Analysis of Crankshaft Speed Fluctuations andAnalysis of ...Analysis of Crankshaft Speed...
Transcript of Analysis of Crankshaft Speed Fluctuations andAnalysis of ...Analysis of Crankshaft Speed...
Analysis of Crankshaft Speed Fluctuations andAnalysis of Crankshaft Speed Fluctuations and
Combustion Performance
Ramakrishna Tatavarthi
Julian VerdejoJulian Verdejo
GM Powertrain
November 10, 2008
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 2
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 3
Introduction
• ti ti f th t l i• motivation for the present analysis
• location of peak pressure – LPP
• can speed-based methods provide similar information?
• LPP background
• traditionally used as a simple means of tracking burn location (CA50)
• avoids complexity of performing a full heat release analysis
• requires cylinder pressure sensors
• primary strengths of LPP
• effective in tracking CA50 (burn location)
LPP f MBT i i i di i [ ]• LPP for MBT is very constant across engine operating conditions [1]
• attractive basis for closed-loop operation
[1] M t k F A M d d M f C li C b ti V i bilit SAE P 830337 1983
Analysis Of Speed Fluctuations 4
[1] Matekunas, F. A. Modes and Measures of Cyclic Combustion Variability. SAE Paper 830337, 1983.
Introduction
• crankshaft speed based methodsp
• examine instantaneous speed waveform over an engine cycle
• how does waveform change as combustion varies?
• subject has been explored extensively [2] – however, the present work differs significantly in 2 respects:
• combustion phasing instead of IMEP/torque – a more modest goalp g q g
• instantaneous instead of average (ie, cylinder event) speed
• LPS – location of peak speed
• potential alternative to LPP for tracking changes in combustion location
• this and other measures will be discussed
[2] Williams, J. An Overview of Misfiring Cylinder Engine Diagnostic Techniques Based on Crankshaft Angular Velocity Measurements. SAE Paper 960039. 1996.
Analysis Of Speed Fluctuations 5
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 6
12 Operating Points Examined
1100 rpm 3800 rpm
260 mg
180 mg
100 mg
Analysis Of Speed Fluctuations 7
Matrix of Burn Locations & Durations(84 Points in Total)
burn duration (10-75%) [deg]
longer burns
burn duration (10 75%) [deg]15 20 25 30 35 40 45
deg
ATD
C]
-1 1 13 25 37 49 61 73
3 2 14 26 38 50 62 74
6 3 15 27 39 51 63 75
• 12 burn locations
• 8 burn durations
catio
n (C
A50
) [d 8 4 16 28 40 52 64 76
10 5 17 29 41 53 65 77
12 6 18 30 42 54 66 78
15 7 19 31 43 55 67 79
19 8 20 32 44 56 68 80
• 84 combinations in total
• varied duration in all 4 cyl’s
late
r bu
rns
burn
loc 19 8 20 32 44 56 68 80
24 9 21 33 45 57 69 81
30 10 22 34 46 58 70 82
37 11 23 35 47 59 71 83
45 12 24 36 48 60 72 84
y
• but varied location only in cyl #3
12 op pts x 84 burns = 1,008 total runs
Analysis Of Speed Fluctuations 8
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 9
Analysis Of Speed Fluctuations 10
Description of GT-Power Model
• four cylinder engine, 2.2L, gasoline SI, port fuel injection
• l d d (i t d f d d ) i l ti• load-mode (instead of speed-mode) simulations
• each operating point set by combination of throttle angle and road inclination
• at given operating point, vehicle speed decreases as burn either advanced or retarded relative to MBT
• rigid crankshaft model – no crank twist or resonance considered
• only one torsional compliance included in the driveline – clutch spring
• strong effect on dynamic response & instantaneous speed waveform
• appropriate lumped inertias and loads represent driveline and vehicle
Analysis Of Speed Fluctuations 11
existing GT-Power
engine modeladditions to model to capture vehicle and driveline
d i d l di
Analysis Of Speed Fluctuations 12
dynamics and loading
Clutch Torsional Damping
• model had difficulty converging at first
damping
ratio = 0.5
80
[Nm/(rad/s)]• system underdamped
• clutch spring stiffness was provided by
12[Nm/(rad/s)]
supplier
• how to assign appropriate damping?
• final value of 50 [Nm/(rad/s)]final pole locations
achieved with
damping of
50 [Nm/(rad/s)]
Analysis Of Speed Fluctuations 13
GT-Power Model of Inline 4-Cylinder Engine
Analysis Of Speed Fluctuations 14
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 15
Cylinder Pressure as CA50 Varied
peak pressure
h h
quick burn
(duration = 25o)
moves to the right as
CA50 is retarded
“good” sensitivity
CA50 locations
TDC 90o
Analysis Of Speed Fluctuations 16
LPP vs CA50all operating points
• location of peak pressure (LPP) vs burn location
(CA50)( 5 )
• amazingly consistent across all operating points
considered
duration = 25o
TDC
]P
[de
g AT
LPP
burn location (CA50)
Analysis Of Speed Fluctuations 17
LPP vs CA50all operating points
• location of peak pressure (LPP) vs burn location
(CA50)
slope = 43o / 46o = 0.93
duration = 25o( 5 )
• amazingly consistent across all operating points
considered TDC
]43o
• good sensitivity – a 10o change in CA50 results in
9o change in LPP P [de
g AT
46o
g
LPP
burn location (CA50)
Analysis Of Speed Fluctuations 18
Cylinder Pressure as CA50 Varied
lLPP loses sensitivity to
changes in
CA50
d h
slow burn
(duration = 45o)
LPP doesn’t move to the
right
CA50 locations
TDC 90o
Analysis Of Speed Fluctuations 19
Cylinder Pressure as CA50 Varied
quick burn
(duration = 25o) peak pressure
h hmoves to the right as
CA50 is retarded
“good” sensitivity
CA50 locations
TDC 90o
Analysis Of Speed Fluctuations 20
LPP vs CA502500rpm / 180mg
• LPP vs CA50
TDC
]P
[de
g AT
LPP
burn location (CA50)
Analysis Of Speed Fluctuations 21
LPP vs CA502500rpm / 180mg
• LPP vs CA50
• greater sensitivity for quicker burns (steeper
slope of blue line)
TDC
]P
[de
g AT
LPP
burn location (CA50)
Analysis Of Speed Fluctuations 22
LPP vs CA502500rpm / 180mg
• LPP vs CA50
• greater sensitivity for quicker burns (steeper
slope of blue line)
TDC
]• less sensitivity for longer burns (flatter slope of
black line)P
[de
g AT
LPP
burn location (CA50)
Analysis Of Speed Fluctuations 23
LPP vs CA502500rpm / 180mg
• LPP vs CA50
• greater sensitivity for quicker burns (steeper
slope of blue line)
MBT points(for bdur=15,20,25,30)
TDC
]• less sensitivity for longer burns (flatter slope of
black line)P
[de
g AT
• MBT operation corresponds to LPP of 10-17 deg
ATDC for range of burn durations considered
LPP
burn location (CA50)
Analysis Of Speed Fluctuations 24
Comments on LPPLPP Sensitivity
• LPP shows strong sensitivity to changes in burn location
ti ti *across entire operating map*
• nearly 1-to-1 relation
LPP S iti it
• LPP loses sensitivity abruptly at a longer burn duration
APC
260 0.90.98-.72
0.89.98-.70
0.88.96-.70
0.89.96-.72
0.87.96-.65
LPP Sensitivity
• LPP loses sensitivity abruptly at a longer burn duration
– on average LPP is only valid for bdurs = 15, 20, 25, 30180 0.94
.98-.870.93.98-.87
0.93.96-.87
0.92.96-.85
100 0 93 0 93 0 92
*results shown in table are based on burn durations = 15, 20, 25, 30
100 0.93.98-.85
0.93.98-.87
0.92.98-.85
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 25
Comments on LPPLPP for MBT
LPP f MBT f 6o o ATDC h• LPP for MBT varies from 16o to 13o ATDC over the
entire operating range
LPP f MBT• however, at each op pt, LPP for MBT changes
appreciably with burn duration – as the burn gets longer,
LPP for MBT advances (moves to the left)
APC
260 ~1618-13
~1517-12
~1415-11
~1314-11
~1314-10
LPP for MBT
180 ~1618-12
~1415-12
~1315-11
~1315-11
100 ~15 ~14 ~13100 1518-12
1417-11
1315-11
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 26
Summary of LPP
• strengths of LPP
• good sensitivity to changes in burn location
(for quick to medium duration burns)
• LPP for MBT is very consistent over entire operating range
• from ~16o to ~13o across operating range
• means for closed loop control
• disadvantages
• loses sensitivity abruptly for longer burn durations
(durations > 30 deg’s)
Analysis Of Speed Fluctuations 27
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 28
Speed Response
• examine instantaneous speed waveform over an engine cycle
• how does waveform change as combustion (burn location & duration) varied?
• how does it change across different operating points?
Analysis Of Speed Fluctuations 29
Examining the Speed Waveform
Analysis Of Speed Fluctuations 30
Examining the Speed Waveform
delta
RP
M
cyl 3
expansion
cyl 1
expansion
cyl 4
expansioncyl 2
expansion
d
Analysis Of Speed Fluctuations 31
Examining the Speed Waveform
delta
RP
M
cyl 3
expansion
cyl 1
expansion
cyl 4
expansioncyl 2
expansion
d
Analysis Of Speed Fluctuations 32
Examining the Speed Waveform
cyl 3
expansion
TDC 180o
Analysis Of Speed Fluctuations 33
Examining the Speed Waveform
b icombustion
peak reciprocating
mass torque
peak
cyl 3
expansiontrough due to
gas compressiong p
at TDC
TDC 180o
Analysis Of Speed Fluctuations 34
Examining the Speed Waveform
cyl 3
expansion
TDC 180o
Analysis Of Speed Fluctuations 35
Examining the Speed WaveformDefining the Metrics
LPS – location peak speed [deg
ATDC]
cyl 3
expansion
LTS – location trough speed [deg ATDC]LTS location trough speed [deg ATDC]
TDC 180o
Analysis Of Speed Fluctuations 36
Examining the Speed Waveform
ca50
10o
cyl 3
expansion
10
TDC 180o
Analysis Of Speed Fluctuations 37
Examining the Speed Waveform
ca50
12o
cyl 3
expansion
12
TDC 180o
Analysis Of Speed Fluctuations 38
Examining the Speed Waveform
ca50
15o
cyl 3
expansion
15
TDC 180o
Analysis Of Speed Fluctuations 39
Examining the Speed Waveform
ca50
19o
cyl 3
expansion
19
TDC 180o
Analysis Of Speed Fluctuations 40
Examining the Speed Waveform
ca50
24o
cyl 3
expansion
24
TDC 180o
Analysis Of Speed Fluctuations 41
Examining the Speed Waveform
ca50
30o
cyl 3
expansion
30
TDC 180o
Analysis Of Speed Fluctuations 42
Ability to Discern Peaks & Troughs
• there are 2 factors that reduce ability to discern peaks & troughs
• increasing engine speed – primary importance
• excessive retarding of the burn – secondary importance
Analysis Of Speed Fluctuations 43
How Speed Waveform Changes with RPM
Analysis Of Speed Fluctuations 44
How Speed Waveform Changes with RPM
1100 rpm
cyl 3
expansion
Analysis Of Speed Fluctuations 45
How Speed Waveform Changes with RPM
1800 rpm
cyl 3
expansion
Analysis Of Speed Fluctuations 46
How Speed Waveform Changes with RPM
2500 rpm
cyl 3
expansion
Analysis Of Speed Fluctuations 47
How Speed Waveform Changes with RPM
3100 rpm
cyl 3
expansion
Analysis Of Speed Fluctuations 48
How Speed Waveform Changes with RPM
3800 rpm
cyl 3
expansion
Analysis Of Speed Fluctuations 49
How Speed Waveform Changes with RPM(1100, 1800, 2500, 3100, 3800rpm)
260
mg
cyl 3
expansion
Analysis Of Speed Fluctuations 50
Ability to Discern Peaks & Troughs
• there are 2 factors that reduce ability to discern peaks & troughs
• increasing engine speed
• excessive retarding of the burn
Analysis Of Speed Fluctuations 51
Ability to Discern Peaks & Troughs
• lose ability to discern as RPM increases
• lose ability to discern as spark is retarded (at some operating points)
threshold
Analysis Of Speed Fluctuations 52
Ability to Discern Peaks & Troughs
• lose ability to discern as RPM increases
• lose ability to discern as spark is retarded (at some operating points)
• speed-based methods limited to 6 of the 12 operating points
threshold
Analysis Of Speed Fluctuations 53
Speed Response
• as engine speed increases• as engine speed increases …
• the ‘gas compression trough’ near TDC disappears
• the ‘hump’ due to combustion disappears
• this is because reciprocating mass effects begin to dominate speed response
• effect increases to the square of engine speed
• thus it appears that instantaneous speed methods are constrained to lower RPM
• at the 2 ‘borderline’ operating points• at the 2 borderline operating points –
ability to detect peaks/troughs disappeared as burn retarded
Analysis Of Speed Fluctuations 54
LTS vs CA50
Analysis Of Speed Fluctuations 55
LTS vs CA50
cyl 3
expansion
LPS location peak speed [degLPS – location peak speed [deg
ATDC]
Analysis Of Speed Fluctuations 56
LTS vs CA50
Analysis Of Speed Fluctuations 57
LTS vs CA50
Analysis Of Speed Fluctuations 58
LTS vs CA50
Analysis Of Speed Fluctuations 59
LTS vs CA501800rpm / 180mg
• LTS becomes more retarded as burn (CA50) is
retarded
• LTS more ‘sensitive’ for shorter burns (steeper p
slope)
• less sensitive for longer burns (flatter slope)
• MBT operation corresponds to ~8o ATDC
TDC
]
p p
S [de
g AT
LTS
burn location (CA50)
Analysis Of Speed Fluctuations 60
LTS vs CA501800rpm / 180mg
• LTS becomes more retarded as burn (CA50) is
retarded
• LTS more ‘sensitive’ for shorter burns (steeper p
slope)
• less sensitive for longer burns (flatter slope)
• MBT operation corresponds to ~8o ATDC
TDC
]
p p
S [de
g AT
LTS
burn location (CA50)
Analysis Of Speed Fluctuations 61
LTS vs CA501800rpm / 180mg
• LTS becomes more retarded as burn (CA50) is
retarded
• LTS more ‘sensitive’ for shorter burns (steeper p
slope)
• less sensitive for longer burns (flatter slope)
• MBT operation corresponds to ~8o ATDC
TDC
]
p p
S [de
g AT
LTS
burn location (CA50)
Analysis Of Speed Fluctuations 62
LTS vs CA502500rpm / 260mg
• LTS becomes more retarded as burn (CA50) is
retarded
• MBT operation corresponds to ~8o ATDC
TDC
]S
[de
g AT
LTS
burn location (CA50)
Analysis Of Speed Fluctuations 63
LPS vs CA50
Analysis Of Speed Fluctuations 64
LPS vs CA50
LPS – location peak speed [deg p p [ g
ATDC]
cyl 3
expansion
Analysis Of Speed Fluctuations 65
LPS vs CA50
Analysis Of Speed Fluctuations 66
LPS vs CA50
Analysis Of Speed Fluctuations 67
LPS vs CA50
Analysis Of Speed Fluctuations 68
LPS vs CA501100rpm / 100mg
• LPS tracks burn location (CA50)
• MBT operation corresponds to ~42o
ATDC TDC
]
ATDC
S [de
g AT
LPS
burn location (CA50)
Analysis Of Speed Fluctuations 69
LPS vs CA501100rpm / 180mg
• LPS tracks burn location (CA50)
• MBT operation corresponds to ~47o
ATDC TDC
]
ATDC
S [de
g AT
LPS
burn location (CA50)
Analysis Of Speed Fluctuations 70
LPS vs CA501100rpm / 260mg
• LPS tracks burn location (CA50)
• MBT operation corresponds to ~50o
ATDC TDC
]
ATDC
S [de
g AT
LPS
burn location (CA50)
Analysis Of Speed Fluctuations 71
LPS vs CA501800rpm / 180mg
• LPS tracks burn location (CA50)
• MBT operation corresponds to ~40o
ATDC TDC
]
ATDC
S [de
g AT
LPS
burn location (CA50)
Analysis Of Speed Fluctuations 72
LPS vs CA501800rpm / 180mg
• LPS tracks burn location (CA50)
• MBT operation corresponds to ~51o
ATDC TDC
]
ATDC
S [de
g AT
LPS
burn location (CA50)
Analysis Of Speed Fluctuations 73
LPS vs CA502500rpm / 260mg
• LPS tracks burn location (CA50)
• MBT operation corresponds to ~40o
ATDC TDC
]
ATDC
S [de
g AT
LPS
burn location (CA50)
Analysis Of Speed Fluctuations 74
Overview
• introduction
• definition of operating map
• d l d i t• speed-load points
• matrix of burn locations & durations
• system model of engine transmission and vehicle• system model of engine, transmission, and vehicle
• pressure based methods – discussion of LPP and LPP for MBT
• instantaneous speed based methods – LPS and LTS
• observations & conclusions
Analysis Of Speed Fluctuations 75
Observations of LTS
• useful metric at only 2 operating pointsy p g p
• surprisingly LTS not useful at 1000rpm, at any of the 3 loads – changes in burn location hardly produce any changes in LTS
• for a specific burn (say bloc=10, bdur=25) it appears that LTS is retarded (moves to the right) as RPM increases, and it advances (moves to the left) as APC inc's
• for a given burn location (say bloc=10), it appears that LTS advances (moves to the left) as burn duration increases
APC
260 -.04 0.07 0.87.83-.91
-- --
LTS Sensitivity
180 -.04 0.87.85-.89
0.90.69-1.00
--
0 83100 0.05 0.83.73-.94
--
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 76
Observations of LTS
• useful metric at only 2 operating pointsy p g p
• surprisingly LTS not useful at 1000rpm, at any of the 3 loads – changes in burn location hardly produce any changes in LTS
• for a specific burn (say bloc=10, bdur=25) it appears that LTS is retarded (moves to the right) as RPM increases, and it advances (moves to the left) as APC inc's
• for a given burn location (say bloc=10), it appears that LTS advances (moves to the left) as burn duration increases
SAPC
260 -.04 0.07 0.87.83-.91
-- --
LTS SensitivityAPC
260 0.90.98-.72
0.89.98-.70
0.88.96-.70
0.89.96-.72
0.87.96-.65
LPP Sensitivity
180 -.04 0.87.85-.89
0.90.69-1.00
--
0 83
180 0.94.98-.87
0.93.98-.87
0.93.96-.87
0.92.96-.85
0 93 0 93 0 92 100 0.05 0.83.73-.94
--
1100 1800 2500 3100 3800 RPM
100 0.93.98-.85
0.93.98-.87
0.92.98-.85
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 77
Observations of LTS
• at a given operating point, LTS for MBT is ~constant (more so than LPS)
• h it i l i f l t th 2 ti i t• however, it is only meaningful at the 2 operating points
APC
260 -3 2 ~97-9
-- --
LTS for MBT
180 -2 ~76-8
~1816-19
--
15100 1 ~1514-16
--
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 78
Observations of LTS
• at a given operating point, LTS for MBT is ~constant (more so than LPS)
• h it i l i f l t th 2 ti i t• however, it is only meaningful at the 2 operating points
fAPC
260 -3 2 ~97-9
-- --
LTS for MBTAPC
260 ~1618-13
~1517-12
~1415-11
~1314-11
~1314-10
LPP for MBT
180 -2 ~76-8
~1816-19
--
15
180 ~1618-12
~1415-12
~1315-11
~1315-11
15 14 13 100 1 ~1514-16
--
1100 1800 2500 3100 3800 RPM
100 ~1518-12
~1417-11
~1315-11
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 79
Observations of LPS
• at a given operating point, LPS tracks CA50 – as burn retarded, LPS retarded
• at a given operating point, sensitivity (slope) is ~constant for the 'nominal' burn durations (15,20,25,30), but then decreases quickly for longer burns
• there seems to be no pattern for sensitivity changing w/ either RPM or APC
• for a given burn (say bloc=10 / bdur=25), it appears LPS retards with increasing APC, and it may advance w/ increasing RPM (this is only a weak effect)
APC
260 0.63.65-.61
0.78.76-79
0.56.71-.32
-- --
LPS Sensitivity
180 0.70.72-.67
0.72.74-.71
-- --
0 72100 0.72.74-.66
-- --
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 80
Observations of LPS
• at a given operating point, LPS tracks CA50 – as burn retarded, LPS retarded
• at a given operating point, sensitivity (slope) is ~constant for the 'nominal' burn durations (15,20,25,30), but then decreases quickly for longer burns
• there seems to be no pattern for sensitivity changing w/ either RPM or APC
• for a given burn (say bloc=10 / bdur=25), it appears LPS retards with increasing APC, and it may advance w/ increasing RPM (this is only a weak effect)
SAPC
260 0.63.65-.61
0.78.76-79
0.56.71-.32
-- --
LPS SensitivityAPC
260 0.90.98-.72
0.89.98-.70
0.88.96-.70
0.89.96-.72
0.87.96-.65
LPP Sensitivity
180 0.70.72-.67
0.72.74-.71
-- --
0 72
180 0.94.98-.87
0.93.98-.87
0.93.96-.87
0.92.96-.85
0 93 0 93 0 92 100 0.72.74-.66
-- --
1100 1800 2500 3100 3800 RPM
100 0.93.98-.85
0.93.98-.87
0.92.98-.85
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 81
Observations of LPS
• for a given operating point LPS for MBT is constant as burn duration is varied• for a given operating point, LPS for MBT is ~constant as burn duration is varied
• it does seem to retard slightly as burn gets longer
• however LPS for MBT is not very consistent across operating points it varies from 39o to 51o• however, LPS for MBT is not very consistent across operating points – it varies from 39 to 51
• tends to retard as APC increases
• tends to advance as RPM increases
APC
260 ~5048-52
~5149-54
~3937-44
-- --
LPS for MBT
180 ~4846-50
~4037-42
-- --
42100 ~4240-44
-- --
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 82
Observations of LPS
• for a given operating point LPS for MBT is constant as burn duration is varied• for a given operating point, LPS for MBT is ~constant as burn duration is varied
• it does seem to retard slightly as burn gets longer
• however LPS for MBT is not very consistent across operating points it varies from 39o to 51o• however, LPS for MBT is not very consistent across operating points – it varies from 39 to 51
• tends to retard as APC increases
• tends to advance as RPM increases
fAPC
260 ~5048-52
~5149-54
~3937-44
-- --
LPS for MBTAPC
260 ~1618-13
~1517-12
~1415-11
~1314-11
~1314-10
LPP for MBT
180 ~4846-50
~4037-42
-- --
42
180 ~1618-12
~1415-12
~1315-11
~1315-11
15 14 13 100 ~4240-44
-- --
1100 1800 2500 3100 3800 RPM
100 ~1518-12
~1417-11
~1315-11
1100 1800 2500 3100 3800 RPM
Analysis Of Speed Fluctuations 83
Concluding Remarks
• instantaneous speed waveform changes appreciably with combustionp g pp y
• as RPM increases, however, speed response dominated by reciprocating mass effects
• combustion information is overwhelmed
• ability to identify peaks & troughs (local max & min) limited to low RPM & high APC
• considering only a subset of engine operating points
• speed based metrics (LPS & LTS) are able to track CA50
• unfortunately, LPS (& LTS) for MBT do not remain very constant across engine operating conditions – difficult for closed-loop control
• GT-Power simulation provided means to explore best case scenario
• GT-Power outputs ‘smooth’ instantaneous speed waveforms –
very difficult to produce in the real-world
• this simulation study provides an estimate of the best we can hope to achieve
• GT P t
Analysis Of Speed Fluctuations 84
• GT-Power support