Downhole flow control device with turbine chamber insert

A downhole flow control device is used to control the production of formation fluids while using flow of the formation fluids to drive a turbine. Flow through a turbine chamber is optimized using a chamber insert that cooperatively defines a reduced chamber volume with the turbine chamber. The chamber insert includes an overhead portion defining a ceiling over the turbine and an arcuate portion contiguous with an arcuate portion of the turbine chamber. The baffle is perforated to allow some flow to exit the reduced chamber volume to a bypass port in a cavity radially outwardly thereof. The turbine may be used for any suitable downhole application, such as an inflow control device or to generate electrical power.