Numerical Study Of Reactivity Controlled Compression Ignition (RCCI) Using Different Combinations Of Multi-component Surrogates For Diesel And Gasoline

RCCI(Reactivity Controlled Compression Ignition)is an advanced,low-temperature dual fuel combustion concept that can help to achieve efficient combustion.The numerical studies can be a cost and time effective way to analyze this combustion concept.And chemical mechanisms play an important role in accurately predicting the experimental results in numerical studies.In this study,a multi-component surrogate has been developed to study the combustion characteristics of RCCI.The mechanism contains 168 species and 680[TRFDIB+(T15+CH5)]reactions and has been validated extensively.The validations have been carried out for individual and mixture of components over a wide range of temperatures and pressures.The mechanism showed a good overall agreement with the experimental data.The combustion characteristics have then been investigated considering the impact of single and multi-component surrogates on chemical and physical properties.First,only chemical properties and then physical properties have been changed followed by a change in both properties by a multi-component mechanism.The in-cylinder pressure heat release rates have been captured well by multi-component surrogate fuel representing both physical and chemical properties of multi-component surrogate[TRFDIB-2 +(T15+CH5)].The NOx emissions have been captured almost accurately by using physical properties of multi-component surrogate(T15+CH5)and chemical properties of single-component(nC7H16)for diesel while single component(iC8H18)for both physical and chemical properties of gasoline.The soot emissions,however,were overpredicted by all cases with the least shown by the case using physical properties of multi-component surrogate(T15+CH5)and chemical properties of single-component(C14H30)for diesel while single-component(iC8H18)for both physical and chemical properties of gasoline.The chemical kinetics analysis was performed at CA5 and CA50 points using sensitivity analysis and consumption reaction pathway analysis that outlined the differences in chemical performance of both the fuels.The sensitivity analysis indicated that multi-component surrogate fuel shows an overall higher sensitivity in producing OH radicals.Similarly,the chemical kinetics analysis showed a higher concentration of reactive OH and CH2O radicals in the reaction pool being produced by multi-component surrogate fuels which resulted in overall more reactivity of the system as compared to the single-component surrogate.Furthermore,the absolute rate of production of CO2 in multi-component surrogate fuel is higher which resulted in more heat release rate.Toluene and cyclohexane are maj or OH consuming elements causing a slower conversion rate in multi-component fuel.They are,however,also responsible for controlling the low-temperature heat release rate and enhancing the high temperature heat release rate.The multi-component surrogate fuel is consumed earlier as compared to single-component fuel.