Experimental and Simulation-Based Investigation of Marine Diesel Engine Performance against Static Back Pressure

In this study, experimental and simulation-based investigations of marine diesel engine performance against static back pressure was carried out. The problem addressed how increased exhaust back pressure, caused by restricted flow or emission devices, affects engine power, fuel use, and thermal conditions. A four-stroke pulse turbocharged marine diesel engine was tested at 15 operating points along the propeller curve, from 1000 rpm (5.7% load) to 2600 rpm (100% load), under three back pressure cases: 0 mWC, 0.25 mWC, and 0.5 mWC. A Mean Value Engine Model was then calibrated and validated against these measurements. At 0.5 mWC back pressure and 1000 rpm, turbine inlet temperature rose from 340°C to 370°C (an increase of 30°C or 8.8%), while at 2600 rpm it rose from 585°C to 600°C (15°C or 2.6%), showing low loads are more sensitive. Fuel consumption increased by about 3% at 42% load under 0.5 mWC back pressure. The pulse turbocharging system delivered 68% more air flow at lowest speed compared to a constant pressure system. The air-excess ratio stayed above 1.9 at 1 mWC back pressure, indicating no smoke. Simulation errors remained within 5% to 12% of measured values for temperature and pressure. The findings prove that pulse turbocharging with small valve overlap greatly improves back pressure handling. Engine operators can use the validated model to set safe back pressure limits without risking thermal damage or smoke. This work contributes a reliable simulation tool for engine design and maintenance under restricted exhaust conditions. It is recommended to keep back pressure below 0.5 mWC at low loads to avoid excessive temperature rise, and to use pulse systems where exhaust restrictions are unavoidable.

Propeller curve, Mean value engine model, Pulse turbocharging

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