Scale down robots with propeller propulsion mechanisms are promising tools for minimally invasive surgery, diagnosis, targeted therapy, drug delivery and removing material from human body. Understanding the movement of micro robots inside fluid-filled channels is essential for design and control of reduced robots inside arteries and conduits of living organisms. Three-dimensional governing partial differential equations of the fluid flow, Stokes equations, are solved with computational fluid dynamics (CFD) to predict velocities of robots, which are compared with experiments for validation, and to analyze effects of blade number, pitch and the radial position of the robot on its swimming speed, forces acting on the robot and efficiency.