Simulation And Experimental Study On The Effect Of Ejector On Thermal Cycle Of Ocean Thermal Energy

With the rapid development of economy,the reserves of fossil energy are gradually reduced,the living environment of human beings is also deteriorating.Therefore,energy conservation,emission reduction and the search for alternative energy have become the top priority of development.There is a large amount of ocean energy in the ocean,among which the ocean temperature difference energy reserves are large,which has the advantages of clean,stable,pollution-free,renewable and so on,and has attracted people’s extensive attention.Ocean thermal energy conversion(OTEC)uses the temperature difference between the ocean surface temperature seawater and the deep cold seawater to change the working medium state,so as to form the pressure difference between the working medium at both ends of the turbine,and then promote the turbine to rotate for power generation.Improving the thermal cycle efficiency is the key to the marine power generation system.Improving the thermal cycle efficiency can increase the net output power and create more economic value.Therefore,how to improve the thermal cycle efficiency simply is quickly becoming the key task of developing ocean energy.In this paper,the ocean thermal energy conversion system will be studied,the ejector will be used to improve the thermal cycle efficiency,meanwhile,the ejector in the cycle will be studied,the performance of the ejector with different structural parameters will be simulated and analyzed,and finally,an experimental platform will be built to verify the simulation results.The specific research content of this paper is as follows:In the first chapter,the principle and classification of the ocean thermal energy conversion cycle are introduced,the development process and current situation of marine thermoelectric energy at home and abroad in recent years are described in detail,the application of ejector in the cycle of marine thermoelectric energy is sorted out,and the principle and advantages of various cycles are described.This chapter also introduces the ejector in detail,including the theoretical development,performance simulation and experimental research.In the second chapter,the ejector thermal cycle and non-ejector thermal cycle are put forward.The thermodynamic laws are applied to model the cycle.MATLAB and physical property query software are used to simulate the cycle.The performance of the two cycles under different sea water temperature,working medium concentration and turbine inlet pressure is analyzed and discussed to find the best operating condition of the system.At the same time,the performance of the two cycles is compared under the same seawater temperature,working fluid mass fraction and turbine inlet pressure,which highlights the superiority of ejector cycle.In the third chapter,the ejector is designed by using the equations of conservation of energy,conservation of mass and conservation of momentum combined with the existing empirical formula.Three kinds of ejector nozzle structures are proposed,namely,the conical nozzle,the conical expanding nozzle and the conical expanding pressurized nozzle.At the same time,the equivalent diameter of the nozzle is changed by using the nozzle needle.Using Solidworks to make three-dimensional modeling of the ejector,designing two-dimensional drawings of the ejector in CAXA,and finally processing seven different structures of the ejector.In the fourth chapter,the ejector is simulated by ANSYS CFD software,the model is established according to the design parameters,the mesh is divided in mesh software,the ejector is calculated in fluent software,the structure of the ejector is changed,the temperature field,pressure field,Mach number and other parameter changes in the ejector are observed,and the ejector ratio is calculated.In the fifth chapter,the thermal cycle test-bed is built,the key equipment in the system is calculated,the layout and control scheme of the whole cycle are designed,the whole system construction process and precautions are introduced in detail,and the starting sequence and shutdown mode of the system are described.In the sixth chapter,summarize the content of this paper,analyze the shortcomings of this study,and provide ideas for future scholars.