Investigation Of Thermoelectric Closed Cycle Power System Of Unmanned Underwater Vehicle

Unmanned underwater vehicle（UUV）has a broad application prospect in the field of military and civilian,which is the priority technology among most countries.Power technology that plays an important role of the UUV is the key point.Now most of the UUV use electric propulsion,but the specific energy of existing battery can’t meet the requirements of UUV on the running time.Therefore,the high density fuel cells or thermoelectric hybrid system are developed with the purpose of finding a new approach to the power system,improving the UUV voyage,enhancing the UUV overall performance.A new kind of thermoelectric hybrid system is proposed for the first time,using Li and SF₆ as the power source and water as the working medium.The system is a kind of ideal UUV power system.with the advantages of low power output,high energy density,no emissions of the product.Fist,the feasibility of the system was demonstrated.Then,the combustion and flow process in the heat pipe reactor was analyzed,and the heat transfer in evaporator and condenser was studied.Next,the flow field characteristics of the micro turbine was discussed.Then,the steady state parameter design method was proposed and systematic dynamic simulation research was carried out.Finally,the experimental verification of the subsystem was did.The major contents are as follows:（1）A new approach of closed cycle power system applied to the UUV was proposed.The simulation model was established.And then the influence of steam parameters on the system thermal efficiency was investigated.Improving the evaporator inlet temperature and pressure,reducing the condenser inlet pressure can improve the efficiency of system.In the end the scope of the parameters was settled.（2）The process of the energy conversion in the heat pipe reactor was studied deeply.The model illustrates mass and energy conservation of Li which flows in the wick and evaporates along the surface was given.The correlation of wick mesh and the effective infiltrating height,the heat flux’s influence to the infiltrating height were both obtained.The steam condensation of Li in the presence of noncondensable gas was investigated.The research can reveal the law of flow and heat transfer in heat pipe reactor,provide the reference to wick design and operation choice.（3）The one dimensional models containing the phase transition process of evaporator and condenser tube were developed.The temperature and pressure distribution along the flow direction were got,while the heat transfer performance were analyzed.Within the scope of the study,the mass flow rate and structure parameters of the heat exchanger affects the heat transfer process mostly,the wall temperature’s influence is weak,and the inlet temperature’s influence is last.The results can provide the reference to the heat exchanger design and performance prediction.（4）A numerical simulation method for the impulse type micro-turbine with partial-air admission were carried out.The parameters of the nozzle and the tubine blade applying to the proposed system are given.Numerical simulation is made to illustrate the flow filed characteristic and the energy convention.The results show that there are non-uniform inflation and airflow deflection in the oblique nozzle exit.Meanwhile,the wake loss and mixing loss exsit among the transition region between the nozzle and the blades.The Mach mumber along the circumferential distribution of the turbine is uneven.The flow field defference between inflow area and non-inflow area are quite obvious.Finally,a method that can make estimation of turbine internal loss by using the power loss coefficient is proposed.This method could give reasonable and effective estimation calculation of turbine efficiency when use the same software.（5）The design method of the steady state parameter of the closed cycle system is built,then the design parameters are given.Moving boundary model of the evaporator and condenser were developed based on mass conservation and energy conservation equations,with the heat exchanger divided into different areas.The steady state model of the turbine and the dynamic model of the liquid trap was established.The dynamic model of the whole system was developed afeter connecting each parts.Dynamic simulation of the system was made with the direct solving method.The results can show the dynamic response of the system with the change of the mass flow rate.The models and simulations could provide reference to the prototype design and system experiment.（6）The heat pipe reactor system and turbine system prototype tests were conducted,which verifed the feasibility and rationality of the design.The running characteristics of the subsystem was got,and it could be the foundation to carry out the integration test in the future.