Numerical Modeling and Analysis of Energy-Assisted Compression Ignition of Varying Cetane Number Jet Fuels for High-Altitude Operation

Computational fluid dynamics (CFD) simulations are performed to study the potential of energy-assisted compression ignition (EACI) strategy for enabling ignition and enhancing combustion of different cetane number jet fuels during high-altitude operation. EACI employs an ignition assistant (IA), which is an advanced glow-plug design with the ability to sustain higher temperatures for prolonged periods, to provide the necessary ignition energy for precise ignition control and enhanced combustion. In the numerical simulations, the combustion chemistry solver is coupled with a multicomponent wide distillation fuel mechanism, energy source modeling, and a turbulence-chemistry interaction model to accurately capture the ignition assisted-combustion. The simulation is first validated against optical engine measurements for cetane number (CN) 48 jet fuel and then transferred to another single-cylinder test engine to study the ignition and combustion characteristics of EACI with CN 35 jet fuel at varying IA temperatures. Simulation results show that EACI significantly improves fuel ignitability. Ignition delay reductions for CN 48 fuel of 57% and CN 35 fuel of 25% are noted at IA temperatures of 1550 K and 1405 K compared to when the IA is switched off. Furthermore, EACI improved the combustion efficiency to 99.7% compared to the 90% estimated for the IA off case in the optical engine.