1. Spray G - Program 9:30 Introduction
Topic 8 – Spray G Nozzle Geometry and Internal Nozzle Flow
Organizer: Chris Powell (Argonne)
9:40 Nozzle Geometry and Near-Nozzle Experiments
Daniel Duke (Argonne)
10:20 Internal and Near-Nozzle Flow Modeling
Ron Grover (GM)
11:00 Break
Topic 9 – Evaporative Spray G
Organizer: Daniel Vaquerizo (CMT)
11:30 Macroscopic Spray Visualization and Modeling
Josh Lacey (Melbourne)
12:10 Spray Mixing Experiments and Modeling
Lama Itani (IFPEN) & Lyle Pickett (Sandia)
12:50 Discussion Period
13:00 Lunch
September 5th, 2015

2. ECN 4 Topic 9: Evaporative Spray G Organizers: Joshua Lacey University of Melbourne Daniel Vaquerizo Sánchez CMT – Motores Térmicos

3. Presentation Contents
Experimental Setup and Techniques
Simulation Techniques
ECN 4 Experimental Results
Experimental Summary
ECN 4 Simulation Results
Simulation Summary
September 5th, 2015

4. Experimental Contributions
Three institutions contributed experimental results
Istituto Motori
CMT – Motores Térmicos
University of Melbourne
September 5th, 2015

5. Simulation Contributions
Two institutions contributed simulation results
Politecnico di Milano
Argonne National Laboratory
September 5th, 2015

6. Previous Contributions
Other institutions that contributed to ECN 3, whose data is used here for comparisons
General Motors
Institut Français du Pétrole Energies nouvelles
Sandia National Laboratories
University of Wisconsin - Madison
September 5th, 2015

7. Spray G Experiments

8. ECN 3 Experimental Techniques
Liquid phase
DBI: SNL, IFPEN, UM
Mie-scattering: SNL, GM, IM
Vapor phase
Schlieren: SNL, GM, IM
General Motors
Sandia National Laboratory
September 5th, 2015

9. ECN 4 Experimental Techniques
University of Melbourne
Liquid phase
DBI: UM
Mie-scattering: UM, IM
Vapor phase
Schlieren: UM, IM, CMT
Liquid and vapor phases are measured simultaneously; frame straddling technique used by UM and IM
Istituto Motori
CMT – Motores Térmicos
C-Mos
Camera
Knife-edge
15° Off-axis mirror
f = 516 mm
f = 516mm
Vessel
Lens f = 90 mm
Lens
f = 200mm
f = 50mm
Schlieren LED
Mie LED
Pin-hole
Heated plate
September 5th, 2015

10. ECN 4 Experimental Techniques
Spray G1 condition of IM and UM setups
IM uses a heated plate to achieve high in-chamber temperatures
UM has cartridge heaters mounted in the metal of the spray chamber to uniformly heat the walls
Istituto Motori
University of Melbourne
September 5th, 2015

11. Experimental Results Spray G1
Liquid measurements from Mie-scattering
IM liquid penetration extends further into chamber as there is less evaporation
Early part of injection event is similar across all experimental setups
ECN 3 Liquid Lengths
ECN 3 Vapor Lengths
September 5th, 2015

12. Experimental Results Spray G3
Liquid lengths were measured with Mie-scattering
As expected, the chief difference between the 20˚C and 60˚C condition, is a decreased liquid residence time, as more fuel is vaporized
Early behavior, while the injector is open, is similar
Most of the deviation occurs well after the injector is shut
Little change in maximum penetration length
Vapor profiles lie on top of one another
September 5th, 2015

13. Experimental Results Spray G2
As before, the increased chamber temperature does not affect maximum liquid penetration length, but does impact residence time
Maximum liquid penetration is similar to 1 bar, non-flashing case, with residence time reduced
Vapor penetrates further and at a different rate than G3 (more vaporization with flashing spray)
September 5th, 2015

14. Mie-scattering and DBI
Both are used to measure liquid phase, but each employs a fundamentally different approach
Mie-scattering exploits the refraction of light through liquid droplets; the signal is the refracted light (lighter pixels)
DBI is a light extinction method in which the dense medium blocks the background illumination; the image formed of the spray is the blocked light (darker pixels)
Mie-scattered image
DBI image
September 5th, 2015

15. Mie vs. DBI Post-Processing
Because there is no “reference” intensity for Mie (black background), we must assign some light level threshold to determine the end of the liquid
DBI is “self-calibrating” as the light background provides a reference intensity; the end of the liquid is denoted by a sharp cut off
September 5th, 2015

16. DBI Dependence on Experimental Apparatus
In practice, the post-processing of DBI still requires some finesse
Optical depth profiles of a spray subjected to the same conditions can vary from one setup to another (because of illumination, collection angle, etc.)
Evaporative conditions are susceptible to uncertainty, as the presence of vapor will steer some light (which appears as darker pixels on the image), which impacts the determination of the liquid location
As a rule of thumb, use a threshold of I/I0 = 0.9 to denote the liquid boundary
Essentially, any light that misses the camera for any reason (blockage by dense medium, small collection angle, vapor scattering the light) results in a signal that appears dark on the image and is treated as liquid spray
September 5th, 2015

17. Spray G DBI versus Mie-scattered Liquid Lengths
Although DBI profiles differ from Mie at Spray G1 and G3 (the most and least evaporative conditions), these differences are not dramatic, even for G1
DBI is the preferred method of ECN, but Mie-scattering is probably still useful in establishing the bounds of liquid length at a given condition (and serves as a good “sanity check” when considering the DBI results from a given setup)
September 5th, 2015

18. Summary of all Liquid Measurements for Spray G1; 6 bar, 300˚C
The early portion of the injection event is consistent across all labs and techniques (up to ~ µs); liquid edges are sharp here, so there is less experimental uncertainty and better Mie/DBI agreement
Significantly more uncertainty after the injector closes; setup and post-processing differences are more apparent in this region
Overall, most of the experimental datasets are consistent for all of the setups, and the two different techniques
September 5th, 2015

19. Spray G Liquid Angle
Nominal cone angle is apparent early in the injection event, although it falls off in some cases for Spray G1 (SNL, UM)
G2/G3 conditions are given at 20˚C chamber temperature
Liquid angle increases at conditions with less vaporization (θG1 < θG2 < θG3)
For a single-hole injector we might expect the G2 condition to have the highest spray angle; multi-hole plume-to-plume flashing-boiling interaction is more complex
September 5th, 2015

20. Comparison of Liquid and Vapor Angles
Vapor and liquid angles at conditions G2/G3 differ slightly at the beginning of the injection event; there is higher variation for G2, where more vaporization occurs
Spray G1 has a significant difference between liquid and vapor envelopes due to substantial evaporation
September 5th, 2015

21. High Speed Movies of Spray G2 and G3
Movies showing G2 and G3 conditions on the left and right, respectively
Mie-scattered liquid is traced in red, Schlieren measured vapor is traced in blue
There are relatively similar spray evolutions at these conditions, though some plume interactions are visible at 0.53 bar
0.53 bar
1 bar
September 5th, 2015

22. Flash-boiling Spray G2
Plume-to-plume interaction is apparent at the 0.53 bar condition
Idle condition in an engine might have a lower pressure and lower superheat degree of fuel further
0.53 bar
1 bar
September 5th, 2015

23. Experiments Summary
Established a wealth of results for the G1 condition
Flash-boiling, while present at the G2 condition, is not severe
The maximum liquid penetrations observed are not significantly different when the chamber pressure is dropped from 1 to 0.53 bar (residence time changes and liquid and vapor penetration rates differ)
We anticipate that increasing the spray superheat degree or decreasing the cone angle will influence the plume-to-plume interaction
September 5th, 2015

24. Spray G1 Simulations

25. ECN 4 Simulation Techniques
ANL
CONVERGE
LES: dynamic structure model for turbulence
“Blob” injections, KH-RT breakup
1 mm baseline cell size with a mm minimum
Polimi
OpenFOAM with LibICE
RANS flow solver, k-ε model for turbulence, Lagrangian approach
Huh injection, Pilch-Erdman secondary breakup
4 mm baseline cell size with a 1 mm minimum
September 5th, 2015

26. Review of CFD Penetration Measurement Specifications
Liquid Penetration
0.1 % Liquid volume fraction threshold
Vapor Penetration
0.1 % Mixture fraction threshold
Measured along injector axis
Zero point is at the injector tip
Penetration
Length
Side View
September 5th, 2015

27. Vapor Simulation Results
Vapor length simulations agrees closely with experiments up to 1000 µs ASI
Overall evolution of vapor (curve shape) is similar between both experimental measurements and simulations
September 5th, 2015

28. Liquid Simulation Results
Maximum liquid lengths match closely to to those from DBI data
The spray behavior of the simulations underpredicts penetration length during a portion of the time the injector is open
Non-aligned spray grid increases cone angle and reduces penetration
Evaporation models are also a likely contributor
Saha and Som, USCAR, 2015
September 5th, 2015

29. PDI Experimental against Modeling – Radial Scan
15 mm
GM Experiments
Polimi Simulations
September 5th, 2015

30. PDI Experimental against Modeling – Transverse Scan
15 mm
GM Experiments
Polimi Simulations
September 5th, 2015

31. Droplet Size Distributions
Radial scans are shown to the right at two points in time ASI
Experimental droplet sizes are relatively constant
Simulations have a wide range of droplet diameters across the radial scan, particularly late in the injection event
September 5th, 2015

32. Experimental Penetration Rates at Spray G1 Conditions
Liquid penetration rates are generated from the time derivatives of penetration length
Simulation axial velocities are slower overall when compared to the experimental results; some of the high-level behaviors with location and time are captured
Radial Scans
Transverse Scans
September 5th, 2015

33. Simulation Summary
Modeling tools are well-developed and clearly capture the complex behavior present in GDI fuel sprays
There is the potential to perform parameter traversals to help better assess the experimental observations (dual-plume cuts for flashing cases, PDI simulations to assess the changes in axial versus radial velocities as flashing-boiling increases)
September 5th, 2015

34. Backup slides
September 5th, 2015

35. ECN 4 Spray G Conditions
Three conditions which correspond to different parts of the operating map of a GDI engine
Spray G1
Stratified mixture, late injection
Spray G2
Throttled, early injection
Flash-boiling of iso-octane at this condition
Spray G3
Unthrottled, homogeneous mixture, early injection
Fuel temperature is maintained at 90˚C in all cases
September 5th, 2015

36. Injection Temperature
ECN 4 Spray G Conditions
Experimental GDI injector and driver provided by Delphi
8 symmetrically spaced nozzle holes
165 µm hole diameter
780 µs total injection time, at all conditions
Nominal spray cone angle of 80°
Fuel is iso-octane
Two ambient temperatures are listed for Spray G2/G3, because much of the data was taken for the “old” conditions of interest; some comparisons between the two conditions will be presented, but most of the data shown is for the 20˚C condition
Spray G1
Spray G2
Spray G3
Injection Pressure
200 bar
Injection Temperature
90°C ( K)
Ambient Temperature
300°C ( K)
20/60°C ( K)
Ambient Density
3.5 kg/m3
0.6 kg/m3
1.1 kg/m3
Nitrogen Pressure
6 bar
0.53/0.5 bar
1 bar
Injected Quantity
10 mg
September 5th, 2015

37. Review of PDI and Spray Plume Scans
The next few slides provide a quick overview of the relevant geometry for PDI scans and the study of individual spray plumes
September 5th, 2015

38. Along a radial line through the spray axis center point
Radial Cross-section
Along a radial line through the spray axis center point
Zero at injector axis, positive outward
Radial Line
15 mm
Side View
Top View
September 5th, 2015

39. Transverse Cross-section
Across the spray perpendicular to the radial line
Zero at spray center point
Experiments put this at 10 mm radial distance
Positive direction clockwise as viewed from injector
10 mm
Spray Plume Center
15 mm
Transverse Line
Side View
Top View
September 5th, 2015

40. Dual-Plume Cross-section
Taken along a line connecting the center-points of two neighboring spray plumes
Zero at center of counter-clockwise-most (as viewed from injector) plume
Positive towards second plume (clockwise as viewed from injector)
15 mm
Dual-plume Line
Side View
Top View
September 5th, 2015

41. High Speed Movies of Spray G2 and G3
Movies showing G2 and G3 conditions on the left and right, respectively
Mie-scattered liquid is traced in red, Schlieren measured vapor is traced in blue
There are relatively similar spray evolutions at these conditions, though some plume interactions are visible at 0.53 bar
0.53 bar
1 bar
September 5th, 2015