why are little jets louder than big jets

[nauga]

Threadjack

Do turbine blades break the sound barrier?

Compressor blades can, especially on large-diameter fans at high power, but turbine blades typically don't on common aviation engines. Diameter is (usually) less and the speed of sound is higher in the hot section.

Nauga,
who says, 'BZZZZZZZ'

 

[SkyDog58]

RJ pilots are compensating.

Do you know the difference between a RJ pilot and his engine?








The engine quits whining when it gets to the gate.

 

[Velocity173]

Threadjack

Do turbine blades break the sound barrier?

Like Nauga said, high bypass fans do because of their large diameter.

The problem for smaller engines isn't the blades going supersonic but supersonic airflow going thru the compressor. Take the little GE-700 / 701s . The airflow does hit supersonic when leaving the impeller to the diffuser but at extreme cold temps the airflow can hit supersonic in the axial section. That's bad and can do damage to the blades and lose lift. That's why compressor speed or NG is limited thru the computer (ECU / DEC) based on an inlet temperature (T2) sensor.

 

[Checkout_my_Six]

Like Nauga said, high bypass fans do because of their large diameter.

The problem for smaller engines isn't the blades going supersonic but supersonic airflow going thru the compressor. Take the little GE-700 / 701s . The airflow does hit supersonic when leaving the impeller to the diffuser but at extreme cold temps the airflow can hit supersonic in the axial section. That's bad and can do damage to the blades and lose lift. That's why compressor speed or NG is limited thru the computer (ECU / DEC) based on an inlet temperature (T2) sensor.

I doubt there is super sonic flow inside the turbine. That would be very inefficient . The noise comes from the shearing of the high speed flows at the exit. It's very dependent on the exit geometries.


Btw. If we are going to discuss high speed internal flows might as well talk about compressor stalls and choked flow.

 

[Velocity173]

I doubt there is super sonic flow inside the turbine. That would be very inefficient . The noise comes from the shearing of the high speed flows at the exit. It's very dependent on the exit geometries.


Btw. If we are going to discuss high speed internal flows might as well talk about compressor stalls and choked flow.

There isn't supersonic flow in the two Ng turbines or the two Np turbines, but it's hits supersonic coming from the 6th stage impeller and CAN hit supersonic in low temps in the axial stages.