Download - IC Engines Modeling
-
7/31/2019 IC Engines Modeling
1/26
MODELING THE UNSTEADYFLOWS IN I.C. ENGINE PIPE
SYSTEMS BY MEANS OF AQUASI-3D APPROACH
G. Montenegro, A. Della Torre, T. Cerri, A. Onorati
Department of Energy, Politecnico di Milano, Milan, Italy
-
7/31/2019 IC Engines Modeling
2/26
Outline
A. Della Torre Paper Number: ICES2012-81181
Motivation and scope
Description of the approach:
Governing equations
Numerical structure and limiting technique
Specialization for the modeling of specific devices
Validation: high performance Aprilia V4 engine:
Pressure pulses in the intake and exhaust ducts
Volumetric EfficiencySound Pressure level
-
7/31/2019 IC Engines Modeling
3/26
Motivations and scope
A. Della Torre Paper Number: ICES2012-81181
1D simulation codes are well-established and reliable tools but ...
Corrective lengths and equivalent 1D duct schemes for 3D components
Equivalent duct schemes are not a-priori known
The optimization of the layout of 3D components is not possible
-
7/31/2019 IC Engines Modeling
4/26
Quasi-3D approach
A. Della Torre Paper Number: ICES2012-81181
Geometry is reconstructed by
means of a network of cells and
ports
The main characteristic lengths in
the space are reconstructed
-
7/31/2019 IC Engines Modeling
5/26
Governing equations
A. Della Torre Paper Number: ICES2012-81181
Based on the formulation of the conservation equations of mass, momentumand energy for unsteady flows
t
+ (U) = 0
U
t+ (UU) = p
e0
t + (e0U) + (pU) = 0
Viscosity of the gas, both in the intake and exhaust system, is very low: it can
be neglected without introducing an excessive approximation (Euler formula-tion)
System of equations is closed with the perfect gas equation of state
-
7/31/2019 IC Engines Modeling
6/26
Numerical Method
A. Della Torre Paper Number: ICES2012-81181
Second order accurate and stable
Pseudo-staggered grid:
Mass and Energy equations are integrated over the cell control volume
Momentum equation is integrated over the port control volume
The method is stabilized adding a diffusion source term to the momen-
tum equation
cell CV port CV
-
7/31/2019 IC Engines Modeling
7/26
Time marching procedure
A. Della Torre Paper Number: ICES2012-81181
PORT
CELL
Shock-tube test case
0 0.2 0.4 0.6 0.8 1x [m]
1
2
3
4
5
Pressure
[bar
]
exactDTM
(b)
Explicit time marching method
Staggered leapfrog method applied to a staggered grid arrangement
Spatial second order accuracy in the resolution of the pressure discontinuities
-
7/31/2019 IC Engines Modeling
8/26
Model specialization
A. Della Torre Paper Number: ICES2012-81181
Cell and port definitions have been specialized to handle particular devicessuch as:
Catalysts (TWC, DOC, SCR ...)
Diesel Particulate Filters
Perforated elements (baffles, pipes)
Filtering devices
Sound absorbing material
-
7/31/2019 IC Engines Modeling
9/26
Perforated Elements
A. Della Torre Paper Number: ICES2012-81181
Perforates are modeled by extending the properties of the port element
The perforated port is characterized by the number of holes nh, hole cross
section Ah, hole length lh and by the total port surface Ac
The momentum equation is solved only for one single hole and applied to allholes
-
7/31/2019 IC Engines Modeling
10/26
Filter cartridge
A. Della Torre Paper Number: ICES2012-81181
Ms = (pDarcy)Apt
LpDarcy =
wwall
KwallUp
Cartridge modeled as a porous media: Darcys law
Thickness of the layer is modeled but not captured by the mesh
-
7/31/2019 IC Engines Modeling
11/26
After-treatment device: catalyst
A. Della Torre Paper Number: ICES2012-81181
single channel 3Dcell
monolith macro cells
external 3Dcell external 3Dcell
w
Macro cell: it contains only a representative channel
1D flow solved in the channel and extended to the others belonging to the
same macro cellGas-wall friction (Churchill)
Vena contractaMs = (UF) |U| fw
2
t + pinoutF
t
L
-
7/31/2019 IC Engines Modeling
12/26
Test Case: Aprilia V4 engine
A. Della Torre Paper Number: ICES2012-81181
Air-box and silencer exibit a complex geometry
1D-quasi3D model is based on pure geometrical dimensions
Engine Type Spark Ignition
Number of cylinder 4-V65o
Total displacement 999.6 x 10-6 [m3]Bore 0.078 [m]
Stroke 0.0523 [m]
Compression ratio 13:1
Number of valves per cylinder 4
Air Management Naturally aspirated
Injection system PFI
-
7/31/2019 IC Engines Modeling
13/26
1D-quasi3D integrated model
A. Della Torre Paper Number: ICES2012-81181
Fully coupled simulation with 1D code (GASDYN)
The same numerical method is applied to 1D pipes and 3D components
-
7/31/2019 IC Engines Modeling
14/26
Air-box and silencer modeling
A. Della Torre Paper Number: ICES2012-81181
Main characteristic lengths are captured
Number of elements: 1634 cells for the air-box, 2934 cells for the silencer
Average mesh spacing is 1.5 - 2 cm
-
7/31/2019 IC Engines Modeling
15/26
Air-box and silencer modeling
A. Della Torre Paper Number: ICES2012-81181
Intake trumpets in a close-coupled
configuration
Interference between the different
cylinders
Wave motion in the air-box strongly
affects the volumetric efficiency
Complex internal layout
Flow reversal, perforates, catalystmonolith, internal pipes
Back-pressure & radiated noise pre-
diction
-
7/31/2019 IC Engines Modeling
16/26
Air-box and silencer modeling
A. Della Torre Paper Number: ICES2012-81181
Intake trumpets in a close-coupled
configuration
Interference between the different
cylinders
Wave motion in the air-box strongly
affects the volumetric efficiency
Complex internal layout
Flow reversal, perforates, catalystmonolith, internal pipes
Back-pressure & radiated noise pre-
diction
-
7/31/2019 IC Engines Modeling
17/26
Validation: pression pulses on the intake
A. Della Torre Paper Number: ICES2012-81181
Pressure pulses in three differ-ent locations
Pulses in the intake runners
are strongly influenced by theinterference between the cylin-
ders
Cylinder 1 : 6500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360Crank angle [o]
0.70
0.80
0.90
1.00
1.10
1.20
1.30
Pressure[Pa
x105]
Measured
1D-quasi3D
Cylinder 4 : 6500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360Crank angle [o]
0.70
0.80
0.90
1.00
1.10
1.20
1.30
Pressure[Pa
x105]
Measured
1D-quasi3D
-
7/31/2019 IC Engines Modeling
18/26
Validation: pression pulses on the intake
A. Della Torre Paper Number: ICES2012-81181
Cylinder 1 : 4500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Crank angle [o]
0.70
0.80
0.90
1.00
1.10
1.20
1.30
Pressure[Pax105]
Measured
1D-quasi3D
Cylinder 4 : 4500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Crank angle [o]
0.70
0.80
0.90
1.00
1.10
1.20
1.30
Pressure[Pax105]
Measured
1D-quasi3D
Cylinder 1 : 12500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Crank angle [o]
0.60
0.75
0.90
1.05
1.20
1.35
1.50
Pressure[Pax105]
Measured
1D-quasi3D
Cylinder 4 : 12500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Crank angle [o]
0.60
0.75
0.90
1.05
1.20
1.35
1.50
Pressure[Pax105]
Measured
1D-quasi3D
-
7/31/2019 IC Engines Modeling
19/26
Validation: pression pulses on the exhaust
A. Della Torre Paper Number: ICES2012-81181
Pressure pulses are gauged downstream of cylin-
der 4
Strong influence of the 4 in 2
in 1 junction on the exhaustline
Cylinder 4 : 6500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360Crank angle [
o]
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
Pressure[Pax
105]
Measured
1D-quasi3D
Cylinder 4 : 12500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360Crank angle [
o]
0.60
0.90
1.20
1.50
1.80
2.10
2.40
Pressure[Pax
105]
Measured
1D-quasi3D
V l i ffi i d b k
-
7/31/2019 IC Engines Modeling
20/26
Volumetric efficiency and back-pressure
A. Della Torre Paper Number: ICES2012-81181
Modeling is based on pure geometrical reconstruction
The quasi3D model allows to investigate the effects of a geometry change
(e.g. air-box internal layout) on the overall engine performances
Optimization of the geometry and the properties of internal devices (perfo-
rates, filtering elements, catalyst)
Volumetric Efficiency
4000 5000 6000 7000 8000 9000 10000 11000 12000 13000Engine speed [rpm]
0.3
0.4
0.6
0.8
0.9
1.1
1.2
Volumetricefficiency/Vmax[-] Measured
1D-3Dcell
Back Pressure
4000 5000 6000 7000 8000 9000 10000 11000 12000 13000Engine speed [rpm]
0.90
1.00
1.10
1.20
1.30
1.40
1.50
Pressure[P
ax105]
Measured
1D-3Dcell
S d l l l l ti
-
7/31/2019 IC Engines Modeling
21/26
Sound pressure level calculation
A. Della Torre Paper Number: ICES2012-81181
Prediction of the acoustic behaviour of the silencing device in real operatingconditions
Optimization of internal layout of mufflers
Effects on both acoustics and performances
0 1000 2000 3000 4000 5000 6000Frequency [Hz]
0
25
50
75
100
125
150
175
SoundPressureLevel[dB]
Without silencer
With silencer
O ti i ti
-
7/31/2019 IC Engines Modeling
22/26
Optimization
A. Della Torre Paper Number: ICES2012-81181
Example: maximization of silencer TL
Parameters: position of the two internal baffles
Other possible targets:
Stand-alone component: TL & pressure drop
Entire engine: SPL & volumetric efficiency
O ti i ti
-
7/31/2019 IC Engines Modeling
23/26
Optimization
A. Della Torre Paper Number: ICES2012-81181
Example: maximization of silencer TL
Parameters: position of the two internal baffles
Other possible targets:
Stand-alone component: TL & pressure drop
Entire engine: SPL & volumetric efficiency
Computational runtime and accuracy
-
7/31/2019 IC Engines Modeling
24/26
Computational runtime and accuracy
A. Della Torre Paper Number: ICES2012-81181
Results comparable to 1D-3D simulations
Computational run-time 2-3 times that of a 1D simulation
The increase of computational runtime compared to 1D is justified by theenhanced predictivity
Cylinder 4 : 6500 rpm
-360 -300 -240 -180 -120 -60 0 60 120 180 240 300 360
Crank angle [o]
0.40
0.60
0.80
1.00
1.20
1.40
1.60
Pressure[Pax105]
Measured
1D 3D coupling
1D-quasi3D Computational runtimes
1D 15 [min]
1D-3D 20 [hours]1D-quasi3D 45 [min]
Conclusions
-
7/31/2019 IC Engines Modeling
25/26
Conclusions
A. Della Torre Paper Number: ICES2012-81181
A stable numerical procedure to perform both acoustic and fluid dynamic sim-ulation of 3D shaped devices has been presented
Specific sub-models for filtering and after treatment devices have been de-
veloped
Engine modeling is based on pure geometrical reconstruction without the
need of resorting to corrective lengths or equivalent ducts schemes
Engine performance parameters can be determined with good accuracy and
low computational effort
Acoustic properties can be evaluated in real operating conditions
DOE shape optimization is affordable
-
7/31/2019 IC Engines Modeling
26/26
A. Della Torre Paper Number: ICES2012-81181
Thank you for your attention!