[Viper2000]

Originally Posted by TomcatViP

Pls take a close look at your doc - Merlin XX. I hve here maximum perf calibration with max speed being plotted. It does not look like anything like a climb setting

Oh and it does come from RR..




I don't see the sense of what your wrote here. You might hve pasted half the sentence from your original doc here

physically given that the SC is accordingly dimensioned (flows and struct) , the heat generated is what will drive the overall efficiency. And what drive away that heat : the flow of air (or air mixture) that is pushed by the impeller blades.

No. The efficiency is the ratio of useful work to input work. In general, we'd use the isentropic adiabatic compression work for the pressure ratio achieved by the system as the definition of the "useful work".

Originally Posted by TomcatViP

Hence there is a max amount of calorific E that a s/c can work with. Raise the oct -> you'll reach sooner the the max sustainable value

This makes no sense.

Better fuel = higher max charge temperature, all other things being equal (which they are for merlin development as the basic piston engine (bore, stroke, CR, valve timing, max rpm etc were the same throughout its production life).

Originally Posted by TomcatViP

This is why I said that Max boost level hve very little chance to be reachable at an alt where the impeller hve alrdy to compensate for lower air density if the eng was not designed for

The engine is flat-rated to a maximum safe boost pressure. The supercharger is designed to deliver this boost WOT at the FTH. Below FTH the supercharger is throttled.

Originally Posted by TomcatViP

Modern supercharger : yes. At the time of BoB hummm that's a pretty acrobatic assumption

Not really. Compare the ease with which RR developed their centrifugal flow jets with the massive difficulty they experienced trying to get the AJ.65 to work. It's all relative.

Modern compressors of all types will have better polytropic efficiency and deliver more work per stage, but the basic trends haven't changed.

Originally Posted by TomcatViP

I wld hve been pls to see a Farman 220 with 4xMerlins. Damn just to see that huge parasol wing being blown away by the engines airstream

By the way, most patent are cross border documents. There is no shame using a Patent from an other country. Aviation is full of this. let us remind that if Aviation pioneer did not get inspiration from each other all over the world, we wld still cross the pound by steaming boat.

I work with patents quite frequently, and hold a couple of my own. They're only cross border if you've got the money to chase the legal paperwork, and they only mean anything much at all if you've got the money to sue whoever might infringe... I don't see why you'd ascribe any particular moral value to the nationality of the inventor to whom a patent you've decided to license is attributed. Most engineers have better things to do...

Originally Posted by TomcatViP

Supercharging the eng was meant to keep power at alt (the rated alt) and increased the fighter perfs (smaller engine) where the bomber stream were expected . Direct benefit were a low perf improvement and climb rate at alt.

Supercharging is really about making the engine smaller.

The non dimensional flow that a piston engine can handle at fixed rpm is basically constant.

Supercharging allows you to cram more absolute mass flow rate into a given non dimensional flow rate.

How you choose to rate the engine is another debate. But in most cases, people only flatrated because fuel quality prevented them from operating WOT at lower altitudes.

Originally Posted by TomcatViP

I hve arldy quoted the Merlin XX data with and without s/c (your 12lb thread)

You'd see that the s/c being driven by the eng shaft use a 7 to 20 % of eng power. Hence teh 1.3k SHP and 1.175k BHP or something like that

No, your data quotes the power consumed by the supercharger, and the power produced by the engine.

This is not the same thing as operating without the supercharger. Without the supercharger you can't get above 0 boost by definition. Hence you get something like 650-850 bhp.

Obviously the Supercharger consumes fewer horsepower than it adds via the boost increase it creates - otherwise nobody would bother!

Originally Posted by TomcatViP

Anyhow, the team that did code those FM game have proved superior man skills in the field. I am looking frwd for the next released giving they can work without too much pressure.

~S

Superior to what? It's not as though there's a whole lot of competition in the Flight sim market these days...