Abstract: The invention provides for a turbine, which includes a duct that may provide an elongate circular internal passage that may have an open upstream end forming an intake and an open downstream end forming an exhaust. The turbine may further include a turbine rotor that may be rotatably mounted in and coaxially with the internal passage and may have at least one rotor blade extending helically along the internal passage so that airflow through the internal passage from the intake to the exhaust may impinge on the rotor blade and may drive the turbine rotor to turn. The duct may further provide at least one intermediate inlet disposed between the intake and the exhaust and part way along the rotor blade.