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Many piston engined aircraft had intakes right behind the prop.
Have a look at the BMW802 - supercharger in front and a plumbers nightmare. The induction losses must have been very high
Bmw 802 engine
Seriously interesting! (Unsure why there'd be induction losses).
Thank you and ''johnbr'' also.
Have a look at this photo and consider the following
.
When the air enters the boxes what happens?
- If the inside of the box is the same shape as the outside the air will become turbulent and Bernoulli's principle will be having a field day.
- If it is round with vanes to assist the directional flow of the air into the pipes to the cylinders the airflow to the "second" cylinders and to cylinders downstream will be obstructed
- When it leaves the box shape Bernoulli's principle will have another play
- View attachment 553548
Its not a good idea to have stuff in the front of an aircooled aircraft engine. Ram air? So having say an under-slung air intake or on top all getting more airflow than they would closer to the engine centerline is not good?
try googling radial engine sueprchargers or cutaways to see what you are dealing with,
View attachment 555917
This is for an R-2800 in a Hellcat. Now stick this on the front with the reduction gear in the middle or behind or?????
You have to get the air through a carb or throttle body at some point.
Hollow propshaft sounds good but how do you get the air out of the propshaft and into the impeller?
You do want the largest, least obstructed and smoothest air passages you can manage.
You also want to be able to reach and perform maintenance on some parts (or swap assemblies) with the least work. Like not have to pull propeller and propshaft to work on supercharger or pull supercharger apart to repair or replace the reduction gear.
View attachment 555918
On the R-2800 and most other large radials (Bristol excepted) the nose contained the reduction gear and the valve gear (cam ring/s) for the front row of cylinders. Impellers in the supercharger ran at around 7 to 10 times crankshaft speed and needed gears that would withstand 200-400hp (depending on engine), Yes you might be able to use a large diameter impeller turning at less rpm (but same tip speed) as the rear supercharger but you are still going to need a gear drive to run it. You are going to need a gear train for the cam ring/s.
You don't need to mount the magnetos on the front of the engine like P & W did but you are going to have an awful lot of stuff on the front of the engine and you are certainly not making the cooling problem any easier.
Note the size of the supercharger on the rear of the engine. The impeller is much smaller than the air passages in the diffuser.