基于有机朗肯循环的水下动力系统研究

Investigation of Organic Rankine Cycle for Underwater Power System

闭式蒸汽朗肯循环是无人水下航行器动力系统的发展方向之一,但存在系统效率低的问题。文中提出了一种输出功率为10 kW的闭式有机朗肯循环。详细介绍了水下热动力系统的工作条件和相关尺寸限制参数。建立了系统热力学模型和涡轮机一维设计方法,设计了在不同工况下的部分进气式小型轴流式涡轮机。利用建立的涡轮机和换热器模型,以提高动力系统效率并满足在水下航行器中应用的尺寸限制为目标,对多种有机工质循环系统的运行特性展开分析。计算结果表明,采用跨临界循环的高温干工质可以大幅度提高系统效率。以环己烷和甲苯为例,系统效率分别为24.38%和22.29%,同时满足了尺寸限制条件,与传统蒸汽朗肯循环相比,系统效率提高了6.77%~8.86%。

The closed steam Rankine cycle is typically employed as a power system for unmanned undersea vehicles, but with low system efficiency. In this paper, a closed-organic Rankine cycle is proposed as an alternative, where the required output power is on the order of 10 kW. The working conditions and associated sizing constraints for a power cycle operating in underwater environments are detailed. The small-scale axial turbine is specifically designed for different operating conditions and incorporated into the thermodynamic model of the system. Using the established thermodynamic model for turbine and heat exchangers, various organic fluids are scrutinized to maximize system efficiency and to ensure the sizing constraint encountered in an underwater environment. Numerical results show that the high-temperature dry fluid with trans-critical cycles can significantly enhance the system efficiency. System efficiencies of 24.38% and 22.29% are obtained using cyclohexane and toluene, respectively, while the sizing constraints are also satisfied. This corresponds to an increase of 6.77%~8.86% in terms of system efficiency compared to conventional steam Rankine cycles. This work provides insights into the potential applications of the organic Rankine cycle for undersea vehicles.