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jjuutinen
Joined: 13 Jul 2003
Posts: 180
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 Posted: Sat Sep 17, 2005 12:47 Post subject: 91/96 +ADI vs. 100/130 |
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Folks, how closely does engine performance match with 91/96 + ADI to the 100/130 alone?The Pilot Manual for the P-38L has limits for operating with Grade 91/96 fuel and the comparison works out as follows:
Take Off (5mins) 100/130=1600 hp/60"/3000 rpm vs 91/96=1325 hp/47"/3000 rpm
In my opinion this info suggests that using the lower grade fuel with ADI prodives at least as good poerformance as the 100/130 alone. |
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szielinski
Joined: 13 Jul 2003
Posts: 94
Location: Canberra, Australia
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| Posted: Mon Sep 19, 2005 00:14 Post subject: |
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Not sure if I'm following this thread -
Are you saying that 100/130 will make 1325hp@47"/3000rpm in that engine? |
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jschauer
Joined: 19 May 2004
Posts: 93
Location: Justin, Texas
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| Posted: Tue Sep 20, 2005 19:30 Post subject: |
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| I dug out my old KC-97 performance manual and looked up both 115/145 verses 100/130. By using 115/145 with ADI you could pull 60 inches MAP. By using 100/130 as an alternate fuel with ADI, you were limited to only 56 inches MAP with a corresponding drop in brake horsepower and torque. So I think it's safe to assume with 91/96 verses 100/130, no it does not provide the same Hp or torque. |
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jjuutinen
Joined: 13 Jul 2003
Posts: 180
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| Posted: Fri Sep 23, 2005 03:58 Post subject: |
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Szielinski, I am saying that the Grade 91/96 allows 1325 hp at 3000 rpm at 47".
Jschauer, I am comparing 100/130 alone vs 91/96 WITH ADI. Your example had both running with ADI. |
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szielinski
Joined: 13 Jul 2003
Posts: 94
Location: Canberra, Australia
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| Posted: Mon Sep 26, 2005 00:35 Post subject: |
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Without knowing how rich the mixture is for the higher PN figure, it's a little hard to tell (for my understanding, anyway).
If 91/96+ADI gives 1600hp @ whatever"/whatever rpm, then yeah, use it, water's cheaper than 100/130 and hp is hp - except if the enrichment uses +++% more fuel that is.
(though jschauer's manual seems to indicate otherwise)
This would be a VERY interesting scenario if fuel was heavier than water - can you imagine, there'd probably be planes that carried 'methanol-only' tanks and collected ice from the surrounding air to mix with it !
[as an aside, if you look around this web-site, there is a story about the guy who designed the injection gear for the R-2800. He noticed the engine would still run even with water spitting out the exhaust stubs - and all the chamber-exposed parts were lovingly steam-cleaned in the process] |
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kmccutcheon
Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA
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| Posted: Mon Sep 26, 2005 09:29 Post subject: Re: 91/96 +ADI vs. 100/130 |
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| jjuutinen wrote: | | In my opinion this info suggests that using the lower grade fuel with ADI prodives at least as good poerformance as the 100/130 alone. |
I have no data on Grade 91/96 gasoline with water injection. However, I do have data that compares wet versus dry takeoff ratings for fourteen engines:
The majority of these engines achieve a power increase of less than 10% with ADI. Most of the rest are in the 15% range, the best being the R-2800 CB16 at 17.1%. The VK-107, the only engine rated on 95 octane fuel, achieves a power increase of 12.5%.
In order to get from 1325 hp (91/96 dry) to 1600 hp (hypothetical 91/96 wet), a power increase of 20.8% is required. This is clearly higher than any other engine in the sample, and I can think of no reason to expect Grade 91/96 detonation characteristics to be improved more with ADI than other fuels.
So what am I missing? What data suggests the nearly 21% increase?
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Kimble D. McCutcheon |
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jschauer
Joined: 19 May 2004
Posts: 93
Location: Justin, Texas
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| Posted: Tue Sep 27, 2005 09:12 Post subject: |
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OK, I went back into my KC-97 charts again and found a couple of notes;
100/130 wet Do not exceed 56.5 inches hg map or 230 TPSI
100/130 dry Do not exceed 56 inches hg map or 212 TPSI
115/145 wet Do not exceed 60 inches hg map or 247 TPSI
115/145 dry Do not exceed 60 inches hg map or 230 TPSI
TPSI - Torque Pressure in Pounds Per Square Inch
Maybe this will help in our discussion. When I get a chance I'll do some more figuring in the charts. |
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kmccutcheon
Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA
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| Posted: Tue Sep 27, 2005 09:27 Post subject: |
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jschauer,
Can you provide RPM for those KC-97 power settings and the "K" factor for the engines so we can calculate horsepower?
Thanks,
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Kimble D. McCutcheon |
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jjuutinen
Joined: 13 Jul 2003
Posts: 180
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| Posted: Wed Sep 28, 2005 19:15 Post subject: |
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| Kim, the R-2800-59 as fitted to later P-47s is given a WER of 2600 hp with ADI. The dry rating of this engine seems to be about 2000 hp. Some data has the WER as 2535, but that still gives over 20% increase over the dry power. I´d very wary of civilian engine ratings as the final word on anything. |
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szielinski
Joined: 13 Jul 2003
Posts: 94
Location: Canberra, Australia
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| Posted: Wed Sep 28, 2005 20:02 Post subject: |
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| Just a thought, could engines with a single exhaust valve benefit most from ADI ? |
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jschauer
Joined: 19 May 2004
Posts: 93
Location: Justin, Texas
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| Posted: Thu Sep 29, 2005 09:27 Post subject: |
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I ran some figures in the KC-97 charts using 15 degrees C OAT, 0 for pressure altitude, 35 degrees F dewpoint.
100/130
wet 227 TPSI
3205 Bhp
dry 205 TPSI
2900 Bhp
115/145
wet 247 TPSI
3500 Bhp
dry 230 TPSI
3240 Bhp
As you can see, wet 100/130 is close to dry 115/145.
Max RPM is 2700
BHP=RPMxTPSIx0.00524
BMEP=792,000xBHP / 4360xRPM
I don't have a K factor, but I hope the above info is helpful. |
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kmccutcheon
Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA
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| Posted: Thu Sep 29, 2005 20:48 Post subject: |
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| jjuutinen wrote: | | Kim, the R-2800-59 as fitted to later P-47s is given a WER of 2600 hp with ADI. |
Not in the Pratt & Whitney “Index of Double Wasp & R-2800 Designated Engines” (dated 5-15-1955). The -59 was a “B” Series engine, none of which have wet ratings greater than 2,300 hp. As a matter of fact, the highest wet rating of any engine in the Index is 2,500 hp for the CB2, CB4, CB14, CB15, CB17, R-2800-99W and R-2800-103W. The largest wet/dry spread is the CB3 (2,400 wet, 2,050 dry, a spread of 17.1%). Most are 2,500 wet, 2,300 dry, a spread of 8.7%.
| Quote: | | The dry rating of this engine seems to be about 2000 hp. |
The 2,000 hp rating for the -59 is in agreement with the P&W Index.
| Quote: | | Some data has the WER as 2535, but that still gives over 20% increase over the dry power. |
Me thinks you have ingested some bad data. What is the source of the 2,600 and 2,535 rating? One other point: I used takeoff wet/dry ratings for my sample because the MIL wet ratings are nearly always quoted at conditions vastly different from any of the dry ratings. For your purposes, conditions (such as altitude) must be similar or identical in order for the comparisons to be useful. Since you are trying to reverse engineer fuel behavior, it is important to draw conclusions from a meaningful statistical sample. The takeoff ratings provide a larger and better sample than do any of the MIL ratings that I have seen.
| Quote: | | I´d very wary of civilian engine ratings as the final word on anything. |
Why? Civilian engines have spec sheets that are just as good as the military ones. Civilian engines had a longer development cycle with better feedback from the field than did their military counterparts.
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Kimble D. McCutcheon |
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kmccutcheon
Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA
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| Posted: Thu Sep 29, 2005 20:54 Post subject: |
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| jschauer wrote: | | I ran some figures in the KC-97 charts using 15 degrees C OAT, 0 for pressure altitude, 35 degrees F dewpoint. |
For 100/130 (3,205 hp wet, 2,900 hp dry) the wet/dry power spread is 10.5%
For 115/145 (3,500 hp wet, 3,240 hp dry) ithe wet/dry power spread is 8.0%
| Quote: | | I don't have a K factor, but I hope the above info is helpful. |
Thank you. The above info is indeed helpful. By the way, in for this example, K = 0.00524. Thanks again for running the numbers.
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Kimble D. McCutcheon |
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kmccutcheon
Joined: 13 Jul 2003
Posts: 298
Location: Huntsville, Alabama USA
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| Posted: Thu Sep 29, 2005 20:56 Post subject: |
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| szielinski wrote: | | Just a thought, could engines with a single exhaust valve benefit most from ADI ? |
One would think so because of the larger exhaust valve and longer heat path, but the data only bears out this contention for the Pratt & Whitney engines. C-W engines (with their even larger valves) got so little additional power from ADI that one wonders why they went to the trouble.
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Kimble D. McCutcheon |
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jjuutinen
Joined: 13 Jul 2003
Posts: 180
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| Posted: Fri Sep 30, 2005 04:14 Post subject: |
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| Bad data? Well, if data supplied to the pilots of "Joint Fighter Conference, NAS Patuxentr River, 16-23 October 1944". That 2535 hp rating is given for the P-47D on the limitation cards distributed to JFC pilots. There was also a P-47M present and its limitation chart had the 2800 hp WER rating. A rating that is not on the P&W index. Since these higher figures are veriafiable from multiple documents like USAAF pilot manuals, I have very little confidence in that P&W index. The fact is that late war P-47Ds, thus R-2800-59s, were cleared to operate at 2600 hp with ADI. |
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