A Comprehensive Study of Effects of Mixing and Chemical Kinetic Models on Predictions of n-heptane Jet Ignitions with the PDF Method

Pei, Yuanjiang; Hawkes, Evatt R.; Kook, Sanghoon

doi:10.1007/s10494-013-9454-z

Cited by 73 publications

(70 citation statements)

References 69 publications

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“…This results in reduced interactions between the spray and combustion processes. This finding is in agreement with previous studies from both experiments [4,17,18] and simulations [43,44]. Figure 4(d) shows that higher ambient temperature results in increased soot production, which is consistent with experimental findings.…”

Section: Correlations Between the Targetssupporting

confidence: 93%

Engine Combustion Network (ECN): Global sensitivity analysis of Spray A for different combustion vessels

Pei

Davis

Pickett

et al. 2015

Combustion and Flame

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a b s t r a c tGlobal sensitivity analysis was conducted on Spray A of the Engine Combustion Network's (ECN) experimental conditions across different combustion vessels from different institutions. The main objective was to understand the influence of differences in boundary conditions on specific targets of interest. A list of experimental initial, boundary, and injection conditions with uncertainty ranges were identified for three different ambient conditions for these combustion vessels. Five targets including the liquid length, vapor penetration length, ignition delay, lift-off length, and soot mass in the domain were extracted from hundreds of 3D computational fluid dynamics (CFD) simulations by simultaneously perturbing all the uncertain variables. Each target was analyzed using a global sensitivity analysis (GSA) method and the relative importance of different variables towards specific targets was identified. The uncertainty in the fuel temperature was found to have a profound influence on the liquid length, however, the influence on vapor penetration length, ignition delay, and lift-off length, was rather subtle. Small uncertainties in the initial turbulence level and nozzle diameter was observed to have a significant influence on the vapor penetration. Variables sensitive to ignition delay also showed similar sensitivity to flame lift-off length. The soot mass in the domain was observed to have a closer correlation with the liquid length at least for higher ambient temperature conditions.

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Section: Correlations Between the Targetssupporting

confidence: 93%

Engine Combustion Network (ECN): Global sensitivity analysis of Spray A for different combustion vessels

Pei

Davis

Pickett

et al. 2015

Combustion and Flame

Self Cite

View full text Add to dashboard Cite

show abstract

“…Bhattacharjee and Haworth [5] compared well-stirred reactor (WSR) model with PDF method for n-heptane and n-dodecane spray flames under engine conditions, concluding that the PDF method performs better due to the fact that the turbulent fluctuations have been taken into account. Pei et al [44,45] simulated diesel engine combustion using composition PDF coupled with Reynolds-averaged k-ε model. Recently, attention has been paid to the FDF (filtered density function) method in conjunction with Large Eddy Simulation.…”

Section: Introductionmentioning

confidence: 99%

Transported PDF Modeling of Ethanol Spray in Hot-Diluted Coflow Flame

Naud

Roekaerts

2015

Flow Turbulence Combust

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This paper presents a numerical modeling study of one ethanol spray flame from the Delft Spray-in-Hot-Coflow (DSHC) database, which has been used to study Moderate or Intense Low-oxygen Dilution (MILD) combustion of liquid fuels (Correia Rodrigues et al. Combust. Flame 162, 759-773, 2015). A "Lagrangian-Lagrangian" approach is adopted where both the joint velocity-scalar Probability Density Function (PDF) for the continuous phase and the joint PDF of droplet properties are modeled and solved. The evolution of the gas phase composition is described by a Flamelet Generated Manifold (FGM) and the interaction by exchange with the mean (IEM) micro-mixing model. Effects of finite conductivity on droplet heating and evaporation are accounted for. The inlet boundary conditions starting in the dilute spray region are obtained from the available experimental data together with the results of a calculation of the spray including the dense region using ANSYS Fluent 15. A method is developed to determine a good estimation for the initial droplet temperature. The inclusion of the "1/3" rule for droplet evaporation and dispersion models is shown to be very important. The current modeling approach is capable of accurately predicting main properties, including mean velocity, droplet mean diameter and number density. The gas temperature is under-predicted in the region where the enthalpy loss due to droplet evaporation is important. The flame structure analysis reveals the existence of two heat release regions, respectively having the characteristics of a premixed and a diffusion flame. The experimental and modeled temperature PDFs are compared, highlighting the capabilities and limitations of the proposed model.

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“…Magnussen's eddy dissipation) [11,12]. With the development of the flamelet model in the 1990s, more advanced turbulent combustion theories started to appear in the field of diesel engine computational fluid dynamics (CFD) [13][14][15], and more recently, all advanced combustion models are being used: CMC [16][17][18][19][20][21], PDF [22][23][24][25], partially stirred reactor [26], generalised flame surface density model [27], FPV models [28] and the flamelet generated manifold method [29].…”

Section: Introductionmentioning

confidence: 99%

Influence of turbulence–chemistry interaction forn-heptane spray combustion under diesel engine conditions with emphasis on soot formation and oxidation

Bolla

Farrace

Wright

et al. 2014

Combustion Theory and Modelling

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The influence of the turbulence-chemistry interaction (TCI) for n-heptane sprays under diesel engine conditions has been investigated by means of computational fluid dynamics (CFD) simulations. The conditional moment closure approach, which has been previously validated thoroughly for such flows, and the homogeneous reactor (i.e. no turbulent combustion model) approach have been compared, in view of the recent resurgence of the latter approaches for diesel engine CFD. Experimental data available from a constant-volume combustion chamber have been used for model validation purposes for a broad range of conditions including variations in ambient oxygen (8-21% by vol.), ambient temperature (900 and 1000 K) and ambient density (14.8 and 30 kg/m 3 ). The results from both numerical approaches have been compared to the experimental values of ignition delay (ID), flame lift-off length (LOL), and soot volume fraction distributions. TCI was found to have a weak influence on ignition delay for the conditions simulated, attributed to the low values of the scalar dissipation relative to the critical value above which auto-ignition does not occur. In contrast, the flame LOL was considerably affected, in particular at low oxygen concentrations. Quasi-steady soot formation was similar; however, pronounced differences in soot oxidation behaviour are reported. The differences were further emphasised for a case with short injection duration: in such conditions, TCI was found to play a major role concerning the soot oxidation behaviour because of the importance of soot-oxidiser structure in mixture fraction space. Neglecting TCI leads to a strong over-estimation of soot oxidation after the end of injection. The results suggest that for some engines, and for some phenomena, the neglect of turbulent fluctuations may lead to predictions of acceptable engineering accuracy, but that a proper turbulent combustion model is needed for more reliable results.

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A Comprehensive Study of Effects of Mixing and Chemical Kinetic Models on Predictions of n-heptane Jet Ignitions with the PDF Method

Cited by 73 publications

References 69 publications

Engine Combustion Network (ECN): Global sensitivity analysis of Spray A for different combustion vessels

Engine Combustion Network (ECN): Global sensitivity analysis of Spray A for different combustion vessels

Transported PDF Modeling of Ethanol Spray in Hot-Diluted Coflow Flame

Influence of turbulence–chemistry interaction forn-heptane spray combustion under diesel engine conditions with emphasis on soot formation and oxidation

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