2 значения m avl.pdf

AVL-BOOST COMBUSTION MODELS

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2 BOOST_CombustionModels_2011_Bras

Spatial Discretization

Single Zone (Zero-Dimensional)

Two Zone (Quasi-Dimensional)

Ignition Type (Mixture Preparation)

Spark Ignition

Compression Ignition

ROHR Type

ROHR Input

ROHR predicted by Combustion Model

Source

Standard BOOST

User Coding

ROHR (Rate Of Heat Release) CLASSIFICATION


SPATIAL DISCRETIZATION / SINGLE ZONE

Governing Equations

Energy Conservation

d

dmh

d

dQ

d

dQ

d

dVp

d

umd BBBB

wFc

c

ccc TRmV

p 1

Perfect Gas Equation

Thermodynamic State Vector

c

c

c

c

c

C

T

pS

FV

CP

FB

Cc

mf

mf

mf

C

n

Gc

mf

mf

mf

C.

1

1

Classic / General Species Transport GCcC /


SPATIAL DISCRETIZATION / TWO ZONE /1

Energy Conservation for burned and unburned Zone

uuubbbc TRmTRmV

p 1

Perfect Gas Equation

Thermodynamic State Vector

unburned

burnedc

S

SS

d

dmh

d

dmh

d

dQ

d

dQ

d

dVp

d

udm

bBB

bBBb

uWb

Fbc

bb

,

,

d

dmh

d

dmh

d

dQ

d

dVp

d

udm uBBuBB

bu

Wuuc

uu ,

,

bbbbc TRmup ,,,,

uuuuc TRmup ,,,,

uBBuBBbBBbBB dmhdmh ,,,,

dVpc

FdQ

WbdQ

WudQ budmh


Vibe Single Zone

ROHR Approach

Parameter Data Source

Fitting Result of Combustion Analysis Tool (BOOST-Burn)

Experience

1

1

myam

c

BTB eym

aQ

d

dQ

c

oy

... Combustion Progress

10

1

ma

BTB eQQ

Released Energy

ROHR INPUT FOR SPARK IGNITION ENGINES /1



Table Single Zone

Data Source

Result of Combustion Analysis Tool

(BOOST-Burn)

Adaptation

For physical reasons preprocessing

performed to guarantee monotonic

increase of Fuel Burned



Hires et al

Required Input

Vibe Combustion Parameters and Ignition

Delay for Reference Operating Point

Vibe Two Zone / Table Two Zone

Same ROHR Approach as for Single Zone

State Vector of Burned Zone allows to calculate:

NOx Production (Extended Zeldovich)

CO Production (Onorati)

State Vector of Unburned Zone allows to calculate:

Required Octane Number

at

t

T

B

nMFB

SOC

UBZ dtepA

ON

1

%851100

Model Approach for Variation of Ignition Delay and Combustion Duration dependent

on Engine Speed

3/23/1

,

s

s

f

f

n

n refref

ref

refcc

3/23/1

s

s

f

f

n

nidid

ref

refref

ref

s ... laminar flame speed

f ... piston to head distance at ignition timing


PREDICTED ROHR FOR SPARK IGNITION ENGINES /1 FRACTAL COMBUSTION MODEL

Motivation

All mentioned ROHR Types require input based on experimental data which show usually a strong dependency on the operating point (speed, load-

signal) of the engine.

For optimization issues (variable valve timing, engine control strategies, ...) a predictive combustion model which handles the influence of residual gas

content and charge motion is required.

This requirement can be fulfilled in a wide operation point range by the new introduced Fractal Combustion Model



Characteristics /1

The Fractal Combustion Model is based on a

physical model of the flame front

propagation:

Geometric Combustion Chamber Input Data leads to a Relation between Piston

Position, Geometric Free Flame Surface

and Burned Zone Volume

Increase of Burned Zone Volume is a function of Laminar Burning Speed and

Geometric Free Flame Surface.

A Simple multiplication => to small values

because

The flame front is a very thin and highly wrinkled surface (wrinkled-flamelet

combustion regime)



Characteristics /2

This wrinkling effect is driven by the in-cylinder turbulent flow and chiefly

responsible for the increased burning rate.

The relation between geometric free and effective (highly wrinkled) flame area can

be described by a fractal structure.

Fractal is a mathematical method describing irregular geometry with self

similarity (length of British coast?).

Mandelbrot Set

Burned Gas

Unburned Gas

SL

SL

SL u

L



Extension to stratified charge

Input possibility for 1D distribution of

fuel vapor and combustion product

concentration (stratified charge) in

the direction of flame propagation

1D distribution can be imported from

AVL FIRE in-cylinder simulation

(standard output )



Project Experience

The fractal combustion model has the potential to predict the influence of the

valve timing variation on the rate of heat

release.

Out of 7 parameters for the combustion model only the 2 turbulence parameters

are function of engine speed and valve

timing.

The tuning of the turbulence parameter is based on 3D CFD results.

BSFC [g/kWh]

Res. Gas [%]


PREDICTED ROHR FOR SPARK IGNITION ENGINES /11 OPEN CHAMBER GAS ENGINE COMBUSTION MODEL

Main features:

2 Zone (unburned/burned) flame propagation model

Arrhenius / Magnussen approach combination for ignition delay simulation

In-cylinder turbulence level (used for the relation between laminar and turbulent

flame speed) is sourced by swirl and

squish flow

Combined with BOOST Classic Gas Properties Preparation Tool which allows

to generate properties for arbitrary fuel

blends (e.g. lean gas as mixture of CH4,

CO2, ), as alternative to general species transport


ROHR INPUT FOR COMPRESSION IGNTION ENGINES /1

Vibe Single Zone

ROHR Approach



Experience

1

1

myam

c

BTB eym

aQ

d

dQ

c

oy

... Combustion Progress

Evaporation Assumption

ROE (Rate of Evaporation) is direct linked to ROHR

d

dQ

Hd

dm B

u

FV 1



Double Vibe (Single Zone)

ROHR Approach

Superposition of 2 Vibe

Functions to meet Premixed

Combustion Peak and/or more

Complex Injection Strategies



Experience

21 Vibe

B

Vibe

BB

d

dQ

d

dQ

d

dQ



Woschni/Anisits

Vibe Two Zone / Table Two

Zone

Same ROHR Approach as for Single Zone

State Vector of Burned Zone allows to calculate:

NOx Production (Extended Zeldovich)

CO Production (Onorati)

Soot Production (Bolochous)

Table Single Zone

Identical to spark ignition engines +

Evaporation Assumption

Required Input

Vibe Combustion Parameters and Ignition Delay for Reference Operating Point

Model Approach for Variation of Combustion Duration and Vibe Parameter m dependent on

Engine Speed and Ignition Delay

5.06.0

,

ref

ref

refccn

n

AF

AF

3.0

,

,

6.0

refIVC

refIVC

refIVC

IVCref

refn

n

T

T

p

p

id

idmm

Ignition delay according to relations found by Andree and Pachernegg (exceeding

Temperature*Time Integral threshold)


PREDICTED ROHR FOR COMPRESSION IGNTION ENGINES /1 AVLMCC COMBUSTION MODEL

AVLMCC Combustion Model

Model Approach

Mixture controlled combustion (MCC) part of

heat release is controlled by fuel

quantity available and the spray

induced turbulent kinetic energy

density.

Premixed combustion

is modeled by a vibe function which

parameters are determined from the ROI

(Rate of Injection) considering Ignition

delay.

Combustion process stages

Injection Turbulence Evaporation Ignition Delay Combustion


PREDICTED ROHR FOR COMPRESSION IGNTION ENGINES /4 AVL MCC COMBUSTION MODEL

PL1

SB1 SB2

MP1

MP2

MP3

MP4 MP5 MP6 MP7 MP8 MP9

MP10 MP11 MP12 MP13MP14 MP15

MP16

MP17 MP18

MP19

MP20

CO1

TC1

J1

J2

J3J4

1

2

3

4 5 6 7 8 9

10 11 12 13 14 15

16 17

18 19

20

21

CO2

CAT122

R1

CO3

23

24

25

J5

2627

J6

J7

28

R2

29

30

C1 C2 C3 C4 C5 C6

MP21

MP22

MP23

MP24

R3

31

CL1

32MP25

R4

33

p_11, T_11

p_21, T_21

p_2_1, T_2_1

p_IM, T_IM

p_41, T_41, NOx_S1, ...

Intake Throttle

EGR Valve

p_EGR, T_EGR

T_EGRHEOp_31_1, T_31_1 p_31_2,

T_31_2

TAZ6TAZ2 TAZ3

Wastegate

Air Cleaner

Charge Air Cooler

Exhaust Gas Treatment Devices

Intake Manifold

-20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120

Crankangle [deg]

RO

HR

[J/d

eg]

0

20

40

60

80

100

120

140

160

180

200

Basis1_Ah_0038.50%.1800

Basis1_Ah_0038_MCC.50%.1800

1-zonig Analyse der 1-zonigen Sim.

1-zonig Analyse der 2-zonigen Sim.

Engine Speed rpm 1800.0

Compression Ratio - 18.500Energy Balance - 1.0149

Burn_bst_MCC_Ah38_B50.cly

BMEP [bar] 8.8542

BMEP [bar] 9.0688

MFB10 [deg] 7.4354MFB10 [deg] 6.7318

MFB50 [deg] 16.648

MFB50 [deg] 16.089

MFB90 [deg] 31.985

MFB90 [deg] 27.916

Calibration Parameters

Cmod combustion constant Cdiss dissipations constant Cturb turbulent constant CNO NOx formation constant Cign ignition delay constant

Project Experience

Parameters are engine specific but for than valid for a wide range

of operating points


PREDICTED ROHR FOR COMPRESSION IGNTION ENGINES /5 HCCI COMBUSTION MODEL

Single Zone HCCI

Simulation based on General Species Transport

CHEMKIN compatible

no CHEMKIN needed

arbitrary no. of species (CO, CO2, H2, O, H, ...)

arbitrary no. of chemical reactions (two sets for unburned

and burned Zone Chemistry) C7H16 + O2 = C7H15-1 + HO2 2.500E+13 0.0 48810.0

C7H16 + O2 = C7H15-2 + HO2 2.800E+14 0.0 47180.0

C7H16 + H = C7H15-1 + H2 5.600E+07 2.0 7667.0

C7H16 + H = C7H15-2 + H2 4.380E+07 2.0 4750.0

C7H16 + OH = C7H15-1 + H2O 8.600E+09 1.10 1815.0

nSpcGas

i

ii

F

d

dwu

d

dQ

1


PREDICTED ROHR FOR COMPRESSION IGNTION ENGINES /6 HCCI COMBUSTION MODEL

6 Zone HCCI Combustion

6 zones

General species transport

Non uniform species distribution in zones

2 Heat Transfer

Zone to zone (engery potential driven)

Boundary zone to wall

Isooctane mechanism (~291 species 875 reactions in CHEMKIN Format)

Kozarac et al.: SAE 2010-01-1083


BOOST CLASSIC / GENERAL SPECIES TRANSPORT

Utilites

Calculated

ROHR

Pre-defined

ROHR

Classic General

Vibe (1zone, 2zone, Hires,...)

Table (1zone, 2zone)

Diesel: MCC

Gasoline: Fractal

HCCI -

User Coded Combustion Models

Set Conditions at SHP

General Species Transport

Flexibility

CHEMKIN Chemistry can be used comfortably in BOOST (HCCI)

Coupling of Combustion-, Emission- and Aftertreatment models


BOOST-FIRE COMBUSTION & EMISSION SIMULATION

BOOST ESE-Diesel Link

3D Combustion through ESE Diesel BOOST

Coupling

BOOST Automatically Initialize and Starts

ESE Diesel Calculations for The Combustion

Phase

Modes of Coupling:

HPC-mode: Combustion

Calculated for One BOOST

Cylinder and ROHR Copied

to the Others

MHPC-mode: Combustion

Calculated for Each BOOST

Cylinder Individually

Engine Simulation Environment - Diesel

2 значения m avl.pdf

Documents

bras rohr input

zone table

spark ignition engines

energy rohr input

predictive combustion

combustion progress

avlboost combustion

ignition timing