Is a chambered fan more efficient than a ducted fan? A chambered fan is not exposed to the oncoming airflow in forward flight.
I am working on a VTOL design that uses a chambered fan.

There will be a wing attached to top of the thrust arms.

Could it produce 12,000 pounds of lift force using a GE T901 with 3,000shp with 8' dia. contra rotating fan?
The design is not very efficient:


It does not use forward airspeed to pre-compress the airflow entering the engine.
It blows exhaust air into the air inlet.
It bends the exhaust flow 180 deg, creating friction and loss of thrust.


Short, straight, unimpeded airflow works best.