Cycle-simulation of two stroke spark ignition engine for the application in general aviation

U ovom radu analiziran je dvotaktni motor s prednabijanjem namijenjem za pogon zrakoplova generalne avijacije. U novije vrijeme zbog sve većih zahtjeva za smanjenjem potrošnje goriva i sve strožim propisima emisija ispušnih plinova, četverotaktni motori su istisnuli uporabu dvotaktnih motora. Analizom je pokazano kako se primjenom izravnog ubrizgavanja i pažljivim konstruiranjem kanala za izmjenu radnog medija mogu postići sasvim zadovoljavajući rezultati potrošnje goriva i emisije ispušnih plinova, istovremeno iskorištavajući veću snagu i ujednačeniji moment dvotaktnog motora. Za simulaciju rada motora koristio se komercijalni programski paket AVL BOOSTTM v2013.2. Na početku je izrađena simulacija motora s pojednostavljenim modelom turbopunjača te su uspoređeni dobiveni rezultati s maksimalno očekivanom efektivnom snagom pri maksimalnoj brzini vrtnje motora. S ciljem što točnije analize definirano je nekoliko kompletnih mapa rada turbopunjača te su uspoređeni rezultati i odabran je turbopunjač koji najbolje odgovara analiziranom motoru. Na kraju je analiziran utjecaj povećane nadmorske visine na rad motora te je opisan koncept dodatnog kompresora pogonjenog elektromotorom (eng. e-booster) kojim se može kompenzirati gubitak snage uslijed niskog tlaka okoline.In this thesis the cycle-simulation of two stroke spark ignition turbocharged engine for the application in general aviation was analyzed. Most recently due to the increasing demands on reduction in fuel consumption and increasingly stringent exhaust emissions regulations, four-stroke engines have squeezed the use of two-stroke engines. The analysis has shown that by using direct injection and by detailed design of intake and exhaust ports, two stroke engines can achieve quite satisfactory results of fuel consumption and exhaust emissions while simultaneously taking advantage of greater power and a more balanced torque of the two-stroke engine. For engine simulation, the commercial version of AVL BOOSTTM v2013.2 software package was used. At the beginning a simulation of the engine with a simplified turbocharger model was made and the obtained results were compared with the maximum expected brake power at maximum engine speed. For a more accurate analysis, several full turbocharger maps have been defined and the results were compared with simplified model and a turbocharger is selected that best suits the analyzed engine. Finally, the influence of increased altitude on engine operation was analyzed and the concept of an additional compressor powered by an electric motor (e-booster) was described to compensate for the loss of power due to low ambience pressure