the quality audit of fuel injectors: best practicesfuel temperature 20 oc 0.0 0.5 1.0 1.5 2.0 2.5 10...
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innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
765-497-3269 765-463-7004
http://www.enurga.com
765-497-3269 765-463-7004765-497-3269765-497-3269 765-463-7004765-463-7004
http://www.enurga.com
The quality audit of fuel injectors: Best practices
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Motivation
Optimization of fuel sprays provide one of the best methods for increased efficiency
Wide variation in injector performance, even from the same manufacturer
Current quality audit methods do not pick up even significant differences
Key question: What can be done to provide for a better quality audit of injectors
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Ranking of Attributes
Method should be repeatable
Sensitive to small differences
Accurately estimate key spray characteristic
Equipment should be easy to operate
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Methods used in Study
Drop sizing using Diffraction
Plume penetration using SCIvel velocimeter
Planar surface area density using SETscan patternator
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Drop sizing principle
Diffraction signal analyzed to provide transient drop sizes
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Image Correlation Velocimetry
Transient and steady state X and Y velocities using high speed shadowgraphs
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Drop surface areas from Patternator
Tomography of extinction data with a sampling frequency of 9.4 KHz
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Test Details (GDI injector)
Injection pressures: up to 20 MPa
Ambient pressures: 40 Kpa to 1.5 Mpa absolute
Fuel temperature: up to 90 OC
Fuels: Gasoline or Heptane
Pressure vessel fitted with AP400 patternatorMaximum field of view is 100 mm
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Sample Results
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Drop Size Distribution
0 100 200 300 400 500 600
0.0
0.1
0.2
Injection Pressure 15 MPaAmbient Pressure 101 KPaInjection time 1.5 msFuel Temperature 20 OC%
vol
ume
in b
in
Diameter (m)
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
Drop size distribution at 1.6 ms
Obscuration is very high
Large peak at high values probably caused by beam wandering
Usually bimodal distribution
Measurements obtained through one plume
Results are average across the 10 mm diameter laser beam
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Mean drop diameter (D32)
0.0 0.5 1.0 1.5 2.0 2.5 3.010
15
20
25
30
Saut
er m
ean
diam
eter
(m
)
Time (ms)
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Average
Injection Pressure 15 MPaAmbient Pressure 101 KPaInjection time 1.5 msFuel Temperature 20 OC
0.0 0.5 1.0 1.5 2.0 2.510
12
14
16
18
20
Injection Pressure 15 MPaAmbient Pressure 101 KPaInjection time 1.5 msFuel Temperature 20 OC
Saut
er m
ean
diam
eter
(m
)
Time (ms)
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Average
All drops from 0 to 500 microns All drops from 0 to 200 microns
Standard deviation in first case is ~ 10% Slightly better during initial phase for second caseDifficult to rank injectors and probably not a good quality audit tool
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Patternator Results
15 bar injection pressure Data collection with injection
pulse Contour maps of surface area
density Data collected for ~ 2 to 3 ms
after injection pulse Analysis based on 5 samples Results are for the entire plane
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Importance of surface areas
0.0 0.1 0.2 0.3 0.4 0.50.0
0.1
0.2
0.3
0.4
0.5
R = 0.962
Surfa
ce a
rea
dens
ity (m
-1)
Mass evaporation rate (kg/hr)
Correlation of fuel evaporation with parametersDrop size = 0.681Velocity = - 0.239Mass flux = 0.903Surface area density = 0.962
Surface area density is the most important parameter to measure if you are interested in obtaining the amount of fuel evaporated at any location in a spray
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Sample Repeatability
0.5 1.0 1.5 2.0 2.5 3.00
50
100
150
200
250
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Average
Tota
l sur
face
are
a (m
m2 )
Time (ms)
Total surface area is the total surface area of all the drops within a 1 mm height in the patternation plane
Standard deviation (other than the first instant) is <5%
If total surface area over entire injection period is taken, standard deviation is less than 0.5%
Ideal variable for ranking and quality audit of different nozzles
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Plume Analysis
Centroids within 200 microns Plume angles within 1/2 degree% distribution in plumes within 1%Improves with more samples
Mean Plume angles (deg)
Standard Error
% area in plume
Standard Error
10.89 0.13 19.32 0.665.73 0.11 4.69 0.1411.53 0.13 21.71 0.9210.48 0.37 17.91 0.7111.51 0.32 23.06 0.249.35 0.36 12.93 0.95
Mean centroid (x,mm)
Standard Error
Mean centroid (y, mm)
Standard Error
3.26 0.12 -5.69 0.19-4.84 0.14 14.3 0.1322.13 0.25 1.97 0.0629.04 0.12 10.75 0.0915.36 0.13 -18.49 0.030.10 0.12 -20.01 0.17
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Comparison with Mechanical Patternator
Mechanical patternator has stagnation planes
Requires extensive time and effort
Spatial resolution not very high for mechanical patternator
Results show that mass flux centers correlate well with surface area centers
-30 -20 -10 0 10 20-30
-20
-10
0
10
20
30
Mechanical SETscan
Plum
e Y
loca
tion
(mm
)
Plume X location (mm)
Fully automated plume analysis for quality audit
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Penetration Distance
Injection pressure 10 MPa gage, Chamber pressure 40 Kpa absolute Fuel temperature 90 OC Plumes overlap
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Repeatability of measurement
0.0 0.5 1.0 1.5 2.00
10
20
30
40
50
60
70
Dis
tanc
e (m
m)
Time (ms)
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Average
Extinction based measurement, similar to the patternator
Standard deviation in all cases (other than the first sample) is ~ 5%
Higher than the patternator since whole field image has some errors due to secondary emission
Can be used for quality audit, but not ideal for ranking of nozzles
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Case study in design/selection of injector
Drop sizes through one plume from 3 injectors:A: 25.4 +/- 2.5 micronsB: 25.5 +/- 2.5 micronsC: 22.1 +/- 2.2 microns
Difficult to choose which is the best
Drop surface areas across entire planeA: 193.2 +/- 3.8 mm2
B: 220.1 +/- 4.4 mm2
C: 199.6 +/- 4.0 mm2
Easy to decide which injector provides the best performance
innovations in quality control
1291 Cumberland Avenue, West Lafayette, IN 47906
Conclusions
There is some variation in the shot to shot characteristics of sprays from fuel injectors
When testing spray under actual operating conditions within a pressure chamber, it is difficult to have a large sample size
Diffraction based measurements may not be ideal for ranking nozzles under such conditions
Extinction based measurements show higher consistency that diffraction or scattering based measurements under real operating conditions
Planar extinction tomography has been shown to be the best method for ranking nozzles or for quality audit purposes.