Modeling Combustion of Methane- Hydrogen Blends in Internal

Università degli Studi di Roma “Tor Vergata”
Modeling Combustion of MethaneHydrogen Blends in Internal
Combustion Engines (BONG-HY)
Prof. Stefano Cordiner
Ing. Vincenzo Mulone
Ing. Riccardo Scarcelli
Index
¾ Target of the Work
¾ Computational Tools
¾ Turbulent Combustion Models
¾ Approach and Results
¾ Conclusions and Future Perspectives
Index
¾ Target of the Work
¾ Computational Tools
¾ Turbulent Combustion Models
¾ Approach and Results
¾ Conclusions and Future Perspectives
Target
¾ Numerical Study of the Influence of Substitution of
Methane with Hydrogen (15% vol.) on Combustion
¾ Numerical Analysis of the Influence of Main Engines
Parameters (Spark Advance and Air Index) on
Performance and Emissions
NUMERICAL-EXPERIMENTAL PROCEDURE
FOR ENGINE OPTIMISATION
Index
¾ Target
¾ Computational Tools
¾ Turbulent Combustion Models
¾ Approach and Results
¾ Conclusions and Future Perspectives
1D Codes: Framework Code (FW2000)
Analysis of the Behaviour of the whole Engine
Integrated Code 0D-1D
•
Zero-dimensional elements
(capacities, cylinder-piston)
•
One-dimensional elements
(ducts, heat exchangers)
•
Joint elements
Volumetric Efficiency Calculation
1
2
3
4
3D Codes: KIVA-3V Code
Analysis of Cylinder - Piston System
•
Open Source CFD code
•
Models of injection, ignition,
turbulent combustion
•
A. L. E. Algorithm
•
Moving Structured Grids
(Piston – Valves Simulation)
Local Description of Combustion Process
Index
¾ Target
¾ Computational Tools
¾ Turbulent Combustion Models
¾ Approach and Results
¾ Conclusions and Future Perspectives
Turbulent Combustion Models
Thermo-Fluid-Dynamics Equations System.
Unknown Terms Closure
~
~
n
⎛ ∂T
⎞
T
p
∂
∂
∂
∂
~
⎜
⎟
cp ⎜ ρ
JT ,α +
ρuα′′T ′′
+ ρ uα
=−
− ∑ hi m& i − qr − c p
⎟
∂xα
∂t i=0
∂xα
∂xα ⎠
⎝ ∂t
(
)
~
~
∂Yi
∂Yi
∂
∂
~
&
ρ + ρ uα
=−
Ji,α + mi −
ρuα′′Yi′′
∂xα
∂xα
∂xα
∂t
(
)
Combustion Model
Turbulence Model (k-ε)
9
Combustion Model: CFM (Flamelet)
Burned Domain
Main Hypothesis
• two zones (burned-unburned)
• laminar local properties (sL)
m& fuel = RΣ = (ρ u s L I 0Y f 0 )Σ
Corrugated
Flame Front
Unburned Domain
CFM constants
Reaction rate
⎛
⎛ ρΣ ⎞ ⎞
∂(ρΣ)
k
βρR sL (ρΣ)
+ ∇ ⋅ (ρuΣ) − ∇ ⋅ ⎜⎜ ρDΣ∇⎜⎜ ⎟⎟ ⎟⎟ = αΓk (ρΣ) −
− (∇ ⋅ u )ρΣ
2
∂t
ε
ρ Y1
⎝ ρ ⎠⎠
⎝
2
Transport equation
sL flame laminar speed
Σ flame surface for volume unit
10
Index
¾ Target of the Works
¾ Computational Tools
¾ Turbulent Combustion Models
¾ Approach and Results
¾ Conclusions and Future Perspectives
Approach
EXPERIMENTAL
SETUP
MODEL CALIBRATION AND VALIDATION
RELIABLE
COMPUTATIONAL
TOOL
PARAMETERS OPTIMIZATION
NO
TARGET
YES
EXPERIMENTAL
TESTS
Approach
¾ First Interaction with Experiments
¾ Interpretation of Experimental Pressure Data
¾ Modifications and Model Validation
¾ Second Interaction with Experiments
¾ Parametric Study to Optimize the Engine
¾ CPU Re-Mapping and Experimental Tests
Experimental Pressure Analysis
AVL instrumentation
¾
¾
¾
Pressure Transducer in Combustion Chamber (sp)
Charge Amplifier (amp)
Optical Shaft Encoder (se)
14
Experimental Pressure Analysis
AVL instrumentation
Pressure Cycle
IMEP
Torque
15
Interpretation of Experimental Data
¾ Analysis of Experimental Pressure Data from ENEA
¾ 1D Simulation to Calculate Cylinder Volumetric
Efficiency (λv)
¾ 3D Simulation to Calibrate CFM Model Constants on
the Engine (Methane Case)
Model Calibration (Methane Case)
Combustion of Methane and Hydrogen Blends
¾ Flame Speed Calculation (Cantera)
& fuel = RΣ = (ρu sL I0Yf 0 )Σ
m
(
sL = f p,T ,φ, xH2
GRI-MECH 3.0 Mechanism
53 Chemical Species
325 Reactions
)
Model Validation (CH4-H2 Blends Case)
Approach Results
¾ First Interaction with Experiments
¾ Interpretation of Experimental Pressure Data
¾ Implementation and Model Validation
¾ Second Interaction with Experiments
¾ Parametric Study to Optimize the Engine
¾ CPU Re-Mapping and Experimental Tests
Pressure Cycle
Chamber Temperature
Performance
[NOX]
Spark Advance Optimization for Stoichiometric
Blends
Higher Flame Speed for
Methane-Hydrogen Blends
Higher Performance
Spark Advance Optimization for Stoichiometric
Blends
Slight ignition time delay
to minimize NOX, while
maintaining performance
Higher Flame Speed for
Methane-Hydrogen Blends
OPERATING CONDITIONS
IGNITION TIME DELAY
1500 RPM 25% LOAD
+2
1500 RPM 50% LOAD
+4
2500 RPM 25% LOAD
+2
2500 RPM 50% LOAD
+4
3500 RPM 25% LOAD
+3
3500 RPM 50% LOAD
+4
Lean Burn Combustion. Performance
10
9.5
9
CH4
MIX lambda 1.0
MIX lambda 1.1
MIX lambda 1.2
MIX lambda 1.3
MIX lambda 1.4
8.5
8
7.5
7
6.5
6
pmi [310:480]
Lean Burn Combustion. Chamber Temperature
CA 380°
λ = 1.0
λ = 1.4
Index
¾ Target of the Work
¾ Computational Tools
¾ Turbulent Combustion Models
¾ Approach and Results
¾ Conclusions and Future Perspectives
Conclusions
¾ The Introduction of Hydrogen into a Methane/Air Mixture
provides Increased Flame Propagation Speed, thus
leading to Higher Performance and Reduced Emissions
(CO2, HC). The increase in [NOX] can be contained by
following two approaches:
¾ A decrease in spark time advance (+4° for all operating conditions)
for stoichiometric mixtures. Results are a decrease in CO2
emissions (-15%) and a slight reduction in performance (-10%)
¾ The utilization of lean mixtures (λ>1.4) with unchanged spark
advance, with a further reduction of CO2 emissions (-20%), even
though performance drastically drop (-50%)
Future Perspectives
¾ Spark Advance Optimization for Lean Mixtures.
Study of Flammability Limits of Methane-Hydrogen
Blends
¾ Development of NOx formation models
¾ Design of combustion chambers and ducts to
improve volumetric efficiency (λv)
Spark Advance Optimization for Lean Mixtures
Increase Spark
Time Advance
Increase Pressure
and Temperature
Increase [NOX]
Università degli Studi di Roma “Tor Vergata”
Modeling Combustion of MethaneHydrogen Blends in Internal
Combustion Engines (BONG-HY)
Prof. Stefano Cordiner
Ing. Vincenzo Mulone
Ing. Riccardo Scarcelli