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GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
A DOE Study of a 3 Cylinder Engine Cyclic Speed Irregularity by
Coupling Isight and GT-Suites. By:
Hatem Orban, Ph.D Advanced Engine Analysis, General Motors
Nov. 4th, 2013
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Outline • Problem statement • GT-Suite Model • Isight DOE • Isight optimization
– Single Objective Optimization – Multi-Objective Optimization
• Conclusions and Future Work.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Introduction: Engine Noise and Vibrations
• Engine vibrations can limit the operating range of the engine which affects the overall vehicle fuel consumption
Engine Cranktrain Cam and
Accessory Drive
Vehicle Body
Transmission and Driveline
Air Radiated Noise
Engine Cover, Noise shields
Torsional Isolators
Hydraulic Mounts, Active Mounts
DMF, Rubber Dampers, Pendulum Dampers, TCC Slip
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Effect of Operating Parameters on Speed Variation
Increased Torque
Idle speed and WOT have to be increased to meet speed variation constraints. Fuel Economy reduced.
4
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Problem Definition • For the same over all engine size
reducing cylinder count reduces frictional losses.
• Two main cyclic speed irregularity targets are used to match NVH targets between 3 cylinder and 4 cylinder engines.
– Cyclic speed irregularity at Idling – Cyclic speed irregularity at WOT.
• Changes to the 3 cylinder engine to meet NVH target include:
– Resizing the flywheel inertia – Using pendulum dampers to reduce the
1.5 order – Adjusting idling speed and min WOT
speed.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
GT-Crank Model
Speed Irregularity Calculation and Output
Dyno-Inertia and Sensors
Cranktrain
Pendulum damper submodel
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Model Features • Since the dynamic behavior was critical at relatively lower
speeds well below the torsional frequency of the cranktrain system a rigid dynamic analysis is used for the system.
• During the analysis the cranktrain is run in the load mode (vs speed mode). This allows the crank to change speed during the cycle.
• The speed irregularity is measured as: – (Max. Speed-Min. Speed)/Average Speed.
• To stabilize the speed. The cranktrain is attached to a dyno inertia with constant speed boundary conditions via soft spring and damper system.
• In addition to speed irregularities, angle deviations is measured between the constant speed dyno inertia and the cranktrain flywheel.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Torque Order and Cyclic Speed irregularity Comparison
• 3 Cylinder engines have higher torque orders than 4 cylinder engines. • Also, as the frequency is lower at the same speed the flywheel inertia is
less effective in reducing cyclic speed variation.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Effect of Pendulum Inertia On Speed Irregularity Constant Flywheel Inertia
Constant Total Inertia
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
ISIGHT DOE and Optimization
• Preliminary runs of the model shows that very large total inertia is required to match speed irregularity of a 3 cyl engine to 4 cyl engine.
• The change in speed irregularity with pendulum inertia is not monotonic. It is affected by engine speed and flywheel inertia.
• In order to achieve required speed irregularity targets with lower inertias both speeds at idling and at wot have to be adjusted.
• A DOE is conducted to map the effects of input variables on speed irregularities.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
DOE: Speed Variation at WOT
Effect of Flywheel inertia and Pendulum Moment of inertia on Speed Variation at WOT.
WOT @ Level 1 Speed
WOT @ Level 2 Speed
WOT @ Level 3 Speed
Pend
ulum
Iner
tia
Pend
ulum
Iner
tia
Pend
ulum
Iner
tia
Flywheel Inertia
Flywheel Inertia
Flywheel Inertia
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
DOE: Speed Variation at WOT
• WOT Speed Level 2 RPM
Flyw
heel
in
ertia
Pend
ulum
in
ertia
Pend
ulum
Iner
tia
Flywheel Inertia
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
DOE: Speed Variation at IDLE
Effect of Flywheel inertia and Pendulum Moment of inertia on Speed Variation at Idle.
IDLE @ Level 1 Speed
IDLE @ Level 2 Speed
IDLE @ Level 3 Speed
Pend
ulum
Iner
tia
Pend
ulum
Iner
tia
Pend
ulum
Iner
tia
Flywheel Inertia
Flywheel Inertia
Flywheel Inertia
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
DOE: Speed Variation at IDLE
IDLE @ Level 1 Speed Flyw
heel
in
ertia
Pend
ulum
in
ertia
Pend
ulum
Iner
tia
Flywheel Inertia
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Single Objective Optimization Problem
Parameter Value
Fly wheel Inertia (kgm2) ***
Pendulum Inertia (kgm2) ***
Total_Iner (kgm2) ***
Idle Speed (rpm) ***
Min Wot speed (rpm) ***
Speed Irregularity @ Idle *** Speed Irregularity @ WOT ***
•The objective of this optimization is to minimize the a weighted sum of the total inertia, idle speed, and wot speed. The weight for the total inertia is greater than weights for speeds.
•Constraints are set on the speed irregularities at idle and at WOT not to exceed limits set from corresponding 4-cylinder engine.
•A single solution is obtained which is dependent on relative weights of the objective functions.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Multi-Objective Optimization
• Objective is to minimize both idle and WOT speeds, a target is set on the total inertia. Speed variations at idle and WOT are set as constraints
• Graphs are for Pareto points that satisfy both speed variation constraints
Idle Speed Contour
Pendulum Inertia
Flyw
heel
Iner
tia
Pendulum Inertia Fl
ywhe
el In
ertia
WOT Speed Contour
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Multi-Objective Optimization
• An approximation surface for the Pareto points is of a great value in the selection of design and operating parameters.
Idle Speed
Contours of Total Inertia
WO
T Sp
eed
Pend
ulum
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Conclusions • A GT-Suite model was developed to include pendulum dampers
effects on cyclic speed variations. • DOE analysis was conducted to under stand effect of flywheel
inertia and pendulum damper inertia on speed variation at idle and at WOT.
• Matching 3 cylinder engine speed variations to 4 cylinder engine while maintaining same operating speeds requires unrealistically large flywheel and/or damper inertias.
• A procedure has been developed to optimize the selection inertia and engine operating parameters based on engine speed variation as a NVH target.
• Multi-objective optimization provides a tool for selection of both design and operating parameters.
GM Powertrain Advanced Engineering GM Confidential
GM Powertrain Advanced Engineering
Looking Forward • Idle speed, WOT speed, and crank train inertia are parameters that affects
both vehicle response and fuel economy in city driving and highway driving. • An approximation surface relating these parameters can be used in
balancing design parameters for a full driving cycle fuel economy optimization.
• Sensitivities of operating parameters to NVH constraints can be established. • Other NVH constraints can be introduced in such as angle deviations which
can be critical for accessory and cam drives. • The same approach can be used in design parameters selections and
establishing operating ranges for engines with cylinder deactivation capabilities. (AFM)
• The tune up of decoupling/isolation schemes parameters and their effectiveness evaluated in similar manner.
• Isolation schemes- such as DMF, torsional isolators, and TCC slip can be built into the GT-Suite model.