Comparative evaluation of the combustion process and emissions of a diesel engine operating on the cetane improver 2-Ethylhexyl nitrate doped rapeseed oil and aviation JP-8 fuel

Abstract

• Diesel engine tested with rapeseed oil (RO) and jet fuel (JF) at 1400 and 2200 rpm. • 2-EHN is more active in reducing the ignition delay of JF rather than RO at both rpm. • MBF 50 and MBF 90 are smaller, but the ITE is a bit lower with the doped JF-24 fuel. • NO x is 49% higher, but smoke 27% lower with doped RO-30 than with JF-24 at 2200 rpm. • The combustion of JF-fuel-sets emits THC less than RO-sets at a speed of 2200 rpm. Rapeseed oil (RO) and JP-8 fuel (JF) as alternatives could be used as diesel fuel supplements in many power sectors however, the low cetane number related drawbacks should be removed to overcome the difficulties in the ignition and to achieve efficient-clean combustion of the fuels. The purpose of the research is to make a comparative evaluation of the cetane enhancer-made effects on the combustion process, cyclic variability, thermal efficiency, smoke, and exhaust emissions. At first, a naturally aspirated engine operated with the undoped RO and JF to identify the baseline parameters for full (100%) loads corresponding to Indicated Mean Effective Pressures (IMEP) of 0.844 and 0.738 MPa at speeds of 1400 and 2200 rpm. Then, the engine operated with the 2-EHN doped fuels 0.10 (RO-10), 0.30 (RO-30) and 10 (JF-10), 24 vol% (JF-24) to get new results needed for comparative evaluation of the benefits and detriments in the combustion process, engine efficiency, smoke, and emissions. The ignition delay was 10.3% and 44.6% shorter, the Indicated Thermal Efficiency (ITE) was 6.1% higher and 1.2% lower, the NO x emissions were a little and 10.3% lower with the doped RO-30 and JF-24 at a speed of 2200 rpm. The coefficients of cyclic variations (COVs) of the IMEP were 9.7% higher and 11.8% lower, the in-cylinder maximum pressure was 22.5% and 29.0% lower, and the increment rate of maximum pressure was 13.5% and 14.9% lower, respectively. Also, RO-30, JF-24 fuels suggested smoke opacity and CO emissions 42.1%, 32.1% and 11.6%, 2.7% higher, THC emissions 1.9 times higher, and 28.6% lower for engine tested conditions.