Post on 09-Apr-2018
Internal Combustion Engines – MAK 493E
MIXTURE PREPERATION in CI ENGINES
Prof.Dr. Cem Soruşbay
Istanbul Technical University
Internal Combustion Engines – MAK 493E
Mixture Preperation
Introduction
Atomization of fuel, sprays
Fuel systems - in-line systems, distributor systems
Common-rail systems, unit pump and unit injector systems
Fuel Atomization
In Diesel engines, fuel-air mixture is prepared as a result of fuel injection into the cylinder at the end of compression stroke (usually before TDC) during a limited time (crank angle) interval.
The purpouse of fuel injection is to provide good mixing of air and fuel in the limited time available, by increasing the surface area of the liquid fuel as a result of atomization
Dividing unit fuel volume into droplets of 100 x 10-6 [m] diameter would increase the total surface area by 10,000 times.
Liquid Atomization
Liquid atomization is effected by internal and external forces.
controlled by Reynolds number defining the balance between inertia effects and viscous effects
Re = u D /
Atomization at Low Speeds
Rayleigh regime : internal effects are dominant
surface tension, fuel density, liquid column diameter
Any disturbance produces break-up of liquid column
Weber : indicated the importance of viscous effects
Heavy fuel, (left) 5000 cS
Diesel fuel (right) 6 cS
Atomization at High Speeds
Atomization at High Speeds
Secondary Atomization
Weber number
DuW h
e
2
Spray Structure
In difusion flames, combustion is controlled by the mixing rate of the fuel and air.
The local conditions in the combustion chamber such as the air-fuel ratio, temperature, pressure control the ignition of the fuel and the combustion process. Heat and mass transfer in the combustion chamber and the fluid flow (air flow) also effects this process.
Spray structure,
core
breakup length
spray tip penetration
Fuel Sprays
Fuel Sprays
Fuel Sprays
Temperature Contours
Temperature distribution inside the cylinder
Diesel Combustion Phases
Droplet Size Distribution
Droplet Size Distribution
Sauter Mean Diameter
p = 2 and q = 3 : Sauter Mean Diameter
indicates the total Area-to-Volume ratio applicable for the whole spray
o
m
o
m
o
m
o
m
D
D
p
D
D
q
D
D
p
D
D
q
pq
qp
dDdD
dVD
dDdD
dVD
dDdD
dnD
dDdD
dnD
D3
3
ii
ii
nD
nDD
2
3
32
Droplet Size Measurements
Droplet Size Measurements
Droplet Size Measurements
Diesel Engines
Fuel system
Injection Pump – in line system
Injection Pump
Injection Pump
Injection Pump – fuel metering
Injector
Injector
Nozzles
Nozzles
Delivery Valve
Direct Injection Diesel Engine
Indirect Injection Diesel Engine
Distributor-Type Injection Pump
1. Injection Timing Adjustement 2. Roller 3. Cam Plate 4. Axial Piston 5. Control Sleeve 6. High-Pressure Chamber 7. Fuel Outflow to Nozzle 8. Leak-Off x. Effective Stroke
Yıldız pompa
Distribütör tipi pompa
Distributor-Type Injection Pump
Diesel Fuel Systems
In-line pumps Common Rail Unit-injector/pump
Common-Rail System (Truck engine)
CR-System Production Location Bursa
Nozzles
Nozzle Holder Assemblies
Pump Elements
Common Rail Injector
Products
Common Rail System for Passanger Cars
Common-Rail System for Heavy Duty Engines
Common-Rail (Truck Rail Basic Design)
RDS
rail pressure sensor
DBV
pressure limiter
valve
Common-Rail System
Tank Prefilter
Other sensors
High
pressure
pump
CP3
Rail
Gear
pump Filter
Rail pressure
sensor
Accelerator
pedal
Engine
speed
(crank)
Engine
speed
(cam)
Other actuators
Control unit
Pressure
limiter valve
High pressure
Low pressure
Injector
Flow limiter
Metering
unit ZME
Fuel System Control
Flow Limiter
Two-step Pressure Limiting Valve
Rail Pressure Sensor Features
Common Rail Fuel Injector (Heavy Duty)
Magnet Group:
- Magnet core
from solid
Armature Group:
- Single piece Armature
Valve Group:
- Reduced control volume
- Improved piston
geometry
Injector body:
- Optimized high pressure bore geometry
- Improved backflow hydraulics
Nozzle:
- Miniature sac hole or
sac hole respectively
- Nozzle guided pushrod
- Single needle guidance
- Flat shoulder
Common Rail Fuel Injector CR-InjectorPrinciple of function
RBOS/EPK1-Ren
0
20
40
60
80
100
120
140
160MPa
0.0 0.5 1.0 1.5 2.0 2.5 3.0
ms
current solenoid
lift of armature
pressure in control chamber
lift of nozzle needle
injection rate
on signal
rail pressure
Common Rail Fuel Injector – First Generation
CRIN 1 – 1st Generation
CR Injector – Principle of Function
CR Injector Map
0
20
40
60
80
100
120
140
160
180
200
220
240
260
280
300
320
340
360
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
10^3
backflow counterpressure: 0 bar and 0.5
bar
low ripple:
spherical valve piston
tip
backflow pressure sensitivity:
armature geometrie optimized,
reduced volume in armature
group and enlarged backflow
bore
ca43/44n7
1600 bar
1000 bar
600 bar
250 bar
linear characteristics at high injection
rates: reduced volume in armature group
-10-505
1015202530354045505560
200 250 300 350 400 450 500 550 600
CR System Roadmap (P Cars and Light DutyTrucks)
98 99 2000 01 02 03 04 05 06 07 08 09
CR 1. Gen. MV 1350 bar
CR 2. Gen. MV 1600 bar
CR 2. Gen. Piezo 1600 bar
CR 3. Gen. Piezo 1800
bar
CR 4. Gen.
Piezo
• 2000 bar
• Pressure amplifier
• New control functions
• EDC17C / 42V
• Fuel metered
high pressure pump with
increased performance
• EDC16C+
• Improved top-head /
Compact injector
• Multiple injection (4 - 5)
• Fuel metered
high pressure pump
• EDC 16C/16C-P
CR Fuel Injector – Comparison
2. Generation
magnet core control chamber
geometry
DGV
intermediate
pin
armature high pressure
bore design
1. Generation
CR Fuel Injector – 2. Generation (for Trucks)
Injector body
CR Fuel Injector – 2. Generation (for Trucks)
Solenoid
CR Fuel Injector – 2. Generation (for Trucks)
Valve Group
High Pressure Pump
High Pressure Pump
CR Systems Status
1. Generation, 1350 bar systems
Euro III achieved with different applications
Low combustion noise with pilot-injection
Production of different applications (3 to 8 cylinders)
2. Generation, 1600 bar
Euro IV achieved with different applications
Combustion noise further reduced with 2 pilot-injections
HD Diesel Engine – EURO IV
Advanced combustion characteristics combustion chamber, swirl, number of nozzle holes
Advanced air management system
high excess-air ratio, λ 1.8 (steady state and transient)
Advanced supercharging system
“super” VGT or electronic powered charger
Close loop EGR system with VGT and linear EGR valve
efficient charge air cooling and EGR cooling
Application with retarded SOI for low EGR Rate
High injection pressure 1600 bar
Oxidation Catalyst for soluble fraction
Sulphur free fuel
Conclusion:
steady state test ESC possible
transient test ETC only possible with all mentioned measures
CR System – Comparison of Injection Strategies
PI MI Pol
Pilot injection Main injection Post Injection
Injector
Crank angle 0° 180°
Needle
lift
Cylin
der
pre
ssure
DI Engine – warm up after cold start at -20O C
0 15
250
750
100
0
125
0
1500
500
0
30
60
20 25 30 35 35 40 45 50 s
35 30 25 45 40 50
%
Op
acity
Speed
Time
rpm without pilot injecton with pilot injecton
Influence of Pilot Injection on Noise and Emissions
0.0 0.5 1.0 1.5 2.0 3.0 2.5 3.5
Pilot injection quantity mm3/stroke
1.9 TDI with CR, speed = 1500 rpm, pme = 5 bar, rail pressure = 800 bar
g/kWh
4.0
3.0
2.0
1.0
0.0
g/kWh
0.8
0.6
0.4
0.2
0.0
Soot
Nois
e
dB (A)
88
86
84
82
80
Soot
Noise
NOX
NO
X
HD Diesel Engine – Post Injection
0
NOx 0
g/kW h
4 6 7 9
0.1
0.2
0.3
0.5
BS
N
210
NOx
g/kW h 230
bsfc
without post injection with post injection
215
220
225
5 8
0.4
0 4 6 7 9 5 8
Variation of start of injection with appended post injection (rail pressure = 900 bar) Fuel quantity of post injection approx. 12 mg/str
SOI = +2
retarded advanced start of main injection
1400 rpm, 75% Load
Common Rail System – Passenger Car
Late post inj. for HC production
(increase of exhaust temp.)
Main injection
Coupled post injection
(soot reduction)
„Split main“ for stable
rich operation (storage cat.)
Pilot injection for
noise reduction
Type Approval Data of HD Engines ( > 85 kW )
0 0 1 2 3 4 5 6 NOx 7
0.05
0.10
0.15
0.20
g/kWh
Euro II (10/95)
Euro III (10/00) So
ot
Euro IV Euro V
State of the art
Low swirl combustion elevated injection pressure injection rate shaping partly EGR
+ cooled EGR part.-trap
NOX-cat. part.-trap
Exhaust Gas Aftertreatment for P Cars
Assessment of aftertreatment for Diesel-PC, EURO IV and up Priority I (PM Reduction):
Particulate trap technology is politically necessary and technically suggestive; short-term market release
Priority II (NOx Reduction):
With market release of low-sulphur fuel NOx trap has high potential; further development necessary; medium-term market release NOx reduction with urea/water remains an individual solution
Diesel Emission Reduction Technologies – P Cars
Lean NOx
Trap
Reductant HC
Added
Reductant
Urea
Oxidation Catalyst
Diesel
Particulate Filter + Selective
Catalytic
Reduction
Less
PM
Lower
NOx
Less
PM
Lower
NOx
Exhaus
t
PM
Exhaust NOx
Exhaus
t
PM
Exhaust NOx
Influence of Pilot Injection on Noise and Emissions
Diesel Emission Reduction Technologies - EGR
High Pressure Amplifier Piston CR System APCRS – Schematic View
700 bar fuel pressure
Fuel tank Injector
High pressure pump
Leakage
Leakage Amplifier piston
Common Rail
High Pressure Amplifier Piston CR System APCRS – Schematic View
700 bar fuel pressure
Fuel tank
Pilot Injection
Injector
Amplifier piston
Common Rail
High pressure pump
Leakage
Leakage
High Pressure Amplifier Piston CR System APCRS – Schematic View
Fuel tank
Pilot Injection
700 bar fuel pressure
Fuel tank Injector Leakage
Leakage Amplifier piston
High pressure pump
Common Rail
High Pressure Amplifier Piston CR System APCRS – Schematic View
Main Injection
700 bar fuel pressure
Fuel tank Injector Leakage
Leakage Amplifier piston
High pressure pump
Common Rail
High Pressure Amplifier Piston CR System APCRS – Schematic View
Fuel tank
Main Injection
700 bar fuel pressure
Fuel tank Injector
Amplifier piston
High pressure pump
Leakage
Leakage
Common Rail
High Pressure Amplifier Piston CR System APCRS – Schematic View
Fuel tank
Main Injection
700 bar fuel pressure
Fuel tank Injector
Amplifier piston
High pressure pump
Leakage
Leakage
Common Rail
High Pressure Amplifier Piston CR System APCRS – Schematic View
700 bar fuel pressure
Fuel tank Injector
Amplifier piston
High pressure pump
Leakage
Leakage
Common Rail
HD-Engine with CRS, Pilot Injection n = 1200 rpm, full load
Possible Black Smoke Reduction with Post-Injection
Unit Injector and Unit Pump for Commercial Vehicles
Unit Pump for Commercial Vehicles
Unit Injector for Passenger Cars
Unit Injector for Passenger Cars
Unit Injector System for Passenger Cars
Unit Injector System – Generations G1 and G2
Time
PNozzle
Generation N1 : 1600 bar
Generation N2 : 1800 bar
Unit Injector for Commercial Vehicles
Applications of Diesel Fuel-Injection Equipment