Giovanni Bonandrini, Rita Di Gioia, Luca Venturoli

Magneti Marelli Powetrain S.p.A.

20 Novembre, 2010

Optimization of the injection strategies

in DISI engines

11-07-2011 22-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• GDI engine: mixture formation

• Injector model

• Injectors comparison

• 3D engine simulation approach

• CFD results and experimental data

• Conclusions

Summary

11-07-2011 32-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• GDI engine: mixture formation

• Injector model

• Injectors comparison

• 3D engine simulation approach

• CFD results and experimental data

• Conclusions

11-07-2011 42-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Mixture formation

TARGET

Quick mixture formation

TARGET

fuel atomization and evaporation

(in all operating condition)

TARGET

Small droplet size

fast and correct mixture formation in GDI engine:

• spray orientation

• spray penetration

• spray droplet size

11-07-2011 52-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Small droplet size

Small nozzle

diameter (D)

High fuel delivery speed

High air density

Low fuel viscosity Low fuel tension surface

TARGET

Small droplet size

High injection pressure

High compression ratio

Super/turbo charging

L/D ratio optimization

(L hole length)

Holes profile

(Sharp hole inlet edge)

Air motion

11-07-2011 62-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• GDI engine: mixture formation

• Injector model

• Injectors comparison

• 3D engine simulation approach

• CFD results and experimental data

• Conclusions

11-07-2011 72-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Injector model

Two multi-hole injectors considered for the analysis (injector 1 and injector 2), with different spray patterns

Flow-rate from 1D injector model (EVI curves)

Instantaeous flow-rate Similar injection flow rate

11-07-2011 82-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Spray test on bench

Spray bench vessel conditions

• Injection pressure 50, 100 and 150 bar

• Vessel back-pressure 1 bar

• Vessel temperature 298 K

• Fluid temperature (n-heptane) 298 K

11-07-2011 92-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• Fluid n-heptane

• Tfluid 298 K

• Tvessel 298 K

• Computational Vessel : L=65 mm, D=80 mm

• 100000 cells

• Mean cell dimension 1 mm

Computational domain

11-07-2011 102-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• Fluid n-heptane

• Tfluid 298 K

• Tvessel 298 K

• Injector vertically oriented

• Break-up model KHRT

• Coalescence model off

Computational domain

11-07-2011 112-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.0002 0.0004 0.0006 0.0008 0.001

Pe

n [

m]

Time [s]

Penetration @ 50bar

Exp

Num

Jet penetration

11-07-2011 122-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.0002 0.0004 0.0006 0.0008 0.001

Pe

n [

m]

Time [s]

Penetration @ 100bar

Exp Num

Jet penetration

11-07-2011 132-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.0002 0.0004 0.0006 0.0008 0.001

Pe

n [

m]

Time [s]

Penetration @ 150bar

Exp

Num

Jet penetration

11-07-2011 142-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

morphology @100bar

0.2ms

Spray morphology

11-07-2011 152-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Spray morphology

morphology @100bar

0.4ms

11-07-2011 162-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Spray morphology

morphology @100bar

0.6ms

11-07-2011 172-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

AUTOREFINESTANDARD

Simulation with autorefinement (Polimi Lib-ICE)

11-07-2011 182-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Sez A-A

A-A

B-B

Sez B-B

AUTOREFINE

AUTOREFINE

STANDARD

STANDARD

Simulation with autorefinement (Polimi Lib-ICE)

11-07-2011 192-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

autorefine

base vs autorefine: grid modification

base grid

Simulation with autorefinement (Polimi Lib-ICE)

11-07-2011 202-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

base vs autorefine: morphology @50bar

autorefine base grid

Simulation with autorefinement (Polimi Lib-ICE)

11-07-2011 212-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.00E+00 2.00E-04 4.00E-04 6.00E-04 8.00E-04 1.00E-03

Pe

n [

m]

Time [s]

Penetration @ 100bar

Num

Num_AutorRefine

Simulation with autorefinement (Polimi Lib-ICE)P

en

etr

ati

on

[m

]

11-07-2011 222-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Single hole injector: solver with coalescence model (Nordin traiectory)

different jet penetration

different jet shape

section

view

frontal

viewsection

view

frontal

view

[m]

Coalescence model

11-07-2011 232-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Coalescence model: execution time

Coalescence model

11-07-2011 242-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• GDI engine: mixture formation

• Injector model

• Injectors comparison

• 3D engine simulation approach

• CFD results and experimental data

• Conclusions

11-07-2011 252-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

LATERAL VIEW

morphology @150bar

injector 1 injector 2

Injectors comparison

11-07-2011 262-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• GDI engine: mixture formation

• Injector model

• Injectors comparison

• 3D engine simulation approach

• CFD results and experimental data

• Conclusions

11-07-2011 272-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Diesel

• Usually only a sector of the domain

(symmetric domain)

• Valve closed cycle

• No valves motion

• Complete engine cycle

• Intake and exhaust ducts in fluid domain

• Valves motion

Engine simulation approach: geometry

GDI

11-07-2011 282-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Diesel GDI

SOI with intake opened valves

SOI with all closed valves

• Injection with intake opened valve

• Simulation of the complete intake cycle

• Injection with intake valves closed

• Simulation of compression only

GRID MOTION���� layering GRID MOTION���� multiple mesh

Engine simulation approach: grid management

11-07-2011 292-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Layering Vs MultipleMesh

Diesel GDI

OPEN VALVES

• To keep an optimum mesh size during piston and valve motion

• Definition of an arbitrary base surface, where layers of cells are added and removed.

• Removal and addition of cells layers handled automatically according to prescribed values of minimum layer thickness.

•No mass loss due to topological changes due to a consistent remapping strategy

• Each mesh is valid for a specified interval of simulation

• During each time step it is possible to:

�move the grid points using automatic mesh motion and/or predefined points motion (simple cases).

� Change the mesh topology (dynamic mesh layering,

sliding interface, attach-detach boundary, adaptive local mesh refinement)

•Mesh-to-Mesh interpolation by inverse, distance-weighted tecnique.

Engine simulation approach: grid management

11-07-2011 302-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

3D engine model of the exhaust, intake and compression strokes

- boundary conditions from 1D complete engine model

- turbulence model: RNG k-ε

- Bai-Gosman wall impingment model (Lib-ICE Polimi)

Point selected for presentation: 1500 rpm, bmep 15 bar

3D engine model

11-07-2011 312-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• GDI engine: mixture formation

• Injector model

• Injectors comparison

• 3D engine simulation approach

• CFD results and experimental data

• Conclusions

11-07-2011 322-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

w/o Injection with Injection

Velocity field with and w/o injection

11-07-2011 332-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Spray analysis and wall impingement

Jet fuel tracers method.

11-07-2011 342-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Spray simulation engine test point condition

Injector spray and wall impingement comparison

11-07-2011 352-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Spray simulation engine test point condition

Injector spray and wall impingement comparison

11-07-2011 362-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

-180 deg - 90 deg

Wall impingement comparison

injector 1

injector 2

injector 1

injector 2

11-07-2011 372-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Lambda distribution @ spark

Injectors comparison

11-07-2011 382-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Lambda < 0.5 distribution @ spark

Injectors comparison : “SOOT FORMATION ZONE “

11-07-2011 392-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Particle measurements on engine bench

Injector performance comparison

Point 1500 rpm, imep 15 bar, Particle Number measurements:

- injector 1 ~ 1.5*10^7 p/ccm

- injector 2 ~ 4.6*10^6 p/ccm

11-07-2011 402-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

• In-engine 3D simulation fundamental for the injection optimization

• 3D-1D model integration necessary for simulation

• OpenFOAM integrated by Lib-ICE useful for GDI engine simulation

Conclusion

11-07-2011 412-day Meeting on Internal Combustion Engine Simulations using OpenFOAM® technology

Thanks to

• Tommaso Lucchini and Polimi ICE Group

• Federico Brusiani (DIEM-Unibo)

Thank you for the attention

Acknowledgments