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Author Topic: Some Engine Charts  (Read 2760 times)

Offline joeblogs

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compression
« Reply #30 on: February 25, 2003, 05:53:23 AM »
working on some charts of engine compression.  Will post soon.

-blogs
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Offline joeblogs

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Compression vs Specific Power
« Reply #31 on: February 26, 2003, 11:10:55 AM »
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.
« Last Edit: February 27, 2003, 03:39:03 PM by joeblogs »
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Offline joeblogs

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Compression vs Supercharging
« Reply #32 on: February 26, 2003, 11:11:48 AM »
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
« Last Edit: February 27, 2003, 03:40:12 PM by joeblogs »
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Offline joeblogs

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Compression vs Fuel Consumption
« Reply #33 on: February 26, 2003, 11:12:39 AM »
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
« Last Edit: February 27, 2003, 03:40:59 PM by joeblogs »
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Offline joeblogs

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Compression vs Octane/PN
« Reply #34 on: February 26, 2003, 11:15:42 AM »
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
« Last Edit: February 26, 2003, 12:32:32 PM by joeblogs »
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Offline Hawklore

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Some Engine Charts
« Reply #35 on: February 26, 2003, 11:42:20 AM »
Dam* and I thought advanced algebra was confusing..
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Offline F4UDOA

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Some Engine Charts
« Reply #36 on: February 26, 2003, 12:10:41 PM »
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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Offline joeblogs

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data + questions
« Reply #37 on: February 26, 2003, 12:46:33 PM »
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

Quote
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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Offline joeblogs

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AVweb articles
« Reply #38 on: March 06, 2003, 10:11:06 AM »
That is a really great series of articles.  - blogs


Quote
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

Tango, XO
412th FS Braunco Mustang
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Offline dtango

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Some Engine Charts
« Reply #39 on: March 12, 2003, 10:05:18 AM »
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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Tango / Tango412 412th FS Braunco Mustangs
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Offline joeblogs

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where did the charts go?
« Reply #40 on: August 02, 2003, 12:17:03 PM »
Hey where did the charts I posted go to?

-Blogs
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Offline VO101_Isegrim

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Some Engine Charts
« Reply #41 on: August 09, 2003, 08:33:18 AM »
Hmm, where is the URL to these charts? Should be interesting to see....
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Offline joeblogs

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Arsenal 24H ?
« Reply #42 on: April 10, 2007, 11:59:56 AM »
It is a French engine, after the war

Quote
Originally posted by straffo
in your 1st chart what is this Arsenal 24H ?
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Offline F4UDOA

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Some Engine Charts
« Reply #43 on: April 10, 2007, 01:13:30 PM »
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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Offline joeblogs

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long time gone
« Reply #44 on: April 10, 2007, 01:31:54 PM »
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

Quote
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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