Istraživanje procesa sagorevanja u dizel motoru pri radu sa biogorivima i recirkulacijom izduvnih gasova

Abstract

U ovom radu je proucavana mogucnost primene alternativnih biogoriva za pogon dizel motora sa direktnim ubrizgavanjem, kao i uticaj ovih goriva na proces sagorevanja i izduvnu emisiju ovog tipa motora. Kao alternativna biogoriva korišceni su metilestri ulja uljane repice, sojinog ulja i otpadnog jestivog palminog ulja. Ova biogoriva su korišcena kao cista (100%) ili u smeši sa standardnim dizel gorivom fosilnog porekla u odnosu 50:50 i u nekim uslovima i u smeši 25%, 50%, 75%. Takode, istražena je i mogucnost primene cistog jestivog rafinisanog suncokretovog ulja bez dodatne obrade ulja pre mešanja sa dizel gorivom u odnosu 50:50. Pored integralnih karakteristika motora: snage, obrtnog momenta, potrošnje usisnog vazduha i goriva, analize izduvnih gasova, protoka recirkulacije izduvnih gasova, snimljeni su tokovi pritiska u cilindru motora i vodu visokog pritiska sistema unrizgavanja i izdizanje igle brizgaca, korišcenjem akvizicionog sistema visokih performansi. Na bazi ovih velicina razvijen je i primenjen model za odredivanje parametara procesa sagorevanja. Koristeci ovaj postupak odredene su sledece karakteristike sagorevanja pri radu sa razlicitim biogorivima i pri razlicitim uslovima: vrednosti maksimalnog pritiska u cilindru motora kao i njihovi položaji u odnosu na SMT, zakoni oslobadanja toplote, periodi zakašnjenja upaljenja, trajanje sagorevanja i razvijene kolicine energije po fazama procesa sagorevanja. Takode je izvršeno ispitivanje uticaja svih korišcenih biogoriva na izduvnu emisiju motora. Istraživanja su vršena u usisnoj i natpunjenoj varijanti motora. Takode je detaljno istražen i uticaj recirkulacije izduvnih gasova na proces sagorevanja i izduvnu emisiju i to u obe varijante motora i sa svim korišcenim biogorivima. Poseban deo istraživanja se odnosio na mogucnost aplikacije komore za sagorevanje originalne konstrukcije sa smanjenim odavanjem toplote i uticaj ovog sistema sagorevanja na tok procesa sagorevanja i sastav izduvnih gasova. Dobijeni rezultati u okviru ovog rada se mogu koristiti pri optimizaciji radnog ciklusa dizel motora sa direktnim ubrizgavanjem u cilju postizanja povoljnije ekonomicnosti i izduvne emisije, pri pogonu biogorivima sa i bez recirkulacije izduvnih gasova.

This dissertation presents the results of biofuels application research in direct injection diesel engine, as well as the influence of these fuels on engine combustion process and exhaust emissions. The methyl esters of rape oil, soya oil, and waste cooking palm oil were used as alternative fuels. These biofuels were used as net fuels (100%) as well as mixed with standard diesel fuel in the ratio 50:50 and in several cases 7%, 25%, 50% and 75%. Also, the research included the experiments with pure edible sunflower oil mixed with diesel fuel in the ratio 50:50. Besides engine integral characteristic: power and torque output, intake air and fuel consumption, exhaust gas analysis, exhaust gases recirculation, the traces of incylinder pressure, fuel injection pressure and injector needle lift were recorded using high speed data acquisition system. On the basis of these data the method of combustion process parameters evaluation was developed and applied. Using this procedure for different biofuels and at different operating conditions, the following combustion parameters were determined: maximum cylinder pressure and temperature and its their position relative to TDC, heat release and the rate of heat release, ignition delay, combustion duration and the amount of heat released in certain periods of combustion process. The research was carried out under the naturally aspirated and supercharged engine conditions. The impact of exhaust gas recirculation on combustion process and exhaust emissions was studied in all operating conditions and with all biofuels. A special part of the research related to the possibilities of application of the specially designed combustion chamber with reduced heat transfer from the gases to the chamber walls. The influence of this system on combustion characteristics and exhaust emissions was studied. The results obtained in this research can be used for optimisation of diesel engine working cycle in order to achieve better fuel economy and exhaust emissions, under the conditions of different biofuels application with and without exhaust gas recirculation.