pm emissions from hcci engines - cambridge particle meeting · pm emissions from hcci engines h.m....
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PM Emissions from HCCI EnginesH.M. Xu, J. Misztal, M.L. Wyszynski
University of BirminghamP. Price, R. Stone
Oxford University
J. QiaoJaguar Cars
Particulate matter and measurement
Cambridge University, 16 May 2008
Presentation outline
• Background
• PM with Gasoline HCCI– Varied valve timing– Varied injection timing– Effect of air temperature– Comparison with SI combustion– Effect of diesel addition
• Summary and conclusions
HCCI – a generic name for new combustion mode
• spontaneous multiple-point ignition
• typically, rather homogeneous mixture and temperature distributions
• capable of running with extremely lean mixtures (AFR>80)
• load can be controlled by fuel quantity or air-EGR dilution
Diesel combustion Homogeneous ChargeCompression Ignition
SI combustion(Oxford Lasers)
Advantages of HCCI/CAI combustion
• Extremely low (1-5% of SI) NOx emissions- absence of high temperature regions
• High fuel economy (approach Diesel’s )- un-throttling, lean combustion possible, increased heat release rate, removal of knock tendency, high CR possible
• Very low cycle-by-cycle variations ? - multipoint flame initiation
• “Smokeless” ?
Combustion images – Wilson et al SAE Paper 2005-01-2129
How much PM is HCCI producing
Kaiser et al, 2002 Kalghatgi et al, 2007
The first measurement of HCCI PM by Ford was ‘surprising’, although clearly HCCI smoke numbers will be low compared to diesel
Comparison of PM for different combustion systems
Stability limit for GDI SI
Motored condition
The load of the GDI engine is regulated by air fuel ratio and stratified charge is used for low load - Data measured at Tsinghua University
Xu et al, 2008 SAE HCCI Symposium
Dieseline- Mixture of gasoline and diesel fuels - Data measured at TsinghuaUniversity Xu et al, 2008 SAE HCCI Symposium
0 1 2 3 4 50
50
100
150
TSDI
Knocking
2007-7-3 13:59:49
HCCI(D0) HCCI(D10) HCCI(D20)
PM
mas
s fra
ctio
n (1
0-6)
IMEP / bar
Knocking
TSDI
Extension of the low load HCCI boundary by Dieseline
IMEP (bar)
Two-stage injectionFor lowest low load Gasoline direction
Load regulated by air fuel ratio
(gasoline swirl injector!)
Direction injection
Dual Cam Profile Switching (CPS)
138.1 mmCon Rod Length
Dual Variable Cam Timing (VCT) UL95 gasolineFuel
11.3 Compression Ratio
79.5 mmStroke89 mmBore3.0L V6 Base Engine
Jaguar HCCI engine
Emission measurement system
Emission characteristics of the Jaguar HCCI engine
Higher PM
Price et al SAE paper 2007-01-0209
PM comparison for HCCI and SI
1. At a higher load condition for IMEP of 5.2-5.4bar, PM with HCCI shows a lower level in both accumulation mode and nucleation mode than SI
2. Varied injection timing (-300 or -340) can make a big difference, greater for that in the case of varied valve strategies (A or B) or SI
Xu et al, 2008 SAE HCCI Symposium
PM for varied injection timings - HCCIHCCI - 1500rpm; λ = 1.0; IVO = 60CAaTDC; EVC = 86CAbTDC
Matching of the injection and the intake valve timing may be important
Xu et al, 2008 SAE HCCI Symposium
0.0
0.5
1.0
1.5
2.0
2.5
3.0
- 350ºbTDCc - 340ºbTDCc - 320ºbTDCc - 300ºbTDCc - 260ºbTDCc0.0
1.5
3.0
4.5
6.0
7.5
9.0Total Mass [ a. u. ]Total [ MN/cc ]NOx/100 [ppm]
HCCI - En.Speed = 1500rpm; λ = 1.0; IVO = 60CAaTDC; EVC = 86CAbTDC
Mas
s [ a
. u. ]
Num
ber [
MN
/cc
]; NO
x [ p
pm ]
PM for lean burn with boosting - HCCI
lean burn significantly reduces PMover the full spectrum
λ λ
Xu et al, 2008 SAE HCCI Symposium
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1 10 100 1000Dp (nm)
dN/d
LogD
p (1
/cm
3)
NA_λ=1.0 BP=0.2_λ=1.3 BP=0.4_λ=1.6
HCCI : IMEP = 5.2 bar - En. Speed = 1500rpm
PM for lean burn with boosting - HCCI
lean burn significantly reduces PM, both in mass and number
Xu et al, 2008 SAE HCCI Symposium
0.0
0.5
1.0
1.5
2.0
NA_λ=1.0 BP=0.2_λ=1.3 BP=0.4_λ=1.60
5
10
15
20
25
30
35
40Total Mass [ a.u. ]Total Number [ MN/cc ]NOx/10 [ppm]
HCCI - NMEP = 5.2 bar - En. Speed = 1500rpm
Mas
s [ a
. u. ]
Num
ber [
MN
/cc
]; N
Ox
[ ppm
]
PM may approach SI for smaller load
There are relatively more larger size of PMs with HCCI at lower load (increase of accumulation mode fractions).
Xu et al, 2008 SAE HCCI Symposium
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1 10 100 1000Dp (nm)
dN/d
LogD
p (1
/cm
3)
SI - IVO=5CAaTDC, EVC=3CAaTDC, EOI=250CAbTDC
SI - IVO=25CAaTDC, EVC=3CAaTDC, EOI=250CAbTDC
HCCI - IVO=65CAaTDC,EVC=98CAbTDC,EOI=350CAbTDC
HCCI - IVO=80CAaTDC,EVC=89CAbTDC,EOI=350CAbTDC
Eng Speed = 1500 rpm; NMEP = 4.2 barIMEP=3.9bar
IMEP=4.3bar
PM may approach SI for smaller load
In one case, PM mass even exceeded SI case for the same load
Xu et al, 2008 SAE HCCI Symposium
0.00
0.05
0.10
0.15
0.20
0.25
0.30
HCCI - IVO=65CAbTDCHCCI - IVO=80CAbTDC SI - IVO=5CAaTDC SI - IVO=25CAaTDC0
5
10
15
20Total Mass [ a.u ]Total Number [ MN/cc ]NOx/100 [ ppm ]
Tota
l Num
ber [
MN
/cc
]; N
Ox/
10 [
ppm
]
Tota
l Mas
s [ a
.u. ]
PM with split injection
PM will fall between the boundaries for one injection in recompression or late induction
Xu et al, 2008 SAE HCCI Symposium
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1 10 100 1000Dp (nm)
dN/d
LogD
p (1
/cm
3)
40%-EOI=250ºbTDCc 60%-EOI=250ºbTDCcEOI=350ºbTDCc EOI=250ºbTDCc
En. Speed = 1500 rpm; IVO = 60CAaTDC, EVC = 89 CAbTDC - NMEP = 4.7 - 5.2 bar
IMEP=4.7bar
IMEP=5.2barIMEP=4.9bar
IMEP=4.85bar
PM with split injection
More pilot injection may increase PM
Xu et al, 2008 SAE HCCI Symposium
0.0
0.1
0.2
0.3
0.4
0.5
40%-EOI=250ºbTDCc 60%-EOI=250ºbTDCc EOI=350ºbTDCc EOI=250ºbTDCc0
5
10
15
20
25
Total Mass [ a.u. ]Total Number [ MN/cc ]NOx/10 [ppm]
En. Speed = 1500 rpm; IVO = 60CAaTDC, EVC = 98 CAbTDC - NMEP = 4.7 - 5.2 bar
Tota
l Num
ber [
MN
/cc
]; N
Ox/
10 [
ppm
]
Tota
l Mas
s [ a
. u. ]
Effect of intake air temperature
bar bar/deg. ºaTDC ºbTDC º C º C MN/cc a. u. % % %
N - 2 4.8 6.0 60 86 56 412 0.90 0.69 41.3 60.9 93.6
N - 3 4.8 4.2 80 81 61 430 0.65 0.36 40.5 60.3 93.5
H - 4 4.8 5.8 60 91 87 391 0.29 0.18 44.3 53.1 93.6
C - 3 4.8 2.4 80 86 45 438 0.57 0.31 50.3 56.0 92.7
TEST
Ambient Charge AirAmbient
Charge AirHeated Charge
AirCooled Charge
Air
ηcombPM No.
50-300nmPM Mass50-300nm ηvolT_In T_ExIVO EGREVCNMEP dp/Θ
A thermal management system incorporating electrical heaters and an intercooler bypass was used to control the intake air temperature. Varied valve timings are used to regulate the engine load
Effect of intake air temperature (1)
N – normal, H – heated, C – cooled inlet air
Higher intake temperature seems to increase the number of PM in nuclei mode
Effect of intake air temperature (2)
The effect of intake temperature on the mass of PM is limited, but apparently more on the number
Summary and conclusions
1. Particulate emissions from HCCI engines are not negligible, especially when taking the number of smaller sized particulates into consideration.
2. In the HCCI engine with NVO, PM varies with valve timing for a given engine speed and relates to engine load and internal EGR rate. When the valve overlap is reduced, both NOx and PM levels increase with engine load..
3. For a given valve timing for the GDI engine, HCCI PM varies withinjection timing. A later injection around the time of intake MOP gives lower PM and NOx emissions, while pilot injection with impingement may increase PM.
4. Particulate emissions from HCCI engines are affected by air-fuel ratio and intake temperature, while the number of smaller sized particulates is more sensitive to engine conditions.
Acknowledgement
The authors gratefully acknowledge relevant research funding from EPSRC and former DTI, industrial support from Jaguar Land Rover Research and Shell Global Solutions, and contributions to the related research from the Birmingham, Oxford and JLR teams including colleagues and students who are currently with us or have moved.
New fuel management
OptimizedCombustion
Engine
OptimizedCombustion
Engine
Conventional compression engines
Conventional spark-ignition Engines
In-direct injection Direct injection High EGR Complex-injection
CR
20
10
15
Gasoline and Diesel Engine Technologies are merging
Multi-fuel injection system – the future of new engines?
• A computer controlled colour printer can printcolourful pictures using 3 original coloured inks –
• If we have 3 different type of fuels, why cant’ a CPU controlled fuel injection system supply a required fuel ‘colour’ (property) for ‘printing a beautiful picture’ – for optimised engine operation at varied conditions?
• Simply, a multi-channel fuel nozzle is required at gas stations to supply the fuels as for printer cartridges!