Large Engines Competence Center · Lucas Eder, M.Sc. CFD Research Engineer Email:...
Transcript of Large Engines Competence Center · Lucas Eder, M.Sc. CFD Research Engineer Email:...
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 1
Large Engines Competence Center
3D-CFD model development and validation for dual-fuel
combustion in large bore engines
L. Eder1, M. Lackner1, H. Winter1, G. Pirker1, A. Wimmer1,2
1LEC GmbH 2Institute of Internal Combustion Engines and Thermodynamics, TU Graz
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 2
Agenda
• Introduction
• Dual fuel combustion simulation: challenges
• Description of modeling framework
• Validation of DF combustion simulation with SCE measurement
data
• Conclusions and further steps
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 3
Agenda
• Introduction
• Dual fuel combustion simulation: challenges
• Description of modeling framework
• Validation of DF combustion simulation with SCE measurement
data
• Conclusions and further steps
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 4
Introduction
• Working principle
• Ignition of a homogeneous natural gas/air
mixture with diesel pilot injection
• Ignition energy provided only by diesel
• Premixed gas/air flame front propagation after
autoignition of the diesel
• Advantages
• Fuel flexibility [7]
• Possibility to operate with different gas
compositions
• Possibility to operate in gas mode but also in pure
diesel mode
• Great reduction in engine-out NOx compared to
monovalent diesel engines [8]
Diesel ignited gas engine concept
Fig.1.: Intake and high pressure phase of the diesel ignited gas engine concept [2]
Gas (Central mixture formation)
Gas (Port fuel injection)
or
Air
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 5
Agenda
• Introduction
• Dual fuel combustion simulation: challenges
• Description of modeling framework
• Validation of DF combustion simulation with SCE measurement
data
• Conclusions and further steps
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 6
Dual fuel combustion simulation: challenges
Overview
Air/gas induction:➢ Provision of a lean, homogeneous
background mixture➢ Proper representation of the flow field
Diesel pilot injection:➢ Operation of the diesel injector in the
ballistic range➢ Very different behavior than with a fully
open needle
Combustion:➢ All combustion regimes are present➢ Interaction of the two fuels has to be
considered regarding ignition delay andlaminar flame speed
Emissions:
Nitric oxides (NOx)
Soot
Unburned hydrocarbons
Knocking
Premixed
DiffusionAutoignition
Dual Fuel
Diesel ignited gas engine
Air
Gas
Fig.2.: Main challenges of dual fuelcombustion for CFD
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 7
Agenda
• Introduction
• Dual fuel combustion simulation: challenges
• Description of modeling framework
• Validation of DF combustion simulation with SCE measurement
data
• Conclusions and further steps
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 8
Description of modeling framework
• Model is able to depict the three different
combustion regimes simultaneously
• Multiple fuel option implemented in the
standard ECFM-3Z model
• Several shortcomings had to be addressed
• Ignition delay prediction for dual fuel applications
• Flame surface density deposition
• Flame front propagation
Combustion models – ECFM-3Z
Fig.3.: Standard ECFM-3Z description , taken from [2,3]
Fig.4.: ECFM-3Z mixing model after diesel pilot injection [4]
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 9
Description of modeling framework
• Physical effect
• The ignition delay varies with the fuel
mixture fraction [9, 10].
• Strong non-linear behavior of the fuel
mixture fraction has been found with
0D reactor simulations [1,4].
• Numerical approach
• Dedicated tabulation with a dual fuel
mechanism
Improvements for the dual fuel combustion modelling
Ignition delay
Fig.5.: 0D simulations for different fuel fractions (top)Selected ignition delay for one ratio with tabulation points (bottom)
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 10
Description of modeling framework
• Physical effect
• After the diesel pilot auto ignites, flame
front propagation starts.
• A flame surface density has to be
provided to the ECFM model as a starting
value
• Numerical approach
• A simple relation for thermal gas
expansion is taken from [6,7], and
modified:
Σ𝑖𝑛𝑖 = 𝐶 ∗ 𝛻 ǁ𝑐 ∗ 1 + 𝑡𝑖
𝑡𝑖 … turbulent intensity
Necessary modifications to the ECFM-3Z combustion model
Flame surface density deposition
Ignitable mixture
Homogeneous background mixture
Developed flame kernel
Diesel (liquid)
Diesel (gas)
Gas expansion Turbulence
Fig.6.: Initial flame surface density deposition fordual fuel modifications
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 11
• Physical effect
• Laminar flame speed varies with the fuel
mixture fraction [6].
• Linear behavior was found from
numerical simulations
[4,5].aaaaaaaaaaa
• Numerical approach
• Interpolation function:
Description of modeling framework
Improvements for the dual fuel combustion modelling
Laminar flame speed
Fig.7.: 1D simulations carried out for the laminar flamespeed of n-heptane/methane/air mixtures
50
100
150
200
250
300
0 0,2 0,4 0,6 0,8 1
Lam
inar
fla
me
sp
ee
d [
cm/s
]Methane fraction of the dual fuel blend [-]𝝋𝒅𝒇 =
𝝂𝑪𝟕𝑯𝟏𝟔
𝝂𝑪𝑯𝟒+ 𝝂𝑪𝟕𝑯𝟏𝟔
𝒔𝑳𝒅𝒇𝟎 = 𝒔𝑳𝑪𝟕𝑯𝟏𝟔
𝟎 ∗ 𝝋𝒅𝒇 + 𝒔𝑳𝑪𝑯𝟒𝟎 ∗ (𝟏 − 𝝋𝒅𝒇)
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 12
Agenda
• Introduction
• Dual fuel combustion simulation: challenges
• Description of modeling framework
• Validation of DF combustion simulation with SCE measurement
data
• Conclusions and further steps
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 13
Validation with SCE measurement data
Measurement setup
Engine Conditions
Point Diesel share (energetic) [%] Global Lambda [-] SOC
1 1.5 Lean Early
2 1.5 Lean Middle
3 1.5 Lean Late
4 1.5 Lean Late
5 1.0 Lean Late
6 0.5 Lean Late
Hardware Summary
Rated speed 1500 rpm
Displacement ~ 6 liter
Swirl/tumble ~ 0/0
Charge air Provided by external compressors
Gas fuel supply External mixture formation via venturi mixer
Diesel injector nozzle 4 x 140° Fig.8.: Single Cylinder Research Engine
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 14
Validation with SCE measurement data
Simulation setup
Meshing
Type ESE diesel sector mesh (90°) with refinement
No. of cells @ TDC ~ 200.000 (0.6 mm in Spray region)
No. of cells @ BDC ~ 380.000Fig.9.: Sector mesh for engine simulations
General setup
Solver AVL FIRE
Temporal discretization Compression 50 us (0.5 deg @ 1500rpm)
Spray / combustion 10 us (0.1 deg @ 1500rpm)
Expansion 20 us (0.2 deg @ 1500rpm)
Turbulence modeling RANS approach, k-ζ-f turbulence model
Spray Lagrangian approach• WAVE breakup• Ducowicz evaporation• O‘Rourke turbulent dispersion
Model calibration according to spray box tests
Combustion ECFM-3Z modelDual fuel adjustments
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 15
Validation with SCE measurement data
Measurement setup
Engine Conditions
Point Diesel share (energetic) [%] Global Lambda [-] SOC
1 1.5 Lean Early
2 1.5 Lean Middle
3 1.5 Lean Late
4 1.5 Lean Late
5 1.0 Lean Late
6 0.5 Lean Late
Hardware Summary
Rated speed 1500 rpm
Displacement ~ 6 liter
Swirl/tumble ~ 0/0
Charge air Provided by external compressors
Gas fuel supply External mixture formation via venturi mixer
Diesel injector nozzle 4 x 140° Fig.10.: Single Cylinder Research Engine
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 16
Validation with SCE measurement data
Results of diesel mass variation
Fig.11.: Pressure trace and normalized heat releaserate for the selected diesel mass variations
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 17
Validation with SCE measurement data
Measurement setup
Engine Conditions
Point Diesel share (energetic) [%] Global Lambda [-] SOC
1 1.5 Lean Early
2 1.5 Lean Middle
3 1.5 Lean Late
4 1.5 Lean Late
5 1.0 Lean Late
6 0.5 Lean Late
Hardware Summary
Rated speed 1500 rpm
Displacement ~ 6 liter
Swirl/tumble ~ 0/0
Charge air Provided by external compressors
Gas fuel supply External mixture formation via venturi mixer
Diesel injector nozzle 4 x 140° Fig.12.: Single Cylinder Research Engine
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 18
Validation with SCE measurement data
Results of early SOC
Fig.13.: ROHR and pressure trace comparison (left)Topdown view into the cylinder with an isosurface of progress variable (right)
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 19
Validation with SCE measurement data
Results of middle SOC
Fig.14.: ROHR and pressure trace comparison (left)Topdown view into the cylinder with an isosurface of progress variable (right)
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 20
Validation with SCE measurement data
Results of late SOC
Fig.15.: ROHR and pressure trace comparison (left)Topdown view into the cylinder with an isosurface of progress variable (right)
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 21
Agenda
• Introduction
• Dual fuel combustion simulation: challenges
• Description of modeling framework
• Validation of DF combustion simulation with SCE measurement
data
• Conclusions and further steps
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 22
Conclusions and further steps
• Conclusions
• Workflow for DF combustion modeling defined
• Dual fuel combustion modeling improvements tested and validated on a single
cylinder research engine
• Optical validation showed good agreement with the simulation
• Further steps
• Generate a tabulated kinetics of ignition (TKI) database [11] for dual fuel mixtures
based on a dedicated dual fuel mechanism
• Generate laminar flame speeds for dual fuel mixtures based on a dedicated dual
fuel mechanism
• Compare ECFM-3Z results with detailed chemistry simulations
LARGE ENGINES COMPETENCE CENTER © LEC GmbH
Dual Fuel Workshop Rostock 3D-CFD model development and validation for dual-fuel combustion 2018-04-26 Slide 23
Funded by comet
CONTACT:
Lucas Eder, M.Sc. CFD Research Engineer Email: [email protected]
LEC GmbH Inffeldgasse 19 A-8010 Graz, Austria Phone: +43 (316) 873-30141 www.lec.at
Thank you for
your attention!
ACKNOWLEDGEMENT:
The authors would like to acknowledge the financial support of the "COMET - Competence Centres for Excellent Technologies
Programme" of the Austrian Federal Ministry for Transport, Innovation and Technology (BMVIT), the Austrian Federal Ministry of
Science, Research and Economy (BMWFW) and the Provinces of Styria, Tyrol and Vienna for the K1- Centre LEC EvoLET. The
COMET Programme is managed by the Austrian Research Promotion Agency (FFG).
The authors would like to express their gratitude for the measurement data provided by CMT-Motores Térmicos (Universitat
Politècnica de València).