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Influence of Trapped Residual Gasses in Air-Diluted Spark Ignited Combustion
Journal Article
03-15-06-0046
ISSN: 1946-3936, e-ISSN: 1946-3944
Sector:
Topic:
Citation:
Clasén, K. and Koopmans, L., "Influence of Trapped Residual Gasses in Air-Diluted Spark Ignited Combustion," SAE Int. J. Engines 15(6):849-881, 2022, https://doi.org/10.4271/03-15-06-0046.
Language:
English
Abstract:
Homogeneous air-diluted spark ignition (SI) is one advanced combustion concept
that is recognized for its potential of efficiency improvement, which can be
utilized in the next-generation, affordable, light-duty propulsion systems.
However, cyclic dispersion and high-load end-gas autoignition of diluted
combustion remain a challenge, preventing necessary nitric oxide (NO) emission
suppression, which, in turn, obstructs market penetration. It is well known that
trapped residual gasses (RG) in the cylinder influence the cyclic dispersion of
combustion by contributing to the total amount of charge dilution which
influences the total mean flame speed and thereby the combustion sensitivity to
cyclic perturbations. However, the amount of trapped RG in the cylinder is
difficult to measure, and therefore, its influence is complicated to assess. In
lean combustion research, the presence of RG is often acknowledged, but few
studies have investigated the influence of a combined dilution of RG and air.
This article aims at assessing the influence of trapped RG on lean combustion
through combining engine experiments with one-dimensional (1D) computer
simulations using a three-pressure analysis (TPA). A TPA utilizes experimentally
acquired data such as crank angle-resolved port and cylinder pressures to
minimize the scope of discretization and predictability of the model to improve
accuracy. The experimental results were replicated in the simulation and
quantities, such as residual gas fraction (RGF) and total trapped in-cylinder
mass, were estimated.
From the performed engine experiments and corresponding simulations, it has been
concluded that RG have a substantial influence on combustion. The total
dilution, the blend of residuals and air, is highly correlated to nitrogen
oxides (NOx) emissions at all investigated operating conditions.
Additionally, at low loads, the total dilution correlates with the dilution
stability limit, rather than air-dilution solely. At high loads, residuals
contribute little to the total dilution, but have been linked to the increased
propensity of knock.