RCCI motorlarının emisyon ve performans karakterinin incelenmesi

The vehicle manufacturers and research institutes are seeking for clean and high efficiency combustion engine due to the increasing demand for crude oil and environment problems in recent years. Although aftertreatment system is capable of reducing engine emissions to a low level, the limitation of these systems that cannot make full use of fuel restricts the improvement in fuel economy. Large amount of researches focus on the LTC (low temperature combustion) strategy, which can achieve both the reduction of emissions and the improvement of fuel economy. RCCI (reactivity controlled compression ignition) is one of the tool to achieve this strategy, which is investigated in this study. The reactivity stratification in RCCI combustion is achieved by utilization of the separate injection system with low-reactivity and high-reactivity fuel introduced into cylinder directly in different injection timing. By using multi-dimensional CFD (computational fluid dynamics) modelling, it could be researched with fast and inexpensive way. In this study RCCI engine investigated with diesel and methanol fuels based on NO and soot emission outputs regarding various mixture mass fractions and different SOI timings with EGR variants. Ecotorq 9L 380PS diesel engine has been used as diesel base case to verify model. AVL Fire ESE Diesel program has been used to get computational results and it has been compared with diesel engine dyno meter results taken from FORD OTOSAN test laboratories. RCCI engine has been studied on 32 different variants overall. These 32 run includes; different SOI timings of methanol between 700-740 degree CA, different SOI timings of diesel between 704.8-714.8 degree CA, various EGR rates between %10 to %30, 7 different methanol mass fraction rated fuel mixtures overall. At first step created AVL Fire diesel engine model has been verified with engine dyno meter test results. This validated model mesh cell size chosen from 5 mesh variant option, regarding sensitivity of pressure, temperature, accumulated heat release, NO mass fraction, soot mass fraction results in order to achieve mesh independency. RCCI engine results reviewed to understand behaviour and characteristics of methanol-diesel fuelled RCCI engine emission and performance. During that study NO mass fraction, NO mass per kWh, soot mass fraction, soot mass per kWh, CO mass fraction, indicated power, mean in cylinder pressure, mean in cylinder temperature, NO and soot distribution over combustion chamber, mean mass, diesel mass fraction in cylinder, methanol mass fraction in cylinder have been investigated and results compared with base diesel case for improvement assessment. Regarding all cases, most problematic part was soot improvement. In 25 cases, NO emission reduced from base diesel case, but soot improvement only achieved in 6 cases. Soot mass reduced cases from base diesel case (Case 1) reviewed. Regarding results; case 2 with 0.184 methanol mass fraction and case 3 with 0.45 methanol mass fraction are successful to achieve soot reduction. With all those cases NO emission reduction also achieved simultaneously. In 6 cases power decrease, which reaches up to %7 percentage, observed. NO and soot reduction percentages calculated from mass per kWh, hence power decrease also calculated and even that emission decrease observed. According to priority best case could be selected. If soot reduction required to be lowest one, case 3.h can be selected, which has 714.8 diesel SOI, 715 methanol SOI, %10 EGR, 0.45 methanol mass fraction. That provides %80 percentage soot reduction and %4 NO reduction. If NO reduction required being lowest one, case 3.j can be selected, that has same attributes with increased EGR rate to 0.25. That provides %62 NO reduction with %51 soot reduction.