Jumo213 exhaust thrust?

[spicmart]

In Manfred Griehl's book about the Fw190/Ta152 he stated that the exhaust thrust of the Jumo213 was stronger than that of the DB603. And thus the Jumo213 had greater propulsion than its rival even it have had less power. Does anybody know more about this, also from a technical point of view?

Thanks

 

[Shortround6]

Exhaust thrust is dependent on the mass of the exhaust, weight of the air +weight of fuel+ weight of any additive (Nitrous or MW/50) times the velocity of the escaping gas. Velocity of the escaping gas is dependent on the preussre in cylinder After teh exhaust valve opens ( to some extent), The shape and length of the exhaust pipes, the size of the nozzle opening at the end AND the atmospheric pressure at the end of the pipe/nozzle.

That gives you the thrust but not the power. Power varies with the speed. The faster you go the more power you get from the same thrust.

For similar engines in the same air frame a lot of the variables get very close together.

However something to consider is that the weight of the fuel/air is the weight needed to run the complete engine, Friction and supercharger (one or two stage) plus shaft horsepower.

 

[delcyros]

The Jumo-213E at critical altitude developed 188 Kp of exhoust jet thrust from trials in high altitude wind tunnel engine stands simulating 200m/s airspeed.
That´s quite a lot when You consider that the Jumo-004D was producing a mere 380 Kp thrust at this altitude when running at 100% load.
This equates to 188kg or 1880N which at a speed of 200m/s(440mph) from Power = force x velocity = 376kW at the shaft.
Factoring in the propellor inefficiencies at high altitudes this probably equates to the aequivalent of ~450kW or ca. 640 hp more power developed by the engine in the first place.
Second order maybe but still to substantial to be ignored.
As you know, to get a 10% increase in speed requires approximtely a cubed increase in power whereas it requires only a squared increase in thrust! It does not come in with increased cooling requirements, too (which would add drag in return)! So it´s maybe not worth to waste that source of power to drive a turbocharger, that´s at least the reason why Rolls Royce invested so much in turbocharging. They tried to find a solution to keep the jet exhoust thrust as a valuable addition to the high altitude performance of the A/C.

 

[tomo pauk]

The RR was never into turbocharging IIRC?

 

[spicmart]

So can one say that the Jumo 213 might have more exhaust thrust (everything being equal) because its cylinder pressure was hight (?)

 

[Shortround6]

What was it's cylinder pressure?

For starters you need IMEP not BMEP and then you need to find out at point the exhaust valves opened. and then do a bunch more calculations.

You also have to say which engine/s you are comparing. A 213A is quite different than a 213E.

 

[spicmart]

Sorry please bear with me that I asked about the technical details I am just a layman.I don't know about prinicples of this.
I just wanted to know if could be that the Jumo had more thrust than the DB.

 

[wuzak]

The RR was never into turbocharging IIRC?

Rolls-Royce very much preferred exhaust thrust over turbocharging, and did a lot of work on ejector exhausts.

 

[Shortround6]

Sorry please bear with me that I asked about the technical details I am just a layman.I don't know about prinicples of this.
I just wanted to know if could be that the Jumo had more thrust than the DB.

It could, I am not going to doubt the the book, without a lot more details about both engines it is very hard to confirm or challenge the statement. Or perhaps say if the statement makes any sense or not. Even with more details we would be working with assumptions instead of the details the engineers of the time had. Only if something looks way, way out of wack could it be challenged.