Er Presidente
Guest
when the engines were equipped with compressor, mechanical, it was possible to have excellent powers even at high altitude, 3000 m, where the rarefied air at 1/2 atmosphere, precipitated the power of the aspired engines....the compression ratio is 6.4, not bad for a supercharged engine of the 1930s.
the ratio of the mechanical centrifugal compressor multiplication, constant at 8.24 per tutte le versini excluding two "semi-superpowered".
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increasing the compression ratio beyond the limit of detonation of the mixture was a "truck" already widespread, the "surcompresses" managed to maintain the nominal power up to 2000 m, but they had a limit. at low altitude, lower than that of maximum power, the pilot had to "partitialize" the "handle" and could not use all the available power, which would quickly destroy the engine for detonation caused by the greater density of the air.
with the compressor the problem was solved in a similar way but with better results at high altitude (then higher than 3000 mt).
a "natural" compression ratio of 6.4 was very high for a supercharged engine, but was incompatible with low altitudes.
the multiplication ratio of the compressor was chosen to have the maximum pressure to the fixed quota of "restoration", above this the power decreased by rarefaction of the air (not more compensated by the compressor) below the pitota tove "cut" the engine to avoid detonation problems.
the multiplication ratio of 8.24 led to turn the compressor to over 20,000 rpm when the engine was at its maximum of about 3000, the "restoration" share was traditionally around 3000 mt (see below in detail).
experimental versions "semicompressed" used a lower compressor regimen, so a lower re-establishment rate, around 2000 meters.
In practice, at the same time as other parameters, the "semicompressed" engine could be less "cut" and, consequently, it had a higher "ground" power, but paying a higher level of performance.
passenger planes (not pressurized) typically did not fly to "extreme" quotas for greater comfort of passengers, and preferred a greater power to land in order to be able to take off from shorter runs or, at equal track, with a "paying" weight greater.
