Particulate Matter Emission From Different Combustion Modes in a 2/4
Stroke Switchable Direct Injection Gasoline Engine
Ojapah M, Zhang Y, Zhao H, and Ganippa L
Centre for Advanced Powertrain and Fuels, School of Engineering and Design,
Brunel University London, UK
Overview
• Introduction
• Experimental Apparatus and test method
• Results and Discussion
• Conclusion
Introduction
• CO2 legislation/Global Warming mandates the
development of more efficient IC Engines – Better Fuel Economy through the engine down-sizing by boosting
or 2-stroke operation, and possibly stratified charge combustion or Controlled Auto Ignition (CAI) at part load operations.
• Increased use of bio-fuels to combat the limited fossil fuels: – Gasoline and Ethanol mixtures: E15 to E85
• Particulate Matter (PM) emission legislation (Euro VI) – Direct Injection gasoline engines produces much more PM
emissions than Port Fuel Injection gasoline engines
Objectives
• In response to the above challenges, an extensive research programme has been set up at Brunel:
1. To develop an advanced single cylinder research facility for research and development of more efficient and cleaner IC combustion engines;
2. to operate the engine in different combustion modes and cycles and evaluate their effects on engine efficiency and emissions;
3. to investigate the effect of bio-fuels on the combustion and emissions.
In particular, the PM emissions were measured under various combustion modes and with different ethanol contents.
Bore × Stroke 81.6mm×66.94mm
Swept volume 0.35L
Compression ratio 11.78:1
Combustion chamber
Pent roof / 4 valves
Valve train Electro-hydraulic actuation
Fuel injection Direct injection
Fuel Standard gasoline (RON 95)
Injection Pressure 100bar
air/fuel ratio Stoichiometric
Intake temperature 25oC
Table 1 Engine specifications
2/4 Stroke Camless Engine
Camless Valve System
• Oil pressure: 100bar.
• Valve Lift: 0~7.3mm.
Brunel Hydra - 4 stroke valve lift profiles
0
1
2
3
4
5
6
7
8
9
10
0 60 120 180 240 300 360 420 480 540 600 660 720
Crank Angle [deg]
Lif
t [m
m]
Inlet 1000 rpmExhaust 1000 rpmInlet 1500 rpmExhaust 1500 rpmInlet 2000 rpmExhaust 2000 rpmInlet 2500 rpmExhaust 2500 rpmInlet 3000 rpmExhaust 3000 rpmInlet 3500 rpmExhaust 3500 rpmInlet 4000 rpmExhaust 4000 rpmInlet 4500 rpmExhaust 4500 rpmInlet 5000 rpmExhaust 5000 rpmInlet 5500 rpmExhaust 5500 rpmInlet 6000 rpmExhaust 6000 rpmInlet 6500 rpmExhaust 6500 rpm
IntakeExhaust
Valve Lift Profiles
Injector
Driver
Injector
Exhaust
Tank
Spa.
Plu.
ETC
Lambda
Test Cell
Control Room
Power
Management
box
AC/DC
12V
VCU Switch
Valve
Signal
Box
CAN
USB
TCP
ETAS INCA
MAP
rCube
(ECU)
•Spark timing
•Injection Timing
•Injection Pulse Width
•Valve Timings
•Valve Lifts High Speed CAN Bus
Supercharger system
Engine Control System
EMS VIE PM Measurement System
• The sample from the
exhaust was allowed to
pass through a charger to
establish a well defined
distribution of electrical
charges on the particles
before it is fed into the
DMA.
•EMS VIE measures
particles within the size
range of 5 to 700 nm,
•Sampling point is 15cm
downstream of the exhaust
valves using 100%
Dilution.
•Particulate number is
displayed on the Y axis in
#/cm3, while the soot
diameter is displayed on
the X axis in nm
Engine Operating Modes
2) 4-stroke Intake valve throttled SI
TDC BDC BDC 1) 4-stroke Throttle-controlled SI
TDC BDC BDC
TDC BDC BDC
3) 4-stroke Positive Valve Overlap SI
TDC BDC BDC
4) 4-stroke Negative Valve Overlap CAI
TDC BDC BDC
5) 4-stroke Exhaust Rebreathe CAI
BDC TDC TDC
6) 2-stroke CAI
BDC TDC TDC
7) 2-stroke SI
Exhaust valve 1
Exhaust valve 2
Intake valve 1
Intake valve 2
Injection Timing
2) 4-stroke Intake valve throttled SI
TDC BDC BDC 1) 4-stroke Throttle-controlled SI
TDC BDC BDC
TDC BDC BDC
3) 4-stroke Positive Valve Overlap SI
TDC BDC BDC
4) 4-stroke Negative Valve Overlap CAI
TDC BDC BDC
5) 4-stroke Exhaust Rebreathe CAI
BDC TDC TDC
6) 2-stroke CAI
BDC TDC TDC
7) 2-stroke SI
Exhaust valve 1
Exhaust valve 2
Intake valve 1
Intake valve 2
Injection Timing
Operating point:
PM Emissions Results (1)
• SI and CAI with NVO produce similar PM emission.
• The number of particles of 15nm or larger in diameter decreases rapidly when the ethanol content is increased from zero to 15%.
• The particle number reaches its minimum value for particles of diameters greater than 18nm.
• Pure gasoline emits more particles at around 20nm diameters.
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 20 40 60
dN
/dln
D(#
/cm
3)
Dp(nm)
4 stroke CAI NVO
E0
E15
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 20 40 60
dN
/dln
D (
#/cm
3)
Dp (nm)
4 stroke SI
E0
E15
• Different PM emissions from two CAI modes
• There is no PM peak at 20nm from CAI with rebreathing
• Similar PM emissions for E15 fuel for both CAI modes
0.00E+00
2.00E+09
4.00E+09
6.00E+09
8.00E+09
1.00E+10
1.20E+10
1.40E+10
0 10 20 30 40 50 60
DN
/dln
D(#
/cm
3)
Dp(nm)
4 stroke CAI
E0
E15
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 20 40 60
dN
/dln
D(#
/cm
3)
Dp(nm)
4 stroke CAI NVO
E0
E15
PM Emissions Results (2)
• E15 generates similar quantity of particles for both modes. • SI with PVO produces much less particle emissions than standard SI
operation. • The enhanced evaporation of gasoline fuel leads to less fuel rich regions
in the combustion process and hence the disappearance of soot particles in the size range of 20nm.
-5.00E+08
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 10 20 30 40 50 60
dN
/dln
D(#
/cm
3)
Dp(nm)
4 stroke SI pvo
E0
E15
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 20 40 60
dN
/dln
D (
#/cm
3)
Dp (nm)
4 stroke SI
E0
E15
PM Emissions Results (3)
PM Emissions Results (4)
• The PM emission from 4- stroke SI and the 2-Stroke CAI display the same trend.
• Increasing the ethanol contents from 15% to 85% has little effect on particle size but it does increases the particle number.
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 10 20 30 40 50 60
dN
/dln
D(#
/cm
3)
Dp(nm)
2 stroke CAI
E0
E15
E85
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
0 20 40 60
dN
/dln
D(#
/cm
3)
Dp(nm)
4 stroke CAI NVO
E0
E15
PM Emissions Results (5)
• The PM emission from 4-stroke SI and the 2-stroke SI display the same trends of reducing particulate numbers as lambda increases
• Increasing lambda from lambda=1 to about lambda=1.7 have some 2 fold effects in particulate number reductions
PM Emissions Results (6)
• SI and CAI with NVO shows similar trends for injection pressures of 130 bar to 150 bar., and both peak at about 18nm
• For 4 stroke SI there is no much effects of increasing the injection pressure on particles emissions.
PM Emissions Results (7)
• There is no PM peak at 18nm for 100 and 115 bar this may possibly be because of the gas exchange process
• For pressures of 130 bar to 150 bar, the PM peak at 20nm and decreases slightly as the injection pressure increases to 150 bar
PM Emissions Results (5)
• Load is varied by boost pressure. Large amount of residuals was trapped in the cylinder when the exhaust valve closes earlier.
• Particles are dominated by soot particles between 50-150nm in diameter.
• The concentration of larger particles between 50nm-150nm increases with increasing load up to 5.4 bar and decreasing for very high loads of 6.2 and 7.1 bar.
• The reduction in smaller particles may be due to faster evaporation of liquid fuel due to higher residual gas temperature at high loads .
Summary • The particle emissions from the DI gasoline engine are
dominated by smaller particles.
• The effect of ethanol content on soot reduction becomes saturated when ethanol concentration reaches 15%, irrespective of the combustion modes.
• The combustion of ethanol and gasoline blends
minimises the presence of soot particles in peak regions of 10nm to 30nm.
• Hotter charge and better mixing are the main parameters affecting the soot particles in the exhaust irrespective of the combustion mode.
Thank You
