Performance Study of Installed an I-65o Type Cylinder at The Upstream of Returning Blade of Savonius Wind Turbine, Comparison With Conventional Savonius Wind Turbine - Sakti, Gunawan; Departemen Teknik Mesin Institut Teknologi Sepuluh Nopember (IPTEK, LPPM, Institut Teknologi Sepuluh Nopember, 2019)