the effect of fuel impact on mixture preparation in si engines with port fuel injection
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
• 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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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.
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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).
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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.
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
Overall Boiling Curves
wb w bT T T
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
Spray Cooling Efficiency
fp w b
fg
c T TJa
h
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
The Effect of Fuel Impact on Mixture Preparation in SI Engines with Port Fuel Injection
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