Build the perfect water cooled engine
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Lighthunmust
Banned
Is this a trick question? An R-2800 in a rain storm of course.
I look forward to reading about more elaborate designs.
I look forward to reading about more elaborate designs.
Readie
Chief Master Sergeant
This will be a good thread.
My answer will be predictable but, I'm going to say the M word anyway
Seriously, it'll be good to read the answers
Cheers
John
My answer will be predictable but, I'm going to say the M word anyway
Seriously, it'll be good to read the answers
Cheers
John
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Shortround6
Major General
A lot features depended on other features or excluded other features. DB and Junkers engines were larger in displacement than the Merlin and Allison but in early war versions didn't weigh anymore. This lighter construction limited rpm and and allowable BMEP.
German fuel injection allowed (it is claimed) lower octane fuel to be used and gave better economy. Rolls-Royce and Allison placed a carburetor on the intake of the supercharger, the vaporization of the gasoline in the supercharger lowered the intake charge temperature by 20-25 degrees C and allowed more boost to be used for a given grade of fuel. You can't use direct fuel injection and get the lower charge temperature. Fuel injection does have some other advantages though, but it is expensive to make and harder to service.
Motor cannon are nice but they take up space at the back of the engine. With simple superchargers this is not a real problem but with the more complicated 2 stage superchargers/intercoolers it is.
larger, slower turning engines don't need as much boost as the small high revving engine so the same simple supercharger can maintain power a bit higher.
A V-12 is the most practical liquid cooled configuration until the you need cylinders over a certain size, Cylinder size in governed by several things like flame speed. Once you need more than 12 cylinders anything but the V-12 has more frontal area. X-16s are probable not a good idea because most of your extra power is sucked up by the extra drag. there are reasons why they jumped from 12 cylinders to 24. and there are reasons why the length of a crankshaft stayed at 6 cylinders.
Any engine is a series of compromises and while a number of engines showed that there was more than one path to reach the same goal you have to realize that not all features can be applied to all engines without some other feature being affected.
Shortround6
Major General
This will be a good thread.
My answer will be predictable but, I'm going to say the M word anyway
Seriously, it'll be good to read the answers
Cheers
John
Since he didn't put a time or price limit (or fuel limit) on it I would say either "G" or "S".
the Lycoming 7755 has to be the "ultimate" if you can just figure out what to put it in
Lycoming XR-7755 - Wikipedia, the free encyclopedia
Lighthunmust
Banned
If I may be so bold as to paraphrase Shortround6: Reality sucks; you can't have your cake and eat it to. I knew this thread would require knowledge way above my head at this time. I have a great amount of reading to do before I take a stab at designing a water cooled engine more elaborate than a R-2800 in a rain storm.
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davebender
1st Lieutenant
Kurfürst - DB 601, 603, 605 datasheets - DB 605 DB/DC
High power in an engine that is relatively compact and light in weight. Fuel economy and reliability are good too. Can accomodate a prop mounted cannon. Fuel can be either B4 or C3 with a simple screwdriver adjustment. Fuel injection eliminates carburetor related performance problems.
High power in an engine that is relatively compact and light in weight. Fuel economy and reliability are good too. Can accomodate a prop mounted cannon. Fuel can be either B4 or C3 with a simple screwdriver adjustment. Fuel injection eliminates carburetor related performance problems.
wuzak
Captain
I would say that if you are after a mid sized engine you take the Allison V-1710 design and give it to Rolls Royce to develop.
Or...you take the Sabre and give it to Rolls Royce to develop. Or when Mead starts to design the P&W X-1800/Xh-2600/XH-3130/XH-3730 convince him to get a licence for manufacture of the Sabre in the US.
I would stop RR making the Eagle22, and get them to make a liquid cooled version of the Pennine. As an air-cooled engine of 2800cid (same as R-2800) it was already making 2750hp on the bench with 12psi boost and 3500rpm. The Eagle 22 was of similar capacity, but much longer and heavier (2 cranks, etc). A liquid cooled Pennine would have been slightly more compact (no need for separate cylinders) and not much heavier, if at all. And you could ramp the boost up significantly.
Or...you take the Sabre and give it to Rolls Royce to develop. Or when Mead starts to design the P&W X-1800/Xh-2600/XH-3130/XH-3730 convince him to get a licence for manufacture of the Sabre in the US.
I would stop RR making the Eagle22, and get them to make a liquid cooled version of the Pennine. As an air-cooled engine of 2800cid (same as R-2800) it was already making 2750hp on the bench with 12psi boost and 3500rpm. The Eagle 22 was of similar capacity, but much longer and heavier (2 cranks, etc). A liquid cooled Pennine would have been slightly more compact (no need for separate cylinders) and not much heavier, if at all. And you could ramp the boost up significantly.
wuzak
Captain
Maybe a V12 with the Griffon bore (6in) and Kestrel stroke (5.5in). That gets you 1867cid/30.6l, and more ability to rev than the Merlin.
If you drop the stroke back to 5in, you get more revability, and 1696cid/27.8l.
If you drop the stroke back to 5in, you get more revability, and 1696cid/27.8l.
wuzak
Captain
When RR were required a new engine in the mid '20s they designed two options - the F and the Eagle XVI. The F would be developed into the Kestrel. The Eagle XVI was an X-16 engine which was slightly smaller than the F/Kestrel (1208cid/19.8l vs 1296cid/21.25l). It had staggered cylinder banks so that fork and blade type rods could be used for pairs of cylinders, and avoided the use of a master rod/slave rod arrangement (which the Vulture, Exe and Pennine all had).
The F was chosen because, among other things, it gave better visibility to the pilot.
Towards the end of the war, or just after it, Stuart Tresilian proposed an X-16 of the same power (2500hp) as a Griffon, using the Griffon's supercharger. It was to have a 3.9in bore, 3.3in stroke for 630cid/7.75l. It would have the supercharger in the front, and an exhaust turbine at the rear, with shafts joining them. The maximum width was to be the supercharger housing, at 26in (660mm). The rpm was to be around 7250, this giving a piston speed of around 20m/s (high for the times). The big end loading was equivalent to a 9 cylinder radial.
The problem with that was the reduction gear would be very heavy, so Tresilian proposed using small blades at higher rpm. With this he estimaed an all up weight of the propulsion system, consisting of engine, reduction gears, radiator, ducting and prop, as 2180lb.
johnbr
2nd Lieutenant
Cool I would love to see a cutaway of it.
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Readie
Chief Master Sergeant
Since he didn't put a time or price limit (or fuel limit) on it I would say either "G" or "S".
the Lycoming 7755 has to be the "ultimate" if you can just figure out what to put it in
Lycoming XR-7755 - Wikipedia, the free encyclopedia
5000 horsepower....jeez.
The Russians had to go one better Dobrynin VD-4K - Wikipedia, the free encyclopedia
Contra-rotating props would be essential with that amount of torque !
Maybe these were the last gasp of the piston engined era and were build because they could be....
Cheers
John
Readie
Chief Master Sergeant
wuzak
Captain
There is the Rolls-Royce Crecy. 1800hp + 600hp+ equivalent in exhaust thrust.
wuzak
Captain
5000hp from 7755 cubic inches is a little shameful for a liquid cooled engine....
wuzak
Captain
It depends on what kind of power we are seeking but here is my take based on the assumption we are talking about an engine in the 2500-2800 hp power class:
-direct fuel injection using Bosch-type pumps
-sleeve valves
-general configuration like that of the Sabre (i.e. 24-cyl H)
-2-stage supercharger following RR practice but with DB type fluid drive
-contrarotating prop reduction gear
-water injection
-direct fuel injection using Bosch-type pumps
-sleeve valves
-general configuration like that of the Sabre (i.e. 24-cyl H)
-2-stage supercharger following RR practice but with DB type fluid drive
-contrarotating prop reduction gear
-water injection
wuzak
Captain
Well, that is the Napier Sabre, but with contrarotating prop reduction gear.
The Pennine was 37.5in/952.5mm high, 39in/990.6mm wide and 106in/2692.4mm long. The length includes contrarotating prop drives and gearbox, plus single stage single speed supercharger. Weight was 2850lb/1293kg.
I believe that a liquid cooled version of the Pennine would not increase in width or height, may be slightly shorter, about the same weight, more with the radiators obviously, but able to make significantly more power.
The Pennine was rated at 2740hp at 3500rpm for takeoff and 2800hp at sea level combat rating.
The Sabre was 40in/1016mm wide, 46in/1168mm high, 82.25in/2089mm long and weight 2360lb/1070kg. It too was fitted with a single stage two speed supercharger, but only single rotation prop reduction gear. Military power for the Sabre VA was 2850hp, WEP 3040hp.
Shortround6
Major General
Are there any constraints on this engine?
"Build me the ultimate engine for the widest range of applications possible"
Like does it have to fit an a fighter the size of a P-47 or smaller?
Most of the late war "monster motors" while they could hit 2500-3000hp were too big to fit anything smaller than P-47, F6F, F4U or Tempest.
The Griffon is the smallest (2165lb) and the 130 version was good for 2420hp at 5,000ft using 25lb of boost. It could give 2,050 at 21,000ft at 25lb boost. This engine used a two stage THREE speed supercharger. It was good for 1280hp at 32,000ft 'Normal'
Indications that it had about hit "it's" limits area piston speed of 3,025ft/min, an output of 7.13hp/sq in of piston area and a BMEP or 311.
The Napair Sabre VII with a 2 speed single stage supercharger was good for 3000hp at take off( 17.25lbs of boost and ADI) and 2760hp at 12,450ft in high gear. 1960hp 'normal' at 18,250ft.
It's indicators are a piston speed of 3,048ft/min, 6.49hp/sq in of piston area and a BMEP of 280.
The Chryser XI-2220 16 cylinder engine was supposed to give 2500hp from sea level to 30,000ft (turbo) using 21 lb of boost and had indicators of piston speed 2975 ft/min, 5.92hp/sq in piston area and BMEP of 261.
For the German fans we have the post war French built Jumo 213 at 2300hp take off at 11lbs boost and with ADI or 2100hp take off at 11lbs dry. a 'Normal' rating of 1500hp 18,050ft.
It's indicators are a piston speed of 3,521ft/min, 7.02 hp/sq in and a BMEP of 263. This is in 1953 and is rated on standard 100/130 fuel which helps eliminate the "was German fuel better or worse" question. The French company was also trying to market an H-24 engine use 4 Jumo 213 6 cylinder engine blocks so I am assuming they had time to figure out the fuel conversion.
The 'indicators' point to the stress on the bearings (piston speed), stress and cooling loads on the piston crown (HP/sq in) and the loads on the engine structure in general (BMEP) BMEP is also limited by the fuel.
While fooling with imaginary designs it is well to keep these indicators in mind. The Jumo 213 is the ONLY production aircraft engine to use piston speeds much over 3100ft/min.
For your consideration the numbers for the last Mercedes Grand Prix car of 1939 are 480hp from a 3 liter engine at 7500rpm. The piston speed was 3444ft/min, the output was 7.32hp/sq in piston area and the BMEP was 305.
The engine used 2.31 Atm of manifold pressure (about 19-20lbs boost, it used a two stage system) and ran on a fuel blend of approximately 86% methanol, 4.4% nitrobenzol, 8.8% acetone, and 0.8 sulphuric ether.
As can be seen, high performance aircraft engines were operating near the limits of Grand Prix racing car engines and doing it at lighter weight, the Mercedes engine weighed 603lbs for it's 480hp and the weight doesn't include a reduction gear, but probably includes fly wheel. Granted things like engines don't "scale" well.
"Build me the ultimate engine for the widest range of applications possible"
Like does it have to fit an a fighter the size of a P-47 or smaller?
Most of the late war "monster motors" while they could hit 2500-3000hp were too big to fit anything smaller than P-47, F6F, F4U or Tempest.
The Griffon is the smallest (2165lb) and the 130 version was good for 2420hp at 5,000ft using 25lb of boost. It could give 2,050 at 21,000ft at 25lb boost. This engine used a two stage THREE speed supercharger. It was good for 1280hp at 32,000ft 'Normal'
Indications that it had about hit "it's" limits area piston speed of 3,025ft/min, an output of 7.13hp/sq in of piston area and a BMEP or 311.
The Napair Sabre VII with a 2 speed single stage supercharger was good for 3000hp at take off( 17.25lbs of boost and ADI) and 2760hp at 12,450ft in high gear. 1960hp 'normal' at 18,250ft.
It's indicators are a piston speed of 3,048ft/min, 6.49hp/sq in of piston area and a BMEP of 280.
The Chryser XI-2220 16 cylinder engine was supposed to give 2500hp from sea level to 30,000ft (turbo) using 21 lb of boost and had indicators of piston speed 2975 ft/min, 5.92hp/sq in piston area and BMEP of 261.
For the German fans we have the post war French built Jumo 213 at 2300hp take off at 11lbs boost and with ADI or 2100hp take off at 11lbs dry. a 'Normal' rating of 1500hp 18,050ft.
It's indicators are a piston speed of 3,521ft/min, 7.02 hp/sq in and a BMEP of 263. This is in 1953 and is rated on standard 100/130 fuel which helps eliminate the "was German fuel better or worse" question. The French company was also trying to market an H-24 engine use 4 Jumo 213 6 cylinder engine blocks so I am assuming they had time to figure out the fuel conversion.
The 'indicators' point to the stress on the bearings (piston speed), stress and cooling loads on the piston crown (HP/sq in) and the loads on the engine structure in general (BMEP) BMEP is also limited by the fuel.
While fooling with imaginary designs it is well to keep these indicators in mind. The Jumo 213 is the ONLY production aircraft engine to use piston speeds much over 3100ft/min.
For your consideration the numbers for the last Mercedes Grand Prix car of 1939 are 480hp from a 3 liter engine at 7500rpm. The piston speed was 3444ft/min, the output was 7.32hp/sq in piston area and the BMEP was 305.
The engine used 2.31 Atm of manifold pressure (about 19-20lbs boost, it used a two stage system) and ran on a fuel blend of approximately 86% methanol, 4.4% nitrobenzol, 8.8% acetone, and 0.8 sulphuric ether.
As can be seen, high performance aircraft engines were operating near the limits of Grand Prix racing car engines and doing it at lighter weight, the Mercedes engine weighed 603lbs for it's 480hp and the weight doesn't include a reduction gear, but probably includes fly wheel. Granted things like engines don't "scale" well.