The radial-inflow turbine is a key component determining the performance of organic Rankine cycle (ORC) systems. Its isentropic efficiency and power output are mainly influenced by the working fluid and operation conditions. Although R245fa is a suitable working fluid for ORC systems, there is limited research concerning full structure numerical simulation and off-design analysis for the radial-inflow turbine using R245fa. In this work, a radial-inflow turbine using R245fa was designed by one dimensional design method and a three dimensional model including volute, stator and rotor was established. According to the developed model, a numerical simulation was carried out using CFD (computational fluid dynamics) method. The effects of inlet temperature, rotor speed and expansion ratio on turbine power and isentropic efficiency were analyzed. Additionally, the range analysis about main factors which influenced the radial-inflow turbine performance was conducted. The results showed that turbine power and isentropic efficiency changed slightly when rotor speed ranged from 80% to 100% of designed value. However, turbine performance decreased rapidly if rotor speed was larger than the designed value. Turbine power and isentropic efficiency increased with the increment of turbine inlet temperature. With the increase of pressure ratio (ratio of inlet pressure to outlet pressure), turbine power increases linearly and there was an optimal pressure ratio for the radial turbine to achieve the highest isentropic efficiency. Under nominal condition, the optimal pressure ratio was 3.23 which was slightly lower than the designed value. Besides, there was a little variation for isentropic efficiency when pressure ratio was larger than that of optimal value. Based on the range analysis, sensitivity of different factors influencing the turbine performance was evaluated. For the turbine output power, the sequence of the factors were listed as: outlet pressure, inlet pressure, rotor speed and inlet temperature. It meaned that turbine power was seriously influenced by outlet pressure and inlet pressure. As for the isentropic efficiency, the rotor speed had the largest impact, followed by the turbine outlet pressure, and the inlet pressure contributed the least.
Zhenkang ZHANG Fanyun ZENG Zhiqi WANG Xiaoxia XIA Ni HE Yanhua HU Jianping ZHANG
. Numerical simulation and range analysis of off-design performance for a radial-inflow turbine[J]. The Chinese Journal of Process Engineering, 2019
, 19(2)
: 246
-253
.
DOI: 10.12034/j.issn.1009-606X.218179
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