Compound supercharging was used on GM Allison V-12 aircraft engines during WW2.Either 2 mechanical blowers or in combination with an exhaust driven supercharger.This was used to give the 1710 cubic inch engines sea level power at 30,000 feet,no so much to add extra power.Other aircraft engines used multispeed superchargers with 2 and 3 spd gearboxes.The Germans used a variable speed hydraulic motor to drive the blower on it's V-12 engines.
The 4300 cubic inch radial air cooled engines by Wright or P&W used an exhaust driven turbine geared to the prop to add wasted power from the exhaust directly to the engine output.
Other tricks used to boost piston aircraft engine's power or reduce detonation was alcohol injection into the intake,nitrous oxide and sodium cooled ehxaust valves.
Late in the war,Allison engines were using supercharger boosting in the range of 45 psi at 4400 rpm,with a 5-1/2 stroke.Oh yeah,V type aircraft engines are called Inlines
