*Laboratory Tests*

*Object of tests.* The tests were carried out with the use of the one-cylinder two stroke crosshead supercharged diesel engine (Figure 4), which is an element of the test stand adapted to investigations on emission exhaust gas components.

To supply the engine during the tests in question, the marine diesel oil (MDO) was used and the fuel injection advance angle (injection timing) changed for three selected values:


*Test program.* The tests were carried out within the broad range of the engine's loading, namely: 40%, 50%, 60%, 70%, and 80% M/Mn (set torque of engine M/nominal torque of engine Mn) and for a constant rotational speed of the engine, set at 220 rpm. At the given rotational speed and successively set loads, measurements of the engine's exhaust gas content were realized for three values of the angle: −13◦ (rated), <sup>−</sup>10◦, and −7◦ before the piston top dead center (TDC).

*Test results and their analysis.* The selected tests results are presented in Figures 7 and 8. Changes to the injection advance angle can be made by adjusting the factory settings. A decrease of the injection advance angle unambiguously makes the NOx content in exhaust gas lower. A decrease of the injection advance angle of −13 degrees to −7 degrees unambiguously makes the NOx content in exhaust gas lower (even more than 18%—see Figure 7). However, it should be remembered that both an advance and delay of fuel injection starting, in relation to the values recommended by the producer and set during static adjustment of the engine, influences not only the exhaust gas content but also other important operational parameters of the engine by changing the combustion process quality. Inter alia, an increase in the specific fuel consumption can be expected.

**Figure 7.** NOx content in exhaust as a function of the engine load and three different advance angles of fuel injection, for a constant rotational speed *n* = 220 rpm.

**Figure 8.** CO2 content in exhaust as a function of the engine load and three different advance angles of fuel injection, for a constant rotational speed *n* = 220 rpm.

The investigations also revealed (see Figure 8) that the advance angles of fuel injection have no significant impact on the change content of carbon dioxide (CO2) in exhaust gas.
