hammo1j
Donor
The Fw 190 was famous for giving a low aerodynamic profile to the radial engine. The BMW 801 used a design whereby a fan assisted the cooling of the engine, not just the normal airflow.
From Wikipedia
The BMW 801 was cooled by forced air from a magnesium alloy cooling fan, 10-bladed in the initial models, but 12-bladed in most engines. The fan rotated at 1.72 times the crankshaft speed (3.17 times the propeller speed).[11] Air from the fan was blown into the center of the engine in front of the propeller gearing housing, and the shape of the housing and the engine itself carried the air to the outside of the cowling and across the cylinders. A set of slots or gills at the rear of the cowling allowed the hot air to escape. This provided effective cooling although at the cost of about 70 PS (69 hp, 51.5 kW) required to drive the fan when the aircraft was at low speed. Above 170 miles per hour (270 km/h), the fan absorbed little power directly as the vacuum effect of the airflow past the air exits provided the needed flow.[11]
The 801 used a relatively complex system, integral to the BMW-designed, matching forward cowling system, to cool the lubricating oil. A ring-shaped oil cooler core was built into the BMW-provided forward cowl, just behind the fan. The outer portion of the oil cooler's core was in contact with the main cowling's sheetmetal, to possibly act as a heat sink. Comprising the BMW-designed forward cowl, in front of the oil cooler was a ring of metal with a C-shaped cross-section, with the outer lip lying just outside the rim of the cowl, and the inner side on the inside of the oil cooler core. Together, the metal ring and cowling formed an S-shaped airflow path, with the oil cooler's core contained between them. Airflow past the gap between the cowl and outer lip of the metal ring produced a vacuum effect that pulled air from the front of the engine outward and forward within the cowl's frontmost inner area just behind the fan, flowing forward across the oil cooler core in a separate airflow path from the rearwards-direction flow that cooled the engine's cylinders, just to provide cooling for the 801's oil. The rate of cooling airflow over the core could be controlled by moving the metal ring slightly forward or aft in order to open or close the gap.[12]
The reasons for this complex system were threefold. One was to eliminate any extra aerodynamic drag that a protruding oil cooler would produce, in this case eliminating the extra drag factor by enclosing it within the engine's forward cowling. The second was to warm the air before it flowed to the oil cooler's circular-shaped core to aid warming the oil during starting. Finally, by placing the oil cooler behind the fan, cooling was provided even while the aircraft was parked. The downside to this design was that the oil cooler was in an extremely vulnerable location, and the metal ring was increasingly armoured as the war progressed.
The Superfortress Wright R-3350 was notorious for blowing certain pairs of cylinders in the back row and that meant regular replacement even if there was no discernable damage.
Now I am not engaged on a German wank here because I believe Allied Tech was actually superior and superiorly applied, but could the BMW fan arrangement have sorted some of the problems on the big Allied radials.
I do remember reading about a German test pilot having his feet toasted by the Fw190 prototype with Kurt's original spinner but this looks like they managed to get the heat exchange/aerodynamics pretty well sorted.
From Wikipedia
The BMW 801 was cooled by forced air from a magnesium alloy cooling fan, 10-bladed in the initial models, but 12-bladed in most engines. The fan rotated at 1.72 times the crankshaft speed (3.17 times the propeller speed).[11] Air from the fan was blown into the center of the engine in front of the propeller gearing housing, and the shape of the housing and the engine itself carried the air to the outside of the cowling and across the cylinders. A set of slots or gills at the rear of the cowling allowed the hot air to escape. This provided effective cooling although at the cost of about 70 PS (69 hp, 51.5 kW) required to drive the fan when the aircraft was at low speed. Above 170 miles per hour (270 km/h), the fan absorbed little power directly as the vacuum effect of the airflow past the air exits provided the needed flow.[11]
The 801 used a relatively complex system, integral to the BMW-designed, matching forward cowling system, to cool the lubricating oil. A ring-shaped oil cooler core was built into the BMW-provided forward cowl, just behind the fan. The outer portion of the oil cooler's core was in contact with the main cowling's sheetmetal, to possibly act as a heat sink. Comprising the BMW-designed forward cowl, in front of the oil cooler was a ring of metal with a C-shaped cross-section, with the outer lip lying just outside the rim of the cowl, and the inner side on the inside of the oil cooler core. Together, the metal ring and cowling formed an S-shaped airflow path, with the oil cooler's core contained between them. Airflow past the gap between the cowl and outer lip of the metal ring produced a vacuum effect that pulled air from the front of the engine outward and forward within the cowl's frontmost inner area just behind the fan, flowing forward across the oil cooler core in a separate airflow path from the rearwards-direction flow that cooled the engine's cylinders, just to provide cooling for the 801's oil. The rate of cooling airflow over the core could be controlled by moving the metal ring slightly forward or aft in order to open or close the gap.[12]
The reasons for this complex system were threefold. One was to eliminate any extra aerodynamic drag that a protruding oil cooler would produce, in this case eliminating the extra drag factor by enclosing it within the engine's forward cowling. The second was to warm the air before it flowed to the oil cooler's circular-shaped core to aid warming the oil during starting. Finally, by placing the oil cooler behind the fan, cooling was provided even while the aircraft was parked. The downside to this design was that the oil cooler was in an extremely vulnerable location, and the metal ring was increasingly armoured as the war progressed.
The Superfortress Wright R-3350 was notorious for blowing certain pairs of cylinders in the back row and that meant regular replacement even if there was no discernable damage.
Now I am not engaged on a German wank here because I believe Allied Tech was actually superior and superiorly applied, but could the BMW fan arrangement have sorted some of the problems on the big Allied radials.
I do remember reading about a German test pilot having his feet toasted by the Fw190 prototype with Kurt's original spinner but this looks like they managed to get the heat exchange/aerodynamics pretty well sorted.
