有机朗肯循环径流式汽轮机结构尺寸及等熵效率研究

针对现有的有机朗肯循环(ORC)理论优化研究中指定膨胀部件等熵效率为定值这一分析方法的不足,研究了不同压比和绝热指数对径流式单级汽轮机结构尺寸和等熵效率的影响,为基于该类膨胀部件的ORC理论优化研究提供膨胀部件等熵效率的取值依据.结果表明:汽轮机制造条件限制了高绝热指数的工质实现高压比的循环工况;A类情形(绝热指数1.1~1.5)下,汽轮机无量纲结构尺寸大体相同,等熵效率变化规律相似;B类情形(绝热指数1.6~2.3)下,汽轮机无量纲结构尺寸和等熵效率均随绝热指数的变化而明显变化;间隙损失是影响A类情形下汽轮机等熵效率变化规律的主要因素;更高的二次流损失和间隙损失是造成B类情形汽轮机等熵效率低于A类情形的主要原因;各个工质工况间汽轮机等熵效率值的差别最大可达15%左右.

Structure Size and Isentropic Efficiency of Single-Stage Radial Turbine Based on Organic Rankine Cycle

With attention to the drawback of specifying expander isentropic efficiency in organic Rankine cycle （ORC） analysis, the structure size and isentropic efficiency of single-stage radial turbine under different pressure ratio and adiabatic index were studied in this paper. Expander isentropic efficiency data were provided for ORC opti- mization based on single-stage radial turbine. The results show that turbine manufacturing conditions limit the working fluid of high adiabatic index to achieve high pressure ratio. In case A （adiabatic index range 1.1--1.5）, turbines have obviously the same dimensionless structure size and the isentropic efficiency variation with pressure ratio is similar under different adiabatic index. In case B （adiabatic index range 1.6--2.3）, the dimensionless structure size and isen- tropic efficiency change obviously with the change of adiabatic index. Tip clearance losses are the main factors that obviously affect isentropic efficiency variation in case A. Turbines have higher secondary flow losses and tip clearance losses in case B, which lead to lower isentropic efficiency compared to that in case A. In all turbine operating condi- tions, variation in turbine isentropic efficiency can reach about 15%.