An improved method of investigation of combustion parameters in a natural gas fuelled SI engine with EGR and H2 as additives

摘要

An improved approach to the classical Rassweiler and Withrow’s mass fraction burned model and an improved data acquisition/processing procedure are employed with the intention of increasing precision while retaining simplicity. A new method to predict the trends of MFB and emissions, based on the online analysis of cylinder pressure is introduced. A diagnostic method to study the heat release rate in a natural gas fuelled engine has been developed for future use. udNatural gas fuelled vehicles are environmentally friendly and it is possible to use a high compression ratio engine with all its associated benefits for efficiency. However, one of the problems associated with the use of natural gas is NOx emission. EGR can be used to reduce NOx, but it leads to unstable combustion. The stability problem can be resolved by the addition of hydrogen, which can be provided by fuel reforming. Based on the beneficial effects of exhaust gas fuel reforming, the effects of EGR, H2 and H2/CO as additives to natural gas are analysed and discussed in terms of combustion indicators derived by the new diagnostic method, in particular in terms of combustion duration (CA for 5/50/95% MFB), IMEP and cycle by cycle variation (COV of IMEP, COV of peak pressure). ud