What is the purpose of the vertical splitter and the NACA duct at the MQ-9 Reaper engine scoop?
The NACA duct is probably routed to a gearbox oil cooler. The turboprop engine has its air inlet at the prop end of the engine, which means a splitter is needed to divide the incoming air flow into two ducts, one on each side of the engine, in order to conduct the air back to the inlet.