and had a SFC of 0.474lb/hp/hr at the continuous rating. Newer versions are a bit heavier, higher powered and a bit more efficient in fuel burn.
 
Well interesting thoughts. Motorcycle engines reving high!!! So on a turbo prop or any turbine the revs are very high. So what is happening is the torque output from a turbine is being multiplied many times by the gear reduction unit, gear drives are torque multipliers, and that torque figured against the final rotational rpms is what will determine the HP output, so there is a bit of cheating with the power out put of turbines. So what is the reduction of a turbine like what is mentioned above? And in another thought can HP even be calculated the same with a turbine? I don't know. I just have a sneaky feeling the basic engine does not put out as much power with out a gear reduction unit unlike a recip.
 

Power will be the same at the output of a gearbox as it was at the input, minus losses in the gearbox. Reduction ratio changes will not alter the power output (unless, for some reason, the change incurs greater losses).
 

Nice try at changing the argument. I was trying to explain why you are not going to get the power "density" or power per cubic in/liter out of a big engine (or one that uses big cylinders) that you can out of a small engine, or small cylinders.

61 cubic motorcycle engine moves 176.5cu/ft of air per minute (assuming 100% efficiency, it won't be). An old Lycoming 0-235 moves 190.4 cu/ft of air.(assuming 100% efficiency, it won't be). Motorcycle makes 145hp@10,000rpm Lycoming makes 115hp@2800rpm Obviously the motorcycle engine is more efficient. It should be, it uses a 12:1 compression ratio vs 6.75 (the Lycoming runs on 80 octane gas). The Motorcycle uses 5 valves per cylinder so we can assume that it is closer to 100% in filling it's cylinders than the 2 valve Lycoming. The older 1000FZRs used four 38mm carbs The Lycoming use one single barrel carb, again better breathing, the motorcycle is water cooled using everything they learned upto the late 80s early 90s. The Lycoming dates from 1942 (developed from a 1940 engine).
Motorcycle uses a 56mm stroke, Lycoming uses a 98mm stroke so obviously the the motorcycle can run almost twice as fast for the same piston speed.

As an experiment lets try scaling the motorcycle up to twice it's displacement. (or as an alternative trying to use it as a V-8). If we change the bore and stroke to 95.62 x 70mm we get a 2011cc engine, now will the 70mm stroke still let us rev to 10,000rpm???? Or will we be limited to closer to 8,000rpm?
the 1000cc engine had .571 sq ft of cylinder wall to dissipate heat through. The 2000cc version has .905 sq.ft of wall area. Or about 80% of the wall area per unit of volume. So poorer cooling IF were try to burn the same amount of fuel per CC or Cubic in per minute (lowering the rpm will help).
I am not going to try to figure out the valve sizes needed to flow the amount of air needed for two liter engine compared to the one liter but the valve "area" is the circumference of the valves times the amount of lift with a correction factor. Trying to fit 5 valves into a 95.62 mm cylinder that flow twice the amount of air as the 5 valves in a 75.5 mm cylinder may be a bit of a problem.




These are some of the fundamental problems in trying to scale an engine up and keep the same specific power output.

We can certainly do much better than the old engines but trying to use vastly different size engines as indicators as to what is possible is misleading.
 

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I'm just curious about something . Is the Ranger 5,000 hp radial still the largest ever built ? And for inlines , what was the most powerful ever built ? I'm talking in terms of aircraft power-plants of course .
As a side note I remember flying a 200hp Ryan Navion . She was like trying to get a truck off the ground . But with the extra 60 hp with a 260 hp engine , she was a much better airplane . Amazing what a little extra horsepower can do .
 
i really think if there was a lack of turbine engines being able to work right perhaps the rare metals used in them were rarer then they were for the germans in WWII. so jet engines were determined to be good but were not profitable we will say (because with out the rare metals TBO's would never have gone up) i dont see any airline using a engine that would need to be ripped off after a single transatlantic flight.. you would probaly see engines today that are close to there WWII era cousins but fuel injection would be the norm, engine RPMS would be higer perhaps instead of 3000PRM u might see 3500 RPM for take off. boost and compression ratios would be higher and they might have gone up higher then 115/150 octane fuel. too add i think the air forces of the world would have a few jet intercepters to augment there piston engine aircraft fleets bombers would be for all intensive purposes piston engined.

my 2cents worth on this subject..
 
The increase in the performance number rating of fuel gets into diminishing returns. More so in production than in engine performance but if you have limited amounts of high PN fuel then where are you?
You also need some of those rare metals (in smaller amounts?) for the high performance piston engines, especially for turbos.

Just for a little historical perspective the increase in lead from 3cc per US gallon to 4cc per US gallon in Sept 1941 increased the potential production of 100 PN fuel by 25% by requiring the less use of scarce alkylate (or other octanes). The US also had gone over to a scheme of government controlled production to try to maximize both refining capacity and allocation of resources.
The introduction of cat cracked gasoline also vastly increased production. With cat cracked gasoline the same supply of alkylate would result in almost twice the quantity of finished 100 PN fuel as with some of the straight run gasoline in use.
Aviation fuel is complicated stuff. You can't just keep mixing in more aromatics and more lead. With lead you get diminishing returns (the improvement from 5cc of lead to 6cc is very small compared to 1cc to 2 ccs) and the more lead you use the more likely you are to lead foul the spark plugs.
You also can't keep increasing the percentage of aromatics as some don't really improve things much beyond 130 PN (some don't even reach 120 PN) and most don't have the same BTUs per pound or gallon that 'gasoline' does so you need to burn more to get the same power.
Some of these additives had other problems. Some being more temperature sensitive than others or giving trouble in long term storage.

Also the air cooled and liquid cooled engines reacted differently. When first tried 100/150 fuels showed very little improvement in air-cooled engines when lean and slightly better to considerably better when rich. In liquid cooled engines it was significantly better than 100/130 and tests in a Packard built Merlin showed a 30% increase power both lean and rich. This was confirmed by the British who allowed around 15% more power to developed when using this fuel.
HOWEVER, the grade 100/150 fuel, when operated at the increased power levels it permitted showed a significantly higher tendency to pre-ignite than 100/130 did when it was operated at it's permissible limit. This resulted in blowing pieces out the RR Merlin supercharger casing at times.

after a lot of trials with different blends/mixtures and arguing about different requirements (120/150 instead of 115/145 for example) 115/145 was standardized about the time of V-E day.
HOWEVER, for every gallon of 115/145 production of 100/130 dropped by 2 gallons. You needed a lot more of the alkylate per gallon of 115/145 and you needed select quality. some grades of alkylate that worked fine in 100/130 was not suitable for 115/145.

At the end of WW II the United Nations was producing 25 million gallons of 100PN fuel per day.
If you had 100% octane (the chemical, not the rating) and you added 4cc of lead per gallon you could get 153/153 PN number fuel but the production would have been limited to about 1 million gallons a day. At the end of the 1940s there were only 6 hydrocarbons known that would give a lean rating of 150 with 4cc of lead. Triptane (as used by the Super Corsairs in the National air races) with 4cc of lead, would give you 150/270 fuel.
BUT
"The octane of the octane scale could be produced in large amounts without serious waste of crude oil at the expense of enormous plant (steel) requirements.
Triptane, however, is a different case since its large-scale production would in the light of present knowledge (1949) not only require astronomical quantities of steel but in addition would waste very large amounts of crude oil. Large-scale triptane production (10 million gallons a day) would furthermore require almost the entire chlorine production of the United States. This may be summarized by stating that no feasible chemical reaction is currently known for large-scale triptane production."
Part in italics is copied from page 653 of a combined book and aircraft engines and fuel. The fuel portion is by S.D. Heron. "Development of Aviation Fuels"

Please note the Army was testing Triptane in 1941 (at $30 a gallon). By the time the book was published (1949/50) the price was down to several dollars per gallon. please note automotive gasoline was selling for 18-23 cents a gallon at the time. Even in the late 50s the idea that the airlines needed any sort of subsidy or under the table "deal" to use kerosene blended with low grade gas vs using some of these exotic high PN number aviations fuels is the stuff of fantasy.

 

Ranger?

Do you mean the Lycoming XR-7755 - Wikipedia

As for in-lines, probably the post war Napier Sabre (I forget the mark number) with 3,500hp at take-off, or the Rolls-Royce Eagle 22 which was rated, depending on source, between 3,200hp and 3,500hp.
 
Yawn !!! Scaling up you keep the basic cylinder dimensions the same, you just add more, for your motorcycle engine experiment. That is how multicylinder engines came about, especially aircraft engines. And stop with the gasoline stuff, no one says we have to use SI and gasoline. Dissipate heat ?, lets go adiabatic, oh just got another great idea, and can't give away all the secrets. Anyone have some out of the box solutions of how to force those pistons down the bores using less energy?
 
PWR4360-59B said:
awn !!! Scaling up you keep the basic cylinder dimensions the same, you just add more, for your motorcycle engine experiment. That is how multicylinder engines came about, especially aircraft engines.
Click to expand...

No kidding, and I thought they invented multi-cylinder engine engines just for the fun of it.
Missed the point again or just ignoring what you don't like? You can scale up dimensions, which runs into real world problems. Or you can just add more cylinders which adds weight, initial cost, size and reduces reliability and adds to overhaul costs.

PWR4360-59B said:
And stop with the gasoline stuff, no one says we have to use SI and gasoline.
Click to expand...
Hmm, upset that your theory about commercial jets being the result of a government conspiracy might not be true?

you only have one basic alternative to gasoline in a reciprocating engine and that is jet/diesel.

Alternative fuels that work in ground vehicles may not work so well in aircraft. Pure peanut oil (which dates back to Otto Diesel himself as a fuel for compression ignition engines) starts to gel at 50 degrees F, there are things that can be done to lower this but this is not a good idea for planes that fly even in the teens let alone higher.

I wonder how well that Yamaha motorcycle engine will work if we yank the plug, replace with a fuel injector and turn it into diesel? where did the 145hp go?

PWR4360-59B said:
Dissipate heat ?, lets go adiabatic
Click to expand...

Yep, just waiting for my patent to approved for my anti-gravity paint too.

They have known about adiabatic for a long, long time. getting it to work in practical fashion has been the stumbling block. Like making the resulting power plant low enough in weight and small enough in volume to actually fit in a moving vehicle and yet powerful enough to move it in a useful manner.
Some of the early jet designers tried to get too tricky with heat exchangers and theoretical cycles, they would up with large, heavy, expensive engines that never made it of the test bench.




 
One example of "large and heavy" is a gas turbine with a recuperator or regenerator (there's a difference, but it's pretty technical). They tend to help more at part power, which is why Lycoming has one in the AGT-1500, but not at high power settings. The AGT-1500 has a pretty flat sfc curve to about 15% power, but its sfc near full power isn't any better than its non-recuperated aero sibling, the PLT-27.
 
I didn't read all 9 pages so I'm not sure if anyone noted this new design. A New England US company has re-designed the Wankel concept and turned it inside out. By doing so, the fragile tip seals on the rotor and now fixed in the housing. It promises high power-to-weight ratios and is slated for testing in some UAVs. It apparently answers all the drawbacks of the Wankel design while retaining the benefits of very few moving parts, low vibration and high RPM. This is from Aviation Week and Aerospace Technology, June 20, 2018 issue, so it's very, very current. The article was longer, but I just wanted to capture the cross-section.

 
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