Combustion Stability Study with Low Cetane Number Diesel and Biodiesel with 2-EHN Addition under LTC Conditions during Cold/Warm Start and Steady State Conditions

Abstract

A single cylinder Diesel engine was used to study combustion stability changes from a cetane number improver: 2-EHN. It has been added to a low cetane number diesel and two biodiesels blends with 20 % of SME or RME. All fuels have been raised to a CN of 51 with 2-EHN. Those fuels have been compared to a reference diesel with a CN of 55. Cold and warm start have been recreated for measurements at three conditions: cranking, engine speed increase and idle. Engine coolant temperature has been set to 20?C and 80?C for cold and warm start respectively. 2-EHN effects on combustion stability have been monitored through the IMEP covariance. Under cold-start, only the low cetane number diesel showed combustion stabilities improvements with 2-EHN addition. Moreover, the combustion stability was better than the reference diesel and the heat release rate show an enhancement of the cold flame. On the contrary, the biodiesel fuels exhibited higher IMEP covariances. Under warm start, all fuels without 2-EHN showed low IMEP covariances. Therefore, the results indicated less effects of the cetane improver on combustion stability. The low cetane number diesel heat release showed higher cold flame heat release when doped with 2-EHN. Results with the reference diesel fuel has the best combustion stability. Lastly, the fuels have been tested for EGR limit for idle, steady state city and extra-urban drives. Results showed a higher EGR limit for all fuels except for the biodiesel prepared with SME, which showed no gain or degradation of EGR limit.