MattJen
Elite Veteran
Location: UK,Gravesend, Kent
| For information,
this was posted in closed thread, which explains about the 2 types of turbines currently on the market..
Matt
The single-stage engine takes the power for the rotors from the shaft of a turbine engine. It is an effective way of doing things for model helicopters but isn’t appropriate for full-size helicopters, as it doesn't make use of the exhaust gases in any way and therefore wastes a lot of energy.
Two-stage engines were developed in full-size aviation to make better use of the power produced by a jet engine.
A jet engine uses the “suck-squeeze-bang-blow” principle and the hot gases streaming out from the exhaust provide propulsion (thrust). However, this is very inefficient and a large amount of the heat energy is wasted. So a method was devised whereby the hot gases were channelled through gas passages and used to turn a second turbine, which powered a turboprop propeller or helicopter rotor.
This gives three main parts to a two-stage engine:
First stage, the jet engine which generates the gases.
Second stage, the gas passage (interstage guide vane) and second turbine (power turbine)
Gearbox, with a shaft from the power turbine and reduction gears transferring the power to a prop or rotor.
Two-stage engines are about 4 times more efficient than the single stage jet engines, giving much more power from the same amount of fuel. That's why passenger planes started to use turboprops and now use turbofans, which are a further development of the same principle.
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