3 Cylinder Speed Variaiton - Gamma Technologies · PDF fileGM Powertrain Advanced Engineering...

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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



Outline • Problem statement • GT-Suite Model • Isight DOE • Isight optimization

– Single Objective Optimization – Multi-Objective Optimization

• Conclusions and Future Work.



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



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



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.



GT-Crank Model

Speed Irregularity Calculation and Output

Dyno-Inertia and Sensors

Cranktrain

Pendulum damper submodel



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.



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.



Effect of Pendulum Inertia On Speed Irregularity Constant Flywheel Inertia

Constant Total Inertia



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.



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



DOE: Speed Variation at WOT

• WOT Speed Level 2 RPM

Flyw

heel

in

ertia

Pend

ulum

in

ertia

Pend

ulum

Iner

tia

Flywheel Inertia



DOE: Speed Variation at IDLE

Effect of Flywheel inertia and Pendulum Moment of inertia on Speed Variation at Idle.

IDLE @ Level 1 Speed



Pend

ulum

Iner

tia

Pend

ulum

Iner

tia

Pend

ulum

Iner

tia

Flywheel Inertia

Flywheel Inertia

Flywheel Inertia



DOE: Speed Variation at IDLE

IDLE @ Level 1 Speed Flyw

heel

in

ertia

Pend

ulum

in

ertia

Pend

ulum

Iner

tia

Flywheel Inertia



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.



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



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



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.



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.

3 Cylinder Speed Variaiton - Gamma Technologies · PDF fileGM Powertrain Advanced Engineering...

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