Methodology for preliminary assessment of the polytropic index of the compression process of a piston compressor based on the average temperature of the cylinder-piston group parts, geometric and operational parameters

Based on the use of integral equations for the equality of the amount of heat removed during the compression process, determined through the polytropic exponent and the Newton-Richmann equation, a method for determining the polytropic exponent of the compression process for constant and variable masses of the working fluid has been developed. A numerical experiment revealed that the average surface temperature of the cylinder-piston group components has the greatest influence on the polytropic exponent of the compression process. The pressure ratio pH/PcS and crankshaft speed have approximately the same effect, significantly less than the effect of . The ratio of the full piston stroke to the diameter is significantly less influential than the above factors, but has a greater influence than the radial clearance in the cylinder-piston group, allowing it to be excluded from consideration. Using a Latin hypercube experimental design and the least-squares method, a second-degree polynomial with correlation terms was constructed. This allows for a fairly accurate determination of the compression process polytropic exponent based on the average wall temperature of the cylinder-piston group, the ratio of discharge to suction pressure, crankshaft speed, and the ratio of full stroke to cylinder diameter. These results can be successfully used in both the design and operation of piston compressors.
EDN: GDWHXC, https://elibrary/gdwhxc

References

[1] Plastinin P.I. Porshnevye kompressory. T. 1. Teoriya i raschet [Piston compressors. Vol. 1. Theory and calculations]. Moscow, KolosS Publ., 2000. 456 p. (In Russ.).

[2] Fotin B.S., Pirumov I.B., Prilutskiy I.K. et al. Porshnevye kompressory [Piston compressors]. Leningrad, Mashinostroenie Publ., 1987. 372 p. (In Russ.).

[3] Shcherba V.E. Rabochie protsessy kompressorov obemnogo deystviya [Working processes of positive displacement compressors]. Moscow, Nauka Publ., 2008. 318 p. (In Russ.).

[4] Shcherba V.E., Bolshtyanskiy A.P., Shalay V.V. et al. Nasos-kompressory [Pump-compressors]. Moscow, Mashinostroenie Publ., 2013. 367 p. (In Russ.).

[5] Shcherba V.E., Pavlyuchenko E.A., Nosov E.Yu. et al. Approximation of the compression process to isothermal in a reciprocating compressor with a liquid piston. Appl. Therm. Eng., 2022, vol. 207, art. 118151, doi: https://doi.org/10.1016/j.applthermaleng.2022.118151

[6] Shcherba V.E. Calculation and analysis of compression and expansion in a piston hybrid power machine with regenerative heat exchange in pump mode. Heat Mass Transfer, 2024, vol. 60, no. 2, pp. 395–404, doi: https://doi.org/10.1007/s00231-023-03435-y

[7] Shcherba V.E., Khodoreva E.V., Bolshtyanskiy A.P. Sposob raboty porshnevogo kompressora s regenerativnym okhlazhdeniem i ustroystvo dlya ego osushchestvleniya [Method of operation of reciprocating compressor with regenerative cooling and device for its implementation]. Patent RU 2801766. Appl. 14.10.2022, publ. 15.08.2023. (In Russ.).

[8] Shcherba V.E., Khait A., Nosov E.Yu. et al. Numerical analysis of unsteady heat transfer in the chamber in the piston hybrid compressor with regenerative heat exchange. Machines, 2023, vol. 11, no. 3, art. 363, doi: https://doi.org/10.3390/machines11030363

[9] Frenkel M.I. Porshnevye kompressory [Piston compressors]. Moscow, Mashinostroenie Publ., 1969. 744 p. (In Russ.).

[10] Plastinin P.I., Shcherba V.E. Rabochie protsessy obemnykh kompressorov so vpryskom zhidkosti [Operating processes of positive displacement compressors with liquid injection]. Moscow, VINITI, 1996. 153 p. (In Russ.).

[11] Jin Y., Guo Y., Zhang S.et al. Study on the dynamic characteristics of the free piston in the ionic liquid compressor for hydrogen refuelling stations by the fluid-structure interaction modelling. Int. J. Hydrog. Energy, 2023, vol. 48, no. 65, pp. 25410–25422, doi: https://doi.org/10.1016/j.ijhydene.2023.03.202

[12] Ye J., Du Z., Xie J. et al. Transient flow performance and heat transfer characteristic in the cylinder of hydraulic driving piston hydrogen compressor during compression stroke. Int. J. Hydrog. Energy, 2023, vol. 48, no. 19, pp. 7072–7084, doi: https://doi.org/10.1016/j.ijhydene.2022.06.319

[13] Guo Y., Wang T., Liu X. et al. Mathematical modelling and design of the ionic liquid compressor for the hydrogen refuelling station. Int. J. Energy Res., 2022, vol. 46, no. 13, pp. 19123–19137, doi: https://doi.org/10.1002/er.8224

[14] Zhou H., Dong P., Zhu S. et al. Design and theoretical analysis of a liquid piston hydrogen compressor. J. Energy Storage, 2021, vol. 41, art. 102861, doi: https://doi.org/10.1016/j.est.2021.102861

[15] Bashta T.M., Rudnev S.S., Nekrasov B.B. et al. Gidravlika, gidromashiny i gidroprivody [Hydraulics, hydraulic machines and hydraulic drives]. Moscow, Mashinostroenie Publ., 1982. 423 p. (In Russ.).

[16] Iman R.L., Helton J.C., Campbell J.E. An approach to sensitivity analysis of computer models: Part I — Introduction, input variable selection and preliminary variable assessment. J. Qual. Technol., 1981, vol. 13, no. 3, pp. 174–183, doi: https://doi.org/10.1080/00224065.1981.11978748

[17] Iman R.L. Latin hypercube sampling. In: Encyclopedia of quantitative risk analysis and assessment. Wiley, 2008, doi: https://doi.org/10.1002/9780470061596.risk0299