Numerical Investigation of the Effects of Number of Rotor and Nozzle Blades on the Performance of an ORC Turbo-Expander
[1]
Ibrahim Gad-el-Hak, Department of Mechanical Engineering, Ain Shams University, Cairo, Egypt.
[2]
Ahmed Eldein Hussin, Department of Mechanical Engineering, Ain Shams University, Cairo, Egypt.
[3]
Ashraf Moustafa Hamed, Department of Mechanical Engineering, Ain Shams University, Cairo, Egypt.
[4]
Nabil Abdel Aziz Mahmoud, Department of Mechanical Engineering, Ain Shams University, Cairo, Egypt.
Organic Rankine cycle (ORC) has the advantage over many other thermodynamic cycles by the fact that it can operate on low grade energy. Therefore, it is called low-temperature ORC. Although, the temperature difference between boiling temperature and condensation temperature is relatively low, practical problems in the turbine may occur in some cases because of high pressure ratio along expansion process. A high-pressure ratio leads to high volume ratio which increases the fluid velocity at rotor exit. In addition, the working fluids of such cycle have relatively low sonic speed. Consequently, choked flow may be occurred at the rotor outlet which affected the isentropic efficiency of the turbine. The present paper provides a numerical investigation on the effect of number of rotor and nozzle blades on the performance of a turbo-expander which is implemented in low-temperature ORC applications. A wide literature exists on selecting the number of rotor and nozzle blades based on the correlation that used in preliminary design of the gas turbine. Optimal selection of the number of both rotor and nozzle blades can be figured out based on performing CFD simulations for a turbo-expander with different number of both rotor and nozzle blades. A radial turbo-expander, which was originally used in the Sundstrand Power Systems T-100 Multipurpose Small Power Unit, is used as baseline geometry to perform this analysis. The numerical study carried out by performing 3D Reynolds-Averaged Navier–Stokes (RANS) simulations on the turbo-expander by using the commercial package ANSYS CFX (version 16.0) including different working fluids R245fa, R236fa, R123, R134a and R1234yf. Peng–Robinson equation of state is adopted in the finite-volume solver ANSYS CFX to determine the real-gas properties. The obtained results showed that, the number of rotor blades that suggested by the correlation used in design of a gas turbine was higher than needs in ORC turbo-expander.
Radial Inflow Turbine, Organic Rankine Cycles (ORC), Number of Rotor Blades, Number of Nozzle Blades, Computational Fluid Dynamics (CFD)
[1]
Quoilin, S.; Van Den Broek, M.; Declaye, S.; Dewallef, P.; Lemort, V. Techno-economic survey of Organic Rankine Cycle (ORC) systems. Renew. Sustain. Energy Rev. 2013, 22, 168–186.
[2]
Qiu, G.; Liu, H.; Riffat, S. Expanders for micro-CHP systems with organic Rankine cycle. Appl. Therm. Eng. 2011, 31, 3301–3307.
[3]
Bao, J.; Zhao, L. A review of working fluid and expander selections for organic Rankine cycle. Renew. Sustain. Energy Rev. 2013, 24, 325–342.
[4]
Quoilin, S.; Declaye, S.; Legros, A.; Guillaume, L.; Lemort, V. Working fluid selection and operating maps for Organic Rankine Cycle expansion machines. In Proceedings of the 21st International Compressor Conference, Purdue, West Lafayette, IN, USA, 16–19 July 2012; p. 10.
[5]
Bajaj, S. S.; Patil, H. B.; Kudal, G. B.; Shisode, S. P. Organic Rankine Cycle and Its Working Fluid Selection—A Review. Int. J. Curr. Eng. Technol. 2016, 4, 20–26.
[6]
Tchanche, B. F.; Lambrinos, G.; Frangoudakis, A.; Papadakis, G. Low-grade heat conversion into power using organic Rankine cycles—A review of various applications. Renew. Sustain. Energy Rev. 2011, 15, 3963–3979.
[7]
Vélez, F.; Segovia, J. J.; Martín, M. C.; Antolín, G.; Chejne, F.; Quijano, A. A technical, economical and market review of organic Rankine cycles for the conversion of low-grade heat for power generation. Renew. Sustain. Energy Rev. 2012, 16, 4175–4189.
[8]
Schuster, A.; Karellas, S.; Kakaras, E.; Spliethoff, H. Energetic and economic investigation of Organic Rankine Cycle applications. Appl. Therm. Eng. 2009, 29, 1809–1817.
[9]
Gao, H.; Liu, C.; He, C.; Xu, X.; Wu, S.; Li, Y. Performance analysis and working fluid selection of a supercritical organic Rankine cycle for low grade waste heat recovery. Energies 2012, 5, 3233–3247.
[10]
Jumel, S.; Feidt, M.; Kheiri, A. Working fluid selection and performance comparison of subcritical and supercritical organic Rankine cycle (ORC) for low-temperature waste heat recovery. In Proceedings of the ECEEE Summer Study on Energy Efficiency in Industry, Arnhem, The Netherlands, 11–14 September 2012; pp. 559–569.
[11]
Sauret, E.; Rowlands, A. S. Candidate radial-inflow turbines and high-density working fluids for geothermal power systems. Energy 2011, 36, 4460–4467.
[12]
Fiaschi, D.; Manfrida, G.; Maraschiello, F. Design and performance predication of radial ORC turboexpanders. Appl. Energy 2015, 138, 517–532.
[13]
Fiaschi, D.; Manfrida, G.; Maraschiello, F. Thermo-fluid dynamics preliminary design of turbo-expanders for ORC cycles. Appl. Energy 2012, 97, 601–608.
[14]
Lopez Sanz, E. Study on a Radial Turbine Stage with Inlet Guide Vanes for an ORC Process with an Electrical Output of 3.5 kW. Master’s Thesis, Universität Stuttgart, Stuttgart, Germany, 2013.
[15]
Gad-el-Hak, I.; Hussin, A. E.; Hamed, A. M.; Mahmoud, N. A. 3D Numerical Modeling of Zeotropic Mixtures and Pure Working Fluids in an ORC Turbo-Expander. Int. J. Turbomach. Propuls. Power 2017, 2, 2.
[16]
Hung, T. C. Waste heat recovery of organic Rankine cycle using dry fluids. Energy Convers. Manag. 2001, 42, 539–553.
[17]
Genetron Refrigerants Modeling Software; Honeywell: New Jersey, United State 2012.
[18]
Whitfield A, Baines NC. Design of radial turbomachines. New York: Longman; 1990.
[19]
Glassman, A. J. (1976). Computer program for design and analysis of radial inflow turbines. NASA TN 8164.
[20]
Jamieson, A. W. H. (1955). The radial turbine. In: H. Roxbee-Cox (Ed.), Gas turbine principles and practice. London: Newnes.
[21]
A. Whitfield, "The Preliminary Design of Radial Inflow Turbines," Journal of Turbomachinery, vol. 112, no. 1, 1990.
[22]
Dixon, S. L.; Hall, C. Fluid Mechanics and Thermodynamics of Turbomachinery; Butterworth-Heinemann: Oxford, UK, 2013.
[23]
Rohlik, H. E. (1975). Radial-inflow turbines. In: A. J. Glassman (Ed.), Turbine design and applications. NASA SP 290, Vol. 3.
[24]
Rodgers, C.; Geiser, R. Performance of a high-efficiency radial/axial turbine. Journal of Turbomachinery, Transactions of the American Society of Mechanical Engineers 1987, 109.
[25]
Jones, A. C. Design and test of a small, high pressure ratio radial turbine. In Proceedings of the ASME International Gas Turbine and Aeroengine Congress and Exposition, The Hague, The Netherlands, 13–16 June 1994.
[26]
Sauret, E. Open design of high pressure ratio radial-inflow turbine for academic validation. In Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Houston, TX, USA, 9–15 November 2012; pp. 3183–3197.
[27]
Peng, D. Y.; Robinson, D. B. A new two-constant equation of state. Ind. Eng. Chem. Fundam. 1976, 15, 59–64.
[28]
Sauret, E.; Gu, Y. Three-dimensional off-design numerical analysis of an organic Rankine cycle radial-inflow turbine. Appl. Energy 2014, 135, 202–211.
