Diesel Combustion and Control Using a Novel Ignition Delay Model 2018-01-1242

The future emission standards, including real driving emissions (RDE) measurements are big challenges for engine and after-treatment development. Also for development of a robust control system, in real driving emissions cycles under varied operating conditions and climate conditions, like low ambient temperature as well as high altitude are advanced physical-based algorithms beneficial in order to realize more precise, robust and efficient control concepts.

A fast-running novel physical-based ignition delay model for diesel engine combustion simulation and additionally, for combustion control in the next generation of ECUs is presented and validated in this study. Detailed chemical reactions of the ignition processes are solved by a n-heptane mechanism which is coupled to the thermodynamic simulation of in-cylinder processes during the compression and autoignition phases. All relevant engine operating conditions, like engine speed, in-cylinder charge mass and temperature as well as the EGR ratio are varied and ignition delay times are calculated. Using a large number of simulation results, a very-fast running ignition delay model is trained and validated against detailed reaction kinetics simulation results. The developed autoignition model can reproduce the results using engine and detailed reaction kinetics simulation with a very good accuracy.

As next step, the developed autoignition model is implemented into a phenomenological combustion model. Experimental investigations are carried out on a single-cylinder heavy-duty diesel engine for validation of the developed model for engine process simulation. Finally, the proposed novel ignition delay model for combustion control is tested using a software in the loop methodology and also on the engine test bench. The new combustion control concept is evaluated, and potentials under transient conditions are evaluated.