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Fast-Running Autoignition Model for Diesel Combustion Modeling and Control, Based on Detailed Reaction Kinetics Simulation
Journal Article
03-11-03-0019
ISSN: 1946-3936, e-ISSN: 1946-3944
Sector:
Topic:
Citation:
Rezaei, R., Tilch, B., and Bertram, C., "Fast-Running Autoignition Model for Diesel Combustion Modeling and Control, Based on Detailed Reaction Kinetics Simulation," SAE Int. J. Engines 11(3):389-300, 2018, https://doi.org/10.4271/03-11-03-0019.
Language:
English
Abstract:
Detailed and reduced kinetic mechanisms have been proposed for description of the
complex chemistry of autoignition processes of n-heptane, as a
representative diesel fuel. These kinetic models are attractive for a detailed
3-D CFD or multi-zone simulation, however the simulation time is normally not
affordable for phenomenological engine process modeling.
For phenomenological combustion models, typically single-to multiple-step
Arrhenius equations are used to model the autoignition processes. Based on the
number of Arrhenius equations and model structure the low-temperature,
high-temperature and the negative temperature coefficient (NTC) behavior can be
modeled. For diesel engine simulation modeling the ignition delay using
Arrhenius equation(s) and a Livengood-Wu integration can deliver fairly good
results, depending on the number of equations and calibration of constant
parameters. However, it needs integration, as in-cylinder pressure and
temperature change in each time step, due to e.g. piston movement.
The aim of this study is development of a novel autoignition model for diesel
fuel combustion which can be used for efficient and fast-running combustion
modeling. The presented model is based on simulation results using realistic
diesel engine geometry under various operating conditions. 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. Finally, advantages of using the proposed novel ignition delay model for
combustion control in the next generation of the engine control units are
discussed.