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Abstract

Owing to increasingly stringent emission regulations imposed by the International Maritime Organization and rising fuel prices, the demand for enhanced energy efficiency and emission control in marine power systems is increasing. This study presents a case study in which the performance of an aging auxiliary generator is restored by modifying the turbocharger nozzle ring. The vessel, a 12-year-old crude-oil tanker, experienced repeated operational issues with its No. 3 generator. This included elevated exhaust gas temperatures, reduced intake air pressure, and frequent turbocharger surges. To address these challenges, the nozzle-ring blade angle was reduced by approximately 2° using spare components, while maintaining the original flow area. Key performance indicators, including exhaust gas temperature, turbocharger rotational speed, intake air pressure, and output stability, were measured under consistent load conditions before and after the modification. The results showed that the exhaust gas temperature dropped to approximately 70 °C, while the turbocharger rotational speed increased by approximately 2,100 rpm, and intake pressure improved from 1.8–2.2 bar. No surging or abnormal vibrations were observed after modification. These findings demonstrate that minor geometric adjustments to the nozzle ring can effectively alleviate performance degradation without the need for full component replacement. Redesigning the nozzle geometry to match combustion flow changes provides a cost-effective and technically feasible maintenance strategy that can prevent power failures and improve energy efficiency. Moreover, this ensures compliance with environmental regulations. This approach has potential applicability to different ship types and engine configurations.

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