Heat, that's how. Airplanes like the Celera 500L don't have sufficient heat or HP to achieve very high speeds. Nor do electric planes.
We all know that prop airplanes, with a few notable big HP exceptions, do not reach jet like speeds. Exceptions include Reno racers, the Soviet era turboprop bombers and the Piaggio Avanti, all of which can go almost as fast as the slowest jets.
The 3200 HP Avanti can reach 400 Knots, world class fast for a turboprop, but it's normal cruise speed is 350 or less. At jet altitudes, the Avanti is simply in the way. And it has plenty of hot jet thrust from it's two hard working turbine engines.
The swept wing TU-95 turboprop bomber cruises at 380Kts and is said to have a top speed of 500Kts (probably downhill) . It takes 60,000 HP to go this fast, along with the counter rotating props and significant jet thrust from the 4 engines.
The Reno air race planes achieve their speed through raw HP, aerodynamics, and the thinner air of Reno. Even then, they are not jet-fast.
The heat of combustion is used in turbine engines (both jet and turboprop) to create the power to drive the turbines. But the heat is also effectively used to achieve high exhaust discharge velocity. The nozzle's discharge velocity is limited by and to the speed of sound. The speed of sound increases with temperature. So the hotter the exhaust, the faster we can move it through the nozzle.
Electric drive is very cold, with no real free heat. The only real way to get jet like speeds would be to create enough heat to raise the nozzle discharge velocity. One way to do this is to have a multi stage fan. The heat of compression can be used to achieve a high discharge velocity.
We all know that prop airplanes, with a few notable big HP exceptions, do not reach jet like speeds. Exceptions include Reno racers, the Soviet era turboprop bombers and the Piaggio Avanti, all of which can go almost as fast as the slowest jets.
The 3200 HP Avanti can reach 400 Knots, world class fast for a turboprop, but it's normal cruise speed is 350 or less. At jet altitudes, the Avanti is simply in the way. And it has plenty of hot jet thrust from it's two hard working turbine engines.
The swept wing TU-95 turboprop bomber cruises at 380Kts and is said to have a top speed of 500Kts (probably downhill) . It takes 60,000 HP to go this fast, along with the counter rotating props and significant jet thrust from the 4 engines.
The Reno air race planes achieve their speed through raw HP, aerodynamics, and the thinner air of Reno. Even then, they are not jet-fast.
The heat of combustion is used in turbine engines (both jet and turboprop) to create the power to drive the turbines. But the heat is also effectively used to achieve high exhaust discharge velocity. The nozzle's discharge velocity is limited by and to the speed of sound. The speed of sound increases with temperature. So the hotter the exhaust, the faster we can move it through the nozzle.
Electric drive is very cold, with no real free heat. The only real way to get jet like speeds would be to create enough heat to raise the nozzle discharge velocity. One way to do this is to have a multi stage fan. The heat of compression can be used to achieve a high discharge velocity.
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