In this study a numerical model of a Wankel expander was developed in order to evaluate the perormances of this device. The model accounts for a variety mechanical, thermal and leakage losses, and can produce a good estimate of the main performance indicators of the exoander, such as Power, torque and indicated cycle.
Also the mechanical loads acting on the secondary components, such as the breathing system, are calculated.
Many geometrical and thermodynamic parameters can be varied in order to investigate different solutions for the design of new components. Among the possible modifications, a smaller intake valve should be consideredin order to lower the admission grade, thus obtaining higher efficiencies and small power reductions.
Leakage flows heavily affect the expander behaviour; leakages due to breathing system ducts can deeply modify the shape of the indicated cycle.
The dynamic analysis of the apex seals reveals that in some angular position they may lose the contact with the stator; the effects of these detachments on the friction and leakage losses are negligible, but thei frequency of the ontact losses may be related to the apex seal wear rate.
Inspite of the rotary valve timing issues, the Wankel expander woperated properly, and can be an interesting solution for small-scale energy generation plants.
References
[1] http://www.tomorrowstechnician.com.
[2] Giacosa, D., 1975. Motori endotermici, 12 ed. Hoepli.
[3] Quaggiotti, V., 1972. Il motore Wankel. Patron.
[4] Quoilin, S., v. D. Broek, M. V. D., Declaye, S., Dewallef, P., and Lemort, V., 2013.
“Techno-economic survey of organic rankine cycle (orc) systems”. Renewable and Sustainable Energy Reviews, 22, pp. 168–186.
[5] Angelino, G., Gaia, M., and Macchi, E., 1984. “A review of italian activity in the field of organic rankine cycles”. In Proceedings of the International VDI Seminar, V. Verlag, ed., Vol. 539, pp. 465–482.
[6] Schuster, A., Karellas, S., Kakaras, E., and Spliethoff, H., 2009. “Energetic and economic investigation of organic rankine cycle applications”. Applied Thermal Engineering, 29(8-9), pp. 1809–1817.
[7] Srinivasan, K. K., Mago, P. J., and Krishnan, S. R., 2010. “Analysis of exhaust waste heat recovery from a dual fuel low temperature combustion engine using an organic rankine cycle”. Energy, 35(6), pp. 2387–2399.
[8] Tchanche, B. F., Lambrinos, G., Frangoudakis, A., and Papadakis, G., 2011.
“Low-grade heat conversion into power using organic rankine cycles - a review of various applications”. Renewable and Sustainable Energy Reviews, 15(8), pp. 3963–3979.
[9] Branchini, L., De Pascale, A., and Peretto, A., 2013. “Systematic comparison of orc configurations by means of comprehensive performance indexes”. Applied Thermal Engineering, 61(2), pp. 129–140.
[10] Clemente, S., 2013. “Small scale cogeneration systems based on organic rankine cycle technology”. PhD thesis, Universit`a degli Studi di Udine.
[11] Lecompte, S., Lemmens, S., Huisseune, H., van den Broek, M., and De Paepe, M., 2015. “Multi-objective thermo-economic optimization strategy for orcs applied to subcritical and transcritical cycles for waste heat recovery”. Energies, 8(4), pp. 2714–2741.
[12] Colonna, P., Casati, E., Trapp, C., Mathijssen, T., Larjola, J., Turunen-Saaresti, T., and Uusitalo, A., 2015. “Organic rankine cycle power systems: From the concept to current technology, applications, and an outlook to the future”. J.
Eng. Gas Turbines Power, 137(10), p. 100801.
[13] Weiß, A., 2015. “Volumetric expander versus turbine - which is the better choice for small orc plants?”. In Proceedings of the 3rd International Seminar on ORC Power Systems, no. 22.
[14] Vivian, J., 2014. “Thermodynamic and economic criteria to select working fluid and configuration of organic rankine cycles for low to medium temperature heat sources”. Master’s thesis, Universit`a degli Studi di Padova.
[15] Badr, O., O’Callaghan, P., Hussein, M., and Probert, S., 1984. “Multi-vane expanders as prime movers for low-grade energy organic rankine-cycle engines”.
Applied Energy, 16(2), pp. 129–146.
[16] Badr, O., Naik, S., O’Callaghan, P., and Probert, S., 1991. “Wankel engines as steam expanders: Design considerations”. Applied Energy, 40(3), pp. 157–170.
[17] Chen, Y., Halm, N. P., Groll, E. A., and Braun, J. E., 2000. “A comprehensive model of scroll compressors part I: Compression process modeling”. In Proceedings of the International Compressor Engineering Conference, no. 1455.
[18] Chen, Y., Halm, N. P., Groll, E. A., and Braun, J. E., 2000. “A comprehensive model of scroll compressors part II: Overall scroll compressor modeling”. In Proceedings of the International Compressor Engineering Conference, no. 1456.
[19] Quoilin, S., Declaye, S., Legros, A., Guillaume, L., and Lemort, V., 2012.
“Working fluid selection and operating maps for organic rankine cycle expansion machines”. In Proceedings of the International Compressor Engineering Conference, no. 1546.
[20] Qiu, G., Liu, H., and Riffat, S., 2011. “Expanders for micro-chp systems with organic rankine cycle”. Applied Thermal Engineering, 31(16), pp. 3301–3307.
[21] Lemort, V., Guillaume, L., Legros, A., Declaye, S., and Quoilin, S., 2013.
“Comparison of piston, screw and scroll expanders for small-scale rankine cycle systems”. In Proceedings of the 3rd International Conference on Microgeneration and Related Technologies.
[22] Badami, M., and Mura, M., 2009. “Preliminary design and controlling strategies of a small-scale wood waste rankine cycle (RC) with a reciprocating steam engine (SE)”. Energy, 34(9), pp. 1315 – 1324.
[23] Cipollone, R., Bianchi, G., and Contaldi, G., 2012. “Sliding vane rotary compressor energy optimization”. In Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Vol. 6.
[24] Krishna, A., Bradshaw, C., and Groll, E. A., 2014. “Analysis of a rotating spool expander for organic rankine cycles in heat recovery applications”. In Proceedings of the International Compressor Engineering Conference, no. 2185.
[25] Bao, J., and Zhao, L., 2013. “A review of working fluid and expander selections for organic rankine cycle”. Renewable and Sustainable Energy Reviews, 24, pp. 325–342.
[26] Silvestri, G. J., Meunier, R., Bowlus, D. A., and Brown, G. A., 1978. Rotary expander engine development program. Tecnical Memorandum 2012, NUSC.
[27] Paci, R., 2011. “Allestimento di un apparato sperimentale per prove su un motore rotativo a vapore per microcogenerazione da energie rinnovabili”. Bachelor’s thesis, Universit`a degli Studi di Pisa.
[28] Antonelli, M., Baccioli, A., Francesconi, M., and Martorano, L., 2015. “Numerical and experimental analysis of the intake and exhaust valves of a rotary expansion device for micro generation”. Energy Procedia, 81, pp. 461–471.
[29] Antonelli, M., Baccioli, A., Francesconi, M., Desideri, U., and Martorano, L., 2015. “Electrical production of a small size concentrated solar power plant with compound parabolic collectors”. Renewable Energy, 83, pp. 1110–1118.
[30] Milianti, L., 2010. “Progetto e realizzazione di un espansore rotativo per microcogenerazione”. Master’s thesis, Universit`a degli Studi di Pisa.
[31] Manfrida, G., and Padula, S., 2010. “Model of a steam wankel expander”. In Proceedings of the 3rd International Conference on Efficiency, Cost, Optimization, Simulation, and Environmental Impact of Energy Systems, Vol. 3, pp. 153–160.
[32] The MathWorks Inc., 2010. Matlab, Release 2010a. Natick, Massachusetts.
[33] Lemmon, E., Huber, M., and McLinden, M., 2013. Refprop, version 9.1.
National Institute of Standards and Technology. Gaithersburg, Maryland.
[34] Incropera, F. P., DeWitt, D. P., Bergman, T. L., and Lavine, A. S., 2011.
Fundamentals of heat and mass transfer, 7 ed. John Wiley and Sons.
[35] Bartrand, T. A., and Willis, E. A., 1993. Rotary engine performance computer program (rcemap and rcemappc). Contractor Report 191192, NASA.
[36] Danieli, G. A., 1976. “A performance model of a wankel engine, including the effects of burning rates, heat transfer, leakage and quenching compared with measured pressure time histories”. PhD thesis, Massachusetts Institute of Technology.
[37] Norman, T., 1983. “A performance model of a spark ignition wankel engine:
including the effects of crevice volumes, gas leakage and heat transfer”. Master’s thesis, Massachusetts Institute of Technology.
[38] Roberts, J. M., 1985. “Heat release estimation and prediction of wankel stratified-charge combustion engine”. Master’s thesis, Massachusetts Institute of Technology.
[39] Danieli, G. A., Ferguson, C. R., Heywood, J. B., and Keck, J. C., 1975. “Analysis of performance losses in a wankel engine”. In Proceedings of the IME Conference on Combustion in Engines, no. C98-75.
[40] Woschni, G., 1967. A universally applicable equation for the instantaneous heat transfer coefficient in the internal combustion engine. Technical Paper 670931, SAE.
[41] Robertson, G., 1977. “Experimental and analytical sudy of a steam vane expander”. PhD thesis, Pennsylvania State University.
[42] Atesmen, K. M., 1975. “Heat transfer in rotary combustion engines”. J. Heat Transfer, 97(2), pp. 288–293.
[43] Jang, K., and Jeong, S., 2006. “Experimental investigation on convective heat transfer mechanism in a scroll compressor”. International Journal of Refrigeration, 29(5), pp. 744–753.
[44] Mathison, M. M., Braun, J. E., and Groll, E. A., 2008. “Modeling and testing of a two-stage rotary compressor”. In Proceedings of the International Compressor Engineering Conference, no. 1892.
[45] Knoll, J., Vilmann, C. R., Schock, H. J., and Stumpf, R. P., 1984. A dynamic analysis of rotary combustion engine seals. Technical Memorandum TM-83536, NASA.
[46] Matsuura, K., Terasaki, K., and Watanabe, I., 1978. “The behavior of a rotary engine apex seal against the trochoidal surface”. Bulletin of JSME, 21(161), pp. 1642–1651.
[47] Matsuura, K., Terasaki, K., and Watanabe, I., 1976. “The relative behavior of a rotary engine apex seal to the walls of a slot”. Bulletin of JSME, 19(137), pp. 1367–1375.
[48] Matsuura, K., and Terasaki, K., 1991. “Measurement and theoretical analysis of the under-seal pressure of rotary engine apex seals.”. Transactions of the Japan Society of Mechanical Engineers Series B, 57(540), pp. 2845–2853.
[49] Warren Rose, S., and Yang, D. C., 2014. “Wide and multiple apex seals for the rotary engine”. Mechanism and Machine Theory, 74, pp. 202–215.
[50] Beard, J. E., and Pennock, G. R., 2000. “Acceleration of the apex seals in a wankel rotary compressor including manufacturing process variation in location of the seals”. In Proceedings of the International Compressor Engineering Conference, no. 1457.
[51] Bianchi, G., and Cipollone, R., 2015. “Friction power modeling and measurements in sliding vane rotary compressors”. Applied Thermal Engineering, 84, pp. 276–285.
[52] Bradshaw, C., 2013. “Spool compressor tip seal design considerations”. In Proceedings of the 8th International Conference on Compressors and their Systems, pp. 341–351.
[53] Gates Mectrol, Inc., 2006. Timing Belt Theory. http://www.gatesmectrol.com.
[54] National instruments, 2012. LabVIEW, v. 12.0. Austin, Texas.
[55] Lorenzoni, F., 2012. “Realizzazione di un programma di acquisizione del ciclo indicato per espansori rotativi di vapore”. Master’s thesis, Universit`a degli Studi di Pisa.