OPTICAL ANALYSIS OF A GDI SPRAY WALL-IMPINGEMENT FOR

S.I. ENGINES

, L. Allocca, S. AlfusoA. MontanaroIstituto Motori – CNR, Napoli – Italy

XV National Meeting, Milano 29-30 Novembre 2007

GENERAL CONSIDERATIONSAttention of International Community on pollutant emissionsand life quality

About 25% of energy consumption and greenhouse gas emissions are due to transportation

The technological challenge in i.c. engines fields is to meet performances and consumption with emission regulations

Sprays from high pressure electronically controlled injection systems are successfully used today both on diesel and gasoline engines

For automotive engine size, the interaction of the fuel with thecombustion chamber wall plays an important role in fuel atomization and its spatial distribution

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Fuel supply systems evolution for SI engines

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Gasoline Direct Injection (GDI) advantages in SI engine

High fuel injection pressure better atomization

High compression ratio

Zero pumping losses

Multimode operation: stratified and homogeneous charge

Good cold starting characteristics

Ignition process control

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Stratified charge

Homogeneous charge

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

The behaviour of the spray impacting on a hot surface, in terms of droplets fragmentation and spatial fuel distribution, influences the mixture formation during the ignition delay with effects on combustion process and pollutant production

In this study is reported, for different injection and ambient conditions, an analysis of the sprays behaviour from a hollow-cone injector for GDI engine, impacting on a heated flat wall.

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

EXPERIMENTAL CONDITIONS - 1

Injected fuel EXXSOL D40 (Tb= 162 °C)

- density: ρ = 760 kg/m3 (T = 40 °C)

- cinematic viscosity: ν = 1.05 cSt (T = 40 °C)

Injector: swirled-type with four rectangular fuel adduction channels

- nominal flow rate: 7.4 g/s at 10 MPa

- nominal primary cone-angle: 60 °

- exit hole diameter: 0.55 mm

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

6.95 – 7.73 – 8.5516 - 8 - 10

Injected fuel [mg/str]

Injection time [ms]Inj. pressure pinj[MPa]

6.95 – 7.73 – 8.5516 - 8 - 10

Injected fuel [mg/str]

Injection time [ms]Inj. pressure pinj[MPa]

25 - 80 - 150 - 2000.1 - 0.6 - 1.26 - 8 - 10

Wall temperature [°C]

Backpressure pamb[MPa]

Inj. pressure pinj[MPa]

25 - 80 - 150 - 2000.1 - 0.6 - 1.26 - 8 - 10

Wall temperature [°C]

Backpressure pamb[MPa]

Inj. pressure pinj[MPa]

EXPERIMENTAL CONDITIONS - 2

PULNIX CCD Camera 768x568 pixels, 8 bit

Nd-YAG pulsed laser sheet (100 μm thickness, 12 ns duration)

Optically accessible high-pressure vessel filled with inert gas (N2)- gas pressure: 0.1 to 5.0 MPa- ambient gas temperature

Image processing softwareXV Nationl Meeting, Milano 29-30 November 2007

Stainless steel flat plate located at 22 mm from the nozzle tip on a x-z-ϕ positioning system

- 200 W electrical heating system- temperature range: 300 – 500 K (+/- 1 K)- mean roughness: 1.077 μm (Rank Taylor Hobson profilometer)

Single-shot mode operation

C.N.R. Istituto Motori Napoli

EXPERIMENTAL SET-UP

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

laser beam

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Laser shooting

pinj= 6.0 MPa pamb= 0.1 MPa Tw= 25°C

t=300 μst=500 μst=800 μst=1000 μs

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Pinj=10.0 MPaPamb =0.1 MPa

Tw=25°C

pinj=8.0 MPapamb=0.1 MPa

Tw=25°C

pinj=6.0 MPapamb=0.1 MPa

Tw=25°C

t=300 μs

t=500 μs

t=800 μs

t=1000 μs

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Pinj=10.0 MPaPamb =0.1 MPa

Tw=25°C

pinj=10.0 MPapamb=0.6 MPa

Tw=25°C

pinj=10.0 MPapamb=1.2 MPa

Tw=25°C

t=300 μs

t=500 μs

t=800 μs

t=1000 μs

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

t=300 μs

t=500 μs

t=800 μs

t=1000 μs

XV Nationl Meeting, Milano 29-30 November 2007

Pinj=10.0 MPaPamb =0.1 MPa

Tw=25°C

pinj=10.0 MPapamb=0.1 MPa

Tw=80°C

pinj=10.0 MPapamb=0.1 MPa

Tw=150°C

pinj=10.0 MPapamb=0.1 MPa

Tw=200°C

C.N.R. Istituto Motori Napoli

400 600 800 1000 120025

30

35

40

45

50

55

60

65

70

75

80

Pinj =10 MPa Pamb=0.1 MPa

wid

th [m

m]

time after SOI [μs]

Tw=25°C Tw=80°C Tw=150°C Tw=200°C

Fuel width for different temperature of the wall

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

Fuel width for different injection pressureXV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

400 600 800 1000 120025

30

35

40

45

50

55

60

65

70

75

80Pamb=0.1 MPaTw=25°C

wid

th [m

m]

time after SOI [μs]

Pinj=6 MPa Pinj=8 MPa Pinj=10 MPa

0.0 0.6 1.2

20

30

40

50

60

70

80

90

100Pinj = 10 MPa

spra

y co

ne a

ngle

[deg

]

Pchamber [MPa]

far cone angle near cone angle

XV Nationl Meeting, Milano 29-30 November 2007

Spray cone-angle vs. backpressure

C.N.R. Istituto Motori Napoli

CONCLUSIONS

Time- and space-evolution of a hollow-cone spray, from a swirled injector and its impact on a flat wall, have been visualized varying the injection pressure, the backpressure and the temperature of the wall

The image processing technique have enabled to obtain information on the shape, structure and morphology of the sprays

The fuel distribution and vortexes of the spray impacted on the wall depend on injection pressure, backpressure and wall temperature configuration

The wall temperature markedly influences the shifting and rebounding of the fuel droplets on the plate contributing to themixture formation process

XV Nationl Meeting, Milano 29-30 November 2007 C.N.R. Istituto Motori Napoli

, L. Allocca, S. AlfusoA. Montanaroby

THANK YOU FOR YOUR ATTENTION

OPTICAL ANALYSIS OF A GDI SPRAY WALL-IMPINGEMENT FOR S.I. ENGINES

XV National Meeting, Milano 29-30 Novembre 2007