department of engineering science university of oxfordactivity coefficients: unifac or nrtl method...
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![Page 1: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/1.jpg)
Department of Engineering ScienceUniversity of OxfordJoe Camm, Safwan Hanis Bin Mohd Murad,
Richard Stone, Martin Davy, (Oxford University)
Dave Richardson (JLR Powertrain Research)
Imaging and Modelling of Gasoline Fuel Sprays
13 June 2017
This work was completed through support of the University of Oxford
Clarendon Fund Scholarship
![Page 2: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/2.jpg)
Overview
Motivation for study of gasoline fuel sprays
Fuel spray chamber
Design
Sample images
Comparison with engine results
Droplet evaporation modelling
Non-ideal fuel mixture behaviour – increasing ethanol content in
gasoline
Summary
13 June 2017
Slide 2
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 3: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/3.jpg)
Gasoline fuel sprays
13 June 2017
Slide 3
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
Improved thermal efficiency…
Charge cooling, controlled fuel delivery,
stratified charge operation…
…but PM emissions greater than from PFI
Locally rich mixture sources:
Unevaporated droplets
Surface fuel films
Inhomogeneity
Focus on
Spray evaporation
Spray structure
Spray penetration
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Atmosperic Spray Rig
• Inject and purge continuously for consistent
injector behaviour (>5 Hz)
• Optical access for imaging, laser diagnostics,
droplet sizing, etc
• Heating to 150oC tip temperature
• 400 bar GDI, 2200 bar diesel
• LabVIEW vi for injector temperature control,
timing synchronization and data acquisition
• Overdriven LED illumination (up to 1 kW)
13 June 2017
Slide 4
Oxford Spray Chamber
and Instrumentation
Set up for:
• GDI injector, with variable orientation
• Spray impingement / heat flux studies
• Single-hole Spray A diesel injector
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 5: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/5.jpg)
Characterizing flash boiling
Fuel saturation pressure ratio
𝑅p > 1 means superheated
𝑝amb is usually 1 atm in Rig
Images taken with 4 µs exposure. Injector energizing time was 2 ms
13 June 2017
Slide 5
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 6: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/6.jpg)
Spray movies
13 June 2017
Slide 6
135degC
(or 90degC at 0.5 bar)90degC
Bespoke thresholding algorithm
20degC
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 7: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/7.jpg)
Effect of superheat level on spray structure
13 June 2017
Slide 7
With this injector, increasing superheat causes greater and greater spray collapse
into a single jet structure, with eventually a greater penetration. Observed in
literature for other GDI injectors
S Murad et al., SAE Technical Paper 2016-01-0991
M Xu et al., SAE Technical Paper 2013-01-1614
Bespoke Spray Image Analysis code developed
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 8: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/8.jpg)
Fuel superheat influence on PM emissions – Sample Results
13 June 2017
Slide 8
• JLR optical engine in homogeneous mode
• Part load (MAP 0.5 bar), 1000 rpm, BMEP ~ 2 bar, air intake at 40℃• Cylinder head (coolant) temperature varied to change fuel superheat
• Injection timing varied
• Lambda = 0.9 or 1.01
• Metal components where possible for PM tests but spray structure
verified during motoring tests, with full optical liner
• Heated sample line – limited nucleation mode PM
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 9: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/9.jpg)
Fuel superheat influence on PM emissions – Sample Results
13 June 2017
Slide 9
Tests and analysis
performed by
Safwan
• Peak at 200 nm
relatively unaffected
by lambda, timing or
spray structure
• Smaller peak greatly
increased with
superheat at medium
timing – severe
impingement
• Early injection timing
resulted in very low
particulate levels –
lower cylinder
pressure and faster
charge motion??
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 10: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/10.jpg)
Multi-component droplet evaporation
13 June 2017
Slide 10
Comprehensive suite of models in MATLAB for single droplet
evaporation
Re-implemented in OpenFOAM for GDI spray simulation
Low pressure modified Raoult’s law: 𝛾𝑖𝑋𝑖𝑃𝑣𝑖 = 𝑦𝑖𝑃 Activity coefficients: UNIFAC or NRTL method
Modifiable at high pressure for gas phase non-ideality, supercritical states and gas
solubility (diesel injection conditions)
Droplet internal composition
Well-mixed (batch distillation)
Unmixed (constant, averaged properties)
Liquid diffusion-controlled ( 𝑋𝑖 = 𝐷L𝑖𝛻2𝑋𝑖) - Effective Diffusivity Model
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
𝑚 = 𝜋𝑑𝜌𝐷FASh′ ln(1 + 𝐵Y), 𝐵Y =Σ𝑌𝑖s
1−Σ𝑌𝑖s
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Multiplicative non-ideal thermodynamic correction factor based on activity coefficient
𝐷L = 𝛤𝐷L,ideal,
𝛤 = 1 + 𝜕 ln 𝛾𝑖 𝜕 ln𝑋𝑖
Bi-component: Well-mixed vs Liquid Diffusion controlled
13 June 2017
Slide 11
Well-mixed approximation used typically – check validity by solving the diffusion equation 𝑋𝑖 = 𝐷𝐿𝑖𝛻
2𝑋𝑖
Liquid diffusion coefficient Temperature and composition dependent
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 12: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/12.jpg)
13 June 2017
Slide 12
Internal droplet composition
Bi-component: Well-mixed vs Liquid Diffusion controlled
e40 blend, initial liquid temperature 100ºC,
ambient at 100ºC, 3 bar
The non-ideal liquid diffusivity is much smaller, causing the diffusion boundary layer to regress inwards without the surface concentration changing greatly. Closer to the unmixed model??
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 13: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/13.jpg)
Multi-component extension
13 June 2017
Slide 13
Had not seen this in literature so extended to N species
Liquid diffusion-controlled model requires N – 1 coupled diffusion equations
Matrix equation: 𝜕 𝑋
𝜕𝑡= 𝐷 𝛻2𝑋
Hydrocarbon species have much higher diffusivity within themselves (better mixing)
Treat as a pseudo-binary mixture: ethanol + hydrocarbons
Only solve one equation, as with ethanol + iso-octane
Units 10-10 m2/s
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
J Camm et al., SAE Technical Paper 2015-01-0924
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Findings from droplet and spray simulations
13 June 2017
Slide 14
Iso-octane/ethanol
Most basic gasoline model
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
Well-mixed model in error, for most
conditions, due to trade-off between
ethanol volatility and ethanol latent heat
7 component model fuel +
ethanol
Well-mixed model over-predicts lifetime.
The continued ethanol presence boosts
droplet volatility
J Camm et al., SAE Technical Paper 2015-01-0924
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Summary
13 June 2017
Slide 15
Fuel spray imaging and image analysis, subcooled and superheated
Spray structure, penetration and evaporation rate
Effects on particulate matter emissions
Detailed modelling of multi-component single-droplet evaporation
Quickly identify trends due to fuel or operating conditions
Identify required modelling complexity for accurate simulations
For gasoline-like fuels (containing ethanol), assess impact of ethanol
on ability of mutually repellent species to mix within the droplet, and
subsequently on evaporation rate
This work was completed
through support of the
University of Oxford
Clarendon Fund
Scholarship
![Page 16: Department of Engineering Science University of OxfordActivity coefficients: UNIFAC or NRTL method Modifiable at high pressure for gas phase non-ideality, supercritical states and](https://reader034.vdocuments.site/reader034/viewer/2022051908/5ffb9ae79fbe2e4ef806c6ae/html5/thumbnails/16.jpg)
New Shock Tube at Oxford
High temperature, high pressure Fuel Spray and Kinetics research
Designed around ECN Spray A condition
Extendable to trans- and supercritical regimes (150 bar, 1500 K)
Test times on order of 3-10 ms
13 June 2017
Slide 16