Anyone know what this is?

[Ivan]

Also, I am not sure, but I am pretty sure turbofans run at a must higher RPM than turboprops do. This engine is not really a turboprop, but a turbofan, not inside a duct.

Internals run the same speed. it's the prop that has the reduction box.

[C]

Also, I am not sure, but I am pretty sure turbofans run at a must higher RPM than turboprops do. This engine is not really a turboprop, but a turbofan, not inside a duct.

Did a little research on this point. Looking a the RPM of the main compressor of a Rolls Royce Trent, it has a max of about 10,000rpm, with the fan rotating at about 7,500.

Looking at a Turboprop example, the Garrett TPE331 has a rotational speed of 40,000rpm, with a propeller speed of 2,000rpm.

Generally, the smaller the engine, the higher the RPM...

[bbstackerf]

Hagar has the answer. The unducted fan delivered a 30% increase in efficiencyover the ducted fans, but they could not get the noise level under the guidelines established around most urban area airports.

Lets build a better engine so we can have the same people who gash about fuel and pollution make it impossible to use because it's too noisy.

[TacitBlue]

...Meanwhile, people drive around with car stereos that rattle your windows from across town.