If Reciprocating engines were still made (Read)

[Ryanjames17]

So here is a new thread on this but im going to lay down a few things

1. Turbine engines are not feasible
1a. Fuel Reasons
1b. Precious metals used in High temp turbine blades are not avlible enough to mass produce the number of turbine blades required for mass use of jet engines.
2. Post WWII economy was not good enough for aircraft engine manufactures to put money into researching ways to get around lack of high temp metals.

to add on the high temp materials lets say it was something of 100 turbo chargers to 1 jet turbine. so the cost would be high enough to be out of reach for most civlian markets and the post WWII economy was not good enough that most aircraft engine manufactures ruled them out as being profitable

Bottom line is jet turbines are out..

so the question is how would of piston engines have evolved Post WWII?

would they have strived for as much power as they could of gotten or economy?

what sort of engines might not have been tossed to the side if jet engines would of been a unviable power plant

 

[wuzak]

Does that mean that turbochargers are out too? They also require high temperature alloys.

BMW's turbo design featured an air cooled turbine.
Wright's power recovery turbines for the R-3350 turbo-compound also used air cooling.
Allison's V-1710-127 (E27) used a turbine developed from the GE C-series turbo (as used on P-47), but at WEP the exhaust temperature was too hot for that. Further development would have seen an air cooled turbine.

Air cooled turbine blades were being developed for the German gas turbines towards the end of the war. I can't recall if any were fitted to the BMW 003 or Jumo 004, but I would be surprised if they were. The next generation of turbines certainly would have featured air cooling.

Conventional wisdom suggests that the reliability of German turbojets was affected by the lack of the metals required for high temperature alloys. That may be the case, but other factors must also have been involved - the situation of the war, for example.

Fuel wise, gas turbines are far less fussy than spark ignition piston engines. If fuel quality is a problem the Merlins, DB605s, etc, of the world will suffer more than turbines.

What about steam turbines? Junkers had designed a 3,000hp steam turbine at the start of WW2, and, IIRC, there were two proposed for the Me 264 program - one of 4,000hp and one of 6,000hp. The Me 264 steam turbines were to run on 35% petrol/65% pulverised coal. The system power-to-weight ratio was said to be similar to that of a piston engine.

Steam turbines have been around since 1884, and by WW2 they were everywhere generating electricity.

Steam turbines run at lower temperatures, so much less of an issue with materials.

Probably not suitable for single engine machines, but certainly viable for big multis, like the Me 264 or Boeing B-29.

 

[Ryanjames17]

i updated that.
well we can say this. for the sake of argument
not sure if its true or not but
turbo chargers could be made with lesser materials and get a much higher service life then a turbine say maybe 400 hours vs under 10 and if they used the precious metals it was 2-5K hours on a turbo and maybe 30-40 hours out of a jet turbine (keep in mind it was not uncomon for post WWII jet engines to have super low TBO's)

but you can make 100+ turbochargers for one turbine material wise but the cost of them is far higher. plus in a poor post WWII (much worse then it was) most airlines, aircraft manufactuers) were unwilling to put forth money on jet engines vs using surplus WWII piston engines and what they already had in the 1940's so turbines were dropped in the 1940's and 1950's we can say more attention was put into piston engines to improve them perhaps longer TBO's with a given poweroutput or perhaps more power, with again no one wanting to mess with costly jet turbines, 1960's perhaps the same story, 1970's we could add that most of the raw material for turbo's being comprised of reclaimed material.

Does that mean that turbochargers are out too? They also require high temperature alloys.

BMW's turbo design featured an air cooled turbine.
Wright's power recovery turbines for the R-3350 turbo-compound also used air cooling.
Allison's V-1710-127 (E27) used a turbine developed from the GE C-series turbo (as used on P-47), but at WEP the exhaust temperature was too hot for that. Further development would have seen an air cooled turbine.

Air cooled turbine blades were being developed for the German gas turbines towards the end of the war. I can't recall if any were fitted to the BMW 003 or Jumo 004, but I would be surprised if they were. The next generation of turbines certainly would have featured air cooling.

Conventional wisdom suggests that the reliability of German turbojets was affected by the lack of the metals required for high temperature alloys. That may be the case, but other factors must also have been involved - the situation of the war, for example.

Fuel wise, gas turbines are far less fussy than spark ignition piston engines. If fuel quality is a problem the Merlins, DB605s, etc, of the world will suffer more than turbines.

What about steam turbines? Junkers had designed a 3,000hp steam turbine at the start of WW2, and, IIRC, there were two proposed for the Me 264 program - one of 4,000hp and one of 6,000hp. The Me 264 steam turbines were to run on 35% petrol/65% pulverised coal. The system power-to-weight ratio was said to be similar to that of a piston engine.

Steam turbines have been around since 1884, and by WW2 they were everywhere generating electricity.

Steam turbines run at lower temperatures, so much less of an issue with materials.

Probably not suitable for single engine machines, but certainly viable for big multis, like the Me 264 or Boeing B-29.

 

[wuzak]

For the transport market, Rolls-Royce were developing the Pennine, an air cooled X-24 sleeve valve engine of around 2,790ci/45.7L (R-2800 was 2,805ci/46L).

Maximum power was 2,740hp. 2,800hp for take-off.

Weight was slightly more than an R-2800, at 2,850lb/1,293kg, but whether that included dual or single rotation reduction gear, I do not know.

The performance was impressive, IMO, for its early stage of development.

For the military market, the Eagle 22 was developed.

It was 2,807ci/46L in capacity, much the same as the R-2800. It was also a sleeve valve engine, but a liquid cooled H-24.

Power was in the range of 3,200hp - 3,600hp. But the engine was massive - 3,900lb/1,769kg and 135.5in long! It was fitted with a two stage supercharger for altitude performance, unlike the single stage supercharger on the Pennine.

Napier may have found a market for the Sabre other than the Tempest. It could compete with the Eagle 22, but was lighter and more compact.

There may have been more effort into a turbocharged installation of the Sabre.

The other Napier project was the Nomad. It would have been used in multi-engine military aircraft, but I am not sure that civilian users would be that keen, as they seemed to prefer air cooled engines. The Nomad's efficiency may have persuaded them, though.

Bristol would continue with Hercules and Centaurus, and may have started on the Orion project, which was an enlarged Centaurus.

Wright would have continued with R-3350 development and probably would have kept R-2600 production going. Maybe they start the R-4090 22 cylinder version again.

Pratt & Whitney had the R-2800 and R-4360 with which to work. They could be used for military or civilian projects. The next development for these was the Variable Discharge Turbine versions. The VDT did away, in some variants, of the engine supercharger to be purely turbocharged. Some were also turbo-compounds.

Allison was already developing turbo-compounds. Had gas turbines not been developed, Allison's turbo-compounds may have found a military market, allowing them to develop the engine to maturity. Engines would have been, no doubt, the V-1710 and V-3420.

Many of these projects after the war were to be turbo-compounds. These put a lot of stress into the turbines, and if high temperature alloys were not available they may not have been able to proceed, though some would cope with air-cooled turbines.

Fighter aircraft would be stuck with maximum speeds of between 500 and 550mph. Bombers could get into the high 400mph range.

Airliners may get into service with cruise speeds above 400mph (as the Republic Rainbow was planned to do), but most would be below that.

Post war there was no new great leap to be had in piston engines. Mostly it would be refinement of the existing engines.

 

[Shortround6]

You are overlooking the fuel situation.

High performance fuel was expensive.

Jet fuel was cheap.

You are also a bit off on the ratio of turbos that could be built vs the number of jet engines.

GE during the war had fooled around with a small turbine engine that used the compressor and turbine from the B-31 turbocharger with a combustion chamber in between (In actuality it hung out one side, the B-31 retaining the original shaft and spacing in the prototype) and this resulted in a development contract for a small engine to power a flying bomb. Changes were made to the turbine. They hoped for 400lbs thrust but only got about 1/2 that before the the program was dropped.
B-29s used two of the B-31 turbos per engine so number of turbos per large aircraft is certainly open to question.
B series turbos went around 130-140lbs for the complete unit. C series turbos as used in the P-47 were over 200lbs.

Amount of rare metals used in the turbines was obviously muchless but then a complete (includes combustion chambers) RR Derwent V engine weighed 1250lbs.
and made 5000lb of thrust. Just about all the early Jets used a single turbine disc but yes they did use stator blades which would increase the need for chrome and nickel.

The amount of metal needed might be closer to 10 or 20 to one than 100 to one. And the resulting engine is 3-4 times more powerful.

As explained in another thread, 115/145 fuel was about as good as it was going to get without a massive investment in refineries and the chemical industry. Unlikely if the world is a poor as your scenario.

Now please note that the R-4360CB2 was rated at 3500hp for take-off and 3250hp take-off dry and 2850 max continuous on 108/135 fuel but was limited to
3250hp take-off wet, 3000hp T-O dry and 2650hp when run on 100/130 fuel.

These end of war or postwar engines were very dependent on high performance fuel. Potential improvements would be pretty much in materials.
24-28 cylinders per engine seems to be pushing the limit. Engines with more were designed and built but none adopted. Vibration problems crop up with the more cylinders and the higher rpm you use. Most anything can be solved if you throw enough time and money at it. Would the improvements be worth it?

 

[Zipper730]

The laws of physics would be different...

 

[Shortround6]

As a further note.
Turbos for small planes/helicopters showed up in the late 1950s.
The AiResearch T1106 was a popular unit and would support a 350-400hp engine but it weighed about 35lbs. and that is without the intercooler. It seems to have shown up in early 60s?

Compressor design has made huge strides but it didn't happen all at once.

 

[MIflyer]

Postwar, they were going to use just kerosene fuel for jets but were told by the oil industry that would not work. You only get a certain amount of kerosene out of a barrel of oil; you actually get more gasoline than kerosene. JP-3 was developed because if they just used the kerosene they would have a lot of gasoline left over; so they came up with a mixture.

Prior to 1900, when the only reason for refining oil was to get kerosene (lamp oil) and tars, they would dump the leftover gasoline in the nearest river. Gasoline was too volatile to be used safely for lights, cooking, making paints, etc.

Eventually, I guess there was enough of a worldwide market to absorb the gasoline produced.

 

[Ryanjames17]

more then point of the thread is more what if they decited/had to to continue with piston engines over turbines for some reason that was actully more then i dont like jet turbines.

 

[swampyankee]

Quite a lot of the advance in the turbines and compressors in turbo- and superchargers came from the gas turbine industry, so some of the advance in piston engines would be slowed.

I'm actually waiting for Jay Leno to get hold of an AGT-1500 and get himself a higher performance Blastolene Special Mk II.

 

[Shortround6]

Postwar, they were going to use just kerosene fuel for jets but were told by the oil industry that would not work. You only get a certain amount of kerosene out of a barrel of oil; you actually get more gasoline than kerosene. JP-3 was developed because if they just used the kerosene they would have a lot of gasoline left over; so they came up with a mixture.

Yes and no.

Depending on the oil field you get a bit more or less kerosene per barrel of crude and/or a bit more "gasoline". That is a minor quibble.

A major quibble is that not all the "gasoline" is the same. In WW I and the 20s some gasoline worked just fine and other gasoline wrecked engines.
It was found (after they developed the octane scale) that some oil fields produced "gasoline" (after using a simple refining process) of around 70 octane which run Spads/ S.E. 5As, Nieuports and Camels just fine. Other oil fields, using the same refining process produced "gasoline" of around 38-40 octane which wrecked engines by the score.
In a world wide supply chain there is more kerosene available than "aviation fuel" because even 70 octane gasoline was pretty useless for anything but basic trainer engines after the mid 30s.
Cat cracked "gasoline" is somewhere in the 80s or low 90s most of the time. The 'cat cracking' allowed for a higher percentage of gasoline from the same barrel of crude. However even cat cracked "gasoline" needs help to become 100 octane (or 100PN) fuel. That can come from the addition of lead compounds, or aromatic compounds or a combination of both. Some feed stocks (crude oil or simply refined gasoline) will never be able to be turned into 100/130 no matter what you add to them. This also limits the total supply of high performance aviation fuel. Trying for 108/135 or 115/145 or the British 100/150 further limited the quantities of base stock that could be used.
There are also production limits on some of the aromatic compounds. Toluene is a pretty good compound to add to gasoline to improve the performance number.
But in wartime the explosives industry is looking for all the toluene it can get for trinitrotoluene (TNT).
It is these added steps in refining and the added materials that increase the cost of aviation fuel over plain old simple gasoline and kerosene and create production bottlenecks.

Straight kerosene may not be that great a jet fuel depending the temperature and the kerosene. It tends to get thick and not flow well at the temperatures that can be found at high altitudes. Maybe not a problem with fighters that have an endurance of only an hour or two but for planes that are going to spend 8-12 hours (or longer) at 30,000ft and above it is something to consider. Mixing in some "gasoline" (even if low grade) might change things enough to keep the trouble away.

 

[AMCKen]

RR Pennine was 2748 cuin (45L) (5.4x5). A 32 cylinder version was proposed (3664cuin) but not built.
Eagle 22 was 2817 cuin (46.2L) (5.4x5.125)

 

[PWR4360-59B]

The whole fuel argument is easy. The use of CI or diesel technology cures that and adds hugely to the efficiency and economy as well.
As far as HP vs weight there are claims of 11k HP from small automotive V8's, yeah yeah I know. But is proof of what can be done. And like others say the whole issue is the cost and engineering required. If there really was an oil shortage believe me they aircraft manufactures would be scrambling to find a super efficient engine and it would not be a turbine.

 

[wuzak]

If oil ran out a turbine could run on other fuels.

Such as hydrogen.
Methanol or Ethanol.
Or biodiesel.

As for efficiency, large turbofans are extremely efficient. Not many piston engines match their efficiency.

 

[Shortround6]

The whole fuel argument is easy. The use of CI or diesel technology cures that and adds hugely to the efficiency and economy as well.
As far as HP vs weight there are claims of 11k HP from small automotive V8's, yeah yeah I know. But is proof of what can be done. And like others say the whole issue is the cost and engineering required. If there really was an oil shortage believe me they aircraft manufactures would be scrambling to find a super efficient engine and it would not be a turbine.

The 11K hp from small automotive V8s is for how long? seconds?
And what is the fuel consumption for that V8 at that power rating?

This is the trouble I have with your posts, you take a snippet of information from one place and a snippet from somewhere else and try to combine them.
From Wiki:
"While nitromethane has a much lower energy density (11.2 MJ/kg (1.21 Mcalth/lb)) than either gasoline (44 MJ/kg (4.8 Mcalth/lb)) or methanol (22.7 MJ/kg (2.46 Mcalth/lb)), an engine burning nitromethane can produce up to 2.3 times more power than an engine burning gasoline. This is made possible by the fact that, in addition to fuel, an engine must burn oxygen in order to generate force: 14.7 kg (32 lb) of air (21% oxygen) is required to burn one kilogram (2.2 lb) of gasoline, compared to only 1.7 kg (3.7 lb) of air for one kilogram of nitromethane"
So your 11000hp engine, while possible, is burning 4 times the amount of nitromethane to make the same power as gasoline and due to Nitromethane carrying some of it's own oxygen and needed a different fuel/air ratio it is burning over 8 times the amount of gasoline to get the high power.
A Dragster can afford to use up 12-22.75 gallons of fuel in under a minute (less than 7 seconds at full power though) but lets see how well your airplane does with fuel that weighs 9.4 lb per gallon.

And this fuel relates to "CI or diesel technology" how? granted you can get a dragster engine to diesel (compression ignite) when it is hot at the end of it's run but that is hardly controlled combustion.

If there was an oil shortage then the supply of exotic fuels like nitromethane would disappear pretty quick.
"Nitromethane is produced industrially by combining propane and nitric acid in the gas phase at 350–450 °C"

So you need a hydrocarbon base.

also from wiki:
"There are no water passages in the block, which adds considerable strength and stiffness. The engine is cooled by the incoming air/fuel mixture and the lubricating oil." Great for a burst of power lasting in the single digits of seconds. I wonder how it works getting an airplane to 20,000ft?

oh yeah
"The engine is warmed up for about 80 seconds. After the warm up the valve covers are taken off, oil is changed and the car is refueled. The run including tire warming is about 100 seconds which results in a "lap" of about three minutes. After each lap, the entire engine is disassembled and examined, and worn or damaged components are replaced."

Wow, what fuel economy, what reliability compared to those maintenance hog turbine engines.

People were able to make small engines yield high power even back in the 30s, They just weren't practical as an engine for commercial travel.
There was an Austin 7 racing engine (which shared no parts with the Austin 7 car.) that made 116hp from 744 ccs in 1937 using mainly methanol for fuel (75%) but the supercharged, DOHC engine weigh 260lbs. For under 230lbs you could either a Blackburn Cirrus minor or a De Havilland Gypsy minor engine of 90hp for aircraft use. for long races the little Auston was detuned to 90-100hp.

Somehow I just don't see an airliner powered by banks of these engines (only one at time connected to the propeller/s) as teams of mechanics strip and overhaul the spare engines in flight as they are used up in a rotating schedule and clutched in and out of the drive system. Wonder what the FAA would say to that proposal

Modern large turbines have gotten to the point where they can equal the specific fuel consumption of a even an economical reciprocating piston engine.
That leaves the piston engine with only the small engine market open to it and perhaps the 400-1000hp engine market but that will take something that doesn't seem to exist at the moment.

I could be wrong. Please post links but please, not to nonsense like that barrel engine( nice engine for what it is but how do you scale it up to to 7-10 cylinders without it getting absurdly large?) or other engines that have been in developemt for 15-20 years and just need another few million to get the bugs out.
They don't have to re-invent aluminium alloys, or titanium or ceramic coatings, or computer chips for engine management. The building blocks exist, if they can't get the engine to work with existing material and computer power then maybe there is something wrong with the basic concept?

 

[wuzak]

oh yeah
"The engine is warmed up for about 80 seconds. After the warm up the valve covers are taken off, oil is changed and the car is refueled. The run including tire warming is about 100 seconds which results in a "lap" of about three minutes. After each lap, the entire engine is disassembled and examined, and worn or damaged components are replaced."

I think you mean a lap of around 3 seconds (1/8 mile?).

TOP FUEL DRAGSTER FAST FACTS - Super Coupe Club of Iowa
"Under full throttle, a dragster engine consumes 11.2 gallons of nitro methane per second; a fully loaded 747 consumes jet fuel at the same rate with 25% less energy being produced."

Not sure I understand this one. A 747 with 4 turbines is surely making more than 11,000hp. Unless they are including energy which is thrown into the air from the exhaust. In which case, why don't they point the exhausts rearwards?

"At the stoichiometric 1.7:1 air/fuel mixture for nitro methane the flame front temperature measures 7050 degrees F."

Great for longevity.


"Spark plug electrodes are totally consumed during a pass. After 1/2 way, the engine is dieseling from compression plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting the fuel flow."

Great for the maintenance crews. Every few seconds during a flight they have to change the spark plugs!

Or maybe this is the CI R4360 speaks of?


"Including the burnout, the engine must only survive 900 revolutions under load."

How far will that get the airliner?


"THE BOTTOM LINE: Assuming all the equipment is paid off, the crew worked for free, & for once, NOTHING BLOWS UP, each run costs an estimated $1,000 per second."

Sounds very economic!


Top Fuel by the Numbers - Motor Trend

"28 Quarts of oil used during warm-up and quarter-mile run. The oil pan holds 70-weight oil mixed with special thickener."

So 7USG of oil consumed in 100s of running time!

 

[Shortround6]

I think you mean a lap of around 3 seconds (1/8 mile?).

Wiki counted a "lap" as 80 seconds or so of warm up, (after which the oil was changed) plus the staging, initial "burn out" to warm up the tires and put fresh rubber on the track and finally, the 1/4 mile run. total run time on the engine, including periods of idling about 3 minutes. Then tear the engine down for inspection/repair and assemble for the next "round/race" if they were the winner and hadn't blown up anything.

 

[PWR4360-59B]

I'm just glad there are some folks that aren't stuck in a box, else inventions and refinements would be nonexistent. Even your precious turbine would not have come to fruition. I like how the one fellow above says they are way more efficient than piston engines, how come my little 50 mpg car doesn't use one?

 

[swampyankee]

I'm just glad there are some folks that aren't stuck in a box, else inventions and refinements would be nonexistent. Even your precious turbine would not have come to fruition. I like how the one fellow above says they are way more efficient than piston engines, how come my little 50 mpg car doesn't use one?

Well, note everybody said that turbines don't scale down well.

Car engines are low-powered by aviation standards. The comparison for a 777 isn't the engine in a dragster or a motorcycle; it's the engine in a Panamax containership.

 

[wuzak]

A gas turbine with the same power as a regular Chevrolet Corvette engine would be considered a microturbine!