fuel effects in advanced combustion -partially … [tdc] [a.u.] const. load & ca50 partially...
TRANSCRIPT
William Cannella Chevron
Fuel Effects in Advanced Combustion -Partially Premixed Combustion (PPC) with Gasoline-Type Fuels
Vittorio Manente, Prof. Bengt Johansson, Prof. Per Tunestal
Lund Institute of Technology Department of Energy Sciences Division of Combustion Engines
Lund, Sweden
Work Done In Collaboration With:
Acknowledgement
SAE Publications: 2009-01-2668 2010-01-0871 2010-01-1471 2010-01-2198
Goals for Advanced Combustion Systems Improve engine efficiency/fuel economy and meet CO2 emissions regulations Lower engine-out NOx and PM/soot emissions to meet stricter regulations Reduce size, costs, and fuel consumption penalties of aftertreatment systems (especially NOx) Operate effectively over wide speed/load range In Europe: Options for mitigating diesel/gasoline supply/demand imbalance
-60 -50 -40 -30 -20 -10 0 100
0.2
0.4
0.6
0.8
1
CAD [TDC]
[a.u
.]
Load & CA50 Const.
Partially Premixed Combustion Characteristics:
Avoid conditions that cause NOx & soot formation in conventional diesel CI combustion -- form of PCCI
Fuel/air mixing intermediate between HCCI & conventional CI combustion (“partial premix”) Better performance than HCCI due to
some fuel/air stratification Approach:
One or two fuel injections
When used, first one placed @ -60 TDC to create homogeneous mixture (Similar to Toyota “Unibus” approach)
Last injection around TDC (to achieve CA50 @ MBT ~5-10˚ ATDC) - Stratification created by this injection triggers combustion.
Same energy content injected per fuel
EGR used to prevent early reaction during compression stroke
Pilot quantity function of:
-Fuel properties
-Operating conditions
Study Objectives
Test effects of properties of different gasoline range blends in HD CI engine operated under
Partially Premixed Combustion Mode
Different fuel properties/composition Different “reactivity”
Different ignition and combustion characteristics Different effective speed/load operating ranges
”Gasoline”Fuel RON MON C H/C LHV [MJ/kg] A/F stoich
FR47335CVX 99.00 96.90 7.04 2.28 44.30 15.10
FR47331CVX 92.90 84.70 6.90 1.99 41.60 14.02
FR47338CVX 88.60 79.50 7.21 1.88 43.50 14.53
FR47330CVX 87.10 80.50 7.20 1.92 43.50 14.60
FR47333CVX 80.00 75.00 7.16 1.97 43.70 14.65
FR47336CVX 70.30 65.90 7.10 2.08 43.80 14.83
FR47334CVX 69.40 66.10 7.11 1.98 43.80 14.68
Ethanol 107.00 89.00 2.00 3.00 26.90 9.00
Fuel Selection Gasoline-type fuels selected based on prior results which suggest gasoline may better achieve goals than diesel fuel in PPC due to higher volatility and longer ignition delay (SAE2006-04-3385, SAE2007-01-0006, SIAT 2009) Blends of refinery gasoline range components:
Studied fuel property effects by blending streams with different compositions and RON’s RON’s ranging from 69-99 Ethanol also tested
50 < ON < 75
90 < ON < 99
Typical Refinery Streams
Gasoline-range streams having octane numbers as low as ~50 exist in refineries and are used to make gasoline blends
Bosch Common Rail
Prail 1600 [bar]
Orifices 8 [-]
Orifice Diameter 0.18 [mm]
Umbrella Angle 120° [deg]
Engine / Dyno Spec
rcgeometric 14.3* [-]
BMEPmax 15 [bar]
Vd 1951 [cm3]
Swirl ratio 2.9 [-]
Issue: Old, first generation Bosch injector – impacts soot emissions
Scania D12 Heavy Duty Diesel Engine – Single Cylinder
* - Standard rcgeometric = 17.1
Engine Characteristics
Preferred PPC operating region:
If lambda is ~ 1.5 and EGR between 45 – 55 %, combustion should occur in the desired temperature range
Low NOx and low HC & CO!!!
In addition, should still be enough O2 to limit soot production.
30 35 40 45 50 55 60 65 701000
1200
1400
1600
1800
2000
2200
2400Adiabatic Flame Temperature
EGR Ratio [%]
Tem
pera
ture
[K]
λ=1λ=1.1λ=1.2λ=1.3λ=1.4λ=1.5λ=1.6λ=1.7λ=1.8λ=2λ=2.5λ=3λ=3.5λ=4
Achieving low CO, HC, NOx & soot: -Controlling T through EGR & λ
Base Test Conditions
Dyno LIMIT
11 2 4 6 8 10 12 14 16 18 20
300
320
340
360
380
400
420
440
Gross IMEP [bar]
Inle
t Tem
pera
ture
[K]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
Injection Parameters
4 6 8 10 12 14 16 18 200
10
20
30
40
50
60
70
80
90
100
Gross IMEP [bar]
Pilo
t Rat
io [%
]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
Higher ON gasolines & ethanol required significant amount fuel in pilot
Higher ON gasolines & ethanol required high Tin to run lower loads
Lower ON gasolines performed best with no pilot
Pilot Ratio vs. Load
T inlet vs. Load
2 4 6 8 10 12 14 16 18 200
0.5
1
1.5
2
2.5
Gross IMEP [bar]
Soot
[FSN
]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
2 4 6 8 10 12 14 16 18 200
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Gross IMEP [bar]
NOx [
g/kW
h]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX NOx below US10 limit for most fuels/conditions
(little to no aftertreatment needed!)
No correlation with RON/MON
Engine-Out NOx and Soot Emissions
0 5 10 15 20 25 300
0.5
1
1.5
2
2.5
3
Gross IMEP [bar]
Soot
[FSN
]
G. ON 99/97G. ON 98/88G. ON 97/86G. ON 93/85G. ON 89/80G. ON 87/81G. ON 80/75G. ON 70/66G. ON 69/66D. CN 52PRF20
Diesel Fuel (CN=52)
Significant improvement in soot when modern injection system used (but DPF still needed for gasolines)
Low RON
EtOH
NOx vs. Load
Soot vs. Load
4 6 8 10 12 14 16 18 20140
145
150
155
160
165
170
175
180
Gross IMEP [bar]
Gros
s Ind
icate
d Sp
ecific
Fue
l Con
sum
ptio
n [g
/kWh] Phase 4, 1300 [rpm]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
2 4 6 8 10 12 14 16 18 2095
95.5
96
96.5
97
97.5
98
98.5
99
99.5
100
Gross IMEP [bar]
Com
busti
on E
fficien
cy [%
]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
Very high combustion and gross indicated efficiencies
over entire load range
2 4 6 8 10 12 14 16 18 2040
42
44
46
48
50
52
54
56
58
60
Gross IMEP [bar]
Gro
ss In
dica
ted
Effi
cien
cy [%
]EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
Efficiencies Combustion Efficiency vs. Load
Gross Indicated Efficiency vs. Load
down to 150g/kwhr!
Gross Indicated Specific Fuel Consumption
Approaching 56%!
2 4 6 8 10 12 14 16 18 200
5
10
15
20
25
Gross IMEP [bar]
Max
Pre
ssur
e R
ise
Rat
e [b
ar/C
AD
]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
Lower ON fuels had lower MPRR’s at high loads
Maximum Pressure Rise Rate (MPRR)
Load Operating Area If Tintake limited to ~330˚K:
o With no Tintake constraints, all fuels tested able to operate at all loads o With reasonable Tintake constraints:
• all fuels tested able to operate at the higher loads • only the lowest RON fuels able to operate at the lowest loads
2 4 6 8 10 12 14 16 18 20300
320
340
360
380
400
420
440
Gross IMEP [bar]
Inle
t Tem
pera
ture
[K]
EthanolFR47330CVXFR47331CVXFR47333CVXFR47334CVXFR47335CVXFR47336CVXFR47338CVX
Tintake vs. Load
-5 0 5 10 15 20 250
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Soot
[FSN
]
Combustion Phasing, CA50, [TDC]
FR47338CVXFR47335CVXFR47334CVX
-5 0 5 10 15 20 250
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
Indi
cate
d NO
x [g/
kWh]
Combustion Phasing, CA50, [TDC]
FR47338CVXFR47335CVXFR47334CVX
Nissan MK type combustion, easier to achieve with fuels with high octane number.
CA50 Sweep: NOx – soot-efficiency
US 2010 Limits
For this engine system and mode of operation, optimal timing appears to be ~5-10˚ATDC
NOx vs. CA50 Soot vs. CA50
Gross Indicated Efficiency vs. CA50
17
Summary • Gasoline PPC enabled simultaneous achievement of high efficiency, low
emissions and acceptable MPRR’s at all loads tested (5-18 bar gross IMEP) in heavy duty CI engine with EGR~50%, λ =1.5, & CA50=5-10˚ATDC • Able to run all gasoline fuels and ethanol at all loads tested
Lower ON fuels could be run with reasonable intake T’s & 0% pilot Higher ON fuels (incl. ethanol) required high intake T’s & significant % fuel in
pilot to run @ lower loads
• Gross indicated efficiency between 52-56% attained for loads higher than 6 bar gross IMEP. (Gross ISFC’s down to 150 g/kwhr)
• Engine-out NOx below US2010 limits without aftertreatment • At highest load soot was between 0.2-2 FSN. (<0.5 FSN with modern
injection system). Acceptable level with DPF’s
• At high loads, Maximum Pressure Rise Rates (MPRR) were best for the lower ON fuels, with values of ~12 bar/CAD