动态透平效率对有机朗肯循环系统性能的影响

向心透平效率随运行参数的变化及工质种类的不同有较大差别,引入向心透平一维分析模型来计算透平效率,分析蒸发温度与冷凝温度对透平效率的影响,比较固定透平效率与动态透平效率有机朗肯循环（ORC）系统的热力性能与经济性能。采用非支配解排序遗传算法（NSGA-Ⅱ）优化ORC系统筛选出最优工质,确定最佳蒸发温度与冷凝温度。同时比较了不同热源温度下固定透平效率和动态透平效率ORC系统的最佳运行参数,分析了透平效率随热源温度的变化。结果表明：透平效率随蒸发温度的降低或者冷凝温度的升高而增大,采用动态透平效率后,系统净输出功随蒸发温度升高而增加趋势减缓,工质排序也发生了变化;对于固定透平效率与动态透平效率ORC系统,经多目标筛选后所确定的最优工质及最佳蒸发温度和冷凝温度均有一定差异,表明若采用固定透平效率会对工质筛选及参数优化造成一定误差;随着热源温度的升高,固定透平效率与动态透平效率ORC系统之间最佳蒸发温度与净输出功差异逐渐增大,说明热源温度越高,采用固定透平效率引起的误差越大。

Influence of dynamic turbine efficiency on performance of organic Rankine cycle system

The centripetal turbine efficiency varies greatly with the change of operating parameters and the type of working fluid, and a one-dimensional analysis model of radial-inflow turbine is introduced. The effects of evaporation and condensation temperature on the turbine efficiency were investigated, and a comparative analysis on thermodynamic and economic performances of the organic Rankine cycle (ORC) system with constant turbine efficiency and dynamic turbine efficiency was presented. NSGA-Ⅱ is employed to conduct multi-objective optimization of ORC system, which was to select the optimal working fluid and determine the optimal evaporation and condensation temperature. Meanwhile, the optimal operating parameters of ORC system with constant and dynamic turbine efficiency were compared, and the variation of turbine efficiency with heat source temperature was studied. The results show that the turbine efficiency increases with the decrement of evaporation temperature or the increment of condensation temperature. After introducing dynamic turbine efficiency, the increment of net power output with increasing evaporation temperature slows down, and the sequence order of some working fluids changed. The optimal working fluid and the optimal operating parameters are different between ORC system with constant and dynamic turbine efficiency, which indicates that constant turbine efficiency will cause errors in selection of optimal working fluids and determination of operating parameters. As the heat source inlet temperature raises, the difference of optimal evaporation temperature and net power output between the ORC system with constant and dynamic turbine efficiency increases. The higher heat source inlet temperature is, the greater error caused by adopting constant turbine efficiency will be.