有机工质向心透平变工况特性的数值模拟与极差分析
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摘要
以R245fa为工质设计向心透平,采用CFD方法对向心透平性能进行全流域三维模拟研究,考察了入口温度、转子转速和膨胀比(进出口压力比)对向心透平工况特性的影响,对主要影响因素进行极差分析。结果表明,向心透平工作转速为设计转速的80%～100%时,输出功率和等熵效率波动较小,工作转速高于设计值时透平性能迅速下降。随入口温度升高,透平输出功率与等熵效率增大;随膨胀比增大,透平输出功率线性增加。透平存在最佳膨胀比使等熵效率最大,且实际运行压比大于最佳膨胀比时,透平等熵效率变化较小。出口压力对向心透平输出功率影响最大,温度的影响最小;转子转速对等熵效率影响最大,入口压力的影响最小。
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 R245 fa 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 R245 fa. In this work, a radial-inflow turbine using R245 fa 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 fluiddynamics) 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.
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 R245 fa 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 R245 fa. In this work, a radial-inflow turbine using R245 fa 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 fluiddynamics) 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.
引文
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[7]马新灵,孟祥睿,魏新利,等.有机朗肯循环低品位热能发电系统向心透平的设计与性能研究[J].中国电机工程学报,2014,34(14):2289-2296.Ma X L,Meng X R,Wei X L,et al.Design and performance study of radial inflow turbine used on organic Rankine cycle waste heat power generation system[J].Proceedings of the CSEE,2014,34(14):2289-2296.
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[9]Shao L,Zhu J,Meng X G,et al.Experimental study of an organic Rankine cycle system with radial inflow turbine and R123[J].Applied Thermal Engineering,2017,124(6):940-947.
[10]李艳,顾春伟.高膨胀比有机工质向心透平气动优化研究[J].工程热物理学报,2013,34(7):1239-1242.LI Y,Gu C W.Aerodynamic optimization study for a radial-inflow organic turbine with high expansion ratio[J].Journal of Engineering Thermophysics,2013,34(7):1239-1242.
[11]邓清华,牛久芳,丰镇平.叶轮顶部间隙对向心透平总体性能影响的研究[J].工程热物理学报,2006,27(3):408-410.Deng Q H,Niu J F,Feng Z P.Effects of rotor blade tip clearance on total aerodynamic performance in a radial inflow turbine[J].Journal of Engineering Thermophysics,2006,27(3):408-410.
[12]Sauret E,Gu Y.Three-dimensional off-design numerical analysis of an organic Rankine cycle radial-inflow turbine[J].Applied Energy,2014,135(15):202-211.
[13]Zheng Y,Hu D S,Cao Y,et al.Preliminary design and off-design performance analysis of an organic Rankine cycle radial-inflow turbine based on mathematic method and CFD method[J].Applied Thermal Engineering,2017,112(5):25-37.
[14]Kim D Y,Kim Y T.Preliminary design and performance analysis of a radial inflow turbine for ocean thermal energy conversion[J].Renewable Energy,2017,106(7):255-263.
[15]Jubori A M A,Al-Dadah R,Mahmoud S,et al.Performance enhancement of a small-scale organic Rankine cycle radial-inflow turbine through multi-objective optimization algorithm[J].Energy,2017,131(5):297-311.
[16]Nithesh K G,Chatterjee D,Cheol O H,et al.Design and performance analysis of radial-inflow turbo expander for OTECapplication[J].Renewable Energy,2016,85(1):834-843.
[17]Sadeghi M,Nemati A,Ghavimi A,et al.Thermodynamic analysis and multi-objective optimization of various ORC(organic Rankine cycle)configurations using zeotropic mixtures[J].Energy,2016,109(8):791-802.
[18]Mueller L,Alsalihi Z,Verstraete T.Multidisciplinary optimization of a turbocharger radial turbine[J].Journal of Turbomachinery,2013,135(4):1965-1976.
[19]Jubori A A,Daabo A,Raya K,et al.Development of micro-scale axial and radial turbines for low-temperature heat source driven organic Rankine cycle[J].Energy Conversion and Management,2016,130:141-155.
[20]Guillaume L,Legros A,Desideri A,et al.Performance of a radial-inflow turbine integrated in an ORC system and designed for a WHR on truck application:an experimental comparison between R245fa and R1233zd[J].Applied Energy,2017,186:408-422.
[2]Badr O,Naik S,Callaghan P O,et al.Expansion machine for a low power output steam Rankine-cycle engine[J].Applied Energy,1991,39(2):93-116.
[3]李燕生,陆桂林.向心透平与离心压气机[M].北京:机械工业出版社,1987:57.Li Y S,Lu G L.Radial inflow turbine and centrifugal compressor[M].Beijing:China Machine Press,1987:57.
[4]王智,吴伟铭,韩中合.基于向心透平热力设计优化的有机朗肯循环工质选择[J].太阳能学报,2015,36(9):2225-2230.Wang Z,Wu W M,Han Z H.Selection of working fluids for organic Rankine cycle based on optimal thermal design for radial turbine[J].Acta Energiae Solaris Sinica,2015,36(9):2225-2230.
[5]Rahbar K,Mahmoud S,Al-Dadah R K,et al.Modelling and optimization of organic Rankine cycle based on a small-scale radial inflow turbine[J].Energy Conversion and Management,2015,91(2):186-198.
[6]Sauret E,Rowlands A S.Candidate radial-inflow turbines and high-density working fluids for geothermal power systems[J].Energy,2011,36(7):4460-4467.
[7]马新灵,孟祥睿,魏新利,等.有机朗肯循环低品位热能发电系统向心透平的设计与性能研究[J].中国电机工程学报,2014,34(14):2289-2296.Ma X L,Meng X R,Wei X L,et al.Design and performance study of radial inflow turbine used on organic Rankine cycle waste heat power generation system[J].Proceedings of the CSEE,2014,34(14):2289-2296.
[8]Kang S H.Design and experimental study of ORC(organic Rankine cycle)and radial turbine using R245fa working fluid[J].Energy,2012,41(1):514-524.
[9]Shao L,Zhu J,Meng X G,et al.Experimental study of an organic Rankine cycle system with radial inflow turbine and R123[J].Applied Thermal Engineering,2017,124(6):940-947.
[10]李艳,顾春伟.高膨胀比有机工质向心透平气动优化研究[J].工程热物理学报,2013,34(7):1239-1242.LI Y,Gu C W.Aerodynamic optimization study for a radial-inflow organic turbine with high expansion ratio[J].Journal of Engineering Thermophysics,2013,34(7):1239-1242.
[11]邓清华,牛久芳,丰镇平.叶轮顶部间隙对向心透平总体性能影响的研究[J].工程热物理学报,2006,27(3):408-410.Deng Q H,Niu J F,Feng Z P.Effects of rotor blade tip clearance on total aerodynamic performance in a radial inflow turbine[J].Journal of Engineering Thermophysics,2006,27(3):408-410.
[12]Sauret E,Gu Y.Three-dimensional off-design numerical analysis of an organic Rankine cycle radial-inflow turbine[J].Applied Energy,2014,135(15):202-211.
[13]Zheng Y,Hu D S,Cao Y,et al.Preliminary design and off-design performance analysis of an organic Rankine cycle radial-inflow turbine based on mathematic method and CFD method[J].Applied Thermal Engineering,2017,112(5):25-37.
[14]Kim D Y,Kim Y T.Preliminary design and performance analysis of a radial inflow turbine for ocean thermal energy conversion[J].Renewable Energy,2017,106(7):255-263.
[15]Jubori A M A,Al-Dadah R,Mahmoud S,et al.Performance enhancement of a small-scale organic Rankine cycle radial-inflow turbine through multi-objective optimization algorithm[J].Energy,2017,131(5):297-311.
[16]Nithesh K G,Chatterjee D,Cheol O H,et al.Design and performance analysis of radial-inflow turbo expander for OTECapplication[J].Renewable Energy,2016,85(1):834-843.
[17]Sadeghi M,Nemati A,Ghavimi A,et al.Thermodynamic analysis and multi-objective optimization of various ORC(organic Rankine cycle)configurations using zeotropic mixtures[J].Energy,2016,109(8):791-802.
[18]Mueller L,Alsalihi Z,Verstraete T.Multidisciplinary optimization of a turbocharger radial turbine[J].Journal of Turbomachinery,2013,135(4):1965-1976.
[19]Jubori A A,Daabo A,Raya K,et al.Development of micro-scale axial and radial turbines for low-temperature heat source driven organic Rankine cycle[J].Energy Conversion and Management,2016,130:141-155.
[20]Guillaume L,Legros A,Desideri A,et al.Performance of a radial-inflow turbine integrated in an ORC system and designed for a WHR on truck application:an experimental comparison between R245fa and R1233zd[J].Applied Energy,2017,186:408-422.