Combustion Performance - PDF Free Download

Analysis of Crankshaft Speed Fluctuations and Combustion Performance Ramakrishna Tatavarthi Julian Verdejo GM Powertrain November 10, 2008

Overview introduction definition of operating map speed-load d points matrix of burn locations & durations 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

motivation for the present analysis location of peak pressure LPP Introduction 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 for MBT is very constant across engine operating conditions i [1] attractive basis for closed-loop operation [1] Mtk Matekunas, F. A. Modes and Measures of Cyclic Combustion Variability. SAE Paper 830337, 1983. Analysis Of Speed Fluctuations 4

Introduction crankshaft speed based methods 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 goal 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

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) longer burns later burns burn loc cation (CA50) [d deg ATDC] burn duration (10-75%) [deg] 15 20 25 30 35 40 45-1 1 13 25 37 49 61 73 3 2 14 26 38 50 62 74 6 3 15 27 39 51 63 75 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 24 9 21 33 45 57 69 81 30 10 22 34 46 58 70 82 37 11 23 35 47 59 71 83 12 burn locations 8 burn durations 84 combinations in total varied duration in all 4 cyl s but varied location only in cyl #3 45 12 24 36 48 60 72 84 12 op pts x 84 burns = 1,008 total runs Analysis Of Speed Fluctuations 8

Analysis Of Speed Fluctuations 10

Description of GT-Power Model four cylinder engine, 2.2L, gasoline SI, port fuel injection load-mode d (instead of speed-mode) d) simulations lti 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 model additions to model to capture vehicle and driveline dynamics and dloading Analysis Of Speed Fluctuations 12

Clutch Torsional Damping model had difficulty converging at first system underdamped damping ratio = 0.5 12 8 0 [Nm/(rad/s)] clutch spring stiffness was provided by 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

Cylinder Pressure as CA50 Varied quick burn (duration = 25 o ) peak pressure moves to the right as CA50 is retarded good sensitivity CA50 locations TDC 90 o Analysis Of Speed Fluctuations 16

LPP vs all operating points CA50 location of peak pressure (LPP) vs burn location (CA50) duration = 25 o amazingly consistent across all operating points considered TDC] P [deg AT LPP burn location (CA50) Analysis Of Speed Fluctuations 17

LPP vs all operating points CA50 location of peak pressure (LPP) vs burn location (CA50) amazingly consistent across all operating points considered good sensitivity a 10 o change in CA50 results in 9 o change in LPP LPP P [deg AT TDC] duration = 25 o slope = 43 o / 46 o = 0.93 46 o 43 o burn location (CA50) Analysis Of Speed Fluctuations 18

Cylinder Pressure as CA50 Varied slow burn (duration = 45 o ) LPP loses sensitivity to changes in CA50 LPP doesn t move to the right CA50 locations TDC 90 o Analysis Of Speed Fluctuations 19

Cylinder Pressure as CA50 Varied quick burn (duration = 25 o ) peak pressure moves to the right as CA50 is retarded good sensitivity CA50 locations TDC 90 o Analysis Of Speed Fluctuations 20

LPP vs CA50 2500rpm / 180mg LPP vs CA50 TDC] P [deg AT LPP burn location (CA50) Analysis Of Speed Fluctuations 21

LPP vs CA50 2500rpm / 180mg LPP vs CA50 greater sensitivity for quicker burns (steeper slope of blue line) TDC] P [deg AT LPP burn location (CA50) Analysis Of Speed Fluctuations 22

LPP vs CA50 2500rpm / 180mg LPP vs CA50 greater sensitivity for quicker burns (steeper slope of blue line) less sensitivity for longer burns (flatter slope of black line) LPP P [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 23

LPP vs CA50 2500rpm / 180mg LPP vs CA50 greater sensitivity for quicker burns (steeper slope of blue line) less sensitivity for longer burns (flatter slope of black line) MBT operation corresponds to LPP of 10-17 deg ATDC for range of burn durations considered LPP P [deg AT TDC] MBT points (for bdur=15,20,25,30) burn location (CA50) Analysis Of Speed Fluctuations 24

Comments on LPP LPP Sensitivity LPP shows strong sensitivity to changes in burn location across entire operating map* nearly 1-to-1 relation APC LPP Sensitivity LPP loses sensitivity abruptly at a longer burn duration on average LPP is only valid for bdurs = 15, 20, 25, 30 260 0.90.98-.72 180 0.94.98-.87 0.89.98-.70 0.93.98-.87 0.88.96-.70 0.93.96-.87 0.89.96-.72 0.92.96-.85 0.87.96-.65 100 093 0.93 093 0.93 092 0.92.98-.85.98-.87.98-.85 *results shown in table are based on burn durations = 15, 20, 25, 30 1100 1800 2500 3100 3800 RPM Analysis Of Speed Fluctuations 25

Comments on LPP LPP for MBT LPP for MBT varies from 16 o to 13 o ATDC over the entire operating range 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 ~16 18-13 LPP for MBT ~15 17-12 ~14 15-11 ~13 14-11 ~13 14-10 180 ~16 18-12 ~14 15-12 ~13 15-11 ~13 15-11 100 ~15 ~14 ~13 18-12 17-11 15-11 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 ~16 o to ~13 o 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

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 RPM cyl 1 expansion cyl 3 expansion cyl 4 expansion cyl 2 expansion Analysis Of Speed Fluctuations 31

Examining the Speed Waveform delta RPM cyl 1 expansion cyl 3 expansion cyl 4 expansion cyl 2 expansion Analysis Of Speed Fluctuations 32

Examining the Speed Waveform cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 33

Examining the Speed Waveform combustion peak reciprocating mass torque peak trough due to gas compression at TDC cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 34

Examining the Speed Waveform cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 35

Examining the Speed Waveform Defining the Metrics LPS location peak speed [deg ATDC] LTS location trough speed [deg ATDC] cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 36

Examining the Speed Waveform ca50 10 o cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 37

Examining the Speed Waveform ca50 12 o cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 38

Examining the Speed Waveform ca50 15 o cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 39

Examining the Speed Waveform ca50 19 o cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 40

Examining the Speed Waveform ca50 24 o cyl 3 expansion TDC 180 o Analysis Of Speed Fluctuations 41

Examining the Speed Waveform ca50 30 o cyl 3 expansion TDC 180 o 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

lose ability to discern as RPM increases Ability to Discern Peaks & Troughs 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 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 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 [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 CA50 1800rpm / 180mg LTS becomes more retarded as burn (CA50) is retarded LTS more sensitive for shorter burns (steeper slope) less sensitive for longer burns (flatter slope) MBT operation corresponds to ~8 o ATDC LTS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 60

LTS vs CA50 2500rpm / 260mg LTS becomes more retarded as burn (CA50) is retarded MBT operation corresponds to ~8 o ATDC TDC] S [deg 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 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 CA50 1100rpm / 100mg LPS tracks burn location (CA50) MBT operation corresponds to ~42 o ATDC LPS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 69

LPS vs CA50 1100rpm / 180mg LPS tracks burn location (CA50) MBT operation corresponds to ~47 o ATDC LPS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 70

LPS vs CA50 1100rpm / 260mg LPS tracks burn location (CA50) MBT operation corresponds to ~50 o ATDC LPS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 71

LPS vs CA50 1800rpm / 180mg LPS tracks burn location (CA50) MBT operation corresponds to ~40 o ATDC LPS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 72

LPS vs CA50 1800rpm / 180mg LPS tracks burn location (CA50) MBT operation corresponds to ~51 o ATDC LPS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 73

LPS vs CA50 2500rpm / 260mg LPS tracks burn location (CA50) MBT operation corresponds to ~40 o ATDC LPS [deg AT TDC] burn location (CA50) Analysis Of Speed Fluctuations 74

Observations of LTS useful metric at only 2 operating gpoints 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 LTS Sensitivity 260 -.04 0.07 0.87.83-.91 -- -- 180 -.04 0.87.85-.89 100 0.05 083 0.83.73-.94 0.90.69-1.00 -- -- 1100 1800 2500 3100 3800 RPM Analysis Of Speed Fluctuations 76

Observations of LTS useful metric at only 2 operating gpoints 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 LPP Sensitivity APC LTS Sensitivity 260 0.90.98-.72 0.89.98-.70 0.88.96-.70 0.89.96-.72 0.87.96-.65 260 -.04 0.07 0.87.83-.91 -- -- 180 0.94.98-.87 0.93.98-.87 0.93.96-.87 0.92.96-.85 180 -.04 0.87.85-.89 0.90.69-1.00 -- 100 093 0.93 093 0.93 092 0.92 100 0.05 083 0.83.98-.85.98-.87.98-.85.73-.94 -- 1100 1800 2500 3100 3800 RPM 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) however, iti is only meaningful at tthe 2 operating points APC LTS for MBT 260-3 2 ~9 7-9 -- -- 180-2 ~7 6-8 100 1 ~15 14-16 ~18 16-19 -- -- 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) however, iti is only meaningful at tthe 2 operating points APC LPP for MBT APC LTS for MBT 260 ~16 18-13 ~15 17-12 ~14 15-11 ~13 14-11 ~13 14-10 260-3 2 ~9 7-9 -- -- 180 ~16 18-12 ~14 15-12 ~13 15-11 ~13 15-11 180-2 ~7 6-8 ~18 16-19 -- 100 ~15 15 ~14 ~13 100 1 ~15 18-12 17-11 15-11 14-16 -- 1100 1800 2500 3100 3800 RPM 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 LPS Sensitivity 260 0.63.65-.61 0.78.76-79 0.56.71-.32 -- -- 180 0.70.72-.67 0.72.74-.71 -- -- 100 072 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) APC LPP Sensitivity APC LPS Sensitivity 260 0.90.98-.72 0.89.98-.70 0.88.96-.70 0.89.96-.72 0.87.96-.65 260 0.63.65-.61 0.78.76-79 0.56.71-.32 -- -- 180 0.94.98-.87 0.93.98-.87 0.93.96-.87 0.92.96-.85 180 0.70.72-.67 0.72.74-.71 -- -- 100 093 0.93 093 0.93 092 0.92 100 072 0.72.98-.85.98-.87.98-.85.74-.66 -- -- 1100 1800 2500 3100 3800 RPM 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 it does seem to retard slightly as burn gets longer however, LPS for MBT is not very consistent across operating points it varies from 39 o to 51 o tends to retard as APC increases tends to advance as RPM increases APC LPS for MBT 260 ~50 48-52 ~51 49-54 ~39 37-44 -- -- 180 ~48 46-50 ~40 37-42 -- -- 100 ~42 40-44 -- -- 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 it does seem to retard slightly as burn gets longer however, LPS for MBT is not very consistent across operating points it varies from 39 o to 51 o tends to retard as APC increases tends to advance as RPM increases APC LPP for MBT APC LPS for MBT 260 ~16 18-13 ~15 17-12 ~14 15-11 ~13 14-11 ~13 14-10 260 ~50 48-52 ~51 49-54 ~39 37-44 -- -- 180 ~16 18-12 ~14 15-12 ~13 15-11 ~13 15-11 180 ~48 46-50 ~40 37-42 -- -- 100 ~15 15 ~14 ~13 100 ~42 18-12 17-11 15-11 40-44 -- -- 1100 1800 2500 3100 3800 RPM 1100 1800 2500 3100 3800 RPM Analysis Of Speed Fluctuations 83

instantaneous speed waveform changes appreciably with combustion Concluding Remarks 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 closedloop 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-Power support Analysis Of Speed Fluctuations 84