Avl

AVL-BOOST COMBUSTION MODELS [email protected]

ROHR (Rate Of Heat Release) CLASSIFICATION  Spatial Discretization

 Single Zone  Two Zone

(Zero-Dimensional) (Quasi-Dimensional)

 Ignition Type (Mixture Preparation)

 Spark Ignition  Compression Ignition  ROHR Type  ROHR Input  ROHR predicted by Combustion Model  Source  Standard BOOST  User Coding

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SPATIAL DISCRETIZATION / SINGLE ZONE Governing Equations 

Energy Conservation

d mc  u  dQ dV dQF dm   pc     w  hBB  BB d d d d d  Perfect Gas Equation

pc 

1  mc  R  Tc V

 Thermodynamic State Vector

 c      pc  Sc    T  c  C   c

C 

   Cc

C

 mf FB      mfCP   mf   FV 

   Cc

G

 mf1    mf    1 .    mf   n



c C /G

BOOST_CombustionModels_2011_Bras

Classic / General Species Transport 3

SPATIAL DISCRETIZATION / TWO ZONE /1

dQF

dQWb pc , ub , mb , Rb , Tb dQWu

hu dmb pc , uu , mu , Ru , Tu

pc dV

 Energy Conservation for burned and unburned Zone

dmbub dV dQ   pc b  F  d d d dmBB ,b dmb   dQWb  h  h   d u d  BB ,b d dmBB ,u dmu uu dV dQ dmb   pc u   Wu  hu  hBB ,u d d d d d  Perfect Gas Equation

pc 

1  mb  Rb  Tb  mu  Ru  Tu  V

 Thermodynamic State Vector

hBB ,b dmBB ,b  hBB ,u dmBB ,u BOOST_CombustionModels_2011_Bras

   Sburned   Sc      Sunburned 4

ROHR INPUT FOR SPARK IGNITION ENGINES /1 Vibe Single Zone  ROHR Approach  m1  dQB a  QBT  m  1  y m  e a y d  c

y

 o  c

... Combustion Progress

 Released Energy  m 1    0     a       QB    QBT 1  e    

 Parameter Data Source  Fitting Result of Combustion Analysis Tool (BOOST-Burn)  Experience BOOST_CombustionModels_2011_Bras

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ROHR INPUT FOR SPARK IGNITION ENGINES /2 Table Single Zone  Adaptation

For physical reasons preprocessing performed to guarantee monotonic increase of Fuel Burned

 Data Source Result of Combustion Analysis Tool (BOOST-Burn)

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ROHR INPUT FOR SPARK IGNITION ENGINES /3 Vibe Two Zone / Table Two Zone

Hires et al  Required Input

 Same ROHR Approach as for Single Zone

Vibe Combustion Parameters and Ignition Delay for Reference Operating Point

 State Vector of Burned Zone allows to calculate:

 Model Approach for Variation of Ignition Delay and Combustion Duration dependent on Engine Speed

 NOx Production (Extended Zeldovich)

1/ 3

 CO Production (Onorati)

 c   c ,ref

 State Vector of Unburned Zone allows to calculate:  Required Octane Number

1 ON  100 A 

t85% MFB



t SOC

BOOST_CombustionModels_2011_Bras

n

pe



B TUBZ

 dt   

1 a

id  id ref

 n f ref     n   ref f 

 n  n  ref

1/ 3

   

 sref    s

 f sref     f   ref s 

  

2/3

2/3

s ... laminar flame speed f ... piston to head distance at ignition timing 7

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, loadsignal) 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

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PREDICTED ROHR FOR SPARK IGNITION ENGINES /2 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)

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PREDICTED ROHR FOR SPARK IGNITION ENGINES /3 FRACTAL COMBUSTION MODEL Characteristics /2

Mandelbrot Set

 This wrinkling effect is driven by the incylinder 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.

Burned Gas

 Fractal is a mathematical method describing irregular geometry with self similarity (length of British coast?).

u’

SL L

SL Unburned Gas SL BOOST_CombustionModels_2011_Bras

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PREDICTED ROHR FOR SPARK IGNITION ENGINES /9 FRACTAL COMBUSTION MODEL 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 )

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PREDICTED ROHR FOR SPARK IGNITION ENGINES /10 FRACTAL COMBUSTION MODEL BSFC [g/kWh]

Project Experience

• The fractal combustion model has the potential to predict the influence of the valve timing variation on the rate of heat release.

Res. Gas [%]

• 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.

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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

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ROHR INPUT FOR COMPRESSION IGNTION ENGINES /1 Vibe Single Zone  ROHR Approach  m1  dQB a  QBT  m  1  y m  e a y d  c

y

 o  c

... Combustion Progress

 Parameter Data Source  Fitting Result of Combustion Analysis Tool (BOOST-Burn)

 Experience  Evaporation Assumption  ROE (Rate of Evaporation) is direct linked to ROHR dmFV 1 dQB  d H u d BOOST_CombustionModels_2011_Bras

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ROHR INPUT FOR COMPRESSION IGNTION ENGINES /2 Double Vibe (Single Zone)  ROHR Approach

Superposition of 2 Vibe Functions to meet Premixed Combustion Peak and/or more Complex Injection Strategies

dQB  dQB   dQ    B   d  d Vibe1  d Vibe2  Parameter Data Source  Fitting Result of Combustion Analysis Tool (BOOST-Burn)  Experience

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ROHR INPUT FOR COMPRESSION IGNTION ENGINES /3

Table Single Zone

Woschni/Anisits

 Identical to spark ignition engines +

 Required Input Vibe Combustion Parameters and Ignition Delay for Reference Operating Point

Evaporation Assumption

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) BOOST_CombustionModels_2011_Bras



Model Approach for Variation of Combustion Duration and Vibe Parameter m dependent on Engine Speed and Ignition Delay

 c   c ,ref

 AFref    AF

 id ref m  mref    id 

  

0.6

  

0.6

 n  n  ref

 pIVC  p  IVC ,ref

   

0.5

  TIVC ,ref    T   IVC

  n       nref

   

0.3

Ignition delay according to relations found by Andree and Pachernegg (exceeding Temperature*Time Integral threshold)

16

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

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

3

Intake Manifold

PL1 31

p_IM, T_IM

Calibration Parameters

25 R3 p_EGR, MP23

T_EGR

4 MP4

CO3

6

MP5

7 MP6

8 MP7

9 MP8

MP9

    

24 R1

p_2_1, EGR T_2_1 MP3 Valve

MP21

23 C1 TAZ2 C2 TAZ3 C3 MP11 MP13 MP12 10 11 12 J2 16 26

MP10 CO2

CO1

5

MP22 27

T_EGRHEO

J5

Charge Air Cooler

J1

MP14 13

p_31_1, T_31_1 MP17

p_21, T_21

C5 TAZ6 C6 MP15 14 15

17

J4

J3

MP16

MP18 p_31_2,

18 R4 2

C4

T_31_2

19 J7

Cmod Cdiss Cturb CNO Cign

combustion constant dissipations constant turbulent constant NOx formation constant ignition delay constant

33 28

MP2

29 TC1

R2

p_11, T_11

MP19

MP1

30

20

CL1 SB1 MP25

Wastegate

J6 32

1

CAT1

21

SB2

22 MP24

MP20

Project Experience

p_41, T_41, Exhaust Gas NOx_S1, ... Treatment Devices

Air Cleaner Burn_bst_MCC_Ah38_B50.cly

Basis1_Ah_0038.50%.1800 Basis1_Ah_0038_MCC.50%.1800

 Parameters are engine specific but for than valid for a wide range of operating points

1-zonig Analyse der 1-zonigen Sim. 1-zonig Analyse der 2-zonigen Sim.

200

Engine Speed rpm Compression Ratio Energy Balance -

180

1800.0 18.500 1.0149

160

ROHR [J/deg]

140

BMEP BMEP MFB10 MFB10 MFB50 MFB50 MFB90 MFB90

120

100

80

[bar] [bar] [deg] [deg] [deg] [deg] [deg] [deg]

8.8542 9.0688 7.4354 6.7318 16.648 16.089 31.985 27.916

60

40

20

0 -20

-10

0

10

20

30

40

50

60

70

80

90

100

110

120

Crankangle [deg]

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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, ...)

C7H16 C7H16 C7H16 C7H16 C7H16

+ + + + +

O2 O2 H H OH

= = = = =

C7H15-1 C7H15-2 C7H15-1 C7H15-2 C7H15-1

+ + + + +

HO2 HO2 H2 H2 H2O

BOOST_CombustionModels_2011_Bras

2.500E+13 2.800E+14 5.600E+07 4.380E+07 8.600E+09

0.0 0.0 2.0 2.0 1.10

48810.0 47180.0 7667.0 4750.0 1815.0

 arbitrary no. of chemical reactions (two sets for unburned and burned Zone Chemistry) dw dQF nSpcGas   ui   i d d i 1 19

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_CombustionModels_2011_Bras

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BOOST CLASSIC / GENERAL SPECIES TRANSPORT

Classic Pre-defined ROHR Calculated ROHR

Utilites 

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

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BOOST-FIRE COMBUSTION & EMISSION SIMULATION

BOOST ESE-Diesel Link

Engine Simulation Environment - Diesel

 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 BOOST_CombustionModels_2011_Bras

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