Turbo-supercharging and aircraft performance

[joeblogs]

Hohun

I have posted two Charts for the R2800-21.

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/p47_sefc.gif

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderpictures/p47_foic.gif

This is the engine that powered all the early P47C/D models. One chart is dated May of 1942. Both have been posted on the bulletin board frequently in the past.

I have two engine calibration curves for the A & B series Double Wasp. Unfortunately these are for engines with a single stage, two speed supercharger. I am pretty sure neither engine had water injection.

The A series engine (S1A4-G) generates 1850 HP at 2600 RPM on war emergency. This power can be maintained for altitutdes from 0-5,000 feet in low blower. This power curve dates from dec 1940.

The B series engine (2SBG) generates 2000 HP at 2700 RPM at sea level in low blower. This power curve dates from Oct 1942.

I have a calibration curve for a postwar engine, but unfortunately it's only for auto-lean.

From another source (1945), I have data on a Double Wasp R-2800 2SB-G (B series) that gives the same military rating as reported above. The associated MAP is 52 inches. The same source specifically refers to a turbosupercahrged engine (Double Wasp R-2800 TSB1-G), a B series engine producing 2000 HP at 2700 RPM at takeoff & military settings. This is the -21 (military designation) initially put into the The P-47C/D.

From that same source (1946), I have a military rating for a C series engine (Double Wasp R-2800 CA15) of 2100 HP at 2800 RPM at essentially sea level. But I have take-off power with ADI of 2400 HP at 2800 RPM. The MAP is 56.5 in + 13lbs. I Imagine the later number refers to the water.

Note the F6f flew a B series engine (-10 or 10/w with ADI in the Navy nomenclature) and the F4u flew the C series (-18 or 18/W).

The P-47C/D was outfitted with the -21 model, a B series engine rated at 2000 HP at 2700 at 25k ft with a GE turbosupercharger and single stage mechanical supercharger. Later versions got better engines (-59 without ADI and -63 with ADI) but these were still B series engines. ADI provided 300 additional HP - But ADI did little above critical altitude. The P47N got a C series engine (-57) producing 2500 HP at 2800 RPM.



Model

[pasoleati]

Joe, I checked out your La-7 figures and the fuel consumption figures appear to be very high. As it can be estimated that the Ash-82 and the R-2600 produce about the same power at the same rpm and boost it appears that the Ash-82 has some 20% higher cruising fuel consumption if those figures are compared to the R-2600 data I have. Weird.

[joeblogs]

You'll have to give me some comparable numbers on the R-2600 as I don't have them.

The table I posted there is derived from a translation of Russian data posted by tilt. When I have a chance I'll go back and check my conversions to American units.

-blogs

Originally posted by pasoleati
Joe, I checked out your La-7 figures and the fuel consumption figures appear to be very high. As it can be estimated that the Ash-82 and the R-2600 produce about the same power at the same rpm and boost it appears that the Ash-82 has some 20% higher cruising fuel consumption if those figures are compared to the R-2600 data I have. Weird.

[pasoleati]

Here it comes from the SEFC on the R-2600-13 (taken from B-25 PM):
2100 rpm/31.5 in/1125 hp/115 gph
2100 rpm/29.5 in/1005 hp/90 gph
2000 rpm/27 in/900 hp/75 gph
1600 rpm/19.5 in/420 hp/33 gph

These are applicable at about 5000-7000 ft. I think you can draw a graph based on this!

[joeblogs]

Pasoleati:

I've made the following comparison chart:  

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/r2600_v_ash82.pdf

The data for the ASH-82FN is from a translation of a Russian flight test report (VVS) translated by Tilt some time ago. The data for the R2600 is from a May 1942 Specific Engine Flight Chart for the B25C/D with a Wright R2600-13 engines.

On the chart, for all but one setting, the fuel consumption of the Russian engine is less than for its American counterpart. But the difference is not that great and is largely explained by differences in manifold pressure for the power settings I have for the two engines.  

The one oddity, as you point out,is at the lowest power setting reported where the R2600-13 seems to have the advantage. For a number of reasons, I would discount that setting though.

First, on the SEFC chart itself, this setting is included under "conditions to avoid." Second,typical crusing HP is 50-60 percent of rated horsepower and yet this lowest setting for the R2600 is less that 1/3 of rated power. Third, other data sources suggest the two engines have comparable fuel economy.

I went back to my data from Wilkinson (Aircraft Engines of the World) and found a number of entries for the ASH-82. These are from the 1949 edition so they are likley to reflect very late models, but that is all I have. In any case, the Specific Fuel Consumption reported for the ASH-82FNW is 0.46, using American measurements. This is a fairly typical value of the fuel economy of a wartime radial engine operated at its most fuel efficient settings.

Wilkinson also reports Specific Fuel Consumption for a number of versions of the Wright R2600 and the number is also 0.46. This is the best value that can be derived from the SEFC chart too.
 
-blogs

Originally posted by pasoleati
Joe, I checked out your La-7 figures and the fuel consumption figures appear to be very high. As it can be estimated that the Ash-82 and the R-2600 produce about the same power at the same rpm and boost it appears that the Ash-82 has some 20% higher cruising fuel consumption if those figures are compared to the R-2600 data I have. Weird.

[HoHun]

Hi Joe,

>I have posted two Charts for the R2800-21.

Thanks, I didn't have these previously! :-)

VERY interesting to see that 18250 rpm are the limit for the turbine. Later versions were limited to 20000 rpm/22000 rpm Norm/WEP.

This seems to be reflected by the lower full throttle height given for 52" Hg boost - 27000 ft in your chart compared to 34000 ft in the later chart.

I hadn't been aware that there were different turbosupercharger versions before the advent of the "C" engine.

>This is the engine that powered all the early P47C/D models.

Do you know which blocks?

>Unfortunately these are for engines with a single stage, two speed supercharger.

I guess that won't help with the supercharged engine, judging by the BMW801 example :-(

>From that same source (1946), I have a military rating for a C series engine (Double Wasp R-2800 CA15) of 2100 HP at 2800 RPM at essentially sea level. But I have take-off power with ADI of 2400 HP at 2800 RPM. The MAP is 56.5 in + 13lbs. I Imagine the later number refers to the water.

56.5" Hg = +13.06 lbs/sqin in British terminology :-)

That value seems to confirm the "C" power from the F4U-4 report and also that the 64" Hg of the later "B" chart must yield more than 2300 HP.

>Note the F6f flew a B series engine (-10 or 10/w with ADI in the Navy nomenclature) and the F4u flew the C series (-18 or 18/W).

Hm, didn't the F4U start out with the R-2800-8(W)? Interesting to see the "C" in broad use in WW2, I thought there were just the few P-47M engines before VE day.

>ADI provided 300 additional HP

That's something where I'm not sure. Some indications point to 2300 HP WEP, but others, including the 64" Hg/2700 rpm chart - which is for a "B" series engine - point to about 2500 HP. I am a bit confused here!

Regards,

Henning (HoHun)

[pasoleati]

Joe, I wouldn´t count on Wilkinson as it is a most unreliable source.

I think the Conditions to avoid remark in the SEFC is an error. After all, most higher powered WW Two aircraft neede to only 25-30% power to reach the best range IAS. See e.g. the P-38L Pilot Manual and the range charts: only 1600rpm/23 InHg is needed for max range cruising. That setting produces about 400 hp per engine, i.e. only 25% power needed for cruising, not 50-60% as you suggested.

[joeblogs]

While it's better to have the actual manufacturers data, I've not found any significant problem with the data reported in Wilkinson. And it has the advantage of using the same metric for measurement across engines, which makes comparisons easier.

In any case, for the Ash-82, there is nothing in Wilkinson that is at variance with the actual Russian data Tilt found.

Perhaps I was not clear in the earlier post. I did not mean to say you could not cruise at 25 percent power, but rather, for American engines at least, this was not typically the most efficient in terms of specific fuel consumption.

Something I have noticed in a number of the American engines I have looked at is that fuel consumption (measured as lbs/hp/hr) at very low power settings is very sensitive to the carburetor being used. Often it is higher than if a bit more power is employed.

-blogs

Originally posted by pasoleati
Joe, I wouldn´t count on Wilkinson as it is a most unreliable source.

I think the Conditions to avoid remark in the SEFC is an error. After all, most higher powered WW Two aircraft neede to only 25-30% power to reach the best range IAS. See e.g. the P-38L Pilot Manual and the range charts: only 1600rpm/23 InHg is needed for max range cruising. That setting produces about 400 hp per engine, i.e. only 25% power needed for cruising, not 50-60% as you suggested.

[joeblogs]

There were several improvements in the GE turbo during the war. I have to find an archived file somewhere with details on that. One was limiting speed but I can't remember the details.

Yes it is rather difficult to compare engines with one vs two stages, or vs turbo. Still looking for more calibration curves for two stage models of this engine (other than for F4u). If anybody's got one, please let me know.

And yes, I made a typo, the initial engine for the F4u was the R2800-8.

I'll see if I can sort engine model's by blocks of the P47 but I seem to recall trying that before and it was problematic with the information I have.

As for a B series engine generating 2500 HP, that has got to be wth ADI, and even then I am not sure we are really talking a B series. You probably have to have 2800 RPM to do it.  But I've seen anomalies like that in documents before.

Thanks for the heads up on the English measurement of MAP. That was my alternative conjecture.

Originally posted by HoHun
Hi Joe,

>I have posted two Charts for the R2800-21.

Thanks, I didn't have these previously! :-)

VERY interesting to see that 18250 rpm are the limit for the turbine. Later versions were limited to 20000 rpm/22000 rpm Norm/WEP.

This seems to be reflected by the lower full throttle height given for 52" Hg boost - 27000 ft in your chart compared to 34000 ft in the later chart.

I hadn't been aware that there were different turbosupercharger versions before the advent of the "C" engine.

>This is the engine that powered all the early P47C/D models.

Do you know which blocks?

>Unfortunately these are for engines with a single stage, two speed supercharger.

I guess that won't help with the supercharged engine, judging by the BMW801 example :-(

>From that same source (1946), I have a military rating for a C series engine (Double Wasp R-2800 CA15) of 2100 HP at 2800 RPM at essentially sea level. But I have take-off power with ADI of 2400 HP at 2800 RPM. The MAP is 56.5 in + 13lbs. I Imagine the later number refers to the water.

56.5" Hg = +13.06 lbs/sqin in British terminology :-)

That value seems to confirm the "C" power from the F4U-4 report and also that the 64" Hg of the later "B" chart must yield more than 2300 HP.

>Note the F6f flew a B series engine (-10 or 10/w with ADI in the Navy nomenclature) and the F4u flew the C series (-18 or 18/W).

Hm, didn't the F4U start out with the R-2800-8(W)? Interesting to see the "C" in broad use in WW2, I thought there were just the few P-47M engines before VE day.

>ADI provided 300 additional HP

That's something where I'm not sure. Some indications point to 2300 HP WEP, but others, including the 64" Hg/2700 rpm chart - which is for a "B" series engine - point to about 2500 HP. I am a bit confused here!

Regards,

Henning (HoHun)

[joeblogs]

Hohun:

Here are some excerpts from an interesting article on Wikipedia

http://en.wikipedia.org/wiki/Republic_P-47

The P47B used the R2800-21.

The initial batch of 602 P47C ordered in Sept 1942 - includes an improved turbo regulator. After 1st 57 of these, they went to the C-1 block with 8" longer fuselage (55 built) followed by 128 C-2s with belly attachment point for a 200 gallon drop tank or 500 lb bomb.

The most Cs built were the C-5 block with R2800-59 and ADI, delivering 2300 HP.

The first 110 D models were identical to C-2s. 12,602 D models were built in a sequence of blocks. The D-1 through D-11 included improved cowl flaps to solve a cooling problem and uprated engines. The D-15 adds plumbing for drop tanks in the wings and internal gas is increased to 375 gallons.

The D-16 to D-23 blocks had many small improvements but also a change to a larger propeller (from 12'2" Curtis Electric to a 13'2" Hamilton Standard or a 13' Curtis Electric).

Curtis built the G series of planes that map to certain blocks of the D series.

Bubble tops appear in the D-26 to D-30 blocks, which also included some improvements to the engine.

The D-40 has the cut down rear fuselage and a new computer gun sight (the K-14)

The XP47J has a lightened airframe and a closely cowled R2800-59(C) engine w up to 2800 HP. The M includes this engine and a GE CH-5 Turbo. 130 were built and saw action in Europe at the end of the war.

The N series has an R2800-77(C). 1816 were built.
 

Originally posted by HoHun
Hi Joe,

>I have posted two Charts for the R2800-21.

Thanks, I didn't have these previously! :-)

VERY interesting to see that 18250 rpm are the limit for the turbine. Later versions were limited to 20000 rpm/22000 rpm Norm/WEP.

This seems to be reflected by the lower full throttle height given for 52" Hg boost - 27000 ft in your chart compared to 34000 ft in the later chart.

I hadn't been aware that there were different turbosupercharger versions before the advent of the "C" engine.

>This is the engine that powered all the early P47C/D models.

Do you know which blocks?

...
Henning (HoHun)

[joeblogs]

This is the fuel consumption pattern for the Wright R2600-13:

http://mysite.verizon.net/vze479py/sitebuildercontent/sitebuilderfiles/sfc_r2600.pdf

-blogs

[HoHun]

Hi Joe,

Thanks for the excerpts from the Wikipedia article! Escpecially the break-down of the P-47C variants was interesting - that the subvariants used different engines can be verified from the Pratt & Whitney index.

(I think there are some inccuracies in the article as well - usually the D-25 and not the D-26 is given as first bubbletop. The paddle-blade propeller is typically quoted for the D-22, etc.)

I've come to the conclusion that the type of the supercharger employed can not be deducted from the engine number as they were not part of the engine package.

That could mean that we have both 2000 HP, high full throttle height P-47s and 2300 HP (water-injected), low full throttle height ones.

It seems that the R-2800-59/-63 were virtually the same as the R-2800-21 except that is was prepared for water injection. Apparently, use of the R-2800-59 doesn't mean that water injection was factory-provided for the P-47 initially, making the situation a bit confusing. (Accordingly, the designation -21W seems bogus, and -59W/-63W apparently weren't used by Pratt & Whitney either. In fact it, it seems that the USAAF didn't use any W designations until fairly late, I suspect until after WW2.)

http://www.enginehistory.org/reference.htm

Regards,

Henning (HoHun)

[joeblogs]

For the Pratt & Whitney's the mechanical supercharger is their own. The problem is that for the turbo's that is GE and there were a number of models. I have almost no documentation on them either. I do know that during the war the turbo controls were gradually improved and the limiting speed of the turbine impellers were increased.

I think you are right about the -59/63 models.

-blogs

Originally posted by HoHun
Hi Joe,

...I've come to the conclusion that the type of the supercharger employed can not be deducted from the engine number as they were not part of the engine package.

That could mean that we have both 2000 HP, high full throttle height P-47s and 2300 HP (water-injected), low full throttle height ones.

It seems that the R-2800-59/-63 were virtually the same as the R-2800-21 except that is was prepared for water injection. Apparently, use of the R-2800-59 doesn't mean that water injection was factory-provided for the P-47 initially, making the situation a bit confusing. (Accordingly, the designation -21W seems bogus, and -59W/-63W apparently weren't used by Pratt & Whitney either. In fact it, it seems that the USAAF didn't use any W designations until fairly late, I suspect until after WW2.)

http://www.enginehistory.org/reference.htm

Regards,

Henning (HoHun)

[gwshaw]

Originally posted by HoHun
It seems that the R-2800-59/-63 were virtually the same as the R-2800-21 except that is was prepared for water injection. Apparently, use of the R-2800-59 doesn't mean that water injection was factory-provided for the P-47 initially, making the situation a bit confusing. (Accordingly, the designation -21W seems bogus, and -59W/-63W apparently weren't used by Pratt & Whitney either. In fact it, it seems that the USAAF didn't use any W designations until fairly late, I suspect until after WW2.)

http://www.enginehistory.org/reference.htm

Regards,

Henning (HoHun) [/B]

Working on a more detailed reply for later. IIRC the -63 was a -21 with factory H2O injection rather than a refit kit. The -59 was the same as the -21/63, but with different magnetos. But the core engine is the same on all of the them, so performance should be identical.

Greg Shaw

[joeblogs]

Some time ago I was asked about which models of the DoubleWasp went into the P47, when, what were the differences. We tossed around what we could find from the web, but thanks to Graham White's new book R2800, things become a little more clear.

The Principal engine used in the P47 models through the F model was the R2800-21. This was a "B" series engine rated at 2000 HP at 2700 RPM for takeoff & military. 5,720 of these engines were built, most by Ford.

But there are two related engines put on later versions of the P47C&D - these are the -59 and -63. The B series engines are practically the same as the -21, except they have ADI offering an additional 300 HP. The only other differences are in things like Fuel grade (125 PN rather than 100 Octane) the exact model of carburetor or the magnetos. The power curves & operating instructions are the same as with the -21. 11,391 of the -59 model were built, nearly all by Ford. 2,029 of the -63 model were built.

The P47N got a "C" series engine - the -73 - offering 2100 HP at 2800 RPM. It was rated on 100/130 PN fuel. I can't tell if this engine had ADI. Chevrolet built these, 2665 in all. A few other cats & dogs also went into the P47N. With ADI, the extra 100 RPM, and very high PN fuel I'll bet this would get to a maximum HP in the range of 2,500.

One thing you notice from White's detail is that a higher model number on an engine does not necessarily mean it was a later, or better engine...

-Blogs

Originally posted by HoHun
Hi Joe,

>See if these help.

Hm, not immediately. I had thought I might be able to see from the specific consumption whether 2300 HP required water injection (which I'm not certain of), but the turbo-supercharged engine are only graphed up to 2000 HP. Do you happen to have R-2800 power plant charts similar to this one?

http://hometown.aol.de/HoHunKhan/p47-d-30-power_small.jpg

The key is that we have boosts and rpms given along with a date - but unfortunately, it's November 1944 so it doesn't tell us much about the timeline of P-47 performance.

If we had more of these, with earlier dates, we could probably figure out the exact history of the P-47 pretty well :-)

Regards,

Henning (HoHun)