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2 Kowalski J.

2 2015

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Model procesu spalania w 4-suwowym silniku okrętowym

Kowalski J.

Mechanik

2015

R. 88, nr 10CD

49--58

W pracy przedstawiono model procesu spalania w 4-suwowym silniku okrętowym o zapłonie samoczynnym dla wyznaczenia zawartości tlenków azotu (NOx) w gazach wylotowych. Prezentowany model jest iteracyjnym modelem 3-wymiarowym, zbudowanym na ruchomej, przestrzennej siatce przestrzeni cylindrowej. Model obejmuje matematyczny opis wtrysku, rozpylania, parowania i zapłonu paliwa oraz rozprzestrzeniania się płomienia w przestrzeni cylindrowej. W celu wyznaczenia udziałów NOx dokonano również opisu wymiany ciepła z elementami konstrukcyjnymi cylindra. Dane wejściowe oraz warunki brzegowe modelu pochodzą z bezpośrednich pomiarów. Model został pozytywnie walidowany na podstawie charakterystyk ciśnienia spalania oraz udziałów NOx i tlenu w gazach wylotowych dla całego rozpatrywanego zakresu obciążeń silnika.

Manuscript presents a model of the combustion process in marine four-stroke diesel engine to determine the nitric oxides fraction (NOx) in the exhaust gas. This is iterative, 3-dimensional model, built on geometric mesh of the engine cylinder chamber. The model includes mathematical description of fuel injection, spray, evaporation and auto ignition and flame propagation in the cylinder. In order to determine the NOx fraction, the heat exchange phenomena description between structural elements of the cylinder has been done. The input data and boundary conditions are collected from the direct measurements. The model has been successfully validated based on the characteristics of the in-cylinder combustion pressure and NOx and oxygen fractions in the exhaust gas for all considered loads of the engine.

The analysis of influence of fuel spray angle on NOx fraction in the exhaust gas from marine 4-stroke diesel engine

Kowalski J.

Journal of KONES

2015

Vol. 22, No. 3

309--316

The manuscript presents the analysis of influence of fuel spray angle on NOx fraction in the exhaust gas emitted from marine 4-stroke diesel engine. Analysis is based on computational fluid dynamic (CFD) model designed because of the motion mesh of combustion chamber of the marine engine cylinder and air inlet and exhaust gas ducts. Presented model consists of models of fuel injection into combustion chamber, breaking-up and evaporation of the fuel, mixing with air and turbulent combustion with heat transfer to construction elements of the engine cylinder. Mentioned CFD model is validated according to boundary and initial conditions taken from direct measurements. The chosen research object is laboratory 4-stroke turbocharged Diesel engine with direct injection of the fuel and mechanically controlled of both cylinder valves and the injector. The conclusion from the analysis is that the increase of fuel spray angle causes the increase of maximum speed of kinetic phase of the combustion and the decrease of maximum speed of diffusion phase of the combustion. The effect of this is the increase of maximum combustion pressure and the decrease of maximum combustion temperature. The result of presented changes in combustion process is the increase of NOx fraction in the exhaust gas. It should be noted that extended increase of the fuel spray angle cause close-up the fuel spray to the cylinder heads wall and the decrease of NOx fraction in the exhaust gas.