Jet-Propelled Remote-Operated Underwater Vehicles Guided by Tilting Nozzles

Abstract

This paper is a study and experimental analysis of a forced jet propulsion system with tilting-type nozzles for slow-moving remotely operated underwater vehicles (ROV's). A test setup simulating the motion of the underwater vehicle was fabricated to investigate the effect of nozzle configurations on the propulsion of such vehicles. Plexiglass nozzles of different conical contraction angles (θ = 4 to 28 deg), different conical expansion angles (θ = 3 to 9 deg), and a straight cylindrical section were used in the study. Tests were carried out underwater, and the parameters measured include thrust, flow rate, angular velocity, and total head. Different circular disk type drag plates were used to simulate the drag of the vehicle underwater. Efficiency of propulsion is the criterion for comparing the performance of each nozzle. An expression for the optimum efficiency was derived neglecting the effect of inlet head recovery, which can be assumed for slow-moving vehicles. The energy loss and loss coefficients in submerged propulsion nozzles were found both theoretically and experimentally. A proposal for the fabrication and testing of an innovative design of a jet-propelled ROV guided by tilting nozzles is presented. The design uses a stepper motor for tilting the nozzles. A comparison is made between stationary and swivel-type configurations. The nozzles were tested for optimum area ratio. The propulsion system and the ROV was designed and checked for stability. The study revealed that for a range of flow rates, one particular nozzle was the most efficient compared to other nozzles.