Utilizing the scavenge air cooling in improving the performance of marine diesel engine waste heat recovery systems

• Published in: Energy (Oxford) Vol. 142; pp. 264 - 276
• Main Authors: Mito, Mohamed T., Teamah, Mohamed A., El-Maghlany, Wael M., Shehata, Ali I.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-01-2018; Elsevier BV
• Subjects: Air cooling; Carbon dioxide; Carbon dioxide emissions; Cooling; Diesel; Diesel engines; Economic conditions; Emission reduction; Emissions control; Energy efficiency; Energy management; Exergy; Exhaust gases; Heat; Heat recovery; Heat recovery systems; Marine diesel engine; Marine engines; Marine propulsion; Parameter identification; Power efficiency; Rankine cycle; Ship power plant; Steam electric power generation; Steam power; Thermodynamics; Waste heat; Waste heat recovery; WHR; WHR; Emission reduction; Marine diesel engine; Ship power plant; Energy management; Rankine cycle
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2017.10.039

This paper aims at improving power generation efficiency of marine diesel engine waste heat recovery systems. It presents a novel technique of integrating the heat rejected in the scavenge air cooling process and the exhaust gas in operating a single and dual pressure steam power generation cycles. Moreover, a thermodynamic analysis of proposed systems was performed to identify the optimum operating parameters for achieving an overall efficiency improvement. The analysis considered the exergy destruction in each component and the energy/exergy efficiencies. A performance analysis was conducted to assess applicability and power output at off design conditions. An evaluation of achieved improvements by suggested designs was presented from both an economical and environmental standpoint. In conclusion, results show that, the recommended cycle increased overall efficiency improvement from 2.8% for the conventional system to 5.1%, with an additional power output of 1210 kW, representing 9.7% of the engine's power. Also, exergy efficiency increased significantly by 6.6% when using the presented system. Furthermore, the waste heat recovery system attained a reduction in fuel consumption of 1538 Ton/year, reducing carbon dioxide emission by 4790 Ton/year.
[Display omitted]
•Different models for waste heat recovery from marine diesel engine are introduced.•The scavenge air is introduced as a heating fluid due to its high temperature.•The scavenge air has high waste heat utilization in compared to the exhaust gas.•The efficiency is enhanced by 5.1% with fuel consumption reduction of 9.7%.