Anthony C. Iannetti and Jeffery P. Moder

Glenn Research Center, Cleveland, Ohio

Comparing Spray Characteristics from Reynolds

Averaged Navier-Stokes (RANS) National

Combustion Code (NCC) Calculations Against

Experimental Data for a Turbulent Reacting Flow

NASA/TM—2010-216735

July 2010

AIAA–2010–578
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Anthony C. Iannetti and Jeffery P. Moder

Glenn Research Center, Cleveland, Ohio

Comparing Spray Characteristics from Reynolds

Averaged Navier-Stokes (RANS) National

Combustion Code (NCC) Calculations Against

Experimental Data for a Turbulent Reacting Flow

NASA/TM—2010-216735

July 2010

AIAA–2010–578

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

48th Aerospace Sciences Meeting

sponsored by the American Institute of Aeronautics and Astronautics

Orlando, Florida, January 4–7, 2010
Acknowledgments

We would like thank to Dan Bulzan, Yolanda Hicks, Nan-Suey Liu, and Mathena Suri Raju for their valuable advice. This work 

was funded by the Subsonic Fixed Wing and Supersonic Fixed Wing programs in Aeronautics Research Mission Directorate.

High Performance Computing (HPC) resources were provided by the NASA Advanced Supercomputer division at

NASA Ames Research Center. We also wish to acknowledge the support of the Graphics and VISualization (G-VIS)

lab at NASA Glenn.

Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

Available electronically at http://gltrs.grc.nasa.gov

Trade names and trademarks are used in this report for identifi cation 

only. Their usage does not constitute an offi cial endorsement, 

either expressed or implied, by the National Aeronautics and 

Space Administration.

This work was sponsored by the Fundamental Aeronautics Program 

at the NASA Glenn Research Center.

Level of Review: This material has been technically reviewed by technical management. 

This report is a formal draft or working 

paper, intended to solicit comments and 

ideas from a technical peer group.

This report contains preliminary fi ndings, 

subject to revision as analysis proceeds.
NASA/TM—2010-216735 iii 

Contents 

1.0 Introduction ............................................................................................................................................. 2

2.0 Experimental Data .................................................................................................................................. 2

3.0 NCC Simulations .................................................................................................................................... 4

3.1 The National Combustion Code ....................................................................................................... 4

3.2 Geometry and Mesh Generation ....................................................................................................... 4

3.3 Operating Conditions ....................................................................................................................... 5

3.4 Chemistry Modeling ......................................................................................................................... 5

3.5 Liquid Phase Modeling..................................................................................................................... 6

3.5.1 Primary Atomization Using a Correlation .............................................................................. 6

3.5.2 Primary Atomization Using a Sheet Break-Up Model ........................................................... 7

3.5.3 Secondary Atomization Models .............................................................................................. 8

3.6 Computational Procedure ................................................................................................................. 8

4.0 Results and Discussion ........................................................................................................................... 9

4.1 Casers Performed ............................................................................................................................. 9

4.2 Comparison of Clip Planes ............................................................................................................... 9

4.3 Droplet Size Comparison ............................................................................................................... 19

4.4 Major Differences Between Steady-State RANS and Transient Flow Studies .............................. 36

4.4.1 Weaknesses of Both the Correlation and Primary Break-Up Modeling Approach .............. 37

5.0 Conclusions ........................................................................................................................................... 37

References ................................................................................................................................................... 37

List of Tables 

TABLE 1.—SINGLE STEP (GLOBAL) CHEMISTRY MODEL .............................................................. 6

TABLE 2.—REDUCED 10 STEP, 12 SPECIES CHEMISTRY MODEL IN CHEMKIN 

FORMAT ...................................................................................................................................................... 6

TABLE 3.—CFD CASES PERFORMED .................................................................................................... 9

List of Figures 

Figure 1.—Picture of the actual single swirler LDI experiment (Cai and Jeng, 2005). ................................ 3

Figure 2.—Overview of a PDPA system, showing the ellipse formed at the beam crossing. 

(Courtesy: Dantec) ........................................................................................................................................ 3

Figure 3.—Single element LDI injector geometry. ...................................................................................... 4

Figure 4.—Computational grid for the single element LDI combustor. The dimensions are in 

meters. ........................................................................................................................................................... 5

Figure 5.—Cumulative drop size distribution (spray initial condition) from the correlation with a 

given SMD of 32 and 42 m. ........................................................................................................................ 7

Figure 6.—A sketch of the transition from the internal flow to the external spray (Ref. 33). ...................... 7

Figure 7.—Contours of temperature [K] using single step chemistry with the atomization 

correlation for primary break-up and various secondary break-up models at the Y = 0 mm midplane. ........................................................................................................................................................... 10

Figure 8.—Contours of temperature [K] using ten step chemistry with the atomization correlation 

for primary break-up and various secondary break-up models at the Y = 0 mm mid-plane. ...................... 11

Figure 9.—Contours of temperature [K] using single step and ten step chemistry with the sheet 

model for primary break-up and various secondary break-up models at the Y = 0 mm mid-plane. ........... 12
NASA/TM—2010-216735 iv 

Figure 10.—Contours of fuel mass fraction (Jet-A, C12H23) using single step chemistry with the 

atomization correlation for primary break-up and various secondary break-up models at the Y = 0 

mm mid-plane. ............................................................................................................................................ 13

Figure 11.—Contours of fuel mass fraction (Jet-A, C12H23) using ten step chemistry with the 

atomization correlation for primary break-up and various secondary break-up models at the Y = 0 

mm mid-plane. ............................................................................................................................................ 14

Figure 12.—Contours of fuel mass fraction (Jet-A, C12H23) using single step and ten step 

chemistry with the sheet model for primary break-up and various secondary break-up models at 

the Y = 0 mm mid-plane. ............................................................................................................................ 15

Figure 13.—Contours of axial velocity [m/s] using single step chemistry with the atomization 

correlation for primary break-up and various secondary break-up models at the Y = 0 mm midplane. ........................................................................................................................................................... 16

Figure 14.—Contours of axial velocity [m/s] using ten step chemistry with the atomization 

correlation for primary break-up and various secondary break-up models at the Y = 0 mm midplane. ........................................................................................................................................................... 17

Figure 15.—Contours of axial velocity [m/s] using single step and ten step chemistry with the 

sheet model for primary break-up and various secondary break-up models at the Y = 0 mm midplane. ........................................................................................................................................................... 18

Figure 16.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 3 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 20

Figure 17.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 5 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 21

Figure 18.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 7 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 22

Figure 19.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 9 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 23

Figure 20.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 12 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 24

Figure 21.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 15 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 25

Figure 22.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 20 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 26

Figure 23.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 25 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 27

Figure 24.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 3 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 28

Figure 25.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 5 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 29

Figure 26.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 7 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 30
NASA/TM—2010-216735 v 

Figure 27.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 9 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 31

Figure 28.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 12 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 32

Figure 29.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 15 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 33

Figure 30.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 20 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 34

Figure 31.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental 

coordinate frame, for CFD and experimental data 25 mm downstream of the injector face in the 

X-Z mid-plane. ............................................................................................................................................ 35

Figure 32.—A PRNS mixing study of a Lean Direct Injection (LDI) combustor swirler. Pathlines 

are colored by axial velocity. The white isosurface of pressure elucidates the vortex core resulting 

from the swirler. (Courtesy: J. Horowitz). ................................................................................................. 36
NASA/TM—2010-216735 1 

Comparing Spray Characteristics from Reynolds Averaged NavierStokes (RANS) National Combustion Code (NCC) Calculations 

Against Experimental Data for a Turbulent Reacting Flow 

Anthony C. Iannetti and Jeffery P. Moder 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Abstract 

Developing physics-based tools to aid in reducing harmful combustion emissions, like Nitrogen 

Oxides (NOx), Carbon Monoxide (CO), Unburnt Hydrocarbons (UHC’s), and Sulfur Dioxides (SOx), is 

an important goal of aeronautics research at NASA. As part of that effort, NASA Glenn Research Center 

is performing a detailed assessment and validation of an in-house combustion CFD code known as the 

National Combustion Code (NCC) for turbulent reacting flows. To assess the current capabilities of NCC 

for simulating turbulent reacting flows with liquid jet fuel injection, a set of Single Swirler Lean Direct 

Injection (LDI) experiments performed at the University of Cincinnati was chosen as an initial validation 

data set. This Jet-A/air combustion experiment operates at a lean equivalence ratio of 0.75 at atmospheric 

pressure and has a 4 percent static pressure drop across the swirler. Detailed comparisons of NCC 

predictions for gas temperature and gaseous emissions (CO and NOx) against this experiment are 

considered in a previous work. The current paper is focused on detailed comparisons of the spray 

characteristics (radial profiles of drop size distribution and at several radial rakes) from NCC simulations 

against the experimental data. Comparisons against experimental data show that the use of the correlation 

for primary spray break-up implemented by Raju in the NCC produces most realistic results, but this 

result needs to be improved. Given the single or ten step chemical kinetics models, use of a spray size 

correlation gives similar, acceptable results. 

Nomenclature

Cp specific hear with respect to pressure 

D32 Sauter Mean Diameter (SMD) 

Dmin minimum droplet group diameter 

Dmax maximum droplet group diameter 

k turbulent kinetic energy 

P3 static pressure at combustor inlet 

Redrop liquid phase droplet group Reynolds Number 

SMD Sauter Mean Diameter (SMD), same as D32

T temperature 

Vdrop liquid phase droplet group velocity vector 

Vgas gas phase velocity vector 

V’

gas turbulent fluctuations of the gas phase velocity vector 

y

+

 non-dimensional turbulent wall boundary layer distance 

 turbulent dissipation 

 
NASA/TM—2010-216735 2 

1.0 Introduction 

The use of combustion Computational Fluid Dynamics (CFD) in the development of combustion 

technology has been greatly facilitated by the advancements made during the last decade in the areas of 

combustion modeling, numerical simulation, and computing platform. Further development of 

verification, validation, and uncertainty quantification will profoundly impact the reliability and utility of 

these modeling and simulation tools. Under the NASA Fundamental Aeronautics Program, an assessment 

of existing computational tools for emissions and flow field is being carried out. As a first step, the 

present effort aims at establishing the baseline for prediction methods and experimental data for Lean 

Direct Injection (LDI) (Refs. 1 to 3) combustion in confined, swirling flows. Combustion codes based on 

Reynolds Averaged Navier-Stokes (RANS), the Partially Resolved Numerical Simulation method (PRNS, 

using a two equation sub-grid model), and traditional Large Eddy Simulation (LES) using Smagorinsky 

type sub-grid approaches will be used; the present paper reports the preliminary investigation using the 

National Combustion Code (NCC). Currently, NASA is partnering through cooperative agreements with 

research groups at Stanford (Ref. 4) and Georgia Tech (Ref. 5) Universities to investigate LDI flow fields 

with LES. 

This paper extends the LDI combustion steady-state RANS CFD analysis of Davoudzadeh (Refs. 6 

and 7) for non-reacting flow and Iannetti et al., (Ref. 8) for reacting spray calculations. Where Iannetti 

compared gas phase quantities such a temperature, emissions, and the reacting gas phase flow field, this 

paper will compare the NCC using a steady-state RANS approach against experimental drop size 

measurements for a confined, swirling, reacting spray flow. This paper will attempt to provide some 

insight into whether experimental correlations or more sophisticated, less empirical, break-up models 

should be used for primary atomization. 

2.0 Experimental Data 

A detailed description of the experimental hardware, facility, diagnostics and results is given by Jun 

Cai, S.-M. Jeng, and R. Tacina (Ref. 9), and by Yongqiang Fu and San-Mou Jeng (Ref. 10). Only a brief 

summary is provided here. The spray measurements used an Aerometrics two-component Phase Doppler 

Particle Analyzer (PDPA) operated in 30° off-axis forward scatter mode. The transmitting and receiving 

lenses had focal lengths of 500 and 300 mm. A 3 W Argon laser was used as the light source. The data 

rate was 300 to 20,000 Hz and an average of 10,000 data points were collected during a 7 sec period at 

each measurement location. Spray velocity components (axial, radial, and tangential) and drop size 

distributions were collected at many axial locations, with around thirty-seven radial locations (–12 to 

24 mm radially from injector center) at each axial location. The comparisons presented in the current 

paper focus on axial locations “near” the injector (3, 5, 7, 9, 12, 15, 20, and 25 mm from injector exit 

face). The experiment is shown in Figure 1. 

Measurements at a particular axial and radial location (relative to the injector centerline) by the PDPA 

system take place in the intersection between the two incident laser beams. The measurement volume is 

defined here as the volume within which the modulation depth is higher than e–2 times the peak core laser 

intensity value and forms an ellipsoid with an essentially circular cross-section. Jeng, Cai, and Fu, do not 

provide enough information to calculate ellipsoidal measurement volume for PDPA system, we estimate 

the laser probe ellipsoidal measurement volume with a minor diameter of 1 mm and a major diameter of 

5 mm. In CFD simulations, computational spray data is collected in an ellipsoidal probe volume (with 

diameters of 1 by 1 by 10 mm) at the same axial and radial locations as the experiment. Figure 2 shows 

such a PDPA probe volume. 
NASA/TM—2010-216735 3 

Figure 1.—Picture of the actual single 

swirler LDI experiment (Cai and Jeng, 

2005). 

Figure 2.—Overview of a PDPA system, showing the ellipse formed at the beam crossing. 

(Courtesy: Dantec) 

X

Y



Detector 1

Detector 2

Scattering plane

Flow

Z






NASA/TM—2010-216735 4 

3.0 NCC Simulations 

3.1 The National Combustion Code 

The National Combustion Code (NCC) is a state of the art CFD program specifically designed for 

combustion processes. A short summary of the features of the NCC pertaining to this paper are: the use of 

unstructured grids (Ref. 11), massively parallel computing—with almost perfectly linear scalability 

(Refs. 12 and 13) on non-spray cases up to four thousand central processing units (CPU), a dynamic wall 

function with the effect of adverse pressure gradient (Ref. 14), low Reynolds number wall treatment 

(Ref. 15), and a cubic non-linear k-epsilon turbulence model (Refs. 16 and 17), lagrangian liquid phase 

spray model (Ref. 18), and stiff laminar chemistry integration. Recently, viscous low-speed 

preconditioning (Refs. 19 and 20) has been added to improve the low-speed convergence of the NCC in 

viscous regions, and the ability to handle multiple sets of periodic boundary conditions has also been 

added. The combination of these features is usually not available in other CFD codes and gives the NCC 

an advantage when computing recirculating, turbulent, reacting, spray flows. Previously, the NCC has 

undergone extensive validation studies for simple flows (Ref. 21), complex flows (Ref. 22), NOx

emissions prediction performance (Ref. 23), and traditional gas turbine combustor/injectors (Ref. 24). 

3.2 Geometry and Mesh Generation 

The single-element LDI swirler configuration is illustrated in Figure 3. Each element consists of an 

air passage with an upstream air swirler and a converging-diverging venturi section. The fuel is injected 

through the center of swirler and the fuel tip is at the throat of the venture. The air swirlers have helical, 

axial vanes with downstream vane angles of 60°. There are six vanes with an inside diameter of 9.3 mm 

and an outside diameter of 22.1 mm. The air then dumps into a 50.8 by 50.8 mm combustion section. 

Since the NCC allows for unstructured elements, the grid may be composed of any type and mix of 

three-dimensional elements. However, hexahedral elements were chosen because they are more efficient 

at filling a volume with a smaller number of elements compared to an all tetrahedral grid. Hexahedral 

elements also allow a better calculation of the normal derivatives that are crucial for accurate boundary 

layer resolution. Approximately 850,000 elements were used (shown in Fig. 4). Current simulations have 

y+ values ranging from 0.5 to 45 (non-dimensional) in various parts of the grid. The “Gridgen” mesh 

generation software was used to create all the grids used in the numerical simulation reported in this 

paper. 

Figure 3.—Single element LDI injector geometry. 
NASA/TM—2010-216735 5 

Figure 4.—Computational grid for the single element LDI combustor. The dimensions are in meters. 

3.3 Operating Conditions 

The gas-phase boundary conditions consist of the inlet to the swirler, the exit of the computational 

domain, and the walls. All walls are treated as no-slip and adiabatic. The air enters the swirler with 

uniform values for axial velocity (20.14 m/s), temperature (294.28 K), turbulent kinetic energy (k = 

1.521 m2

/s2) or 5 percent turbulence intensity level, and specific dissipation ( = 2.015 W/kg). The gasphase exit boundary condition is a uniform static pressure of 1 atm (101325 Pa), while the equivalence 

ratio is 0.75. The measured pressure drop (as a percentage of P3) during the experiments was measured at 

4 percent. The fuel nozzle used is a Parker-Hannifin 90°, hollow cone, pressure swirl atomizer which has 

the flow number of 0.75. 

3.4 Chemistry Modeling 

Ideally, we would prefer to use detailed chemical kinetic models. There are two problems with this 

approach: (1) Jet-A is a fuel and not a substance, and there are no universally accepted surrogate fuel 

models for Jet-A; (2) the computational costs associated with these models make them impractical when 

fine computational grids are used. Originally, a single-step, global chemistry model was used, shown in 

Table 1. This model was based on propane kinetics (Ref. 25), which are close to Jet-A’s reaction rates. 

The Jet-A fuel is modeled as single species (C12H23) in both gas-phase and liquid-phase solvers. The gas 

is treated as ideal mixture with five-coefficient curve fits for Cp (T) of each species and a CHEMKIN 

treatment of transport properties (species and ideal mixture rules). The single-step model allowed an 

easier start up in the solution process, by reducing the computational requirements during the ignition 

phase. Single-step models do not allow emissions calculations, only heat release. Because of this, a 

reduced ten-step, twelve species model based on propane kinetics (Refs. 26 and 27) was used, as shown in 

Table 2. The mechanism was developed by a gradual reduction of reaction steps and species using 

sensitivity techniques. The reduced mechanism also describes the formation of Carbon Monoxide and 

Nitrogen Oxide. However, only one nitrogen-oxide species, NO, has been used in the reduced 

mechanism. NO in the reduced mechanism represents the whole family of nitrogen oxides including nitric 

oxide by Zeldovich (Ref. 28) reactions, prompt NO reactions by Fenimore (Ref. 29), and nitrogen oxide 

formation through nitrous oxide. 
NASA/TM—2010-216735 6 

TABLE 1.—SINGLE STEP (GLOBAL) CHEMISTRY MODEL 

Reaction A 

(mole – cm – sec– K)

n E 

(cal/mole) 

1 4 C12H23 + 71 O2 => 48 CO2 + 46 H2O 

 GLO / C12H23 0.10 / 

 GLO / O2 1.65 /

8.60E+11 0.00 3.00E+4 

TABLE 2.—REDUCED 10 STEP, 12 SPECIES CHEMISTRY MODEL IN CHEMKIN FORMAT 

Reaction A 

(mole – cm – sec – K) 

n E 

(cal/mole) 

1 4 C12H23 + 47 O2 => 48 CO + 46 H2O 

GLO / C12H23 0.1 / 

GLO / O2 1.6 /

1.46E+13 0.00 3.40E+4 

2 H2 + O2 <=> H2O + O 3.98E+11 1.00 4.80E+4 

3 H2 + O <=> H + OH 3.00E+14 0.00 6.00E+3 

4 H + O2 <=> O + OH 4.00E+14 0.00 1.80E+4 

5 CO + OH <=> CO2 + H 1.51E+07 1.28 –7.58E+2 

6 H2O + O2 <=> 2O + H2O 3.17E+12 2.00 1.12E+5 

7 CO + H2O <=> CO2 + H2 5.50E+04 1.28 –1.00E+3 

8 N2 + O <=> N + NO 1.00E+14 0.00 7.50E+4 

9 N + O2 <=> NO + O 6.30E+09 1.10 6.28E+3 

10 N + OH <=> NO + H 3.80E+13 0.00 0.00E+0 

3.5 Liquid Phase Modeling 

The liquid Jet-A spray is evolved using a dilute spray Lagrangian solver4 which neglects any dropdrop interactions. Turbulence effects follow the KIVA-II approach (Ref. 30) of adding a turbulent 

fluctuation velocity to gas-phase velocity when calculating droplet drag and vaporization. The 

evaporation model includes solution of internal drop temperature distribution (thirteen point one 

dimensional mesh, finite-difference solution of a Hill vortex model) and a droplet regression rate 

employing three different correlations depending on droplet Reynolds number, Redrop (where Redrop is 

based on the relative speed Vgas + V’

gas – Vdrop). 

Two different primary atomization models and two different secondary break-up models are 

described below. 

3.5.1 Primary Atomization Using a Correlation 

The liquid spray injection is modeled using a specified drop size distribution at injector exit face. The 

specified drop size distribution uses a Sauter Mean Diameter (SMD) of D32 = 32 m and D32 = 42 m, a 

3-D hollow cone with a half-cone angle of 14° and 32 circumferential streams leaving the injector. The 

original SMD of 32 m for the injection droplet size was based on previous dropsize data and experience 

with Parker Hannifin LDI fuel injectors. A new SMD of 42 m was based on pressure swirl atomizer 

correlations from Lefevbre (Ref. 31). Drop size distributions are currently based on a widely used 

correlation (Ref. 32) but other correlations may be considered. Figure 5 shows the cumulative drop size 

distribution, the mass fraction of droplets at a given size diameter (the spray initial condition used), from 

the correlation with a SMD of 32 and 42 m. The liquid temperature, mass flow rate and drop speed are: 

 Tdrop = 300 K 

 Liquid mass flow rate = 0.415E-03 kg/sec 

 Drop speed = 20 m/s 
NASA/TM—2010-216735 7 

Figure 5.—Cumulative drop size distribution (spray initial condition) from the correlation with a given 

SMD of 32 and 42 m. 

Figure 6.—A sketch of the transition from the internal flow to the external spray (Ref. 33). 

3.5.2 Primary Atomization Using a Sheet Break-Up Model 

The Liquid Instability Sheet Atomization (LISA) model for primary break-up was used. This was 

originally formulated by Schmidt et al., (Ref. 33) and refined by Chryssakis et al., (Ref. 34). The LISA 

mathematical model was coded in Fortran 95 as a module by the company CFDRC (via NASA’s Small 

Business Innovative Research program) and integrated into the NCC by Raju (Ref. 35). Figure 6 shows 

the primary atomization process assumed in the LISA model. Essentially, a film sheet is produced from 

the rotating flow inside a pressure swirl atomizer. This then forms ligaments which further tear to form 

droplets. 
NASA/TM—2010-216735 8 

3.5.3 Secondary Atomization Models 

The Rayleigh-Taylor, a model that describes break-up due to long waves in a decelerating flow, and 

the Enhanced Taylor Analogy Break-up (ETAB), initially designed for diesel fuel injection and improved 

version of the Taylor Analogy Break-up (TAB) model, were used to model the secondary atomization that 

occurs downstream stream of the primary break-up. These are described in detail in Raju. 

During all Lagrangian spray integrations in NCC, each spray particle represents a number of actual 

droplets which for that spray particle are all assumed to behave in the same way and thus have the same 

drop diameter, internal droplet temperature distribution, and for multi-component drops, the same internal 

droplet species composition. The sheet break-up atomization model injects a user-defined number of 

spray particles with each particle having the same drop diameter. When primary atomization occurs, the 

number of spray particles remains the same, but the drop diameter at break-up is determined by randomly 

sampling from a predefined drop distribution function. Thus, while the drop size of all injected spray 

particles was initially the same, as each particle undergoes primary atomization, a distribution of drop 

sizes results (but the number of spray particles tracked during the simulations remains unchanged). Also, 

all secondary break-up models in NCC currently only change the drop diameter associated with a given 

spray particle; no new spray particles are created by any of the secondary break-up models. 

3.6 Computational Procedure 

The simulations are steady-state and solve the Favre-averaged transport equations for species, 

momentum and energy, as well as a two-equation k- turbulence model. Staging was used in the solution 

process; cold-flow calculations and initial combustion calculations were performed using a single-step 

chemistry model with lagrangian spray until a steady state solution was obtained. The final stage of CFD 

calculations was performed by switching from the one-step chemistry model to the reduced chemistry 

model; this was done by changing the input chemistry-parameters of the code. It is important to note that 

no turbulence—chemistry interaction model was used for this case, so called “laminar chemistry”. So, 

averaged temperature and averaged mass fractions are used to compute the reaction rate. For this case, we 

believe this an appropriate as an engineering assumption, because for this particular case, turbulent kinetic 

energy (k) is below 20 m2

/s2, with the peak occurring at the tip of the fuel injector. 

Calculation of the source term due to chemical kinetics uses the explicit “reference species” approach 

described in the KIVA-II manual. In the current implementation, the explicit “reference species” 

integration of chemical kinetics source is performed using three sub-iterations within each pseudo-time 

step of gas-phase Runge-Kutta integration in pseudo-time. 

The NCC computations for reacting and non-reacting flow were run in general until the flow residuals 

were reduced three orders of magnitude. The mass flow rates at the boundary conditions were also 

monitored as a convergence criterion. Dissipation (JST type) was set at 0.0 for second order dissipation 

(2) and 0.1 for fourth order dissipation (4) (Ref. 36). The value of k2, the constant that scales the second 

order dissipation gradient switch, was set at 0.50. Setting the second order dissipation to zero is absolutely 

necessary to accurately resolving flow features, like jets. A CFL number of 1.0 was used. A cubic, nonlinear k-epsilon model with a variable Cmu coefficient was used. This model was selected because of the 

swirling flow. A dynamic wall function with pressure gradient effects was used to model near wall 

turbulent flow effects. 

Computations were performed on a variety of computer platforms, namely SGI ICE computer 

“RTJones” at NASA Ames and Linux clusters Glenn. The “RTJones” supercomputer was preferred 

because it was considerably faster because of its high speed, low-latency interconnect. This interconnect 

was important because the Lagrangian spray model created a load unbalance in compute nodes. The high 

speed interconnect seemed to mitigate the load imbalance. It takes approximately one week to complete a 

single LDI combustion case using 96 processors. After the baseline run was completed, new runs starting 

from the baseline case took about one to five days depending on the chemistry model and secondary 

break-up model used. 
NASA/TM—2010-216735 9 

4.0 Results and Discussion 

4.1 Casers Performed 

The combustion CFD cases calculated with the NCC are shown in Table 3. A total of twelve cases 

were performed. 

TABLE 3.—CFD CASES PERFORMED 

Case Chemistry model Primary break-up model Secondary break-up model 

1 Single step Correlation with 32 m SMD Rayleigh-Taylor 

2 Single step Correlation with 32 m SMD Enhanced Taylor Analogy Break-up 

3 Single step Correlation with 42 m SMD Rayleigh-Taylor 

4 Single step Correlation with 42 m SMD Enhanced Taylor Analogy Break-up 

5 Ten step Correlation with 32 m SMD Rayleigh-Taylor 

6 Ten step Correlation with 32 m SMD Enhanced Taylor Analogy Break-up 

7 Ten step Correlation with 42 m SMD Rayleigh-Taylor 

8 Ten step Correlation with 42 m SMD Enhanced Taylor Analogy Break-up 

9 Single step Sheet break-up Rayleigh-Taylor 

10 Single step Sheet break-up Enhanced Taylor Analogy Break-up 

11 Ten step Sheet break-up Rayleigh-Taylor 

12 Ten step Sheet break-up Enhanced Taylor Analogy Break-up 

4.2 Comparison of Clip Planes 

Clip planes in Figures 7 to 15 attempt to show how the different atomization models affect the overall 

flow field. Figures 7 to 9 show how the break-up models affect temperature. For the single step kinetics 

model, very little difference is observed when using the droplet size correlation and the different 

secondary break-up models. The ten step kinetics models are much more sensitive to the type of 

secondary atomization models used, probably because of grid density. The overall flame shape is roughly 

the same. When looking at Figure 9, we observed a dramatically different flame shape from using the 

correlation for primary atomization. These results indicate the droplet sizes produced by the sheet breakup model are too large. Figures 10 to 12 show the unburnt fuel vapor (C12H23, Jet-A). Similar to the 

temperature contours, little difference is seen when using the correlation with single step kinetics. Using 

ten step kinetics, we generally see smaller regions of fuel vapor than in the single step case, except for the 

42 m SMD with the ETAB model. The sheet break model produces very small regions of fuel vapor, 

and regions appear to exist on the sides of the combustor wall. This also indicted large droplet sizes being 

produced. Figures 13 to 15 qualitatively show that the flow field is not affected by the different 

atomization models. This indicates that the mean recirculation zone is fairly stable and insensitive to heat 

release. 
NASA/TM—2010-216735 10 

Figure 7.—Contours of temperature [K] using single step chemistry with the atomization correlation for primary 

break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 11 

Figure 8.—Contours of temperature [K] using ten step chemistry with the atomization correlation for primary break-up 

and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 12 

Figure 9.—Contours of temperature [K] using single step and ten step chemistry with the sheet model for primary 

break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 13 

Figure 10.—Contours of fuel mass fraction (Jet-A, C12H23) using single step chemistry with the atomization correlation 

for primary break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 14 

Figure 11.—Contours of fuel mass fraction (Jet-A, C12H23) using ten step chemistry with the atomization correlation 

for primary break-up and various secondary break-up models at the Y = 0 mm mid-plane. 
NASA/TM—2010-216735 15 

Figure 12.—Contours of fuel mass fraction (Jet-A, C12H23) using single step and ten step chemistry with the sheet 

model for primary break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 16 

Figure 13.—Contours of axial velocity [m/s] using single step chemistry with the atomization correlation for primary 

break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 17 

Figure 14.—Contours of axial velocity [m/s] using ten step chemistry with the atomization correlation for primary 

break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 18 

Figure 15.—Contours of axial velocity [m/s] using single step and ten step chemistry with the sheet model for primary 

break-up and various secondary break-up models at the Y = 0 mm mid-plane. 

 
NASA/TM—2010-216735 19 

4.3 Droplet Size Comparison 

Figures 16 to 23 compare CFD versus experimental data for the D10 droplet size (simple average), 

while Figures 24 to 31 compare CFD versus experimental data for the D32 mean size, the Sauter Mean 

Diameter (SMD, an approximation of mean droplet surface area). The plots show radial rakes in the X-Z 

mid-plane (experimental coordinates) at 3, 5, 7, 9, 12, 15, 20, and 25 mm downstream from the injector 

face (approximately 7 mm from the injector tip, which is located at the narrowest portion of the swirler 

venturi). 

Figures 16 and 17 show a good comparison for the correlation versus experimental data, except for 

the sheet break-up model, which shows a droplet size over-prediction by at least a factor of five. Given 

these results, it is obvious that the sheet break-up model produces droplets that are too large. Staying with 

the correlation (both droplet sizes) we basically observe a decrease in the center instead of a peak. 

However, this difference is fairly small. The CFD shows no droplets in the center starting at 9 mm 

downstream of the injector face. This gap becomes more pronounces and the rakes move toward 25 mm. 

Experimental data set one does not show this gap, and is surprisingly even at an approximately constant 

50 m. Experimental data set two does not show any droplets in the center, starting a 20 mm from the 

injector face. 

Looking at the D32, Figure 25 shows that the correlation produces fairly constant droplet size, with a 

slight decrease in the center, while the experimental data produces a local minimum at the center, with 

two symmetrically peaks moving radially outward (“a volcano”). The correlation under-predicts the SMD 

by a factor of two, while the sheet break-up model over-predicts by a factor of two and a half. As we 

move downstream, generally the comparison improves, but we see that using the correlation, we get a 

minimum for the CFD droplet size in the radial center versus a peak shown by the experimental data. 

Figure 26 surprisingly shows a good comparison for the sheet break-up model using the RT secondary 

atomization model. As with the D10 droplet size, the D32 CFD results show no droplets in the center 

beginning at 9 mm from the injector face. Qualitatively, the correlation at least has a similar shape as the 

experimental data. 20 mm downstream (Fig. 30), the correlation compares well with the second set of 

experimental data. 

Given both the D10 and D32 droplet sizes, it seems that the use of the given correlation for primary 

atomization gives better results. At this time, we cannot conclude with secondary atomization model is 

more accurate, because they appear to be producing similar results. 
NASA/TM—2010-216735 20 

Figure 16.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 3 mm downstream of the injector face in the X-Z mid-plane. 

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 21 

Figure 17.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 5 mm downstream of the injector face in the X-Z mid-plane. 

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 22 

Figure 18.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 7 mm downstream of the injector face in the X-Z mid-plane. 

 

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One
NASA/TM—2010-216735 23 

Figure 19.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 9 mm downstream of the injector face in the X-Z mid-plane. 

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 24 

Figure 20.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 12 mm downstream of the injector face in the X-Z mid-plane. 

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One
NASA/TM—2010-216735 25 

Figure 21.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 15 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 26 

Figure 22.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 20 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250 1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250 1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 27 

Figure 23.—Line Plots of D10 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 25 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D10 [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One
NASA/TM—2010-216735 28 

Figure 24.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 3 mm downstream of the injector face in the X-Z mid-plane.

 

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 29 

Figure 25.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 5 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 30 

Figure 26.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 7 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One
NASA/TM—2010-216735 31 

Figure 27.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 9 mm downstream of the injector face in the X-Z mid-plane.

 

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 32 

Figure 28.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 12 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One
NASA/TM—2010-216735 33 

Figure 29.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 15 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 34 

Figure 30.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 20 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

Exp_Set_Two

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One

Exp_Set_Two
NASA/TM—2010-216735 35 

Figure 31.—Line Plots of D32 [microns] versus the radial axis X [mm], in the experimental coordinate frame, for CFD 

and experimental data 25 mm downstream of the injector face in the X-Z mid-plane.

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 1Step Corr 32micron RT

1Step Corr 32micron ETAB

1Step Corr 42micron RT

1Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250 10Step Corr 32micron RT

10Step Corr 32micron ETAB

10Step Corr 42micron RT

10Step Corr 42micron ETAB

Exp_Set_One

X (Exp Coord) [mm]

D32 (SMD) [micron]

-20 0 20 0

50

100

150

200

250

1Step Sheet RT

1Step Sheet ETAB

10Step Sheet RT

10Step Sheet ETAB

Exp_Set_One
NASA/TM—2010-216735 36 

4.4 Major Differences Between Steady-State RANS and Transient Flow Studies 

Results from PRNS simulations at NASA Glenn Research Center, and LES flow simulations from 

Stanford and Georgia Tech have shown that a strong vortex core influences the flow field near the LDI 

fuel injector tip. Figure 32 shows the vortex core and unsteady streak lines from a PRNS simulation. This 

vortex is an unsteady flow feature and its mean cannot be approximate through current turbulence 

modeling techniques and will probably never be modeled, the resolution of this flow feature will always 

have to have some “directly resolved technique.” It is believed that this flow feature enhances dispersion 

the spray droplets, and greatly improves the emission reduction performance of this LDI fuel injector. 

Therefore, we believe future single swirler LDI simulations should always be PRNS or LES transient 

flow simulations to accurately compute injector/combustor performance. 

Figure 32.—A PRNS mixing study of a Lean Direct Injection (LDI) combustor swirler. Pathlines are colored by axial 

velocity. The white isosurface of pressure elucidates the vortex core resulting from the swirler. (Courtesy: J. 

Horowitz).

 
NASA/TM—2010-216735 37 

4.4.1 Weaknesses of Both the Correlation and Primary Break-Up Modeling Approach 

The use of correlations, even for a specific fuel injector for LDI combustor, is that the flow field 

cannot be decoupled from the atomization process. Without out a standalone fuel injector, spray droplet 

measurements usually cannot be accurately measured; including the venturi in most LDI designs usually 

does not allow optical access for PDPA measurement. Also, as shown by numerous CFD results 

(including this one), combustion occurs in the primary atomization area, which is another coupling 

process. 

The problem with using break-up models is that at some point, they use correlated film thickness data 

from Lefebvre, and assume some type of distribution shape. In this paper, based on the spray size 

comparison, it appears that the χ

2

 statistical correlation in the current implementation of the LISA model 

is not a valid assumption. Rosin-Rammler, the distribution used in the correlation, should be tried instead. 

We believe the film thickness, at the very least, must be directly computed. If possible, the 

atomization process should be directly simulated with combustion; perhaps up to 3 mm downstream of 

the fuel injector tip, and then continue the calculation with lagrangian dilute spray modeling. 

5.0 Conclusions 

We have thoroughly explored the single swirler LDI validation case with a variety of primary and 

secondary break-up atomization models. Comparisons against experimental data show that the use of the 

correlation for primary spray break-up implemented by Raju in the NCC produces most realistic results, 

but this result needs to be improved. Given the single or ten step chemical kinetics models, use of a spray 

size correlation gives similar, acceptable results. For current LDI simulations, a spray size correlation 

should be used over the current sheet break-up model. We believe this case needs to be further explored 

by directly calculating the film thickness of the pressure swirl atomizer used in the single swirler LDI 

case, and the use of LES as a flow solution method. 

References 

1. Tacina, R., Mansour, A., Partelow, L., Wey, C., “Experimental Sector and Flame-Tube Evaluations of 

a Multipoint Integrated Module Concept for Low Emission Combustors,” GT–2004–53263, ASME 

Turbo Expo 2004, Vienna, Austria, 2004. 

2. Tacina, R., Wey, C., Laing, P., and Mansour, A., “Sector Tests of a Low-NOx, Lean-Direct-Injection, 

MultiPoint Integrated Module Combustor Concept,” GT–2002–30089, 2002. 

3. Tacina, R., Wey, C., Laing, P., and Mansour, A., “A Low NOx Lean-Direct Injection, MultiPoint 

Integrated Module Combustor Concept for Advanced Aircraft Gas Turbines,” NASA/TM—2002-

211347, Porto, Portugal, July 9–12, 2001. 

4. El-Asrag H., and Pitsch H., “Radiation-spray Coupling for Realistic Flow Configurations,” Center for 

Turbulence Research Annual Research Briefs, Stanford University, Stanford, CA, USA, 2008. 

5. Patel, N., Menon, S., “Simulation of Spray–Turbulence–Flame Interactions in a Lean Direct Injection 

Combustor,” Combustion and Flame, vol. 153, pp. 228–257, 2008. 

6. Davoudzadeh, F., Liu, N.-S., “Validation of the National Combustion Code (NCC),” Presentation, 

Ultra-Efficient Engine Technology Program Technical Forum, NASA Glenn Research Center, 

October 27–29, 2003. 

7. Davoudzadeh, F., Liu, N.-S., “Numerical Prediction of Non-Reacting and Reacting Flow in a Model 

Gas Turbine Combustor,” GT–2004–53496, Proceedings of the ASME Turbo Expo, Vienna, Austria, 

2004. 

8. Iannetti, A.C., Liu, N.-S., Davoudzadeh, F., “The Effect of Spray Initial Condition on Heat Release 

and Emissions in LDI CFD Calculations,” NASA/TM—2008-215422, Glenn Research Center, 

Cleveland, OH, USA, 2009. 
NASA/TM—2010-216735 38 

9. Cai, J., S.-M. Jeng, S.-M., “The Structure of a Swirl- Stabilized Reacting Spray Issued from an Axial 

Swirler,” AIAA–2005–1424, 43rd AIAA Aerospace Sciences Meeting & Exhibit, 10–13, Reno, NV, 

USA, 2005. 

10. Fu, Y., Jeng, S.-M., Tacina, R., “Characteristics of the Swirling Flow Generated by an Axial Swirler,” 

Proceedings of GT2005 ASME Turbo Expo 2005: Power for Land, Sea and Air June 005, RenoTahoe, Nevada, USA, 2005. 

11. Stubbs, R., M., and Liu, N.-S., “Preview of the National Combustion Code,” AIAA 97–3114, 33rd 

AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, July 6–9, Seattle, WA, USA, 

1997. 

12. Quealy, A., Ryder, R., Norris, A., and Liu, N.-S., “National Combustion Code: Parallel 

Implementation and Performance,” NASA/TM—2000-209801, 2000. 

13. Quealy, A., “National Combustion Code Parallel Performance Enhancements,” NASA/CR—2002-

211340. 

14. Shih, T.-H., Povinelli, L.A., Liu, N.-S and Chen, K.-H., “Generalized Wall Function for Complex 

Turbulent Flows,” NASA/TM—2000-209936, 2000. 

15. Chien, K.Y., “Prediction of Boundary Layer Flows with a Low – Reynolds Number Turbulence 

Model,” AIAA J., vol. 20, no. 1, pp. 33–38, 1982. 

16. Shih, T.-H., Chen, K.-H., Liu, N.-S., Lumley, J.L., “Modeling of Turbulent Swirling Flows,” 

NASA-TM–113112, Glenn Research Center, Cleveland, OH, 1998. 

17. Shih, T.-H., Chen, K.-H., and Liu, N.-S., “A Non-Linear k-epsilon Model for Turbulent Shear 

Flows,” AIAA Paper 98-3983, 1998. 

18. Raju, M.S., “LSPRAY-II: A Lagrangian Spray Module,” NASA/CR—2004-212958, 

Glenn Research Center, Cleveland, OH, 2004. 

19. S. Venkateswaran, J.M. Weiss, C.L. Merkle, Y.-H. Choi, “Propulsion-Related Flowfields Using 

Preconditioned Navier-Stokes Equations,” AIAA–92–3437, 1992. 

20. S. Venkateswaran, C.L. Merkle, “Efficiency and Accuracy Issues in Contemporary CFD 

Algorithms,” AIAA–2002–2251, 2002. 

21. Chen, K.-H., Norris, A.T., Quealy, A., and Liu, N.-S., “Benchmark Test Cases for The National 

Combustion Code,” 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 

Cleveland, OH, USA, July 13–15, 1998. 

22. Iannetti, A., Tacina, R., Jeng, S.-M., and Cai, J., “Towards Accurate Prediction of Turbulent, ThreeDimensional, Recirculating Flows With the NCC,” NASA/TM—2001-210761, AIAA–2001–0809, 

2001. 

23. T.-H. Shih, A. Norris, A. Iannetti, C.J. Marek, T.D. Smith, N.-S. Liu, and L.A. Povinelli (NASA, 

Glenn Research Center, Cleveland, OH, “A Study of Hydrogen/Air Combustor Using NCC,” 

AIAA–2001–808, Aerospace Sciences Meeting and Exhibit, 39th, Reno, NV, Jan. 8–11, 2001. 

24. Iannetti, A.C., Chen, K.-H., “An Initial Comparison of National Combustor Code Simulations Using 

Various Chemistry Modules With Experimental Gas Turbine Combustor Data,” 

AIAA–2000–0330, 38th AIAA Aerospace Sciences Meeting, Reno, NV, USA, 2000. 

25. C.K. Westbrook and F.L. Dryer, “Simplified Reaction Mechanisms for The Oxidation of 

Hydrocarbon Fuels In Flames,” Combust. Sci. Technology, vol. 27, p. 31, 1981. 

26. Penko, P.F.; Kundu, K.P.; Siow, Y.K.; and Yang, S.L., “A Kinetic Mechanism for Calculation of 

Pollutant Species in Jet-A Combustion,” AIAA–2000–3035, 2000. 

27. Kundu, K.P.; Penko, P.F.; and VanOverbeke, T.J., “A Practical Mechanism for Computing 

Combustion in Gas Turbine Engines,” AIAA–99–2218, 1999. 

28. Zeldovich, Y.B. The Oxidation of Nitrogen in Combustion and Explosions. Acta Physicochimica 

URSS 21. pp. 577–628, 1946. 

29. Fennimore, C.P., 13th Symposium. (Int) Comb., p. 371, 1971. 

30. Amsden, A.A., O’Rourke, P.J., and Butler, T.D., “KIVA-II: A computer program for chemically 

reactive flows with sprays,” Report Number LA-11560-MS, Los Alamos National Lab, 1989. 
NASA/TM—2010-216735 39 

31. Lefebvre, A.H., Atomization and Sprays, Hemisphere Publishing Corporation, New York, NY, USA, 

1989. 

32. El Banhawy, Y. and Whitelaw, J.H., “Calculation of the Flow Properties of a Confined KeroseneSpray Flame,” AIAA Journal, vol. 18, no. 12, pp. 1503–1510, 1980. 

33. Schmidt, D.P., et al., “Pressure-Swirl Atomization in the Near Field,” SAE Paper 1999-01-0496, 

1999. 

34. Chryssakis, C., et al., “Fuel Spray Simulation of High-Pressure Swirl-Injector for DISI Engines and 

Comparison With Laser Diagnostic Measurements,” SAE Paper 2003-01-0007, 2003. 

35. Raju, M.S., “Numerical Investigation of Various Atomization Models in the Modeling of a Spray 

Flame,” NASA/CP—2005-214033, QSS Group, Glenn Research Center, Cleveland, OH, 2005. 

36. Swanson, R.C., and Turkel, E., “Multistage Schemes with Multigrid for Euler and Navier – Stokes 

Equations,” NASA-TP-3631, 1997. 
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14. ABSTRACT

Developing physics-based tools to aid in reducing harmful combustion emissions, like Nitrogen Oxides (NOx), Carbon Monoxide (CO), 

Unburnt Hydrocarbons (UHC’s), and Sulfur Dioxides (SOx), is an important goal of aeronautics research at NASA. As part of that effort, 

NASA Glenn Research Center is performing a detailed assessment and validation of an in-house combustion CFD code known as the 

National Combustion Code (NCC) for turbulent reacting flows. To assess the current capabilities of NCC for simulating turbulent reacting 

flows with liquid jet fuel injection, a set of Single Swirler Lean Direct Injection (LDI) experiments performed at the University of Cincinnati 

was chosen as an initial validation data set. This Jet-A/air combustion experiment operates at a lean equivalence ratio of 0.75 at atmospheric 

pressure and has a 4 percent static pressure drop across the swirler. Detailed comparisons of NCC predictions for gas temperature and 

gaseous emissions (CO and NOx) against this experiment are considered in a previous work. The current paper is focused on detailed 

comparisons of the spray characteristics (radial profiles of drop size distribution and at several radial rakes) from NCC simulations against 

the experimental data. Comparisons against experimental data show that the use of the correlation for primary spray break-up implemented 

by Raju in the NCC produces most realistic results, but this result needs to be improved. Given the single or ten step chemical kinetics 

models, use of a spray size correlation gives similar, acceptable results.

15. SUBJECT TERMS

Combustion; Computational fluid dynamics; Turbulent flow; Sprays 

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