HIGH-SPEED PHOTOGRAPHY AND PHASE DOPPLER … · SIAMUF 2006 Petter Dahlander What is flash boiling?...
16
Department of Applied Mechanics Petter Dahlander SIAMUF 2006 HIGH-SPEED PHOTOGRAPHY AND PHASE DOPPLER ANEMOMETRY MEASUREMENTS OF FLASH-BOILING MULTI-HOLE INJECTOR SPRAYS FOR SPRAY-GUIDED GASOLINE DIRECT INJECTION - An experimental study using a spray chamber
Transcript of HIGH-SPEED PHOTOGRAPHY AND PHASE DOPPLER … · SIAMUF 2006 Petter Dahlander What is flash boiling?...
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
HIGH-SPEED PHOTOGRAPHY AND PHASE DOPPLERANEMOMETRY MEASUREMENTS OF FLASH-BOILINGMULTI-HOLE INJECTOR SPRAYS FOR SPRAY-GUIDED
GASOLINE DIRECT INJECTION
- An experimental study using a spray chamber
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
What is flash boiling?
• Fuel of high temperature expands into a low pressure environment(This is sometimes called a superheated injection.)
• Due to the low pressure environment, the boiling point(s) is lowered.
• Due to the fast phenomenon (typically ~ms) the fuel temperaturedoes not change during the expansion through the injector.
• Fast phenomenon – the latent heat cannot be conducted by surfaceevaporation
• Instead – rapid and explosive bubble growth inside of the droplets.
-> We can expect the sprays to change!! – But how much?!
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
The difference between a normal injection..and a superheated injection
So, what parameters control flash-boiling?
1-2: Normal injection3-4: Superheated injection causing flash boiling
-> Fuel temperature and ambient pressure!
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Motivation of work
• Liquid fuel distribution?
• Droplet sizes?
• Droplet velocities?
How is a multi-hole injector spray influenced byflash boiling? How is the following influenced?
When varying parameters: • Fuel temperature• Ambient pressure
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
In an engine the varied parameterscorrespond to:
• Throttled condition
• High fuel temperature
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Experimental setup
• Temperature controlled injector mounting case• Vacuum pump to reach sub-atmospheric pressures
Spray chamber
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Experimental setup
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Experimental boundary conditions
• 6-hole injector (horseshoe shaped configuration)• Fuel pressure 10 MPa• Injection duration 2 ms• Fuel: Single and multi-component• Fuel temperature: 293, 325, 372 K• Ambient pressures: 30, 55, 80 kPa• Ambient temperature: 293 K
Measurement method: High-speed video and Phase Doppler
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
• Low fuel temperature• Atmospheric pressure
• Increased fuel temperature• Below atmospheric pressure
• Further increased fuel temperature• Much below atmospheric pressure
• No flash-boiling• Spray plumes are clear
• Medium flash-boiling• Spray plumes are blurred
• Strong flash-boiling• Spray plumes cannot be discerned
Side view Below view
Examples of Flash-Boiling sprays
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Single-component fuel (Iso-octane)
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Multi-component fuel
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Results from Phase Doppler: Drop sizes(based on Iso-octane)
0 10 20 30 40 500
5
10
15
20
25
30
Drop diameter [ ?m]
Probability [%]
30 kPa, 293 K80 kPa, 293 K30 kPa, 372 K80 kPa, 372 K
18 22 26 30 34 380
10
20
30
40
50
Radius [mm]
SMD [?m]
30 kPa, 293 K80 kPa, 293 K30 kPa, 372 K80 kPa, 372 K
Data from 40 mm downstream
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Conclusions
• Flash-boiling dramatically:– Change the fuel distribution
– Improves atomization
• Driving force is the temperature difference between the fuel as itexits the nozzle and the boiling point at the pressure condition thefuel expands to (sometimes called superheat). Therefore flash-boiling increases when:– Fuel temperature is high.
– The ambient pressure is low.
• Multi-component fuel – flash boiling increase as compared withsingle-component fuel due to the lower boiling points.
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Acknowledgements
• CERC (Combustion Engine Research Centreat Chalmers) for finicial support
• GM R&D for supplying the injector
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
Conclusions on Flash-Boiling• Flash-boiling does not occur suddenly (no clear
boundaries)• The difference between different fuel is remarkable!• Flash-boiling starts when the fuel temperature is increased
to the boiling point of the lightest component of the fuel• Spray formation change dramatically:
– No clear spray plumes– Umbrella angle decreases– Distribution of fuel different– Clear vortex can be seen– New plumes are being created between original plumes
• Temperature is the most important parameter– At 30 kPa/non-heated fuel, clear spray plumes can be seen– At 80 kPa/heated fuel leads to flash-boiling
• In agreement with the litterature: Flash-boiling is favorablefor atomization
Department of Applied Mechanics
Petter DahlanderSIAMUF 2006
PDA: Axial velocities
18 22 26 30 34 380
10
20
30
40
50
60
70
80
90
Radius [mm]
Axial velocity [m/s]
30 kPa, 293 K80 kPa, 293 K30 kPa, 372 K80 kPa, 372 K
