A fluid driven turbine apparatus includes a hollow body and rib plates annularly disposed in the hollow body. A vane module is disposed in the hollow body and co-axially connected to a shaft extending axially through the hollow body. The rib plates surround the vane module and are spaced apart from the vane module by an annular gap. The annular gap has a width gradually enlarged in a top-to-bottom direction. When fluid flows into the vane module and is diverted sideward to the annular gap, large sand grains carried by fluid may pass through an enlarged lower portion of the annular gap without getting stuck therein and abrading the rib plates and the vane module.