OPTIMIZATION OF INTERCOOLING PARAMETERS FOR CHARGED AIR IN MARINE DIESEL ENGINES
Abstract
Introduction. The efficiency of marine diesel engine power plants is primarily determined by the performance of their turbocharging systems, which must supply sufficient intake air pressure to the cylinders. At high compressor pressure ratios, nearly the entire exhaust-gas turbine power output is consumed by the compressor, leaving limited potential for waste-heat recovery or efficiency improvement. A promising method to reduce compressor power consumption is two-stage compression with intercooling, which increases air density, reduces compression work, and improves overall turbocharger efficiency. Deep intercooling enabled by waste-heatdriven ejector or absorption refrigeration systems is of particular interest. However, the optimal split of the total pressure ratio between the low- and high-pressure stages, as well as the required intercooler outlet temperature, remains to be fully defined for marine applications. Purpose. The purpose of this research is to evaluate the influence of intercooler depth and post-intercooler air temperature on the energy characteristics of a two-stage turbocharging system for marine diesel engines, and to determine the optimal pressure-ratio split (πк1/πк2) that minimizes compressor power consumption and maximizes turbine power availability for onboard use. Results. A thermodynamic analysis was performed for a two-stage compressor with various post-intercooler temperatures (tПО2 = 20–80°C) and ambient inlet temperatures (20 and 40°C). The results were compared with a baseline single-stage turbocharger (total pressure ratio = 4). The ratio of compressor powers (N/NПО) exhibits a distinct optimum at πк1/πк2 ≈ 0.8–1.5, corresponding to a 5–15 % reduction in compressor power compared to the baseline. Deep intercooling to tПО2 = 20–40°C yields the most significant savings (12–15 %), although such temperatures require refrigeration beyond the capability of seawater cooling. Deeper cooling also shifts the optimal value of πк1/πк2 toward lower ratios. Temperature drops of 50–100°C across the heat exchangers were identified, providing design guidance for the steam generator and evaporator of waste-heat-driven refrigeration machines. The resulting increase in available turbine power enables it to be used either for electrical generation or to assist the main engine shaft power during cruising. Conclusions. The study confirms the effectiveness of two-stage turbocharging with intercooling in improving the energy efficiency of marine diesel engines. Optimal intercooling parameters and pressure ratio splits were identified, resulting in significant reductions in compressor work and freeing up turbine power for practical onboard applications. Deep intercooling yields the most considerable benefit but requires refrigeration-based cooling. The findings offer practical guidance for designing advanced turbocharging and heat-recovery refrigeration systems in modern marine propulsion plants.
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References
2. Radchenko R., Kornienko V., Radchenko M., Mikielewicz D., Andreev A., Kalinichenko I. Cooling intake air of marine engine with water-fuel emulsion combustion by ejector chiller. Modern Power Systems and Units (MPSU 2021) : Proceedings of the V International Scientific and Technical Conference, Kraków, Poland, May 19–21, 2021. E3S Web of Conferences. 2021. Vol. 323. Article 00031. 5 p. Published online 10 Nov 2021. DOI: https://doi:10.1051/e3sconf/202132300031.
3. Pyrysunko M., Radchenko A., Tkachenko V., Zubarev A., Andreev A. Marine diesel engine inlet air cooling by ejector chiller on the vessel route line / In: Advances in Design, Simulation and Manufacturing V. DSMIE 2022. Lecture Notes in Mechanical Engineering. Springer, Cham. 2022. С. 259–268. DOI: https://doi:10.1007/978-3-031-06044-1_25.
4. Sun Y., Sun P., Zhang Z., Zhang S., Zhao J., Mei N. Performance Prediction for a Marine Diesel Engine Waste Heat Absorption Refrigeration System. Energies. 2022. 15 (19). 7070. DOI: 10.3390/en15197070.
5. Tian W., Du D., Li J., Han Z., Yu W. Establishment of a two-stage turbocharging system model and analysis on influence rules of key parameters. Energies. 2020. 13 (8). 1953. DOI: https://doi.org/10.3390/en13081953.
6. Grönman A., Sallinen P., Honkatukia J., Backman J., Uusitalo A. Design and experiments of a two-stage intercooled electrically assisted turbocharger. Energy Conversion and Management. 2016. Vol. 111. Pp. 115–124. DOI: https://doi.org/10.1016/j.enconman.2015.12.055.
7. Watson N., Janota M. S. Turbocharging the Internal Combustion Engine. London, Bloomsbury Academic. 1982. DOI: https://doi.org/10.1007/978-1-349-04024-7.
8. Heim K. Existing and Future Demands on the Turbocharging of Modern Large Two-stroke Diesel Engines. Engineering, Environmental Science. 2014. URL: https://www.semanticscholar.org/paper/Existing-and-Future-Demands-on-the-Turbocharging-of-Heim/b31bcb22e187744ff24d153f5c3119c3c8f7004d
9. MAN Energy Solutions. Influence of ambient temperature conditions. Copenhagen SV, Denmark. 2023. URL: https://www.man-es.com/docs/default-source/marine/tools/5510-0074-03.pdf?sfvrsn=fa9e1cee_6
10. Wärtsilä Corporation. Combustion engine power plants: White Paper. Vaasa (Finland), 2021. Wärtsilä Corporation. URL: https://www.wartsila.com/docs/default-source/power-plants-documents/downloads/whitepapers/general/wartsila-bwp-combustion-engine-power-plants.pdf
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