Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: joeblogs on February 21, 2003, 11:24:20 PM
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NOTE! IF YOU DOWNLOADED THE TEXT AND CHARTS PRIOR TO THE AFTERNOON OF FEB 23RD, THERE WAS AN ERROR IN THE DATA. THE TEXT AND CHARTS HAVE BEEN CORRECTED.
I have been assembling a data set of information on about 80 separate engines of at least 800 CU displacement produced by about 35 companies in seven nations (France, Germany, Italy, Japan, UK, USA, and USSR). There are many different versions of certain engines (Cyclones, Merlins, Double Wasps, etc), and I have at least some information on about 400 different models.
The source data is a series of books published by Paul Wilkinson (Aircraft Engines of the World) published throughout the 1940s. This source is a little thin on Japanese and Russian engines, so I am looking to augment this with information from other sources (Help!)
I've just begun to analyze this data, but I'll provide some tidbits in several posts that follow this one.
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Figure 1 presents data on maximum horsepower vs. engine displacement. There's a pretty obvious linear relationship between the two. Most engine models with the same displacement generate about the same horsepower.
I've identified most of the important engine families on the figure. A vertical sequence of dots typically represents the development of a particular engine (e.g. Merlin or Double Wasp). Some of these sequences are rather large, indicating how far some good designs could be stretched with better fuels, better supercharging, and internal strengthening.
But there are clearly some outliers. These include Continental's X-1430 experimental engine (based on Wright field's "hyper cylinder"), Rolls Royce's Eagle and a few very late model Griffon and Merlin engines. There's also the Napier Sabre VII. All of those are liquid cooled engines. Among the air cooled engines, the outliers include an E model of the Double Wasp, and Wright's turbo compound Cyclone 18.
Speaking of differences between the performance of air and liquid cooled engines, there appears to some systematic differences that vary over engine size:
For displacements under 2000 cu, it appears that liquid cooled engines enjoy a slight advantage over their air cooled brethren.
From 2000-2500 cu it looks like a toss-up.
From 2500-3500 cu, the air cooled engines have the advantage, but there are only a few liquid cooled engines that large.
Among the monster engines--all post war models-- there are two liquid cooled French designs (Arsenal's 24H and Hispano Suiza's 24Z) and two air cooled designs (Pratt and Whiteny's Wasp Major and Bristol's coupled Centaurus). To my knowledge, the only one of these engines produced in quantity was the Wasp Major.
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Figure 2 shows the relationship between engine horsepower and weight. Again there is pretty linear relationship between these two variables for most engines. Liquid cooled engines have slight advantage here, and for a few engines a substantial one. They should, as I am using dry weight here (not including the weight of a radiator, coolant, or oil). Including a radiator and coolant should increase the the gross weight of a liquid cooled power plant by 20-40 percent.
There are 33 liquid cooled engines with an HP/dry weight ratio of 1 or higher. These include late war models of the Merlin, Griffon, Allison V-1710, the DB 601E, and the Jumo 213A. The extreme outliers among the liquid cooled engines include a late model Griffon, Napier's Sabre VII, the post war Hispano 12Z, Continental's hyper engine, and the Russian M107.
The 11 air cooled engines with an HP/dry weight ratio of 1 or higher include late war models of the Double Wasp, Cyclone 9, and the post war models of Bristol's Hercules and Centaurus.
More on this later. But I'll leave the debate over coolant and form drag to someone else.
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Figure 3 presents the distribution of Specific Fuel Consumption (lbs of fuel per horsepower per hour) at cruise settings for about 200 engines.
The average SFC is about 0.45. Quite a few have a worse fuel economy. Somewhat surprisingly, these consist of many models of the Rolls Royce Merlin and Griffon engines. I had thought that liquid cooled engines would be somewhat more fuel efficient than air cooled engines, but this is often not the case (I think because the best of these are run at higher RPMs).
A number of engines have a better SFC, around 0.42. These consist almost completely of the later versions of Pratt and Whitney's Twin Wasp (1830 cu) and Double Wasp (2800 cu) engines, Bristol's Hercules (2360 cu) and Centaurus (3270 cu) engines, and a few models of Allison's V-1710 liquid cooled engine.
The most fuel efficient engines, with an SFC under 0.40, are the Turbo Compound version of the Wright 3350 and Pratt and Whitney's Wasp Major (4360 cu). Both of these engines were not produced in quantity until after the war.
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Figure 4 shows that that SFC seems to improve with the octane/performance rating of the fuel (the bars for engines rated on 87 octane avgas tend to be further to the right than the bars for engines rated on 100 octane, and so on). I'm not yet sure whether it's the gas or the vintage of engine that explains the better performance (older engine models are typically rated on lower octane fuels).
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Hi Joe,
Great charts! :-)
>I'm not yet sure whether it's the gas or the vintage of engine that explains the better performance (older engine models are typically rated on lower octane fuels).
It's my impression that it's the fuel. Higher octance fuel contains more energy. If you'd map not specific fuel consumption, but energetical effectiveness eta (the ratio of energy output to energy input), the older engines probably would be a bit closer to the newer ones.
By the way, while eta is a dimensionless value, SFC is not (though it often seems to be listed as such). It's lbs/HPh (pounds of fuel per horsepower per hour). German values are often given as g/PSh (grams per horsepower per hour), so this information helps with conversions :-)
Regards,
Henning (HoHun)
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Hi Joeblogs,
>The average SFC is about 0.45. Quite a few have a worse fuel economy. Somewhat surprisingly, these consist of many models of the Rolls Royce Merlin and Griffon engines.
It's important to remember that the specific fuel consumption is calculated based on shaft horsepower. Some engines like the Jumo 213 produced considerable amounts of exhaust thrust in addition to the shaft horsepower (for the Jumo 213E, this could be equivalent to another 500 HP shaft power at high altitude, high speed and special emergency power). I believe the Rolls-Royce engines were pretty good with regard to thrust, too, though of course at cruise settings it made less of an impact.
(German calculations showed that a turbo-supercharger was better for range than exhaust thrust, but that exhaust thrust gave better high-speed power. The conclusion was that turbo-superchargers were to be used for bombers, while fighters should have ejector exhausts. Since the German turbo-superchargers never really got into series production, this was mostly academical though, and both Focke-Wulf and BMW actually tried to create turbocharged fighters anyway.)
>The most fuel efficient engines, with an SFC under 0.40, are the Turbo Compound version of the Wright 3350 and Pratt and Whitney's Wasp Major (4360 cu). Both of these engines were not produced in quantity until after the war.
Another very fuel-efficient engine was the Junkers Jumo 205, which achieved 170 g/HPh (0.37 lbs/HPh). Of course, it was a Diesel engine, so it had to be good! :-)
If you're not familiar with the Jumo 205: It was an upright six-cylinder inline engine with no cylinder heads, but opposing pistons pushing into the cylinder from both ends symmetrically. Accordingly, it had a crankshaft on top of the engine as well as at the bottom of the engine, and fresh air and exhaust were routed in and out of the cylinder through slits in the cylinder walls. The fuel was injected from the walls as well, and as a Diesel, the engine relied on self ignition. This was an important feature as it meant no high-tension ignition electrics were required, as in the 1930s the problem of insulating the ignition system for high-altitude operations hadn't been fully solved yet.
Late in WW2, the Jumo 207 came out which even had a turbo superharger, but it seems this only served to increase the high-altitude capability of the engine, not to improve its specific fuel consumption.
Regards,
Henning (HoHun)
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HoHun -
Can you point me to an equation for deriving eta from sfc and fuel grades? If you are referring to overall efficiency of the engine I guess we can compare the energy in a pound of fuel to horsepower implied by the SFC number.
I was thinking of doing something different, which is to map all octane numbers into performance numbers using some engineering charts developed in the war. More on that later.
In the data I have, the only way exhaust thrust enters into the calculation is via a tubo-supercharger, and it is evident that well developed examples have a lower SFC.
One thing I have noticed is that there is not a really big improvement in SFC until one gets to engines rated at 115 PN avgas. These are end of war and post war engines.
A lot of engines rated on 91-92 octane actually have better SFC than engines rated 100 octane. The reason, I think, is that the former were mature engines developed for commercial markets (Cyclone 9 and Twin Wasp) where SFC really mattered. The latter were new engines (Cyclone 18 and Double Wasp) used by the military through the war.
As for diesels,I have some data on a number of models, but I did not enter them in my data set.
The best diesels should have a better SFC than the gas engines and that is why both France and Germany developed some excellent examples for flying boats.
-blogs
Originally posted by HoHun
Hi Joe,
Great charts! :-)
>I'm not yet sure whether it's the gas or the vintage of engine that explains the better performance (older engine models are typically rated on lower octane fuels).
It's my impression that it's the fuel. Higher octance fuel contains more energy. If you'd map not specific fuel consumption, but energetical effectiveness eta (the ratio of energy output to energy input), the older engines probably would be a bit closer to the newer ones.
By the way, while eta is a dimensionless value, SFC is not (though it often seems to be listed as such). It's lbs/HPh (pounds of fuel per horsepower per hour). German values are often given as g/PSh (grams per horsepower per hour), so this information helps with conversions :-)
Regards,
Henning (HoHun)
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neat stuff!
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do you have the info stil in excel to? If so I'd love to have it.. the first graph you have there displays linear behavior but there's alot of scatter.. I do alot of statistics work for my research and i'd like to try a multiple linear regression to see if I can add in some other factors like maximum boost to get a better fit.
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hohun your explanation for why higher octane equals lower sfc doesn't make sense. it really does not contain more energy. the reason for lower sfc corresponding to higher octane is that higher compression ratios could be obtained with higher octane since you prevent detonation, and if you look at the otto cycle you'll see higher compression ratio = higher thermodynamic efficiency.
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Hi Zigrat,
>hohun your explanation for why higher octane equals lower sfc doesn't make sense. it really does not contain more energy
OK, I admit I was just guessing there :-) Thanks for the correction!
Regards,
Henning (HoHun)
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Hi Zigrat,
>the first graph you have there displays linear behavior but there's alot of scatter.. I do alot of statistics work for my research and i'd like to try a multiple linear regression to see if I can add in some other factors like maximum boost to get a better fit.
The scatter is indeed remarkable, especially as the second graph shows much less of it.
I'd say that shows that the old saying "There's no replacement for displacement but more displacement" is actually wrong - boost pressure and engine speed can easily make up for it :-)
However, that the scatter in the second graph is so much lower seems to indicate that using the same technology, you always get close results for the same engine weight regardless whether you concentrate on displacement, boost or rpm.
Regards,
Henning (HoHun)
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Hi Joe,
>One thing I have noticed is that there is not a really big improvement in SFC until one gets to engines rated at 115 PN avgas. These are end of war and post war engines.
It may actually be that the engine control techniques and technology play a big role in getting a better specific fuel consumption. From what I've heard from civilian pilots, improved instrumentation enabled the pilots of C-54/Constellation type transports to hit the point of best economy with much greater precision than the cruder instruments typical for WW2 military aircraft.
An important role seems to have been played by the BMEP display (brake mean effective pressure), which gave the pilot (or rather the flight engineer) a very accurate reading of the actual power output of the engines.
>The best diesels should have a better SFC than the gas engines and that is why both France and Germany developed some excellent examples for flying boats.
I wasn't aware of the French engines! Do you have some examples?
The Jumo 205 was used not only in the Dornier Do 26 flying boat, but also in the Ju 86 reconnaissance aircraft. (Its high-altitude capability was the main reason for employing it in the latter - it was directly responsible for the development of the HF Spitfire marks.)
Regards,
Henning (HoHun)
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Yes I have a book that mentions the importance of improved instruments.
I've got some data on BMEP, but it'll have to wait until I get these taxes done....
-Blogs
Originally posted by HoHun
Hi Joe,
>One thing I have noticed is that there is not a really big improvement in SFC until one gets to engines rated at 115 PN avgas. These are end of war and post war engines.
It may actually be that the engine control techniques and technology play a big role in getting a better specific fuel consumption. From what I've heard from civilian pilots, improved instrumentation enabled the pilots of C-54/Constellation type transports to hit the point of best economy with much greater precision than the cruder instruments typical for WW2 military aircraft.
An important role seems to have been played by the BMEP display (brake mean effective pressure), which gave the pilot (or rather the flight engineer) a very accurate reading of the actual power output of the engines.
>The best diesels should have a better SFC than the gas engines and that is why both France and Germany developed some excellent examples for flying boats.
I wasn't aware of the French engines! Do you have some examples?
The Jumo 205 was used not only in the Dornier Do 26 flying boat, but also in the Ju 86 reconnaissance aircraft. (Its high-altitude capability was the main reason for employing it in the latter - it was directly responsible for the development of the HF Spitfire marks.)
Regards,
Henning (HoHun)
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It was suggested that one reason for the higher output to weight ratios is that water cooled engines could be run at a higher BMEP (brake mean effective pressure). In otherwords, water cooled engines could take more supercharging. Figure 5 shows that more engines with a higher BMEP were liquid cooled rather than air cooled.
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Figure 6 plots maximum horsepower to weight against BMEP as a crude way to control for differences in supercharging. Again there is a linear relationship and again the liquid cooled engines tend to dominate when dry weight is used in the calculation.
The evolution of engine models is also evident in this chart. Later versions of liquid cooled and air cooled engines (labeled in red) tend to have both higher BMEP and higher ratios of output to dry weight. Most of the early versions of engines, which are not labeled, are clustered in the lower left hand corner of the diagram. Even early Merlins have unremarkable power to weight and BMEP.
Notice that some of the really good German engines do not have a particularly high BMEP, but they do tend to have a good ratio of output to weight. Low BMEP may reflect the lower octane gas used in German engines. But high output to weight clearly reflects good design.
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Figure 7 shows the distribution of maximum RPMS (typically at take-off) for air and liquid cooled engines. Liquid cooled engines can generally be run at higher RPMs than can air cooled engines at this time. That is usually explained on the basis of cooling and differences in valve gear (pushrod vs cams).
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I was thinking of Clerget's 14F (a radial) and 16H (a 16 cyclinder V).
-Blogs
Originally posted by HoHun
Hi Joe,
I wasn't aware of the French engines! Do you have some examples?
The Jumo 205 was used not only in the Dornier Do 26 flying boat, but also in the Ju 86 reconnaissance aircraft. (Its high-altitude capability was the main reason for employing it in the latter - it was directly responsible for the development of the HF Spitfire marks.)
Regards,
Henning (HoHun)
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The Napier Sabre was liquid cooled.
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Yep yer right, It was miscoded.
I have corrected the charts and text in the preceeding posts.
Thanks for pointing this out.
-blogs
Originally posted by Nashwan
The Napier Sabre was liquid cooled.
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The reason for increased fuel efficiency in the engines using higher octane is that engines requiring higher octane have higher static compression ratios and/or higher boost supercharging systems.
The higher cylinder pressure in engines with higher static compression ratios and/or higher boost makes more efficient use of fuel. It also makes more horsepower and torque (actually horsepower is just the rate at which an engine makes torque, which is the rotational force that actually does the work). This of course assumes all else being equal.
Good examples can be found in the history of the V1710 Allison engines. Later engines had more static compression (the early models were all under 6.5:1, as low as just under 6:1, while later engines were over 6.5:1, some near 7:1) and were run at higher boost levels. The later engines had more horsepower and better fuel efficiency.
In many cases, you find that engines with low static compression ratios run at higher boost levels make more PEAK horsepower. However, they are very slow to accelerate when they are not running at high boost, and they are much less efficient. Engines with lower compression are also more prone to foul spark plugs. Higher boost levels are more prone to cause headgasket and cylinder head failures.
Other things to notice are that turbocharged engines tend to be more efficient than engines with crank driven superchargers. The reason being that the faster you spin a crankdriven supercharger the more boost increases, but also more power is absorbed. At a certain point, the amount of power absorbed will begin to increase much faster than the amount of power gained by the increase in boost.
The turbocharger is more efficient because it uses the heat and expansion of exhaust gases to compress air in the intake tract. Using these gasses does not absorb power from the crankshaft. However, at some point, depending on the size of the turbocharger in relation to the size of the engine, the backpressure in the exhaust will increase to the point where no more power is gained by the increased boost level.
One reason for the increased power per cubic inch of displacement of the German engines was the fact that German engine manufacturers were the world leaders in FUEL INJECTION. True fuel injection eliminates problems like flooding, starvation, and poor mixture distribution.
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Great posts joeblogs!
HoHun Said:
It may actually be that the engine control techniques and technology play a big role in getting a better specific fuel consumption. From what I've heard from civilian pilots, improved instrumentation enabled the pilots of C-54/Constellation type transports to hit the point of best economy with much greater precision than the cruder instruments typical for WW2 military aircraft.
I think that sums up some of the things that could be explored regarding the relationship between SFC's and fuel octane.
Here's an insightful article from AvWeb on the topic of fuel mixture, SFC, and engine readings for reference.
AvWeb Fuel Mixture Article (http://www.avweb.com/news/columns/182084-1.html)
Tango, XO
412th FS Braunco Mustang
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Originally posted by Captain Virgil Hilts
>The reason for increased fuel efficiency in the engines using >higher octane is that engines requiring higher octane have higher static compression ratios and/or higher boost >supercharging systems.
I think the logic goes the other way. Higher octane/PN fuels permit higher compression and supercharging because, for such fuels, detonation occurs at a higher temperature.
>The higher cylinder pressure in engines with higher static >compression ratios and/or higher boost makes more efficient >use of fuel. It also makes more horsepower and torque (actually >horsepower is just the rate at which an engine makes torque, >which is the rotational force that actually does the work). This of >course assumes all else being equal.
A higher detonation temperature implies less need for fuel cooling, that is adding extra fuel that is not fully burned just to cool the cylinder via evaporation of the fuel.
Horsepower and torque are clearly related, but the mapping from one to the other depends on the reduction gearing (if any) that is used.
>Good examples can be found in the history of the V1710 Allison >engines. Later engines had more static compression (the early >models were all under 6.5:1, as low as just under 6:1, while >later engines were over 6.5:1, some near 7:1) and were run at >higher boost levels. The later engines had more horsepower >and better fuel efficiency.
Noticed that pattern in the data. Bill Gunston points out that it is only recently that you see an aircraft piston engine with a compression ratio of 10. The Wright's orginal engine had a compression ratio over 4, but they had to go back to just 4 because of overheating (actualy detonation).
I'll have to look into the relationship between compression ratios and fuel economy. If efficiency means specific fuel consumption, the adantage seems to lie with air cooled radials at somewhat lower average manifold pressures (BMEP) rather than highly supercharged water cooled engines that tend to run at higher RPMS.
>Other things to notice are that turbocharged engines tend to be >more efficient than engines with crank driven superchargers. >The reason being that the faster you spin a crankdriven >supercharger the more boost increases, but also more power is >absorbed. At a certain point, the amount of power absorbed will >begin to increase much faster than the amount of power gained >by the increase in boost.
>The turbocharger is more efficient because it uses the heat and >expansion of exhaust gases to compress air in the intake tract. >Using these gasses does not absorb power from the crankshaft. >However, at some point, depending on the size of the >turbocharger in relation to the size of the engine, the >backpressure in the exhaust will increase to the point where no >more power is gained by the increased boost level.
Roughly 50 percent of the enegry in avgas is dissipated through hot exhaust. Overall piston engine efficiency is on the order of about 25 percent (i.e. about one-quarter of the energy in avgas gets to the propeller), so any gains from harnessing energy in the exhaust is imoportant. The first big gain was the turbo supercharer folowed by turbos that connected to the crankshaft via a quil drive (turbo compounds).
Superchargers were notoriously inefficient in the 1920s and 1930s. After hiring an engieer with a background in fluid mechanics, Rolls Royce developed some of the best gear driven examples during the mid 1940s.
Both Wright and Pratt and Whitney began to design their own gear driven superchargers in the early 1940s when they recognized significant gains could be made there if some R&D was spent. Wright went on to develop its own turbo superchargers, replacing the ubiquitous GE models after the war.
The Germans did not have the most efficient gear driven superchargers during the war. They would not have had even that had the British not sold them superchargers designed for the Rolls Royce Kestrel in the late 1930s.
One thing the Germans did have, in addition to good fuel injection systems, was a reliable variable speed coupling for their superchargers. That allowed them to get more out of a single stage supercharger than the Americans (for example) could get out single stage, two speed superchargers. At the very end of the war, some American engines (including the Allison) were offered with variable speed superchargers.
By the late 1940s, turbo superchargers could capture roughly 20 percent of the energy in the exhaust gases. In other words, turbos became nearly as efficient as a piston engine. As soon as that ocurred, it was only natural that the turbo itself would replace the internal combustion engine for many applications.
>One reason for the increased power per cubic inch of >displacement of the German engines was the fact that German >engine manufacturers were the world leaders in FUEL >INJECTION. True fuel injection eliminates problems like flooding, >starvation, and poor mixture distribution.
This is a good point. Much of that technology ws mastered in the process of developing good diesel engines.
-Blogs
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in your 1st chart what is this Arsenal 24H ?
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It is a postwar French design, a liquid cooled engine with 24 cylinders arranged in an "H" configuration.
France re-orgainzed its aircraft industry before and after the war. So all these different names appear even though the actual designs tend to follow from previous vintages of the established firms like Gnome-Rhone or Hispano-Suiza.
-Blogs
Originally posted by straffo
in your 1st chart what is this Arsenal 24H ?
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thanks !
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Originally posted by straffo
in your 1st chart what is this Arsenal 24H ?
It was composed of 4 12H cylinder blocks in vertical opposed pairs driving 2 crankshafts geared to a common propeller shaft and displacing 140L.
The Arsenal 12H engine was based on the Jumo213.
H-S also produced a H-24 engine, the 24Z, from 2 of their 12Z type engines.
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a monster so :)
I was not aware that Arsenal made anything else than the VG33 for exemple
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Originally posted by straffo
a monster so :)
I was not aware that Arsenal made anything else than the VG33 for exemple
Slight error, it was the 24H Tandem that was 140L.
The 24H weighed 1900kg and was rated at 4000hp.
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working on some charts of engine compression. Will post soon.
-blogs
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Figure 8 plots specific power (the ratio of horsepower to dry weight) against engine compression. There are a number of interesting observations. Note that the German water cooled engines have reletivley high compression ratios, which may explain why they stand out in Figure 6. This corresponds to the intuition in Captain Virgil Hilts' post.
For air cooled engines there is a positive relationship between compression ratios and specific power. Note also there is an evolutionary trend towards higher compression ratios as we move from older to more modern air cooled engines.
That pattern is weaker for the water cooled engines where there seems to be a tendency to fix a compression ratio and increase specific power by other means (presumably supercharging). This is particularly true for engines made by Rolls Royce and Allison. Note also that if we take out the X-1430 and the Sabre VII, there does not seem to be any strong relationship between specific power and compression ratios for water cooled engines.
Note that, controlling for compression ratio, the advantage in terms of specific power of liquid cooled engines over air cooled ones is obvious.
The outlier on this chart, in terms of compression ratio is the DB601-N, which I believe was the racing engine that won the Bf109 all its world records.
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Figure 9 plots brake mean effective pressure (BMEP) against compression ratios.
Note again that the best water cooled engines tend to have a higher BMEP and this is more evident once we control for compression ratio. If you compare this figure to the previous one, it is clear that once you control for compression ratios there is a pretty tight relationship between BMEP and specific power.
There is not a clear relationship between BMEP and compression ratios for water cooled engines, but there clearly is a positive relationship for air cooled engines.
-Blogs
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Figure 10 plots specific fuel consumption (lbs of fuel per horsepower per hour) against compression ratios.
It was suggested that engines with higher compression ratios are more fuel efficient. The figure suggests that any relationship is weak, particularly for water cooled engines. There is some hint of a positive relationship for air cooled engines.
Note that expcept for a handful of models of the Griffon and the V-1710, the engines with the best fuel economy are clearly air cooled.
-Blogs
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Figure 11 plots SFC against compression ratios, but this time I have broken out the fuel ratings of the engines.
Controlling for the type of fuel consumed, there does not seem to be any relationship between SFC and compression ratios. The possible exception may be for those engines rated on 87 octane if we focus on the Siddely-Armstrong Cheetah or 91-92 octane if we focus on the Isotta Frashini Delta RC20. But neither of these represent state of the art engines.
I was somewhat surprised to see lower octane fuels used at high compression ratios. I think the reason is that what really matters for detonation will be manifold pressure (proxied by BMEP in this thread).
-blogs
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Dam* and I thought advanced algebra was confusing..
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JoeBlogs,
Questions.
1. Can you post the spreadsheet you are doing your comparisons on? The JPG's can't be used to check which dots represent which engines.
2. SFC at the most efficient engine settings are all in the .40 to .50 range for modern engines. How about at mil power. It seems as if the R2800 is way out of line at .87 SFC. How does the ASH, Merlin, Jumo, Griffon, Allison and Cyclone engines compare at similar power settings?
3. In your opinion what was the most efficient WW2 engine throughout the power range?
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F4uDOA - I have to look into the copyright question before I can post all the data.
The data I have cannot really answer the second two questions.
I have one specific fuel consumption for a given model of engine, supplied by the manufacturer. That number is derived from a cruise setting, but I am not 100% sure it is even the cruise settings specified elsewhere in the tables.
I recently discovered that engine makers published books or binders of engine curves. I know Pratt and Whitney did. There are power curves and I'll bet there are also fuel consumption curves. I've seen manuals posted on the web that may have these charts, but they have been too expensive for me to purchase (typically several hundred $). I am looking into some old public library collections.
The only data I've got so far on fuel consumption at military settings was posted in previous threads. So I can't say if the military number I've calculated is off.
My data is pretty much limited to one or two models of the Double Wasp (from government spec sheets and manuals). I have some of the data I need for certain models of the Cyclone 9, Twin Wasp, and the V-1710. But I am always missing a variable. There is also that chart for the P-51 someone posted, but it is unreadable.
-blogs
Originally posted by F4UDOA
JoeBlogs,
Questions.
1. Can you post the spreadsheet you are doing your comparisons on? The JPG's can't be used to check which dots represent which engines.
2. SFC at the most efficient engine settings are all in the .40 to .50 range for modern engines. How about at mil power. It seems as if the R2800 is way out of line at .87 SFC. How does the ASH, Merlin, Jumo, Griffon, Allison and Cyclone engines compare at similar power settings?
3. In your opinion what was the most efficient WW2 engine throughout the power range?
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That is a really great series of articles. - blogs
Originally posted by dtango
Great posts joeblogs!
I think that sums up some of the things that could be explored regarding the relationship between SFC's and fuel octane.
Here's an insightful article from AvWeb on the topic of fuel mixture, SFC, and engine readings for reference.
AvWeb Fuel Mixture Article (http://www.avweb.com/news/columns/182084-1.html)
Tango, XO
412th FS Braunco Mustang
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Yeah, good stuff huh? :). Really like the stuff that John Deakin has put together! Very insightful!
Tango, XO
412th FS Braunco Mustangs
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Hey where did the charts I posted go to?
-Blogs
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Hmm, where is the URL to these charts? Should be interesting to see....
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It is a French engine, after the war
Originally posted by straffo
in your 1st chart what is this Arsenal 24H ?
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JoeB,
Long time no talk.
Have you seen the test on the F4U and F6F on Mike Williams web page? Apparently they varied the carbarator impact pressure to achieve better performance results.
I have Graham Whites book but I don't see much reference to Carbarator impact pressure. Have you seen reference this elsewhere?
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Been working way too much...
I've not seen Williams work. I have found a number of sources that discuss the significant variations in performance that resulted from tweaking the carburetors on these planes, especially on the F6f.
We often forget these were essentially the first aircraft to get the Double Wasp and the engine was only in the beginning of its development cycle when the war broke out.
-Blogs
Originally posted by F4UDOA
JoeB,
Long time no talk.
Have you seen the test on the F4U and F6F on Mike Williams web page? Apparently they varied the carbarator impact pressure to achieve better performance results.
I have Graham Whites book but I don't see much reference to Carbarator impact pressure. Have you seen reference this elsewhere?
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Joe, since this thread is in discussion again, could you re-post the charts?
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I could see them this morning, did they go away?
-Blogs
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Hello Mark:
The page for which you give me credit is really a joint effort with Neil Stirling, however, we have also had help from knowledgeable folks such as yourself.
Joeblogs: The pages Mark is referring to are as follows:
F6F Performance (http://www.wwiiaircraftperformance.org/f6f/f6f.html)
F4U Performance (http://www.wwiiaircraftperformance.org/f4u/f4u.html)
Off topic - we’d like to do a section on USSR aircraft. Is there is anywhere here who can read/translate Russian and would like to partner with us?
Mike
p.s. Reading back on this thread I see a couple of fellows here who have helped us out or provided valuable feedback; thanks guys.
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If the passages are short, I might be able to persuade a friend to help.
-Blogs
Originally posted by mw
Hello Mark:
The page for which you give me credit is really a joint effort with Neil Stirling, however, we have also had help from knowledgeable folks such as yourself.
Joeblogs: The pages Mark is referring to are as follows:
F6F Performance (http://www.wwiiaircraftperformance.org/f6f/f6f.html)
F4U Performance (http://www.wwiiaircraftperformance.org/f4u/f4u.html)
Off topic - we’d like to do a section on USSR aircraft. Is there is anywhere here who can read/translate Russian and would like to partner with us?
Mike
p.s. Reading back on this thread I see a couple of fellows here who have helped us out or provided valuable feedback; thanks guys.
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Originally posted by joeblogs
I could see them this morning, did they go away?
-Blogs
I can't see them, but could be on my end. Anyone else see or not see them?
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The links to the original charts are below.
Figure 1: Horsepower and Displacement (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_disp.gif
Figure 2: Horesepower to Weight (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_wt.gif
Figure 4: Fuel Economy as a Function of Octane
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/fe_2.gif
Figure 5: Brake Mean Effective Pressure (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/bmep.gif
Figure 6: Horsepower/Weight, controlling for Brake Mean Effective Pressure (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_wt_bmep.gif
Figure 7: Maximum RPM (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/rpm.gif
Figure 8: Output as a Function of Compression Ratio (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/hp_lb.gif
Figure 9: Brake Mean Effective Pressure vs Compression Ratio (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/bmep_comp.gif
Figure 10: Specific Fuel Consumption as a Function of Compression Ratio (air cooled vs liquid cooled)
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/sfc_comp.gif
Figure 11: Specific Fuel Consumption as a function of Compression Ratio and Octane
http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/sfc_comp2.gif
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fabulous material. It will take me some time to absorb.
-Blogs
Originally posted by mw
Hello Mark:
The page for which you give me credit is really a joint effort with Neil Stirling, however, we have also had help from knowledgeable folks such as yourself.
Joeblogs: The pages Mark is referring to are as follows:
F6F Performance (http://www.wwiiaircraftperformance.org/f6f/f6f.html)
F4U Performance (http://www.wwiiaircraftperformance.org/f4u/f4u.html)
Off topic - we’d like to do a section on USSR aircraft. Is there is anywhere here who can read/translate Russian and would like to partner with us?
Mike
p.s. Reading back on this thread I see a couple of fellows here who have helped us out or provided valuable feedback; thanks guys.
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That is a heck of a volume and must be absorbed in small doses. He does talk a bit about carburation problems on the R2800-10, but not in great detail.
-Blogs
Originally posted by F4UDOA
JoeB,
Long time no talk.
Have you seen the test on the F4U and F6F on Mike Williams web page? Apparently they varied the carbarator impact pressure to achieve better performance results.
I have Graham Whites book but I don't see much reference to Carbarator impact pressure. Have you seen reference this elsewhere?