Study on the Simplification Calculation Model of Marine Diesel Engine Exhaust Flow Based on Air-Fuel Ratio

Abstract

Because of the large discharge of marine diesel engines, direct measurement is difficult and complicated. In order to obtain accurate data of marine diesel engine exhaust flow, the carbon balance method is generally used for calculation, but the carbon balance method has iterative operation, adopts wet concentration calculation, and does not consider sulfur oxide components, thus resulting in errors in the calculation results. In this paper, according to the calculation model of air-fuel ratio proposed by S H Chan, the law of conservation of C, H, and O atoms is observed, sulfur oxides in the exhaust are considered, and a new exhaust flow calculation model based on air-fuel ratio is obtained. This calculation model is the first to directly use dry gas concentration in the calculation model of air-fuel ratio. Then, the simplified calculation model is obtained by ignoring CO and simplifying coefficient A∗, the difference between the carbon balance method, ignoring CO, and the simplified model is compared, and then the exhaust flow value and exhaust density are calculated by the test data. The simplified calculation model can also calculate the mass flow rate of carbon dioxide, unburned hydrocarbon, and carbon monoxide. Finally, a software program is developed for the simplified calculation model, which is convenient for quick calculation and quick acquisition of exhaust flow data, thus laying a solid foundation for the application of the simplified calculation model in real ships.