PSI - Issue 16

Jacek Eliasz et al. / Procedia Structural Integrity 16 (2019) 273–280 Jacek Eliasz et al. / Structural Integrity Procedia 00 (2019) 000 – 000

275

3

Physical parameters are density, viscosity, surface tension and compressibility. They affect directly the parameters of the fuel injection stream. The chemical properties include the structure of the molecule and the content of carbon atoms in it. These factors affect the duration of the ignition delay by affecting the activation energy ( E a ). By reducing its value, the self-ignition delay can be shortened. The fuel capability for self-ignition is determined by the cetane number LC (3). The higher its value gives the better the fuel's ability for self-ignition (Kurczynski et al. (2018)).

618.84 25  LC

E



.

(3)

a

Paraffin hydrocarbons are the largest group in the chemical composition of fuels used for self-ignition engines Osipowicz et al. (2014). It is possible to change their chemical properties by the process of dehydrogenation of paraffin hydrocarbons to olefinic form with the release of a free hydrogen molecule (4):

2 +2 2 2 C H +2 C H +H n n n n  .

(4)

Hydrogen, due to the wide limits of flammability, high diffusion coefficient, high capacity and burning rate, can shorten the self-ignition delay time in the conditions prevailing in the combustion chamber (Balyts'kyi et al. (2017), Balyts'kyi et al. (2013)). The presence of hydrogen in the injected fuel also affects its physical properties. The period of ignition delay depends on the rate of evaporation and mixing of the fuel with the air. The presence of a hydrogen molecule in the stream can accelerate the process of evaporation of fuel due to high volatility, which implies higher values of diffusion coefficient, especially in plant-origin fuels. In addition, hydrogen has a heating value 2.8 times higher than conventional fuels. The high hydrogen diffusion coefficient in the air ensures easy formation of a homogeneous combustible mixture. Summing up the discussed issue, it can be concluded that as a result of the dehydrogenation of paraffin hydrocarbons to the olefinic form with the release of a free hydrogen molecule, it is possible to increase the cetane number and reduce the activation energy value under the conditions prevailing in the combustion chamber, which will shorten the self-ignition delay and improve the ecological parameters of the biofuel-powered engine (Osipowicz et al.(2014), Ambrozik et al. (2015), Kurczynski et al. (2018)).

2. Presentation of changes made to the fuel injector atomizer

Changes made to the fuel atomizer are shown in Fig. 2. The fuel flows into the atomizer through the delivery channel (2) and gets to the space where there is a part of non-working needle, which has been modified according to the (Osipowicz et al. (2014)) flowing around it. A platinum catalytic coating was applied to the non-working areas of the needle (4, 5) (Fig. 2).

Fig. 2. Atomizer with a catalytic coating applied to the non-working parts of the needle 1 – atomizer, 2 – fuel supply channel, 3 – precision needle pair, 4, 5 – catalytic coating on the non-working parts of the needle.