109 e3b against spitfire II

[TomcatViP]

Originally Posted by Seadog

The proof is in the pudding. The Merlin III/12lb boost was producing much more power than equivalent DB601 engines:

This is true but only because of the higher boost level ..... hence a slightly more shaft power consuming s/c (the RAF had to build a high alt engine with lower cubic inches)... hence ...

Originally Posted by Seadog

this diag depict Merlin without s/c (test on grd) and a DB with SC!

But it is true that Merlin had a superior TBO although I am not sure what the value were for the BoB period

By the way with this curve I am not sure that the FC would hve selected "your Merlin" as the max power requirement was for high alt (at the time 20kfeet (my own guess) )

[TomcatViP]

Originally Posted by Al Schlageter

Now this is hilarious coming from Barbi when all he can produce is,

"The proposed changes to units equipped with Bf 109 were as follows:

OKL, Lw.-Führüngstab, Nr. 937/45 gKdos.(op) 20.03.45"

(it is not an original document either)

unit - on hand - serviceable - type
"I./JG 27 - 29 - 13 - Bf 109 K
III./JG 27 - 19 - 15 - Bf 109 K and some 109 Gs
III./JG 53 - 40 - 24 - Bf 109 K and some 109 Gs
IV./JG 53 - 54 - 27 - Bf 109 K and some 109 Gs"

for the use of 1.98ata boost on 109K-4s.

Just have to love that double standard.

Pls stay focused on facts and BoB period - Thx

[Seadog]

Originally Posted by TomcatViP

This is true but only because of the higher boost level ..... hence a slightly more shaft power consuming s/c (the RAF had to build a high alt engine with lower cubic inches)... hence ...


this diag depict Merlin without s/c (test on grd) and a DB with SC!

But it is true that Merlin had a superior TBO although I am not sure what the value were for the BoB period

So what figures do you propose for HP?

240 hrs was the BofB TBO figure for the Merlin. It was raised progressively to about 350 hrs by 1945, for combat aircraft.

[TomcatViP]

Originally Posted by Viper2000

It doesn't matter whether you're injecting fuel or water, the latent heat reduces the temperature rise through the compressor, which is analogous to an increase in compressor efficiency.

Great ! but don't forget the Mass flow : Lowered Heat + increased Mass Flow = higher efficiency

[TomcatViP]

Originally Posted by CaptainDoggles

In one of Viper's earlier points he argues that if you don't care about emissions and purposely run a bit rich, then minor variations in fuel/air ratio will not cause problems. Temperatures on the downstream side of the supercharger ought to be plenty high enough to cause evaporation of the fuel droplets, particularly if you aren't intercooling.

On a turbocharged, intercooled engine I'd wager that direct injection would be superior since the turbo is already much more thermodynamically efficient than a supercharger. But on a supercharged engine where the supercharger can pull as much as 30% of the crankshaft's power it's a sound engineering decision to try to increase that efficiency foremost.

I think you summed it up.

[TomcatViP]

Originally Posted by Crumpp

A simple illustration of that basic principle.

1006 J/kgC – Specific Heat Capacity of Normal Air

460 J/kgC – Specific Heat Capacity of Steel

2100 J/kgC – Specific Heat Capacity of Gasoline

To change the temperature of a mass of 1 Kg of each by 2 degrees….

Air = 1006 J/kgC * 1kg* 2 C = 2012J
Fuel = 2100J/kgC*1kg*2 C = 4200J
Steel = 460J/kgC * 1kg * 2 C = 920J

Our 4200J of fuel energy goes to cool the 15C air…

4200J * 1kg /1006J/kgC = Change in T = 4.17 C

15C - 4.17C = 10.83C

I understand your (strong) point). Don't forget the stochio ratio (1 to 8 (?)) that even the above result.

Sry for the red thumb down... I hve really no idea how it came here

[Al Schlageter]

Originally Posted by TomcatViP

Pls stay focused on facts and BoB period - Thx

Just pointing out the double standard that Barbi uses.

[TomcatViP]

Originally Posted by Seadog

So what figures do you propose for HP?

240 hrs was the BofB TBO figure for the Merlin. It was raised progressively to about 350 hrs by 1945, for combat aircraft.

Everywhere I look it's a 1150/75 value ON the Spitfire. What ever we think logic would ask for a lower value than the latter XX that is well documented (see my post for the Merlin XX on the Hurri)

[Kurfürst]

Originally Posted by Seadog

From what I can gather on the web, the DB601 also had a 100 hr TBO versus 240 for the Merlin. Does anyone have other figures?

TBO for DB 601A-1 was 200 hours. RR TBOs were understood as a figure that 1/3 of the engines could satisfy, and if a single cause of failiure did not amount to more than 2/3 of the cases IIRC.

[Kurfürst]

Originally Posted by Al Schlageter

Now this is hilarious coming from Barbi when all he can produce is,

"The proposed changes to units equipped with Bf 109 were as follows:

OKL, Lw.-Führüngstab, Nr. 937/45 gKdos.(op) 20.03.45"

(it is not an original document either)

unit - on hand - serviceable - type
"I./JG 27 - 29 - 13 - Bf 109 K
III./JG 27 - 19 - 15 - Bf 109 K and some 109 Gs
III./JG 53 - 40 - 24 - Bf 109 K and some 109 Gs
IV./JG 53 - 54 - 27 - Bf 109 K and some 109 Gs"

for the use of 1.98ata boost on 109K-4s.

Just have to love that double standard.

There's no sign of "proposed" in the original document. See for details: http://www.kurfurst.org/Engine/Boost...arance198.html