*Laboratory Tests*

*Object of tests.* The tests were carried out with the use of the one-cylinder two stroke crosshead supercharged diesel engine, which is an element of the test stand adapted to investigations on emission exhaust gas components (Figure 4). The Wimmer MRU/2D analyzer with measuring accuracy of ≤±5% and a resolution of 1 ppm was used to measure the composition of the exhaust gases.

To supply the engine during the tests in question, the marine diesel oil (MDO) and its mixtures with rape oil esters (RME) of the following proportions were prepared:


The MDO had a density of 831 kg/m<sup>3</sup> and the RME of 883 kg/m3. As a result of the mixing, the biofuel had a density of 839 kg/m<sup>3</sup> in the first case and 840 kg/m<sup>3</sup> in the second case.

*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 a given rotational speed and successively set loads, measurements of the engine's exhaust gas content during combusting by the engine were realized: The MDO alone, and the two above specified mixtures (i.e., 15% of RME in MDO, and 20% of RME in MDO). The results obtained from the tests during the supply of the engine with the MDO alone was assumed as the reference point for determination of the influence of combustion of the MDO/RME mixtures on the engine's exhaust gas content.

**Figure 4.** Test stand: (**a**) block diagram: 1—L-22 diesel engine, 2—water brake, 3—torsiometer, 4—gauge for crankshaft position marking and rotational speed measuring, 5—combustion pressure transducer, 6—injection pressure transducer, 7—computer, 8—exhaust gas analyzer, 9—analog/digital converter; (**b**) engine L22-view.

*Test results and their analysis.* The selected tests results are presented in Figures 5 and 6. On the basis of the exhaust gas analysis, it can be stated that combustion of MDO with 15% addition of RME caused, on average, a drop of the NOx content by 35% (for higher engine loads—70% and 80% M/Mn) and that during combusting of the MDO with the 20% addition of RME, the drop, on average, exceeded 57% (for higher engine loads—70% and 80% M/Mn), as shown in Figure 5.

**Figure 5.** NOx content in exhaust gas as a function of the engine load for different kinds of fuel at a constant rotational speed *n* = 220 rpm.

**Figure 6.** CO2 content in exhaust gas as a function of the engine load for different kinds of fuel at a constant rotational speed *n* = 220 rpm.

It can also be noted that the combustion of MDO with the 15% and 20% addition of RME, especially for higher engine loads (70% and 80% M/Mn), causes a clear drop in CO2. This drop is exceeded by 33% in the combustion of MDO with the 15% addition of RME and exceeded by 57% in the combustion of MDO with the 20% addition of RME (Figure 6).

### **4. Change of Fuel Injection Parameters-Change Advance Angles of Fuel Injection**

The possibility of reducing NOx emission by changing the fuel injection parameters has been noted [9]. The fundamental parameter for an injection system is the advance angle of fuel injection. You can expect that change of the advance angle of fuel injection affects the composition of exhaust gases, including toxic component emissions. This thesis is confirmed by the research carried out by the author, described in follow section.
