Knock analysis of bio-butanol in TISI engine based on chemical reaction kinetics

Abstract

The knocking combustion of n-butanol (bio-butanol) combined with exhaust gas recirculation (EGR) in turbocharge direct injection spark ignition (TISI) engine with high compression ratio is studied. Mainly analyze the influence of EGR rate and composition on knock combustion and the indication effect of unconventional emission of free radicals on knock. The research results show that adding appropriate EGR can reduce the engine knock intensity, but the introduction of a large amount of EGR can cause the knock intensity to increase. When the EGR rate is 8%, the MAPO is less than 0.1 MPa, indicating that knocking combustion does not occur in the cylinder. When the EGR rate is increased to 15%, the MAPO is greater than 0.15 MPa, indicating that knocking combustion is intensified. Knock combustion is mainly concentrated on the intake side, which is related to the flame propagation speed. The addition of EGR can reduce the temperature in the cylinder, mainly because the specific heat capacity of H2O and CO2 in the EGR component is relatively large, which can significantly reduce the temperature of the mixture. The variation of CH2O, CH3CHO and C2H4 can reflect the knock intensity of the mixture in the cylinder. In conclusion, the introduction of EGR into the TISI engine can effectively reduce the knock intensity. The variation of mixture composition can better reflect the knock region and knock intensity.