Numerical studies on a novel air path design featured with the sequential turbocharging and the low-pressure exhaust gas recirculation for the marine two-stroke engine fulfilling the IMO Tier Ⅲ regulation

Yujun Tang, Jinbao Liu, Min Liu, Jinfeng Feng, Kangyao Deng, Sipeng Zhu, Shuzhan Bai and Guoxiang Li

Energy, 2025, vol. 328, issue C

Abstract: As an effective technology for reducing NOx emissions, exhaust gas recirculation (EGR) has been extensively applied to comply with Tier Ⅲ regulations in marine two-stroke engines. Nevertheless, the high-pressure EGR (HP-EGR) system imposes higher requirements on the design and control of the turbocharging system, particularly when sequential turbocharging is employed to enhance fuel efficiency. In this paper, a novel sequential turbocharging low-pressure EGR (LP-EGR) scenario is proposed. Detailed thermodynamic and numerical analyses of sequential turbocharging combined with LP-EGR and HP-EGR are then conducted and compared with a special focus on scavenging and combustion processes. The results show that optimal fuel economy in multi-mode operations is achieved by sequential turbocharging LP-EGR and HP-EGR employing the equivalent flow area ratio of large and small turbines of 6:4 and 7:3, respectively. Meanwhile, a reduced large turbine throttle valve opening and an increased cylinder bypass rate are required for the NOx emission reduction in LP-EGR and the scavenging air pressure restoration in HP-EGR at part loads, respectively. Compared to sequential turbocharging HP-EGR, the combined fuel consumption of sequential turbocharging LP-EGR featuring a simpler structure is improved by 1∼4 g/kW·h and 1–3 g/kW·h in Tier Ⅱ and Tier Ⅲ operation, respectively.

Keywords: Marine two-stroke engine; Sequential turbocharging; Exhaust gas recirculation; Multi-mode operation; Fuel economy (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:328:y:2025:i:c:s0360544225022169

DOI: 10.1016/j.energy.2025.136574

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