A Physical 0D Combustion Model Using Tabulated Chemistry with Presumed Probability Density Function Approach for Multi-Injection Diesel Engines 2010-01-1493
This paper presents a new 0D phenomenological approach to
predict the combustion process in diesel engines operated under
various running conditions. The aim of this work is to develop a
physical approach in order to improve the prediction of in-cylinder
pressure and heat release. The main contribution of this study is
the modeling of the premixed part of the diesel combustion with a
further extension of the model for multi-injection strategies.
In phenomenological diesel combustion models, the premixed
combustion phase is usually modeled by the propagation of a
turbulent flame front. However, experimental studies have shown
that this phase of diesel combustion is actually a rapid combustion
of part of the fuel injected and mixed with the surrounding gas.
This mixture burns quasi instantaneously when favorable
thermodynamic conditions are locally reached. A chemical process
then controls this combustion.
In the present model, the rate of heat release by combustion for
the premixed phase is related to the mean reaction rate of fuel
which is evaluated by an approach based on tabulated local reaction
rate of fuel and on the determination of the Probability Density
Function (PDF) of the mixture fraction (Z), in order to take into
consideration the local variations of the fuel-air ratio. The shape
of the PDF is presumed with a standardized β-function. Mixture
fraction fluctuations are described by using a transport equation
for the variance of Z. The standard mixture fraction concept
established in the case of diffusion flames is here adapted to
premixed combustion to describe the inhomogeneity of the fuel-air
ratio in the control volume. The detailed chemistry is described
using a tabulated database for reaction rates and cool flame
ignition delay as a function of the progress variable c.
Premixed zone volume and total entrained ambient gas mass flow
rate are calculated using a detailed spray model. The
mixing-controlled combustion model is based on the calculation of a
characteristic mixing frequency which is a function of the
turbulence density, and on the evolution of the available fuel
vapor mass in the control volume.
The developed combustion model is one sub-model of a
thermodynamic model based on the mathematical formulation of the
conventional two-zone approach. This zero-dimensional model
incorporates several sub-models describing turbulence,
vaporization, and fuel introduction rate. The purpose of this
approach is to directly relate physical model parameters to
operating conditions and engine parameters.
Numerical results from simulations are compared with
experimental measurements carried out on a 2-liter Renault diesel
engine. For all investigated operating conditions, simulated
cylinder pressure and heat release rate traces show a good
agreement with experimental measurements.
Citation: Bordet, N., Caillol, C., Higelin, P., and Talon, V., "A Physical 0D Combustion Model Using Tabulated Chemistry with Presumed Probability Density Function Approach for Multi-Injection Diesel Engines," SAE Technical Paper 2010-01-1493, 2010, https://doi.org/10.4271/2010-01-1493. Download Citation
Nicolas Bordet, Christian Caillol, Pascal Higelin, Vincent Talon
Institut PRISME - Univ. of Orleans, Renault
International Powertrains, Fuels & Lubricants Meeting