Experimental observations of fuel sprays in gasoline engines
Transcript of Experimental observations of fuel sprays in gasoline engines
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Experimental observations of fuel sprays in
gasoline engines
S. Begg
The Sir Harry Ricardo Laboratories
Centre for Automotive Engineering
13th April – Workshop- New mathematical tools for modelling the processes in IC engines: a
dialogue between mathematicians and engineers
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Contents of presentation
• Current objectives in gasoline engine research
• Progression in gasoline fuel injection systems
• Key characteristics of fuel sprays
• Optical diagnostics commonly applied to sprays
• The Phase Doppler anemometer
• Conclusions and modelling challenges for fuel sprays
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Current objectives in gasoline engine research
• Significant simultaneous reduction in emissions and consumption
• Direct injection, downsizing, boosting, VVA technologies...
• Fuel injection system optimisation
• Metering, variable needle lift, phasing, targeting, atomisation,
multi-shot, fuel blends...
• Engine management system
• Crank-angled resolved, poor cycles identified, multi-strike ignition...
Understanding the fuel injection process is key to the mixture
preparation... the ‘trial and error’ approach is no longer adequate...
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Progression in fuel injection systems
• Single point and multi-point port fuel injection (PFI)
• 2-12 bar fuel pressure / fixed OVI and CVI injection timing
• High cyclic variations, poor lean operation, poor tolerance to EGR
• 1st generation direct injection (G-DI)
• 10-120 bar fuel pressure / range of injection timings
• Optimised flow structures / stratification of charge
• Sensitivity to fuel injector location and spray characteristics
• Relatively high ubHC and NOx emissions
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Progression in fuel injection systems
• 1st generation direct injection (G-DI)
• 10-120 bar fuel pressure / range of injection timings
• Single and multi-hole solenoid
(Preussner et al., (1998))
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Progression in fuel injection systems
• 2nd generation direct injection- high degree of specialism
• 150 - ?? bar fuel injection pressure / variable needle lift / multi-shot
• Outward pintle or multi-hole, solenoid and piezo
BMW stratified, 16° Spark plug / Injector
Images courtesy of collaborative project with Uni. Of Cardiff and Ricardo, 0.3 to 0.9 ms ASOI, 200 bar, ambient pressure gas
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Progression in fuel injection systems
• 2nd generation direct injection
• 200 bar fuel injection pressure/ outward pintle solenoid injector
• Laser light-sheet (Mie scattering) highlights head vortex-ring-like structures
Images courtesy of collaborative project with Uni. Of Cardiff and Ricardo, 0.3 to 1.2 ms ASOI, E85 at 200 bar, ambient pressure gas
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Key characteristics of the fuel spray
• Spray geometry (cone, separation, deflection angles)
• Length scales (penetration/impingement)
• Droplet atomisation ‘quality’
• Time scales (0.1 to 100 ms range)
• Shot-to-shot repeatability
• Vortex ring-like structures
Fuel Mass Flow RateFuel Injection Pressure
Air Entrainment
Droplet Drag
Injector Phasing/Duration
Spray Penetrationand Breakup
Spray Shape
Local Air Flowfield
Heat Transfer andEvapouration
Droplet SizeDistribution
33°
20°16°
Images courtesy of collaborative project with Uni. Of Cardiff and Ricardo
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Optical diagnostics commonly applied to sprays
• Photographic
• Planar Mie techniques
• Planar inelastic scattering techniques
• Phase Doppler Anemometry1 2
1Nouri et al., 2007,
2(Fansler et al., (2006))
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Optical diagnostics commonly applied to sprays
• Simple static chamber
50 mm
2 mm
470 mm
Fuel injector
Spray chamber section
Measurement
grid
Exhaust
Transmission
optic
Gauze layers
Drain
Purge air
Automated traverse
Fuel supply
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Optical diagnostics commonly applied to sprays
• Steady-flow rig
Modified Production
BMW Valvetronic Engine
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Optical diagnostics commonly applied to sprays
• Fired, optical engine
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Spray imaging- chamber
PFI multi-stream Off-axis pressure-swirl
Flat fan
Fan
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o
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8 mm
• axial and radial waves
• droplet stripping
• asymmetry
• ‘hesitation’ due to
necking of the liquid
stream
Combining Spray Imaging with PDA
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Top-entry G-DI – effect of in-cylinder pressure
Early Injection60° - 121°
Late Injection301°- 318°
Onset
Middle
End
Spray imaging- motored engine
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Phase Doppler anemometer (PDA)
• Conventional PDA
Light receivingoptics
z
y
x
q
f
Liquid Spray ofknown refractive index
Continuous medium of knownrefractive index
y
y
Location ofPhoto detectors
Scattering plane
),,,(),,( nqSII izyx fq
pdq
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Phase Doppler anemometer (PDA)
• Polar distribution of light intensity Brewster’s angle used to
collect first order refraction p=1
180 0
330 210
240 300
270
150
120
90
60
30
180 0
210
150
240
120
270
90 60
300
30
330
0.1pd
10pd
q
fqfq
sinsin
coscoscos121coscoscos12
2
2
n
nnd p
360 °
0
dmeasured
Phase Shift (deg.),
Diameter, d
1-3
1-2
1-2
1-3
d1-2max
d1-3max
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Phase Doppler anemometer (PDA)
• Typical features of time series at two locations in a high-pressure spray
r = 0, x = 15 mm r = 10, x = 15 mm
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PDA– Spray chamber
Initial Phase Quasi-steady Phase Trailing Phase
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Distance
(mm)
Injector ‘D’ Injector ‘F’ Injector ‘G’
0
20
40
60
80
0
20
40
60
80
Fully-developed Spray Region
Droplet Velocity Distribution
Droplet Diameter Distribution
Combining imaging with PDA– Spray chamber
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Vortex ring-like structures
- Development of a generalised vortex ring model
Chronological sequence of high-speed photographs, (left
to right) recorded using a laser light sheet, in a G-DI
spray in an optical engine with full glass cylinder liner
The distribution
of the vorticity
magnitude for
t=3.75 ms
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Phase Doppler anemometer (PDA)
• Vortex-ring like features in a high-pressure spray
Injector axis
Penetration depth
Spray width
Vx1
Vx3
Vx2
2Ro
x
rl
vωx
vωr
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Phase Doppler anemometer (PDA)
t = 4.50 ms
• Reconstruction of the spatial distribution of the droplet velocity and size
• Data ensemble-averaged within arbitrary time bins
• Track features (e.g. translation of region of maximal vorticity)
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Vortex ring-like structures
Chronological sequence of high-speed photographs, recorded using a
laser light sheet, (left to right) in a static spray chamber, 150 bar fuel
pressure, 6 barg gas pressure, 1 to 10 ms ASOI, gasoline fuel.
Images courtesy of collaborative project with Uni. Of Cardiff and Ricardo
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25
Gas Face z=0
z=-9
z=-10
z=-14
-35 -30 -25 -20 -15 -10 5-5 0
QUARTZ ANNULUS BUILD
MEASUREMENT
PLANES
POSITIVE VELOCITY
VECTOR
INJECTOR INCLINATION
SPARK PLUG INCLINATION
Phase Doppler anemometer (PDA) – motored engine
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Phase Doppler anemometer (PDA) –motored engine
• Comparison of static chamber results with reciprocating engine
Stratified operationHomogeneous operation
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Phase Doppler anemometer (PDA)
• Comparison of higher order number and moment mean diameters for
reciprocating engine (e.g. d30)
Homogeneous operation
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Phase Doppler anemometer (PDA)
• Comparison of higher order number and moment mean diameters for
reciprocating engine (e.g. d30)
Stratified operation
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Conclusions and modelling challenges for fuel
sprays
• Future experiments must address a single injection event
• to capture the characteristics at crank angle resolution
• within a single cycle and from one consecutive cycle to the next
• correlation with poor cycles of combustion
• Modelling must incorporate the finer details
• evolution of vortex ring models
• fuel injection and gas flow coupling
• multi-component fuels and fuel blends
• integration of chemical kinetic models with physical models
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Acknowledgements
• EPSRC and equipment loan pool
• University of Cardiff (Prof. P. Bowen, Dr M. Alonso and Dr P. Kay)
• Ricardo UK Ltd
• DTI/TSB 2/4 SIGHT and 2/4 CAR programmes
• Staff and students of the CAE
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Experimental observations of fuel sprays in
gasoline engines
S. Begg
Centre for Automotive Engineering
www.brighton.ac.uk/cae