The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection

The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection


António L. N. Moreira

João Carvalho

Miguel R. O. Panão

IN+, Center for Innovation, Technology and Policy ResearchMechanical Engineering DepartmentInstituto Superior Técnico


BackgroundPrimary Droplets

Fuel InjectorIntake Manifold

Air Flow

Secondary Breakup

Spray/Wall Interaction mechanismsWall Film

Evaporation of droplets

Intake Valve

Wall Film Evaporation

Super CriticalFilm Flow

Airblast

Liquid Fuel

Elsaer, Samenfink, Hallman and Wittig (1994)

Primary Droplets

Fuel InjectorIntake Manifold

Air Flow

Secondary Breakup

Spray/Wall Interaction mechanismsWall Film

Evaporation of droplets

Intake Valve

Wall Film Evaporation

Super CriticalFilm Flow

Airblast

Liquid Fuel

Elsaer, Samenfink, Hallman and Wittig (1994)

16% of total HC emissions due to liquid films.- Cheng et al. (1993) -

15% of injected fuel remains liquid inside combustion chamber

1.5 increase factor in HC emissions between engine cold-start and heated engine.

- Meyer and Heywood (1999) -

COLD START AFTER WARM UP


Background

c p fg satf h ,D,U, ,k, ,C , ,h , T 0

Nu = a Rem Prn Wep 0.94

0.53 0.33

W eNu 0.34

Re Pr

Arcoumanis and Chang, Experiments in Fluids, vol. 16, pp. 105-119, 1993.

Temperatura da Superfície (ºC)Fl

uxo

de C

alor

(W

/m

)

FilmEvaporation

Vaporization/Boiling

Transition

Leidenfrost


1. To quantify the effects of all surface, flow and fluid properties on the heat transferred in PFI systems

Nu = a Rem Prn Wep Jaq Ecw

2 2

0p p satc

fg p sat

C C Th D UD U D Uf ' , , , , ,

k k h C T


• Resistance = 8 – 12 tresponse 10 s• Signal gain = 300• Temperature acquired at 50kHz• Electronic noise = 0.3ºC

Simultaneous measurements of droplet dynamics and surface thermal behaviour


2 2

0p p satc

fg p sat

C C Th D UD U D Uf ' , , , , ,

k k h C T

1.51

50.254

ReNu 3.4 10

Ja

Nu = a Rem Prn Wep Jaq Ecw

New Correlation

Temperatura da Superfície (ºC)

Flux

o de

Cal

or (

W/m

)

FilmEvaporation

Vaporization/Boiling

Transition Leidenfrost

Panão and Moreira, Thermo- and fluid dynamics characterization of spray cooling with pulsed sprays, Experimental Thermal and Fluid Science, in Press.


1. To quantify the effects of all surface, flow and fluid properties on the heat transferred in PFI systems;

2. To quantify spatial and injection conditions effects in systems with simultaneous fuel injector activation (cold start and acceleration enrichment).


20 - 20(mm)

r = 2 mm

Working ConditionsInjection frequency = 10, 15, 20 and 30 HzDuty Cycle = 0.05, 0.075, 0.1 and 0.15 (tinj = 5ms)Wall temperature = 125, 150, 175, 200 and 225ºC


Nseries

Step 1 – Calculate Ensemble-Average Series

Average over 70 Series

ensemble-average series

series th

Ni series

w w1i 1series

1T r,0,t T r,0,t

N

w1

Tr,

0,t

ºC


Step 2 – Phase-Average Wall Temperature

-5% of Tw(t=0)

valid injections (Nvinj)

ensemble-average series

w1

Tr,

0,t

ºC

vinj th

Ni valid injection

w w2 1i 1vinj

1T r,0,t T r,0,t

N


Step 3 – Total Average Heat Flux

Phase-AverageWall TemperatureTransient Profile

Reichelt et al., Int. J. Heat Mass Transfer 45 (2002), pp579.

-0.02 0 0.02 0.04 0.06tim e (sec)

-4

-3

-2

-1

0

w2

Tr,

0,t

ºC

2q

r,0,

tM

W/m

iq r ,tinstantaneous heat fluxCALCULATION


Reichelt et al., Int. J. Heat Mass Transfer 45 (2002), pp579.

-0.02 0 0.02 0.04 0.06tim e (sec)

-4

-3

-2

-1

0

-20 -16 -12 -8 -4 0 4 8 12 16 20r (m m )

0

0 .1

0 .2

0 .3

0 .4

2q r kW /m

Tw = 125ºCfinj = 10Hz

injT

* *i inj i

0

q r f q r , d

time-average heat flux

2q

r,0,

tM

W/m


Panão and Moreira, Thermo- and fluid dynamics characterization of spray cooling with pulsed sprays, Experimental Thermal and Fluid Science, in Press.

finj = 30 Hz tinj = 5 ms

r = 0 mm


1. To quantify the effects of all surface, flow and fluid properties on the heat transferred in PFI systems;

2. To quantify spatial and injection conditions effects in systems with simultaneous fuel injector activation (cold start and acceleration enrichment);

3. To develop a methodology to describe the overall thermal interaction acounting for the complex non-linear interactions within the area of impact.


Step 3 – Total Average Heat Flux

R

w injimpact 0 R

1q T ,f q r drd

A

total average heat flux

-20 -16 -12 -8 -4 0 4 8 12 16 20r (m m )

0

0 .1

0 .2

0 .3

0 .4 2q r kW /m

Tw = 125ºCfinj = 10Hz

OVERALLBOILINGCURVE


f

fi nj injp b fuel fg

maximpact

m t fq C T T h

A

R

w injimpact 0 R

1q T ,f q r drd

A

w inj

sc

max

q T ,f

q

Step 4 – Spray Cooling Efficiency

spray cooling efficiency


Overall Boiling Curves

wb w bT T T


Spray Cooling Efficiency

fp w b

fg

c T TJa

h




A novel methodology is developed to quantify the heat removed a pulsed spray.

Total average heat flux increases with injection frequency due to the associated increase of net mass flux.

Nukiyama temperature is independent of injection frequency.

Spray cooling efficiency is larger for CHF and lower injection frequencies.

A new correlation for the heat transfer coefficient has been developed based on simultaneous measurement of the spray characteristics and surface thermal behaviour:

1.51

50.254

ReNu 3.4 10

Ja

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The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection