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The two-stage supercharger has different gearing settings, and can be switched between different levels of boost. It's important to note that there are negative effects of supercharging along with the power benefits. These are: Overheating - this is the main problem, and can lead to the fuel igniting before it is supposed to. The second is power loss - driving the supercharger unit itself consumes engine power. This is a minor effect though, compared with the huge boost of power that the supercharger brings.
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Perfectly explained!
was the system (speaking about WW2 engines) that switch from the 1st stage to the 2nd and back always automatic or sometimes manual? Which kind of system did it use? Electromagnetic clutch? Had the pilot a chance to change the boost pressure manually?
Thanx!
Simon, wasn't a silly question at all. I certainly learned something!OK, I will have a go...
When you are sucking air into the engine to mix with fuel for combustion, the amount of air depends on the ambient air pressure. This means you are limiting the power you can get from each piston stroke, because you can't physically get any more air into the cylinders. As you fly at higher altitude, the air pressure is less, so your aircraft actually loses power as you climb...
The 'fix' is to run a very high speed pump which actually compresses the air before it's sucked into the cylinder. Simply put, it is a fan, driven from the engine itself, which sucks air in at 'ambient' pressure and boosts the pressure to above the normal range. More pressure means more oxygen, which means more fuel can be burned, and more power produced. So the supercharger will normally produce more power at all altitudes, but is specially effective high up, as it counteracts the effect of low pressure.
The two-stage supercharger has different gearing settings, and can be switched between different levels of boost. It's important to note that there are negative effects of supercharging along with the power benefits. These are: Overheating - this is the main problem, and can lead to the fuel igniting before it is supposed to. The second is power loss - driving the supercharger unit itself consumes engine power. This is a minor effect though, compared with the huge boost of power that the supercharger brings.
A quick note about Turbochargers:
A turbocharger or 'turbo' does exactly the same thing as a supercharger, the only real difference being that the turbo is driven by exhaust gas instead of mechanical gears or shafts. If anything is called 'turbo' and is say a razor, computer processor, vacuum cleaner, etc. this is basically a lie. Turbo means turbocharger, and if there's no internal combustion engine involved, then the term is meaningless BS...
...You can control a super better and EZ'er smoother power ... A turbo is harder to control and has a big step in power when the power comes on...
But no lose in power to run the turbo...
...
And, actually, there is a small penalty for a turbo; the amount of exhaust backpressure with a turbo is somewhat greater than in a normally aspirated engine, so the piston has to work a little harder to get the exhaust out of the cylinder. However, compared to a supercharger, this is negligible so, in essence, you are almost getting "something for nothing".
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Actually, you can control a turbocharger to some degree by varying the amount of exhaust that goes out the wastegate; the wastegate is usually controlled by an exhaust valve that regulates how much of the engine's exhaust goes to the turbo, and how much simply gets dumped overboard (hence the "waste" part of wastegate). With the wastegate closed, 100% of the exhaust goes to the turbo; with the wastegate open, only a very small percentage of the exhaust goes to the turbo. IIRC, on the original turbosuperchargers (that's what they called them originally), the wastegate was controlled manually by the pilot, but there were too many problems with overboosting (and the consequent destruction of a very expensive engine!), so an automatic system was devised (don't know all of the details on that; I'm sure someone else here probably knows a lot more than I do about this).
And, actually, there is a small penalty for a turbo; the amount of exhaust backpressure with a turbo is somewhat greater than in a normally aspirated engine, so the piston has to work a little harder to get the exhaust out of the cylinder. However, compared to a supercharger, this is negligible so, in essence, you are almost getting "something for nothing".
...ejector exhausts on the Spitfire XIV gave an extra 47mph (maximum) ...
does anyone have a drawing or picture of the supercharger drive on a B-17 (R-1820 engine)? I´m curious how did it work as the engine was in the vertical position and the supercharger in horizontal position so they didn´t have common axis...on my opinion...
On the engines with the supercharger mounted on its back it´s clear...