Thermodynamic Simulation Analysis of Variable Buoyancy Device for Underwater Gliders

Abstract

The heat generated by its driving motor and pump affects the internal structure of the device when a variable-buoyancy device on an underwater glider is operating, thus posing risks to its normal operation. To address this problem, the finite element method was used to establish a thermodynamic simulation model of the variable-buoyancy device. The temperature field distribution of the piston of the device in the ideal uniform motion state at the points where it reaches thermal equilibrium at different water depths was simulated. Moreover, the temperature characteristics of the variable buoyancy device change with water depth were obtained. The results show that among the selected working conditions with different water depths, the temperature reached its lowest at a water depth of 500 m and was highest at the sea surface. At the sea surface and depth of 100 m, the highest temperatures of the device at thermal equilibrium were found on the right piston, which were 31.49 and 26.90°C respectively. Under other working conditions, the highest temperatures of the device at thermal equilibrium were found in the gland of the pump model. Furthermore, the temperature field distribution of the variable buoyancy device at the points when it reaches thermal equilibrium at a depth of 1 500 m at different motor speeds was simulated, and the temperature characteristics of the variable buoyancy device changing with motor speed were obtained. The results show that among the selected working conditions with different motor speeds, the temperature of the device at thermal equilibrium reached its highest, which is 40.95℃, when the motor speed was 5 000 r/min and was found on the gland of the pump model. The simulation results indicate the high-temperature locations of the device during operation, thereby providing an important reference for analyzing whether key parts of the variable buoyancy device cannot operate properly because of overheating.

Keywords

• underwater glider
• variable buoyancy device
• thermodynamic simulation
• temperature field