【作者】 刘彤；

【导师】 陈贵军； 姜东岳；

【作者基本信息】 大连理工大学 ， 热能工程， 2023， 硕士

【摘要】 海洋中具有大量的能量和生物矿质能源,目前已出现多种海洋资源勘探和监测的技术,其中水下滑翔机因其体积小、能耗低和灵活性好等优点被广泛研究和应用。相较于电池驱动的水下滑翔机,海洋热能驱动的水下滑翔机因其续航能力较好且探索范围较大受到广泛关注。热机是整个系统正常工作的重要组件,热机内部填充的温差驱动工质的性能参数对海洋热能驱动水下滑翔机的滑翔效率具有重要影响。本文在海洋热能驱动水下滑翔机的工作背景下,首先设计了一种新型的活塞式蓄热发动机,其结构简单,传动方式稳定,工作受低温环境影响较小;在该设计结构的基础上,建立了海洋热能热-功转换的理论模型,对系统获取海洋热能的速率、海洋热能的能量转换程度和输出功率等参数进行了预测。为进一步提高活塞式蓄热发动机的热-功转换能力,针对活塞式蓄热发动机的工质进行了改性研究,确定石蜡类相变材料正十六烷(C16)为基础工质,并为其筛选了正十八烷(C18)、正二十烷(C20)和正二十四烷(C24)作为改进剂,之后通过实验测定制备的复合相变材料的相变温度和体积变化率等参数。最后,根据实验结果确定最佳复合相变材料为C16:C24=9:1(按质量分数),最佳改进剂为正二十四烷,添加比例为10%,其体积收缩率和体积膨胀率分别较正十六烷提高了26.67%和30.74%。同时,通过Materials Studio软件和分子动力学方法对相变材料C16和C16:C24=9:1进行模拟,模拟结果和文献数据误差较小,证明了采用的模拟方法的可靠性,并利用模拟结果对相变过程的微观结构变化和添加C24后体积变化率增大的原因进行了分析讨论。最后,利用理论模型计算正十六烷的工作性能参数,计算数据与文献中数据的误差在允许范围内,证明了理论模型的可靠性。利用理论模型计算C16和C16:C24=9:1的工作参数,对比分析说明制备的大体积变化率复合相变材料C16:C24=9:1的工作性能优于正十六烷,该种材料较正十六烷可以在相同海洋温差条件下获得更大的体积膨胀率,拓宽浮力变化区间,提升海洋热能向机械能的转换效率。完成上述研究内容后,利用理论模型分析了系统性能参数随不同工作条件的变化情况,并给出了提高系统工作性能的方法。更多还原

【Abstract】 The ocean contains a lot of energy and biomineral energy.Currently,various technologies for marine resource exploration and monitoring have emerged,among which underwater gliders are widely studied and applied because of their small size,low energy consumption,and good flexibility.Compared to battery powered underwater gliders,thermal underwater gliders have received widespread attention due to their good endurance and wide exploration range.The thermal engine is an important component for the normal operation of the entire system.The performance parameters of the temperature difference driven working medium filled in the thermal engine have an important impact on the glide efficiency of the thermal underwater glider.In this paper,under the background of the thermal underwater glider,a new type of piston type thermal storage engine is designed,which has a simple structure,stable transmission mode,and is less affected by low temperature environments;on the basis of this design structure,a theoretical model for the thermal power conversion of ocean thermal energy was established,and parameters such as the rate at which the system obtains ocean thermal energy,the degree of energy conversion of ocean thermal energy,and the output power were predicted.In order to further improve the thermal power conversion capability of piston thermal storage engines,modification research was conducted on the working fluid of piston thermal storage engines,paraffin phase change material N-hexadecane(C16)was determined as the basic working medium,and N-octadecane(C18),N-eicosane(C20),and N-tetradecane(C24)were selected as modifiers.Subsequently,parameters such as phase change temperature and volume change rate of the prepared composite phase change material were determined through experiments.Finally,based on the experimental results,the optimal composite phase change material is determined as C16:C24=9:1(by mass fraction),the optimal modifier is N-tetradecane,and the addition ratio is 10%.Its volume shrinkage and volume expansion rates are 26.67% and 30.74% higher than N-hexadecane,respectively.At the same time,two phase change materials,C16 and C16:C24=9:1,were simulated using Materials Studio software and molecular dynamics methods.The simulation results have a small error compared to the data provided in the literature,indicating the reliability of the simulation method used.The simulation results were used to analyze and discuss the microstructure changes during the phase change process and the reasons for the increase in the volume change rate after adding C24.Finally,the performance parameters of N-hexadecane were analyzed using a theoretical model,and the error between the calculated results and the literature data was within the allowable range,this demonstrates the reliability of the theoretical model.Using theoretical models to calculate the operating parameters of C16 and C16:C24=9:1,comparative analysis shows that the prepared large volume change rate composite phase change material C16:C24=9:1 has better performance than N-hexadecane,this material can achieve a larger volume expansion rate than N-hexadecane under the same ocean temperature difference conditions,broaden the range of buoyancy changes,and improve the conversion efficiency of ocean thermal energy to mechanical energy.After completing the above research,analyzed the changes in system performance parameters under different operating conditions using theoretical model,and methods to improve system performance were proposed.更多还原