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Research Papers: Fuel Combustion

Large Eddy Simulation of High Reynolds Number Nonreacting and Reacting JP-8 Sprays in a Constant Pressure Flow Vessel With a Detailed Chemistry Approach

[+] Author and Article Information
Luis Bravo

Mem. ASME
U.S. Army Research Laboratory,
Vehicle Technology Directorate,
4603 Flare Loop Drive,
Aberdeen Proving Ground, MD 21005
e-mail: luis.g.bravo2.civ@mail.mil

Sameera Wijeyakulasuriya

Mem. ASME
Convergent Science, Inc.,
6400 Enterprise Ln,
Madison, WI 53719
e-mail: sameera.wijeyakulasuriya@convergecfd.com

Eric Pomraning

Mem. ASME
Convergent Science, Inc.,
6400 Enterprise Ln,
Madison, WI 53719
e-mail: pomraning@convergecfd.com

Peter K. Senecal

Mem. ASME
Convergent Science, Inc.,
6400 Enterprise Ln,
Madison, WI 53719
e-mail: senecal@convergecfd.com

Chol-Bum Kweon

U.S. Army Research Laboratory,
Vehicle Technology Directorate,
4603 Flare Loop Drive,
Aberdeen Proving Ground, MD 21005
e-mail: chol-bum.m.kweon2.civ@mail.mil

1Corresponding author.

Contributed by the Internal Combustion Engine Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received February 12, 2016; final manuscript received February 16, 2016; published online March 24, 2016.Editor: Hameed Metghalchi.This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

J. Energy Resour. Technol 138(3), 032207 (Mar 24, 2016) (12 pages) Paper No: JERT-16-1088; doi: 10.1115/1.4032901 History: Received February 12, 2016; Revised February 16, 2016

In military propulsion applications, the characterization of internal combustion engines operating with jet fuel is vital to understand engine performance, combustion phasing, and emissions when JP-8 is fully substituted for diesel fuel. In this work, high-resolution large eddy simulation (LES) simulations have been performed in-order to provide a comprehensive analysis of the detailed mixture formation process in engine sprays for nozzle configurations of interest to the Army. The first phase examines the behavior of a nonreacting evaporating spray, and demonstrates the accuracy in predicting liquid and vapor transient penetration profiles using a multirealization statistical grid-converged approach. The study was conducted using a suite of single-orifice injectors ranging from 40 to 147 μm at a rail pressure of 1000 bar and chamber conditions at 900 K and 60 bar. The next phase models the nonpremixed combustion behavior of reacting sprays and investigates the submodel ability to predict auto-ignition and lift-off length (LOL) dynamics. The model is constructed using a Kelvin Helmholtz–Rayleigh Taylor (KH–RT) spray atomization framework coupled to an LES approach. The liquid physical properties are defined using a JP-8 mixture containing 80% n-decane and 20% trimethylbenzene (TMB), while the gas phase utilizes the Aachen kinetic mechanism (Hummer, et al., 2007, “Experimental and Kinetic Modeling Study of Combustion of JP-8, Its Surrogates, and Reference Components in Laminar Non Premixed Flows,” Proc. Combust. Inst., 31, pp. 393–400 and Honnet, et al., 2009, “A Surrogate Fuel for Kerosene,” Proc. Combust. Inst., 32, pp. 485–492) and a detailed chemistry combustion approach. The results are in good agreement with the spray combustion measurements from the Army Research Laboratory (ARL), constant pressure flow (CPF) facility, and provide a robust computational framework for further JP-8 studies of spray combustion.

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References

Figures

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Fig. 1

Ignition delay of C10H22/air mixture with φ = 1.0, and pressures of 11, 13, 40, and 80 bar. The solid symbols indicate measured data [27]. The solid lines and open symbols indicate the predicted ignition delay using the parent mechanism [15,16] and skeletal mechanism, respectively.

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Fig. 2

Ignition delay of TMB (C9H12)/air mixture with φ = 0.5, and pressures at 10 and 20 bar. The solid symbols indicate measured data [28]. The solid lines and open symbols indicate the predicted ignition delay using the parent mechanism [15,16] and skeletal mechanism, respectively.

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Fig. 3

ROI measurement for conditions: JP-8 fuel, rail pressure 1000 bar, and diameter 90 μm (Table 2, case 4). Measurements from Ref. [31].

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Fig. 4

Instantaneous liquid and vapor penetration profiles as a function of time (case 2). Injection and back pressures 1000 bar, 60 bar, respectively, chamber density 22.8 kg/m3.

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Fig. 5

Multishot ensemble averaged transient spray penetration results for multiscale nozzle and comparison to measurements. (Top) liquid (bottom) vapor phase profiles. Measurements from Ref. [30]. The finest cell sizes used in these cases are underlined in Table 3.

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Fig. 6

Effects of nozzle orifice dimension on spray penetration parameters with multiple realizations conducted using high fidelity LES. Measurements from Ref. [30]. The finest cell resolutions used are shown within parentheses in figure legends.

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Fig. 7

Comparison of measurements [30] and simulations: (column 1) Mie/Schlieren spray experimental images (column 2) density contours (column 3) and temperature contours of LES calculations. The finest cell sizes used in these cases are underlined in Table 3.

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Fig. 8

Peak chamber individual species mass fractions of YCH20 formaldehyde and YOH hydroxyl. Grid sensitivity study with parent and skeletal mechanism at Δxmin = 125 μm resolution level.

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Fig. 9

Peak chamber individual species mass fractions of YCH20 formaldehyde and YOH hydroxyl. Grid sensitivity study with parent and skeletal mechanisms at Δxmin = 125 μm resolution level.

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Fig. 10

Effect of grid refinement Δxmin= {500, 250, 125} μm on the spray combustion transient parameters including (left) peak chamber temperature and (right) peak chamber temperature

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Fig. 11

Time series of temperature (K) contours is shown at (left) 0.5 ms, (middle) 1.0 ms, and (right) 1.5 ms. The finest grid resolution used is Δxmin=125μm.

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Fig. 12

Transient JP-8 reacting spray contours at t = 0.5, 1.0, and 1.5 ms of (top) hydroxyl species mass (middle) mixture fraction and (bottom) turbulent kinetic energy. The finest grid resolution used is 125 μm.

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Fig. 13

Time history of the {min, max, average} number of species used in the DMR strategy. Also shown is the number of species in the parent mechanism.

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Fig. 14

(Left column) Ignition delay of C10H22/air mixture and comparison with experiments from Ref. 27. (Right column) ignition delay of C10H22/TMB surrogate mixture, the solid lines indicate the predicted ignition delay using the parent chemical mechanism [25,26], and dashed lines indicate skeletal chemical mechanism.

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