Benefits of Direct Injection in Hydrogen Engines

Benefits of Direct Injection in
Hydrogen Engines
ERC Research Symposium
Madison, WI
June 6, 2007
°
Brad Boyer - H2ICE Research
Ford Motor Company
1
Agenda
General targets, emission approaches
Hydrogen properties
Limitations with Port Fuel injection
Rationale for Direct-Injection
Inherent benefits
DI Combustion Development
Efficiency and emissions of alternative combustion modes
Comparison to gasoline
E450 H2ICE Shuttle
Conclusions
2
H2ICE Research Targets
Emissions
Target: SULEV or Better
Efficiency
Performance
Target: Equal to Naturally
Aspirated Gasoline
H2ICE
Research
Target: 25-35% over gas
(Comparable to Diesel)
Competitive with Fuel Cell
(when hybridized)
Implementation
Target: Transparent to
Customer
3
Emissions with H2ICE
NOx Emissions
NOx emissions are the only regulated emission of
significance with H2ICE
Opportunities for reducing NOx
» Lean Operation (Φ≤0.4)
» Lean aftertreatment (LNT, LNC, SCR)
Multi-injection with DI
Water injection
» TWC - PFI throttling/high EGR or DI required
CO2 and Carbon Based Emissions
Produced entirely from combustion of engine oil
Reduced 99+% compared to gasoline
4
Agenda
General targets, emission approaches
Hydrogen properties
Limitations with Port Fuel injection
Rationale for Direct-Injection, inherent benefits
DI Combustion Development
Efficiency and emissions of alternative combustion modes
Comparison to gasoline
E450 H2ICE Shuttle
Conclusions
5
Hydrogen Properties
•Stoichiometric Power Density vs. Gasoline
DI H2 / Gasoline = 120 / 43.5 * 14.7/34.4 = 117%
•Combustion phasing (flame velocity scales with phi)
•Knock, high autoignition temperature (~130 octane)
•No soot / wall wetting constraints
Source: NHA 2006 paper
•Thermal Losses ( < 1/4 quench
distance of gasoline/air)
• Pre-ignition concerns
6
Agenda
General targets, emission approaches
Hydrogen properties
Limitations with Port Fuel injection
Rationale for Direct-Injection, inherent benefits
DI Combustion Development
Efficiency and emissions of alternative combustion modes
Comparison to gasoline
E450 H2ICE Shuttle
Conclusions
7
Power Density Limitations
with Port Fuel Injection (PFI)
0.9
BLD
0.8
Knock
Preignition
Backfire
CR=12.2 2.3L NA 3000 RPM
0.7
Knock
Preignition
Φ
0.6
0.5
0.4
MBT
0.3
Backfire
Misfire
0.2
70
60
50
40
30
20
Spark (CA BTDC)
10
0
-10
-20
8
4000 rpm / 0.6 phi / PFI
Cyl1PresTrace vs deg
140
120
Knock
100
80
b
a
r
Misfire
Preignition
60
40
Backfire
20
0
-20
-200
0
200
400
deg (Engine Cycle = 227-228)
600
800
1000
9
Single Cylinder H2ICE, 16:1 CR, 4000
RPM, Phi = 0.61, PFI
100
1st
2nd
3 rd
10
1
1 0 .0 0
1 0 0 .0 0
1 0 0 0 .0 0
0 .1
10
PFI is phi-limited at medium to high engine speeds
Max Equivalence Ratio
NA unless noted
1.0
0.9
0.8
Phi_max
0.7
0.6
0.5
0.4
0.3
0.2
500
1000
12.5 Zetec
14.7 Zetec
12.2 2.3L
12.2 2.3L SC
12.0 Single
16.0 Single
1500
2000
2500
3000
3500
Speed (RPM)
4000
4500
5000
5500
H2 Combustion Challenges
3 types of Abnormal Combustion
Pre-ignition is undesirable combustion during the compression stroke initiated
prior to spark.
Backfire/Flashback is undesirable combustion that occurs before the intake
valve closes and can be seen in the intake manifold (with PFI).
Knock is spontaneous ignition of a portion of the end gas occurring after spark.
Hydrogen has a low ignition energy and wide limits of flammability.
This makes hydrogen engines particularly prone to pre-ignition.
Pre-ignition sources
Hot spots (spark electrodes, valves, engine deposits
Bulk gas igniting rich spot
Ignition system interactions (static, dwell initiation etc.)
12
Why Hydrogen DI?
Inherent Benefits
Power density improvement
Air is not displaced by H2 during intake stroke
Elimination of backfire
H2 injection after intake valve closing
Recovery of a portion of tank energy
Ideally inject at TDC
Tank 350 or 700 bar, rail 20-250 bar typically
Reduced pre-ignition tendency
Late injection results in less compression heating, incylinder residence time and exposure to hot spots
13
Gasoline
H2
H2
H2
H2
Fuel
PFI
PFI
Cryogenic PFI
DI
PFI Positive
Displacement
Supercharger
Vol. Effy.
Volumetric Efficiency Comparison
Base
70%
~115%
102%
125+%
(Source:
HyICE)
Graphic source: HyICE
14
DI Volumetric Benefit Confirmed
1.5
Up to
30%
benefit
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.0
0.1
0.2
0.3
0.4
0.5
Φ _mass
0.6
0.7
0.8
0.9
1.0
15
Dynamometer Development
Agenda
•
Single cylinder test engine
•
Typical Phi/EOI Sweep
•
Various Combustion/Injection Modes
• PFI
• Single (early) DI
• Multi-Injection DI
• Stratified DI
•
Interesting PV Plots
16
DI Single Dynamometer Installation
17
Research Engine Specifications
Type
Ford dedicated design
Displacement
0.5 L
Compression ratio
10-16 variable
Max. speed
7000 RPM
Max. cylinder pressure
120 bar
Number of valves
2 intake, 2 exhaust
Valve Sizes
35mm intake
30mm exhaust
Valvetrain
DOHC, direct acting mechanical bucket,
toothed belt, 230 deg duration event
Max. valve lift
9.5 mm / 9.5 mm
Lubrication
Dry sump
Cylinder liner
Wet
18
Typical Early DI Phi Sweep
130.0
6000.0
120.0
ISFC (gm/kWh)
FGNOX (ppm)
5000.0
4000.0
3000.0
2000.0
110.0
100.0
90.0
80.0
1000.0
0.0
70.0
0.1
0.3
0.5
0.7
0.9
1.1
0.1
0.3
0.5
0.7
0.9
1.1
0.1
0.3
0.5
0.7
0.9
1.1
180.0
30.0
160.0
25.0
20.0
EOI (deg BTDC)
COV IMEP (%)
140.0
15.0
10.0
120.0
100.0
80.0
60.0
5.0
40.0
0.0
20.0
0.1
0.3
0.5
0.7
Phi.ratio
0.9
1.1
Phi.ratio
19
EOI Sweep – 1500 rpm / Cont. PW
90.0
88.0
8640.0
86.0
84.0
6640.0
82.0
ISFC
FGNOX (ppm)
7640.0
5640.0
4640.0
78.0
76.0
3640.0
74.0
2640.0
72.0
1640.0
40.0
80.0
70.0
60.0
80.0
100.0 120.0 140.0 160.0 180.0
40.0
60.0
80.0
100.0 120.0 140.0 160.0 180.0
Early Injection
820.0
1.0
0.9
800.0
0.8
0.7
0.6
760.0
Phi
IMEP (kPa)
780.0
740.0
0.4
Start of OVI
0.3
720.0
0.2
700.0
0.1
680.0
40.0
0.5
0.0
60.0
80.0
100.0 120.0 140.0 160.0 180.0
EOI (BTDC)
40.0
60.0
80.0
100.0 120.0 140.0 160.0 180.0
EOI (BTDC)
20
Cylinder Pressure – 2000 RPM Single Inj DI
90
80
Phi = 0.17
Phi = 0.3
Cylinder Pressure (bar)
70
Phi = 0.4
Phi = 0.5
60
Phi = 0.6
Phi = 0.7
50
Phi = 0.8
Phi = 0.9
40
Phi = 1
30
20
10
0
-80
-30
20
70
120
170
Crank Angle (degree)
21
1500 rpm / Const. PW
1.8
1.6
1.4
40 EOI
130 EOI
180 EOI
1.2
Log P (bar)
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
1.5
1.7
1.9
2.1
2.3
Log V (cc)
2.5
2.7
2.9
22
Single DI – Medium Load
BDC
IVC
TDC
No displacement
of air with H2
Single
DI
Injection
Late Injection for
maximum pressure
recovery (stability
limited)
Poor mixing time
High NOx 0.5-0.6
Late Injection for reduced
residence time and preignition risk
23
Typical PFI vs. Early DI Phi Sweep
8990.0
240.0
7990.0
220.0
6990.0
200.0
FGNOX (ppm)
5990.0
180.0
ISFC
4990.0
3990.0
-
120.0
1990.0
100.0
990.0
80.0
10.0
60.0
0.3
0.5
0.7
0.9
1.1
70.0
0.1
0.3
0.5
0.7
0.9
1.1
0.1
0.3
0.5
0.7
0.9
1.1
170.0
60.0
150.0
mEOISetD_1 (deg)
50.0
SPARK (deg)
140.0
2990.0
0.1
40.0
PFI
30.0
DI
20.0
10.0
0.0
-
160.0
130.0
110.0
90.0
70.0
50.0
30.0
10.0
10.0
0.1
0.3
0.5
0.7
Phi.ratio
0.9
1.1
Phi.ratio
24
1500 rpm / 0.6 Phi
2.0
1.5
PFI
Single Inj. DI
Log P (bar)
1.0
0.5
0.0
-0.5
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
Log V (cc)
25
Multi-DI - Medium Load
BDC
IVC
TDC
Low NOx all
No displacement
of air with H2
Multi DI
Late Injection for maximum
pressure recovery (stability
limited) 0.4 Phi
Inj 1
Secondary Inj at
ideal location for
pressure recovery
Secondary 0.2 Phi
Locally Rich
Injection into flame
Inj
2
26
Single Injection vs. Multi-injection
1500 rpm
8000
Multi-injection
Single Injection
FGNOx (ppm)
7000
6000
5000
4000
3000
Significant
Reduction
in FGNOx
2000
1000
0
0.5
0.6
0.7
0.8
0.9
1
Phi.Ratio
27
Single Injection vs. Multi-injection
1500 rpm
95
ISFC (gm/kWh)
90
Multi-injection
Single Injection
85
Some to no
ISFC penalty
80
75
70
0.5
0.6
0.7
0.8
Phi.Ratio
0.9
1
28
1500 rpm / 0.6 Phi
2.0
1.5
PFI
Single Inj. DI
Multi-Inj. DI
Log P (bar)
1.0
0.5
0.0
-0.5
1.5
1.7
1.9
2.1
2.3
2.5
2.7
2.9
Log V (cc)
29
Stratified DI – Medium Load
BDC
Poor mixing time
High NOx below 0.6
IVC
TDC
Near Ideal late Injection
timing for maximum
pressure recovery (stability
limited) 0.4 Phi
Late Injection for
reduced residence time
and pre-ignition risk
No displacement
of air with H2
Stratified
DI
Minimal Additional
Compression Work
Injection
30
Early vs. Stratified Injection
30.0
130.0
120.0
25.0
IMEP01_COV (%)
110.0
ISFC
100.0
90.0
80.0
20.0
15.0
10.0
70.0
5.0
60.0
0.0
0.1
0.3
0.5
0.7
0.9
1.1
170.0
70.0
150.0
60.0
130.0
SPARK (deg)
EOIT (BTDC)
Stratified Injection
90.0
70.0
50.0
0.5
0.7
0.9
1.1
0.1
0.3
0.5
0.7
0.9
1.1
40.0
30.0
20.0
10.0
30.0
0.0
10.0
-
0.3
50.0
Early Injection
110.0
0.1
10.0
0.1
0.3
0.5
0.7
Phi.ratio
0.9
1.1
10.0
Phi.ratio
31
Early vs. Stratified Injection
4490
3990
FGNOX (ppm)
3490
2990
2490
1990
1490
E a rly In je c tio n
S tra tifie d In je c tio n
990
490
-1 0
0 .1
0 .3
0 .5
0 .7
0 .9
1 .1
Phi
Higher FGNOx concentration at lower Phi
32
2.0
1500 rpm / 0.4 Phi
Single DI vs. Stratified DI
Single DI
Stratified DI
1.5
Log P (bar)
1.0
0.5
0.0
-0.5
-1.0
1.0
1.5
2.0
Log V (cc)
2.5
3.0
33
Hydrogen Combustion Modes
BDC
IVC
TDC
Inj - Low
PFI
Inj – Hi Load
Inj - Low
Single DI
Inj – Hi Load
Inj 1 - Low
Multi DI
Inj 1 – Hi Load
Stratified DI
Hi Load ( >0.7) same as Single DI
Inj 2 - Low
Inj 2 - Hi
Inj - Low
Inj – Hi Load
34
ISFC and NOx of Various Strategies
110
PFI
Early DI
Stratified DI
Multi-injection
105
100
ISFC (gm/kWhr)
95
90
85
80
75
70
65
60
9000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
Equivalence Ratio
8000
7000
FGNOX (ppm)
PFI
6000
Early DI
Stratified DI
5000
Multi-Injection
4000
3000
2000
1000
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Equivalence Ratio
0.8
0.9
1.0
1.1
35
Partial Efficiency Map
Heat losses (high phi)
Heat transfer,
residence time
High pumping losses
Too lean, poor
stability
FORD CONFIDENTIAL
36
Single Injection with Spark Retard vs. Multi
Injection @ MBT Equal NOx and Efficiency
3000 rpm / 0.6 Phi / 8.5 bar NMEP / 400 ppm
2.0
Injection #2 30% @ TDC
BOI
Log P (bar)
1.5
Multi-injection, Spk = 16°
1.0
Single-injection, Spk = 6°
0.5
Injection #1 70% @ 90° EOI
Injection 65° EOI
0.0
-0.5
1.5
2.0
2.5
Log V (cc)
3.0
37
1500 rpm / 861 A/F
300 cycle avg / No Misfire
2.0
1.5
Log P (bar)
1.0
0.5
0.0
-0.5
-1.0
1.0
1.5
2.0
2.5
3.0
Log V (cc)
38
Agenda
General targets, emission approaches
Hydrogen properties
Limitations with Port Fuel injection
Rationale for Direct-Injection, inherent benefits
DI Combustion Development
Efficiency and emissions of alternative combustion modes
Comparison to gasoline
E450 H2ICE Shuttle
Conclusions
39
Thermal Eff. of Gasoline and H2 DI
1500 rpm
0.45
H2DI
Thermal Efficiency
0.4
0.35
98 RON Gas
Pumping loss
0.3
ITE Gasoline
ITE H2 HB DI
NTE Gasoline
NTE H2 DI
0.25
0.2
0
200
400
600
800
1000
1200
1400
NMEP
40
Power Density Comparison
14
12
BMEP (bar)
10
H2 PFI
H2 DI
Gasoline
8
6
4
2
0
1000
2000
3000
4000
5000
6000
Engine Speed (rpm)
41
H2 DI vs. Gasoline PFI
1500 rpm / WOT
2.0
1.5
Log P (bar)
1.0
Fast / efficient
combustion
H2 DI
Gasoline PFI
(over 9 bar/deg
max rise rate,
NVH concern)
Knock limited
0.5
0.0
-0.5
-1.0
1.0
1.5
2.0
2.5
3.0
Log V (cc)
42
NOx Emissions Comparison
Gasoline, H2, Boost, DI
10000
Port H2 Injection
Naturally Aspirated
NOx (ppm)
8000
Port H2 Injection/
Supercharged & Intercooled
Benefit w/
boost
6000
Benefit w/ DI
4000
Projected Direct H2
Boosted – Multi-Injection
PFI Gasoline
2000
Direct H2 Injection /
N.A. – Multi-Injection
0
0
2
4
6
8
10
12
14
16
18
20
BMEP (bar)
Engine Load
43
Torque Comparison
Gasoline, H2, Boost, DI
Engine Load, BMEP (bar)
16
Port H2 Injection/
Supercharged & Intercooled
14
Direct H2 Injection, NA
12
10
PFI Gasoline, NA
Port H2 Injection
Naturally Aspirated (NA)
8
6
4
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
Speed (RPM)
44
Increasing System Efficiency
Hi-Level Injection and Boost System Comparison
Power
Density
PFI - NA
TWC
Capable (phi
= 1.0)
Lean NOx
Strategy
(phi < 0.4)
Backfire / Preignition Risk
Rail pressure
requirement
Throttling or
VCT
Major challenge
Vol Efficiency
Lean PFI w/
boosting
High boost
requirements
PFI w/ boosting
Aftertreatment at
phi >0.5, Boost
requirements
DI - NA
20-100 bar rail
pressure
DI injector
durability
DI w/ boosting
80+ bar rail
pressure
DI injector
durability
(multi-inj)
45
Injector comparisons
90
Evaluation of injector
ISFC (gm/kWhr)
geometry on mixing
and engine efficiency
9H
7H
13H
85
80
75
70
65
60
300
500
700
900
1100
1300
IMEP (kPa)
160
140
EOI (°BTDC)
120
60 deg
120 deg
100 deg
100
9H
7H
13H
80
60
40
60 deg
20
0
0.1
0.3
0.5
0.7
Phi
0.9
461.1
134°
134°
t = 1.02 ms
65.38
3.2 bar
27.59
Comparisons of Spray shapes in a Vessel
(Pinjection = 100 bar)
t = 1.00 ms
University of Wisconsin – ERC
Multi-jet modeling
1.0 bar
ERC developed multi-jet gas injection
physics models with bench
experimental validation
Experimental spray chamber and
Schlieren visualization technique
47
Ideal Mixture Distrubution
Well mixed core at phi = 0.4
•Well mixed core at phi 0.3-0.5
•Late cycle injection near TDC
•Heat losses to wall and piston minimized
with air boundary layer
48
Development Summary
Promising results with H2ICE DI Development
Power Density (low to mid BMEP exceeds gasoline, top comparable)
NOx emission trends (multi-injection offers significant benefits)
Thermal Efficiency meets or exceeds PFI everywhere
Confirmation of inherent DI benefits
Volumetric efficiency improvement vs. H2-PFI
Backfire elimination
Tank energy recovery
Challenges include
Excessive rate of pressure rise at high load (potential pilot injection solution)
High exhaust temperatures at full load, high speed (>900 C at 5000 RPM),
Optimization of injection event
» Spray, mixing, & combustion phasing are critical to H2-DI
49
Hydrogen DI Benefits vs. PFI
Inherent
Power density improvement
Air is not displaced by H2
during intake stroke
Injection Process
Reduced thermal losses with
charge stratification
minimal wall contact with fuel
Elimination of backfire
H2 injection after intake valve
closing
Recovery of a portion of tank
energy
Ideally inject at TDC
Tank 350 or 700 bar, rail 20250 bar typically
Reduced pre-ignition
tendency
Low NOx, multi-injection
strategies
Pressure rise rate control
with multi-injection
Improved thermal efficiency
Increased CR potential
Late injection results in less
compression heating, incylinder residence time and
exposure to hot spots
50
E-450 H2ICE Shuttle Bus Fleet
E-450 chassis with aftermarket Shuttle Bus body
6.8L Supercharged Hydrogen Internal Combustion Engine
(H2 ICE), Port Fuel Injected
350 Bar/5000 PSI Hydrogen Fuel Storage System
Hydrogen Management System
Compliant (not certified) to Canadian and Federal
standards
Vehicle Range: 150 - 200 miles
Emissions: 2010 Phase II Compliant
Engine Performance:
» 310 ft-lb @3000 rpm
» 235 hp @4000 RPM
Performance & Reliability equivalent to 2004 Ford CNG
Shuttle Bus
Vehicle Variable Cost (Pilot Volumes): $250K
Customer 2-3 year leases begin: 4Q2006
51
!"#$%&'
Fuel Rail Assemblies
-Greater Volume
Intake Manifold
-Purpose Designed
( ) ) *
Supercharger/Intercooler
-3300cc Twin Screw
-Water-to-air intercooler
PCV System
-External oil
separator
Fuel Injectors
-Designed for H2
FEAD
-Supercharger
-2nd alternator
Spark Plug
-Iridium tipped
Head Gasket
-Rated for 100 bar
Ignition Coil
-High energy
-Reduced feed
forward spark
Damper
-Tuned for H2
combustion
Valves/Seats
-Premium material
Piston/Rod/Rings
-Forged Eutectic piston
-Forged steel rods
New oil formulation
-Low ash content
- Extra corrosion
inhibitors
52
Acknowledgements
National Laboratory Collaboration
Argonne:
Steve Ciatti, Henry Ng, Thomas Wallner
Lawrence Livermore:
Salvador Aceves, Dan Flowers
Sandia:
Chris White, Joseph Oefelein, Dennis Siebers
Oak Ridge:
Johney Green, Todd Toops
University Interactions
University of Wisconsin – ERC
53