Laboratory Study on Influence of Air Duct Throttling on Exhaust Gas Composition in Marine Four-stroke Diesel Engine

Presented paper shows results of laboratory tests on the relationship between the throttling of a cross area of an air intake duct and the composition of exhaust gas from the marine engine. The object of research is a laboratory four-stroke diesel engine, worked with a load from 50kW to 250kW at a constant speed. During the laboratory, tests over 50 parameters were measured of the engine with technical condition recognized as a “working properly” and with a simulated the air intake duct throttling. The simulation consisted of inserting the throttling flanges to the air intake duct before compressor, limiting duct cross-sectional area by 20% and 60% respectively. The results of laboratory research confirm that the effect of the air intake duct throttling on the engine thermodynamic parameters is clearly visible only at considerable throttling. In the case of measuring the composition of exhaust gas, both mole fractions and emissions of gaseous components markedly affected even at low throttling. For example, 20% throttling of the cross section of the air intake duct increase the mole fraction of carbon monoxide in exhaust gas almost 44% during working the engine with load equal to 250kW, and only 10% of the temperature after air cooler. Keep in mind that the temperature after air cooler was an engine parameter, which undergoes the greatest change during the simulation of that malfunction. The conclusion is that the results of measurements of the composition of exhaust gas may contain valuable diagnostic information about the technical condition of the air delivery to the engine system.