The Flame Characteristics Of Gasoline Surrogate Mixtures Under O₂/CO₂Atmosphere

With the continued growth and rapid development of China’s automobile industry andcar ownership, engine fuel shortages and exhaust emissions of pollutants bring enormouschallenges to the safety and environmental development of China’s energy. Using surrogatemixtures, developing new engine combustion technology, such as HCCI, EGR, and so on,are the way to achieve clean and efficient combustion engine. As O2/CO2mixed intake aircan simultaneously control CO, HC, NOx emissions in the gasoline engine, and also cancontrol knocking phenomenon, combustion temperature in cylinder, this paper constructedseveral mechanisms about gasoline surrogate mixtures based on RMG’s rate-basedalgorithm. It analyzed the flame characteristics of gasoline combustion under O2/CO2atmosphere in the view of chemical kinetic mechanism.At first, n-heptane, iso-octane, PRF reaction mechanisms were built under airatmosphere using RMG software. It not only broadened range of application for then-heptane mechanism built by RMG before, but also was consistent with ignition delaytimes evaluated by Lawrence detailed mechanism under different conditions. Ignition delaytimes of the negative temperature coefficient region, low and high temperature, and flamespeed in normal temperature and pressure described by these three mechanisms matchedwith the literature. In addition, ignition characteristics were assessed by the mechanism ofiso-octane constructed under O2/CO2atmosphere, and the results were much closer to theexperimental values than Lawrence mechanism. The mechanism of TRF was built underO2/CO2atmosphere, and ignition characteristics of pure components, multi-componentsubstances were satisfactory.Secondly, ignition delay times, adiabatic flame temperature and laminar flamepropagation speed of gasoline surrogate mixtures were calculated based on TRF mechanismunder different initial temperatures and initial pressures, equivalence ratios, O2concentrations and CO2concentrations. The results showed that: for gasoline surrogatemixtures, initial pressure, CO2and O2concentration have significant impacts on theignition delay times at low temperature than that at high temperature, respectively. With theincrease of O2concentration, the decrement of ignition delay time decreases, and the growth of flame speed is more obvious under O2/CO2atmosphere. By increasing O2concentration from19%to29%, adiabatic flame temperature increases about400K undertwo kinds of atmosphere, flame speed raises three times. After replacing20%N2with CO2,adiabatic flame temperature drops150-200K. Increasing CO2concentration from0%to30%, adiabatic flame temperature drops about210K, flame speed reduces by more than50%. As CO2concentration increases, the decrement of flame speed becomes graduallysmaller.