simulating diesel engine transients

AUTOMOTIVE RESEARCH CENTER

SIMULATING DIESEL ENGINE TRANSIENTS

Zoran S. Filipi, Guoqing Zhang, Stephen Riley and Dennis N. Assanis

W. E. Lay Automotive Laboratory

Automotive Research Center

The University of Michigan

ARC Conference on

Critical Technologies for Modeling & Simulation of Ground Vehicles

June 3 - 4, 1997.


ACKNOWLEDGMENTS

Arvind Atreya, Claus Borgnakke, David Dowling, Scott Fiveland, Steven Hoffman, Samuel Homsy, Xiaoliu Liu, Fadi Kanafani, Kevin Morrison, Donald Patterson, Michalis Syrimis, Deanna Winton

The authors also appreciate the technical collaboration with Dr. Nabil Hakim, Mr. Jim Hoelzer, Mr. Craig Savonen, and Mr. Tim Prochnau of Detroit Diesel Corporation, an industrial member of the ARC.

Professor Naeim Henein and other members of the ARC research team at Wayne State University for making experimental results measured on the Deutz single- cylinder engine available for model validation purposes.


MOTIVATION

Need to evaluate and optimize advanced turbocharged diesel systems through the use of simulation models.

Predictive diesel system model crucial for mobility and fuel economy studies of the ground vehicle.

Single-cylinder transient diesel engine module needed as a basic building block for the complex, multi-cylinder engine system simulation.


OBJECTIVES

Develop a high-fidelity diesel engine cylinder module.

Provide capability for simulation of the transient engine operation on the crank-angle basis.

Integrate in-cylinder modules to create a multi-cylinder engine simulation in a flexible, easily reconfigurable, graphical software environment.

Validate the multi-cylinder engine transient performance predictions against measurements.

Integrate the multi-cylinder engine model with the ancillary components to generate the engine system simulation.

Integrate the engine system with the driveline and the vehicle dynamics model.


MODELING APPROACH

Extend the non-linear, phenomenological steady-state diesel engine cycle simulation to include engine dynamics on the crank-angle basis .

Include an instantaneous torque model as a necessary prerequisite for yielding accurate predictions of the cyclic fluctuations of the crank shaft angular velocity.

Instantaneous torque, and hence crankshaft speed fluctuate in response to the cyclic nature of the gas pressure force and the slider-crank kinematics - this is accentuated for single-cylinder engine operation. Hence, the approach to modeling is to:


Features of the Non-Linear, Quasi-Steady Diesel Engine Model

Parent simulation: Assanis and Heywood (1986)

The system of interest is the instantaneous contents of a cylinder. The system is open to the transfer of mass, enthalpy, and energy in the form of work and heat.

Phenomenological combustion model - Watson (1980)

Convective heat transfer model is based on turbulent flow in pipes. Radiative heat transfer is added during combustion.

Characteristic velocity and length scales are obtained from an “energy cascade” turbulent flow model.

Quasi-steady, adiabatic, one-dimensional flow equations are used to predict mass flows past the intake and exhaust valves.


Behavior of cycle process sub-models during transients

A series of steady-state calculations performed for different operating conditions likely to occur during a transient sequence

Parametric study #1: The effect of engine speed on cycle parameters

0

20

40

60

80

100

120

0

500

1000

1500

2000

300 350 400 450

600 rpm1200 rpm1800 rpm

CRANK ANGLE [deg]

RA

TE

OF

HE

AT

RE

LEA

SE

[1/s]

Rate of HR

PRESSURE

P inlet = 1.0 bar, mfuel/cyc

= 0.085 g TE

MP

ER

AT

UR

E [K

]

GASTEMPERATURE

a)

0

5

10

15

20

25

30

35

0

20

40

60

80

100

0 80 160 240 320 400 480

600 rpm1200 rpm1800 rpm

CRANK ANGLE [deg]

Rate of HT

TURBULENCEINTENSITY

P inlet = 1.0 barm

fuel/cyc= 0.085 g

b)


Behavior of cycle process sub-models during transients - cont.

Parametric study #2: The effect of the boost pressure on cycle parameters

-40

0

40

80

120

160

0

100

200

300

400

500

600

700

800

300 350 400 450

Pim=2.3 barPim=1.65 barPim=1.0 bar

CRANK ANGLE [deg]

PRESSURE

1200 rpm

Φ = 0.57

Rate of HR

b)

0

100

200

300

400

0 40 80 120 160 200 240

Pim=2.3 barPim=1.65 barPim=1.0 bar

INLE

T M

AS

S F

LOW

[g/s

]

CRANK ANGLE [deg]a)


Single-Cylinder Engine Dynamic System

ENGINE CYCLE

SIMULATION

OPERATORCOMMAND

FUEL SYSTEM

AMBIENT CONDITIONS

Ωe Ωe

Ω - rotational speedτ - torque

FRICTION MODEL

τb

EXTERNAL LOAD

ENGINE DYNAMICS

τL-

+ Ωe

τe

τF-+

Ωe

Key inputs to the cycle simulation: the operator command, the fueling rate and the ambient conditions.

Key input to the engine dynamics model: Brake torque from the cycle model and the external load imposed by the dynamometer or the vehicle.

Design parameters needed: masses of the engine moving parts, polar moments of inertia of the engine and the load.

Key output parameter: the instantaneous value of the angular shaft velocity, which is a necessary input for computing overall cycle parameters, including the engine torque, at the next instant in time.


Instantaneous Engine Torque

rF p p

Bpres cyl atm= − ⋅( )

2

4

Π

vF m m ainer pg rcr= − + ⋅( )

a R

R

= + +−

+

+−

ω λ λλ

ω λλ

22 4

2 2 3 2

2 2 1 2

2

1

11

cos(cos sin )

( sin )

˙ sincos

( sin )

/

/

Θ Θ ΘΘ

Θ ΘΘ

r r rF F Fpstn pres iner= +

r rC Fpstn= (

cos)

1

β

r rT Fpstn= +

(sin( )

cos)

Θ ββ

TORQUE T R= ⋅

R = Stroke/2; L - connecting rod length; λ = R/L;Θ - crankshaft angular position and β - angle of swing of the connecting rod

R

β

Θ

CFpstn

N

T

Fpres

L

The pressure force:

The inertial force:

while the linear acceleration of reciprocating components is:

The resultant force on the piston:

The torque on the shaft:

Force in the directionof the connecting rod:

The tangential force on the crank journal:


0

500

1000

1500

2000

2500

3000

0 5 10 15 20 25 30

ENGINE: Deutz F1L 210 D

ENGINE MOMENT OF INERTIA: 0.386 kgm2

FUEL/CYCLE: 40 mm3

EXTERNAL LOAD: 0 Nm

MEASURED

PREDICTED

EN

GIN

E

SP

EE

D

[rpm

]

ENGINE CYCLE NUMBER

ValidationComparison of predicted and measured crankshaft speed fluctuations during engine free acceleration


Overall Transient Model Behavior- cont.Predicted crankshaft speed fluctuations during an

elementary engine transient.

Both the amplitudes and the periods of cyclic fluctuations gradually decrease as the mean engine speed increases.

800

1000

1200

1400

1600

1800

2000

2200

2400

0.00

0.02

0.04

0.06

0.08

0.10

0.0 0.5 1.0 1.5 2.0 2.5 3.0

SINGLE CYLINDER CI ENGINEBore = 0.13 m, Stroke = 0.16 m

MOMENT OF INERTIA = 1.4 kgm2EXTERNAL LOAD = 0 Nm

EN

GIN

E S

PE

ED

[rp

m]

MA

SS

OF

FU

EL/C

YC

LE [g]

TIME [s]

enginespeed

fuel per cycle


Overall Transient Model Behavior- cont.Predicted single-cylinder cyclic torque fluctuations

during an elementary engine transient.

-1000

-500

0

500

1000

1500

2000

2500

0 100 200 300 400 500 600 700

SINGLE CYLINDER CI ENGINEBore = 0.13 m, Stroke = 0.16 mENGINE SPEED: 900 - 2160 rpmEXTERNAL LOAD: 0 Nm

EN

GIN

E T

OR

QU

E [

Nm

]

CRANK ANGLE [deg]

2160 rpmhigh idle

900 rpmno load

900 rpm100 % fuel

2160 rpm100 % fuel


Multi-Cylinder Engine Simulation Assembled in SIMULINK

In-cylinder diesel engine code converted to FORTRAN-MEX file with appropriate external links in order to be able to generate a multi-cylinder simulation in SIMULINK and test the newly developed models.


0

20

40

60

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320 340 360 380 400 420

experimentsimulation

Cylinder

Pressure

(bar)

Crank Angle (deg)

Experimental Validation

0

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2000

2500

50

100

150

200

250

300

350

400

450

0 5 10 15 20 25 30

RPM - PREDICTEDRPM - MEASUREDEXTERNAL LOAD

BOOST PRESS.

Engine

Speed

(rpm

);

External

Load

(N

m)

Intake

Manifold

Pressure

(KPa)

Time (s)

VALIDATION

OF

SUB-MODELS

VALIDATION

OF THE

ENGINE

RESPONSE

Pressure Transducers / Heat Flux Probesin all Cylinders

Three-Component Force Transducer for Engine Vibrations Studies

The Engine: DDC-60 Six-Cylinder, Turbocharged, Intercooled, Direct Injection Diesel


In-Cylinder Module in the Context ofthe Flexible Powertrain Simulation

The UM in-cylinder model embedded in the multi-cylinder engine block.

Flexible Powertrain Simulation developed in SIMULINK by the University of Wisconsin team.

• HIERARCHICAL

• INTERACTIVE

• CHOICE OF SUB-MODELS

• EASILY RECONFIGURABLE


HILL CLIMBING

8

10

12

14

16

18

20

22

-0.1

-0.05

0

0.05

0.1

0.15

0 2 4 6 8 10

VEHICLE

SPEED

(mph)

VEHICLE

ACCELERATION

(g’s)

TIME (s)

M916A1 SEMI, Gross Curb Weight 126,000 lb

ax

v

x

5

10

15

0 2 4 6 8 10

WHEEL

VERTICAL

LOAD

(lb*1000)

TIME (s)

M916A1 SEMIGross Curb Weight 126,000 lb

FRONT

FRONT REAR

REAR


HILL CLIMBING - cont.

FRONTWHEELS SLIPPING

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

2.8

0 2 4 6 8 10

WHEEL

SPEED

(rev/s)

TIME (s)


FRONT

REAR

-1000

0

1000

2000

3000

4000

5000

0 2 4 6 8 10

WHEEL

LONG.

FORCE

(lbf)


FRONT

REAR


HILL CLIMBING

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0.22

0 1 2 3 4 5 6 7 8

FU

EL

INJE

CT

ED

(g/

cycl

e)

TIME (s)

1400

1500

1600

1700

1800

1900

2000

2100

2200

0 1 2 3 4 5 6 7 8

EN

GIN

E S

PE

ED

(rp

m)

TIME (s)

Fuel System Response Engine Speed Response


-2000

-1000

0

1000

2000

3000

4000

5000

6000

0 1 2 3 4 5 6 7 8

TO

RQ

UE

(N

m)

TIME (s)

HILL CLIMBING

Converter Out

Indicated

Torque Transients

Converter Pump


SUMMARY AND CONCLUSIONS

A steady-state, phenomenological, zero-dimensional model has been used as the foundation for the development of a transient, single-cylinder, engine simulation module.

The transient extension has involved the implementation of instantaneous engine torque and engine dynamics models on a crank-angle basis.

The transient simulation has been successfully validated against experimental results from a single-cylinder engine.

Multy-cylinder engine response has been validated against transient test results for the DDC 60 engine.

Integrated powertrain-vehicle simulation provides the capability to study complex interactions between the engine, driveline, vehicle structure and the terrain.

simulating diesel engine transients

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