Research On The Performances Of A Thermal Glider

Ocean thermal energy has a great exploration potential with large reserves. According to the requirements of range ability on Automation Underwater Vehicles in military and scientific research, this thesis studies the performances of a glider driven by ocean thermal energy. This thesis emphasizes on the research of the motion process and working mechanism of the driven system.In the motion analysis, the thesis studies the motion mechanism and energy efficiency in gliding. The established dynamic equilibrium equation based on the force analysis shows that the outside bladder would be better fixed close to the glider stern, thus the displacement of the buoyancy center changed by the bladder volume change will have sound effect on the pitch angle adjustment. The energy exchange analysis indicates that gliding energy efficiency is dependant on the lift drag ratio of the wings and gliding angle of the hull. Through the calculation in this thesis, it can be concluded that enhancing the lift drag ratio can largely improve the energy efficiency when the gliding angle is in the range of 10to 40 degree, and when lift drag ratio is fixed, there exists a special gliding angle for the maximum of the efficiency, which provide theoretical basis for the design of operating parameters.The driven system mechanism study develops around the working processes of its components.This thesis gives detailed research on the thermal cycle of the working gas in the accumulator and its influences on the gliding depth and energy saving effect. Results show that one thermal cycle is composed of gas compression, pressure keeping, gas expansion, re-pressure keeping and energy complement in one zigzag gilding range. Reducing the polytropic exponent differences in gas compression and expansion and accumulator volume usage can increase the gliding depth. The actual design should balance the gliding depth and accumulator volume use which is related with the needed compartment space. Based on the energy analysis of the thermal cycle, the thesis calculates the dissipative coefficient of the thermal driven system related with the electronic ones and reveals the requirements for energy saving effect of the thermal driven system.In order to improve the buoyancy adjusting performance, this thesis is the first to establish a mathematic and simulation model by Simulink based on volume change of the adjusting components. The results show that the negative buoyancy adjusting system may self-regulate, while the positive buoyancy adjusting range is dependent on the filling pressure of the working gas which must be great than the sea depth pressure, and guide a proper path for the optimization of the valve port's flowing area to meet the design requirement.Phase change heat transfer research is the most important in this thesis. Numerical calculation on the phase change process is conducted based on the enthalpy model. The simulation indicates that the total time of Solid-Liquid phase change is much shorter than that of the Liquid-Solid phase change, due to the convection heat transfer between liquid PCM and the sea water. Reducing the radius of the working fluid tube can significantly improve the phase change efficiency. The accurate length of period when the phase change material keeps in solid or liquid can be worked out for the determination of the critical gliding depth range and check valves'action order to ensure the circulation catachrestic of the thermal driven system.For experiment, a thermo cline simulation system with heat pump is proposed in this thesis, and the construction of the experimental system creates conditions for underwater gliding testing.This thesis reveals the key factors of the glider's working processes and give directions for the control rules of the driven system by numerical calculation and dynamical simulation, which provides theoretical predictions for the glider design, making the whole system under good control and meeting design requirements.