Simulation and Experiment of Auto-Ignition Characteristics for Diesel Fuel in O₂/CO₂ Atmosphere

To calculate the ignition characteristics of diesel fuel in O₂/CO₂ atmosphere, an ignition delay model was proposed for n-heptane in the atmosphere of 65% O₂ and 35% CO₂. The effects of O₂ and CO₂ on the chemical reaction rate were considered. Then, the relationship between the temperature and the ignition delay was obtained and the calculation formula of ignition delay time was also derived. After using the steady state method to reduce the chemical reaction process of diesel fuel, the ignition delay time of diesel fuel in the atmosphere of air and of 65% O₂ plus 35% CO₂ were determined respectively. Besides, a constant volume combustion bomb test system was established to visualize the ignition process of diesel fuel in the atmosphere of air and of 65% O₂ plus 35% CO₂ respectively. The ignition delay time, the flame lift-off length and the combustion pressure variation were compared and analyzed by the visualization tests. The Results show that the new ignition delay model can well predict the ignition process of diesel fuel in the atmosphere of 65% O₂ and 35% CO₂. In this atmosphere, the ignition delay time is 50% shorter than that in the air atmosphere and the flame lift-off length is also shorter. It is also found that the injection pressure has an effect on the ignition delay time and the peak combustion pressure in the constant volume combustion bomb.