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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 Research Mechanical Engineering Department Instituto Superior Técnico.

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slide1

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 Research

Mechanical Engineering Department

Instituto Superior Técnico

slide2

16% of total HC emissions due to liquid films.

- Cheng et al. (1993) -

15% of injected fuel remains liquidinside 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

slide3

FilmEvaporation

Vaporization/Boiling

Transition

Leidenfrost

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

Nu = a Rem Prn Wep

slide4

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

slide5

Simultaneous measurements of droplet dynamics and surface thermal behaviour

  • Resistance = 8 – 12   tresponse  10 s
  • Signal gain = 300
  • Temperature acquired at 50kHz
  • Electronic noise =  0.3ºC
slide6

FilmEvaporation

Vaporization/Boiling

Transition

Leidenfrost

Nu = a Rem Prn Wep Jaq Ecw

New Correlation

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

slide7

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

  • To quantify spatial and injection conditions effects in systems with simultaneous fuel injector activation (cold start and acceleration enrichment).
slide8

- 20

20

(mm)

r = 2 mm

Working Conditions

Injection frequency = 10, 15, 20 and 30 Hz

Duty Cycle = 0.05, 0.075, 0.1 and 0.15 (tinj = 5ms)

Wall temperature = 125, 150, 175, 200 and 225ºC

slide9

Step 1 – Calculate Ensemble-Average Series

Nseries

Average over  70 Series

ensemble-average series

slide10

Step 2 – Phase-Average Wall Temperature

-5% of Tw(t=0)

ensemble-average series

valid injections (Nvinj)

slide11

Step 3 – Total Average Heat Flux

Phase-Average

Wall Temperature

Transient Profile

instantaneous heat flux

CALCULATION

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

slide12

time-average heat flux

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

Tw = 125ºC

finj = 10Hz

slide13

r = 0 mm

finj = 30 Hz

tinj = 5 ms

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

slide14

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

  • To quantify spatial and injection conditions effects in systems with simultaneous fuel injector activation (cold start and acceleration enrichment);
  • To develop a methodology to describe the overall thermal interaction acounting for the complex non-linear interactions within the area of impact.
slide15

Step 3 – Total Average Heat Flux

Tw = 125ºC

finj = 10Hz

total average heat flux

OVERALL

BOILING

CURVE

slide16

Step 4 – Spray Cooling Efficiency

spray cooling efficiency

slide21

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

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.