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EN
The manuscript presents the model of the air flow through the air inlet duct of the marine 4-stroke engine. Presented model are computational fluid dynamic modelbased on dimensions and the construction of the real air intake duct. The measurement parameters from real object are used to the model validation. Mentioned measurements of the air flow are conducted by Venturi orifice for different loads of the engine and the different flow characteristics of the air intake duct. The results from computational fluid dynamic model are useful to calibration the orifice by setting the orifice module. The orifice module changes up to 6% of the mean values for all considered loads of the engine and throttling’s of the air intake duct. The approximation the flow characteristic for other throttling’s of the air intake duct was conducted also. The obtained approximation is useful tool to calculate the air flow to the engine for the different throttling’s than measured. Linear dependence between the air mass flow and the power of the engine at the constant engine speed was observed. The throttling of the cross section area of the air intake duct causes changing the characteristic in accordance to a second order polynomial. The maximum error of obtained approximation compared to measured values not excided 4% and mean error for all measured loads and throttling’s not exceeded 0.12%.
EN
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.
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