Labolatory study on influence of the exhaut 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 exhaust outlet 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 equal 750rpm. During the laboratory tests over 50 parameters were measured of the engine with technical condition recognized as a "working properly" and with simulated the exhaust outlet duct throttling. The simulation consisted of changing the angle of the barrier mounted in the exhaust duct after the turbine, limiting duct cross-sectional area. Results of laboratory research confirm that the best indicator of the throttling of the exhaust gas duct among considered thermodynamic parameters of the engine is pressure of exhaust gas after turbine. Unfortunately mentioned pressure is usually very little and for this reason technically difficult to measure during on-board operation. In the case of measuring the composition of exhaust gas, the throttling of the exhaust gas duct causes visible changes of the oxygen and carbon oxide quantity in the exhaust gas. Other measured gaseous components changed not significant during the throttling of the exhaust gas. 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 exhaust gas duct of the marine engine.