The Modeling of Fuel Mass Fraction Variance Transport in Turbulent Stratified Flames: A Direct Numerical Simulation Study

Jets in cross flow are one of the fundamental issues for mixing studies. As a first step in this paper, a generic geometry of a jet in cross flow was simulated to validate the CFD (Computational Fluid Dynamics) tool. Instead of resolving the whole injection system, the effective cross-sectional area of the injection hole was modeled as an inlet surface directly. This significantly improved the agreement between the CFD and experimental results. In a second step, the calculated mixing in an ALSTOM EV burner is shown for varying injection hole patterns and momentum flux ratios of the jet. Evaluation of the mixing quality was facilitated by defining unmixedness as a global non-dimensional parameter. A comparison of ten cases was made at the burner exit and on the flame front. Measures increasing jet penetration improved the mixing. In the water tunnel the fuel mass fraction within the burner and in the combustor was measured across five axial planes using LIF (Laser Induced Fluorescence). The promising hole patterns chosen from the CFD computations also showed a better mixing in the water tunnel than the other. Distribution of fuel mass fraction and unmixedness were compared between the CFD and LIF results. A good agreement was achieved. In a final step the best configuration in terms of mixing was checked with combustion. In an atmospheric test rig measured NOx emissions confirmed the CFD prediction as well. The most promising case has about 40% less NOx emission than the base case.

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A direct numerical simulation study on the possibility of macroscopic turbulence in porous media: Effects of different solid matrix geometries, solid boundaries, and two porosity scales

Physics of Fluids ◽

10.1063/1.4949549 ◽

2016 ◽

Vol 28 (6) ◽

pp. 065101 ◽

Cited By ~ 21

Author(s):

M.-F. Uth ◽

Y. Jin ◽

A. V. Kuznetsov ◽

H. Herwig

Keyword(s):

Numerical Simulation ◽

Porous Media ◽

Direct Numerical Simulation ◽

Media Effects ◽

Simulation Study ◽

Solid Matrix

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Dynamics of triple-flames in ignition of turbulent dual fuel mixture: A direct numerical simulation study

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2018.09.018 ◽

2019 ◽

Vol 37 (4) ◽

pp. 4625-4633 ◽

Cited By ~ 8

Author(s):

Tai Jin ◽

Kai H. Luo ◽

Xujiang Wang ◽

Kun Luo ◽

Jianren Fan

Keyword(s):

Numerical Simulation ◽

Direct Numerical Simulation ◽

Simulation Study ◽

Fuel Mixture ◽

Dual Fuel

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Computational fluid dynamics analysis of the effect of mixture heterogeneity on combustion process in a premixed charge compression ignition engine

International Journal of Engine Research ◽

10.1243/146808705x30585 ◽

2005 ◽

Vol 6 (5) ◽

pp. 487-495 ◽

Cited By ~ 4

Author(s):

K Saijyo ◽

T Kojima ◽

K Nishiwaki

Keyword(s):

Mass Fraction ◽

Initial Conditions ◽

Combustion Process ◽

Length Scale ◽

Compression Ignition ◽

Compression Ignition Engine ◽

Heterogeneous Distribution ◽

Fuel Mass ◽

Computational Fluid Dynamics Analysis ◽

Fuel Mass Fraction

We analyzed the interrelationships between mixture heterogeneity and reaction in a premixed charge compression ignition (PCCI) combustion, using large eddy simulation (LES) in conjunction with a reaction kinetics model. The aim of this analysis is to find the statistical characteristics of the mixture heterogeneity in a turbulent flowfield for moderating the PCCI combustion and for increasing an output limit, which is restricted by a severe knock. Several different initial conditions of heterogeneity of an air-fuel or air-fuel-EGR gas mixture were given at the intake valve closing time by a new method, which generated statistically reasonable turbulent fluctuations in both velocity and fuel mass fraction fields. The autoignition and combustion behaviours were analysed for several different sets of the r.m.s. and the length scale of the fluctuations in the fuel mass fraction. The analyses show that the combination of a larger r.m.s. value and a longer-length scale of the fluctuations in fuel mass fraction is effective to slow the combustion in a hot flame reaction phase and to avoid knocking. The analytical results also show that the heterogeneous distribution of an EGR gas has a considerable effect in making the combustion slower, even when a fuel-air mixture is homogeneous.

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