Research on Calibration, Economy and PM Emissions of a Marine LNG–Diesel Dual-Fuel Engine

Abstract

In order to convert the marine diesel engine into an LNG (Liquefied Natural Gas)–diesel dual-fuel engine and ensure its power and emission characteristics, a new calibration method is proposed, and the fuel substitution ratio, economy and detailed particulate matter emission law after the engine is calibrated using this method are studied. The calibration method takes the peak pressure in the cylinder and the exhaust temperature as constraints and uses the diesel mass substitution ratio as the objective function. Based on the proposed calibration method, the engine is calibrated by setting up a calibration test bench. The test obtains the distribution characteristics of the diesel mass substitution ratio under various operating conditions of the engine. The results show that the proposed calibration method allows the dual-fuel engine to achieve the same power performance as the original engine. At the same time, the diesel mass substitution ratio of the calibrated dual-fuel engine can reach up to 95% (800 r/min @ 800 Nm, 900 r/min @ 800 Nm and 1000 r/min @ 800 Nm). The substitution ratio in the range of 900 r/min~1200 r/min at a common speed is more than 70%, and the average diesel mass substitution ratio under all working conditions is 71%. Furthermore, the study of engine economy shows that the BSFC (brake specific fuel consumption) of the dual-fuel mode is higher than that of the pure diesel mode when working under external characteristics, propulsion characteristics and different loads at 1000 r/min speed. This is more obvious when the load is small, and the two are closer when the load is medium or high; however, the fuel cost when the engine works in dual-fuel mode is much lower than that of the pure diesel mode. In the usual speed and load range, the particulate matter emission test shows that its particle size distribution, total number of particles and particle volume are significantly reduced in the dual-fuel mode.

Keywords

• calibration
• LNG–diesel dual fuel
• substitution ratio
• particulate matter emission