Nutshell Details of Merlin Engines - P-51...

[jamespohl]

Help Requested,

I am a retired, ME thermodynamics educator. I've written briefly about the P-51. Please look at the URL!

P-51 Mustang | THERMO Spoken Here!

I have GENERAL air standard engine calculations to address engine function as "Basic Engine," "Turbo-Charged," "Super-Charged" and "Super-Charged-Intercooled."
I intend to www-code the calculations I have (presently written p&p) once I make them specific to the Merlin - P-51 combination.

I greatly need someone to tell me typical Merlin characteristics, e.g., cylinders, compression ratio, and other aspects not clear to me now.

Should you know OVERALL about the Merlin and P-51, might we write? Please help me with my tasks!

Thank you in advance for your knowledge of this history.


Jim Pohl

 

[airplane176]

Jim,

I collect military aircraft information, including engines. Se my website at: U.S. and German Military Aircraft Database, 100+ Years Worth. All Merlins have the following characteristics: Bore 5.4 inches, stroke 6 inches, compression ratio 6.0:1. The P-51 engines - V-1650-3,7,9 were all 2-stage, 2-speed supercharged. What other information do you need?

Roger

 

[hrandy]

I took a quick look at your Mustang page and I think you made some simple errors. The combat weight of a P-51D (the first version with six .50 caliber Browning M2 machine guns) was over 8000 lbs. The usual .50caliber API round weighed 43 grams which I think is about 0.01 lbs. not 0.1 lbs. The M2 browning fired at a rate of about 750 rounds per minute or about 12.5 rounds per second. Six M2s would take over thirteen seconds to fire 1000 rounds. The M2 would burn out it's barrel if fired for more than 3 or 4 seconds. I believe most pilots fired a 2 or 3 second burst leaving at least a few seconds for the M2s to cool and also to observe the results of the first burst.

If I'm correct in my guess about the weight of round calculation being off by a factor of ten then the effect on the speed of the Mustang would be negligible. Even if we plug the numbers from the Hispano-Suiza MK2 20 mm cannon (typically 4 guns firing 130 grams rounds at about 2900 FPS and 750 RPM) into your formulas the effect of the weapons is small especially when the mass of the Typhoon and Tempest fighters that used these weapons is typically about 40% more than the Mustang.

 

[GregP]

Hi JamesPohl,

There was never a P-51 with a mass of 5,400 pounds, even the prototype. They usually went from 7,500 to 10,500 pounds.

Most performancer figures are calcaulted at 8,000 pounds, where is is an 8-g aircraft. At any higher weight, the g- limit is 64,000 divided by 8,000.

So, at 10,000 pounds it is a 6.4-g aircraft.