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Overview of Ricardo's CFD modelling tools

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Overview of Ricardo's CFD modelling tools Powered By Docstoc
					Gasoline & Diesel Engineering Fluid Simulation Tools
Ricardo Japan TSA Visits November 2005
RD.05/406501.1

© Ricardo plc 2005

Agenda

 Background

 Combustion System Simulation

 Intake, Exhaust and Aftertreatment System

 Engine Thermal Modelling

 Crankcase Breathing

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 Vehicle Simulation

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Agenda

 Background  Combustion System Simulation

 Intake, Exhaust and Aftertreatment System
 Engine Thermal Modelling  Crankcase Breathing  Vehicle Simulation

© Ricardo plc 2005

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Background
 Simulation technology has ability to reduce product development cycle significantly

 Principal requirements are: – Robust analysis methodology capable of capturing major physical parameters through direct modelling or correlated database information – Rapid analysis toolset to provide engineering direction for component / system / powertrain development – Validated modelling approach allowing predictive application to engineering projects

© Ricardo plc 2005

Presentation will outline fluid simulation application processes to allow technologies application on powertrain development projects leading to reduced product development cycles

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Agenda

 Background  Combustion System Simulation

 Intake, Exhaust and Aftertreatment System
 Engine Thermal Modelling  Crankcase Breathing  Vehicle Simulation

© Ricardo plc 2005

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Combustion System Simulation

 Combustion system tools and techniques research forms primary stages in application of simulation to combustion system development  Tools and techniques allow predictive application of some modelling technology to development Experimental techniques to measure fundamental physical processes for basic validation of CFD codes Ongoing detailed tools and techniques programme measuring gasoline and diesel fuel spray behaviour under realistic engine operating conditions Development of modelling processes following fundamental validation for application to engineering programmes Continual process of methodology evolution and development with validation against test programmes where applicable
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© Ricardo plc 2005

Fuel Spray Measurement and Validation

 Gasoline spray and mixture measurement – Quiescent fuel spray characterisation – MIE scattering measurements in motored engine • homogeneous operation • stratified operation – Quantitative LIF measurement

Mie Camera

Optical Engine

Laser Sheet

Viewing Annulus LIF Camera

 Diesel spray and mixture measurement – Quiescent spray bomb characterisation – Ricardo Diesel spray rig • Provides cylinder conditions close to engine cylinder conditions
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 Validation techniques applied to VECTIS and Star CD
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Combustion System

Gasoline Engine Application Process

 Gasoline combustion system design support

 3D CFD simulation applications include – PFI and GDI combustion system development – Cold start mixture preparation simulation – Combustion and emissions prediction for conventional or HCCI operation – Knock prediction development

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Gasoline Engine Application Process

 Principal issues for simulation focus – Geometry definition • Model exactly what will or has been tested – Spray modelling • Injector characterisation and spray match – Wall film prediction – Boundary conditions • Flow conditions (high speed pressure data from 1D / test) • Thermal boundary conditions
© Ricardo plc 2005

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Combustion System

Case Study – Gasoline HCCI

 Ricardo Gasoline Engine HCCI combustion Research

Two-stroke engines Conventional engines

Modelling tools WAVE VECTIS

Four-stroke engines Conventional engines

Optical engines

1-D

3-D

Optical engines

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Combustion system design
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Combustion System

Case Study – Gasoline HCCI

 Uncertainties encountered in the modeling study of HCCI engine combustion – Charge inhomogeneity • Thermal inhomogeneity • Composition inhomogeneity – Trapped conditions • High percentage of trapped residuals, difficult to measure experimentally

 Simulation strategy – Full 3-D CFD simulation to cover all processes included in the engine cycle – Multi-cycle simulation approach to eliminate the uncertainties regarding trapped conditions – Compact ignition and combustion models for computational efficiency
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Combustion System

Case Study - 2-stroke Gasoline HCCI

 Engine Configuration – Upright intake ports – 4 poppet valves – Pent roof combustion chamber – Flat piston – Swept volume 325cc – Compression ratio 9.0 – Loop scavenging

TDC

 Valve and injection timing
IVC
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EVO CA

EVC
SOI BDC

IVO

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Combustion System

Case Study - 2-stroke - Simulation Cases

Case number Engine speed [rev/min] IMEP [bar] Overall AFR
4.5 4.0 IMEP [bar] 3.5 3.0 2.5 2.0 1.5
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A 2250 1.967 19.39

B 2753 2.61 18.67

C 3255 3.834 19.17

D 3258 1.566 19.15

C
HCCI Operation B A D

1.0 1000

1500

2000 2500 Engine Speed [rev/min]

3000

3500
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Combustion System

Case Study – 2-stroke – Simulation Approach

 Start position after the end of combustion but before exhaust valve opening – Initial cylinder pressure from experimental measurement – other initial conditions estimated  Pressure boundary conditions applied at the intake port entrance and exhaust port exit – Boundary pressures taken from the recorded dynamic pressures from engine test  Multi-cycle combustion simulation performed until a cyclically-converged solution obtained – Ignition control variable and combustion species re-initialized once every cycle  Ignition model scaling coefficient Cig tuned in the first case, then kept unchanged for the remaining simulations – No tuning of combustion model performed
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Combustion System

Case Study – 2-stroke – Simulation Results: In-cylinder Processes

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Combustion System

Case Study – 2-stroke – Simulation Results: Charge Inhomogeneity

 Under 2-stroke operation the in-cylinder charge inhomogeneity can be significant  A quantitative description of inhomogeneity can be provided by using the distribution density function – DDF - a probability density function of the representative variables
25.0

Distribution density function

20.0 15.0 10.0 5.0 0.0 0.30

310deg 320deg 330deg 340deg 350deg

CA CA CA CA CA

0.35

0.40

0.45

0.50

0.55

0.60

0.65

0.70

Residual mass fraction
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Combustion System

Case Study – 2-stroke – Simulation Results: NOx Emission

 NOx prediction based on the extended Zeldovich mechanism, considering thermal NO only  NOx volume fraction monitored at the far end of exhaust port and averaged over a cycle

Case number Measured NOx [ppm] Predicted NOx [ppm]
 Correct trend and order of magnitude  A general over-prediction of 30%

A 13.1 0.046

B 164.6 223.2

C 520.6 715.9

D 34.0 53.6

 Under-prediction in Case A may be attributed to neglecting prompt NOx
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Combustion System

Diesel Engine Application Process

 HSDI combustion system development simulation support – 1D performance simulation • Advanced air handling and EGR system development • Advanced aftertreatment modelling – 3D CFD simulation • Fuel – air mixing and combustion for bowl design and swirl development • Combustion prediction for emissions modelling – Intake port development • Steady state air motion development
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© Ricardo plc 2005

Combustion System

Diesel Engine Application Process

 Pragmatic approach for rapid application to diesel combustion system simulation – 3D CFD analysis for base system definition • Rapid assessment of critical hardware – Swirl level, chamber design • Specification of initial system for engine demonstration – FIE requirements – Air motion requirements • Full load/part load compromise – Compression ratio selection – Combustion chamber geometry definition • Combustion modelling for emissions prediction – Engine testing for detailed development using DoE based calibration • Tuning of protrusion and nozzle flow • Engine calibration – EGR rate, injection timing, injection specification
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© Ricardo plc 2005

Diesel Engine Application Process

 Combustion system issues for accurate simulation
– Geometry definition • Compression ratio volume match • Trapped mass – Imposition of boundary conditions for closed cycle simulation – Multiple full cycle simulations to converge trapped conditions – Coupled 1D/3D in-cylinder for complete engine system modelling – Spray modelling • Fundamental spray match has developed accurate process for modelling – Combustion modelling • Application of RTZF model in VECTIS

© Ricardo plc 2005

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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance
Methodology – Overall Approach  Geometry assembly – Closed volume at IVC  Mesh generation

© Ricardo plc 2005

 Analysis – Fuel/air mixing only – Analysis starts at IVC • Post-processing • Results analysis and engineering review is always critical
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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance

Methodology - Fuel Spray Modelling  Multi-dimensional modelling of in-cylinder flow and spray – Gas phase • Equations solved in 3-D, Cartesian co-ordinates for conservation of mass, momentum, energy and k- turbulence model – Liquid phase • Discrete droplet model • Lagrangian tracking of droplet parcels and heat and mass transfer through mesh for PDE solution • Sub-models – Huh-Gosman atomisation model – Secondary droplet break-up • Reitz-Diwakar • Liu-Mather-Reitz • Patterson-Reitz – Droplet-turbulence interactions – Droplet-droplet interactions • Validated against diesel spray rig
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© Ricardo plc 2005

Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance
Methodology – Results Analysis  Velocity and fuel vapour field plots require experience and time to interpret – Move towards quantitative representations of data though development of objective measures to quantify changes – Criteria developed and measurable parameters correlated against engine data  Assessment methodology for fuel/air mixing – 2 level zone analysis • Combustion chamber split into distinct zones • Equivalence ratio and fuel vapour distribution within each zone is assessed

© Ricardo plc 2005

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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance

 Combustion system demonstrator program requiring “right first time” development approach  Program targets – Rated power > 60 kW/l – Peak torque > 200 Nm/l – EURO 4 emissions level

 Results shown for initial nozzle specification study comparing 6 hole against 7 hole for the same flow specification

© Ricardo plc 2005

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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance
Methodology – Results Overview

6 vs 7 Hole Nozzle Study - Favourable Zone
300

Fuel/Air Mixture Mass (mg)

250 200 150 100 50 0 340 350 360 370 Crankangle (deg)
Case1l_Stoich Case1d_Stoich Case1l_Rich Case1d_Rich

6 hole nozzle shows improved mixing within favourable zone Increased combustible mixture present
380 390 400

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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance
Methodology – Results Overview

6 vs 7 Hole Nozzle Study - Unfavourable Zone
100 90

Fuel/Air Mixture Mass (mg)

80 70 60 50 40 30 20 10 0 340 350 360 370 Crankangle (deg)
Case1l_Stoich Case1d_Stoich Case1l_Rich Case1d_Rich

380

390

400

7 hole nozzle shows worse mixture retention - Increased combustible and rich mixture close to bore wall

© Ricardo plc 2005

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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance
Methodology – Results Overview

6 vs 7 Hole Nozzle Study - Zone D
200 180

Fuel/Air Mixture Mass (mg)

160 140 120 100 80 60 40 20 0 340 350 360 370 Crankangle (deg)
Case1l_Stoich Case1d_Stoich Case1l_Rich Case1d_Rich

7 hole nozzle shows less bowl interaction with reduced mixture in Zone D
380 390 400

© Ricardo plc 2005

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Combustion System

Case Study – Diesel Fuel/Air Mixing for High Performance

Comparison of Combustion System Performance from Test Data
Comparison of Smoke vs AFR Performance at 4000rev/min 3

Filter Smoke /(FSN)

6 hole nozzle shows improved smoke/AFR trade off performance
2

1 6 hole - 1.25mm protrusion - Case 1l 7 hole - 1.25mm protrusion - Case 1d 0

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14

16

18

20

22

24

26

28

Spindt AFR
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Case Study – Diesel Combustion Modelling

Ricardo Two Zone Flamesheet Model Explanation  Overview – Auto-ignition by delay probability integral – Simplified coherent flamesheet model with two-zone gas representation – Emissions chemistry post-processing  Two-zone model – Burnt and unburnt  Each zone has its own enthalpy, fuel mass fraction and air mass fraction  Transport equations solved for
– 6 mass fractions, 1 auto-ignition PDF, 4 segregation mass fractions, 2 emissions, 3 enthalpies

 3 temperatures calculated for each cell – Overall, burned and unburned
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 Fast reactions based on chemical equilibrium calculations – 11 species
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Case Study – Diesel CFD Combustion Simulation

Analysis Process  Two-stage simulation – Compression stroke simulation from IVC to SOI • Swirl imposed as solid body rotation at IVC (based on steady flow rig data) • Trapped mass calculated based on measured fuelling and air/fuel ratio (including EGR) • Solving for momentum, continuity, turbulence and energy – Spray and combustion simulation from SOI to EVO • Spray: Lagrangian discrete droplet method with Patterson-Reitz droplet breakup model • Combustion: RTZF combustion model • NOx: extended Zeldovich NOx model
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© Ricardo plc 2005

Case Study – Diesel CFD Combustion Simulation

Operating Conditions

 HSDI engine running at full load – 4000 rev/min full load – Injection timing swing

 Combustion modelling prediction – Development of fuel/air mixing analysis process – Animation showing temperature distribution within chamber at rated speed full load
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Case Study – Diesel CFD Combustion Simulation

Combustion Modelling Results  Cylinder pressure trends well produced

Measured vs Predicted Pmax
170

Maximun Cylinder Pressure [Bar]

160 150 140 130 120 110 100 -18 -16 -14 -12 -10 -8 -6

Measured Vectis

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-4

-2

Start of Injection [CAdeg]
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Case Study – Diesel CFD Combustion Simulation

Combustion Modelling Results  NOx emissions trend well reproduced
Measured vs Predicted NOx
3000 Measured 2500 2000 Vectis

NOx [ppm]

1500 1000 500 0 -18 -16 -14 -12 -10 -8 -6 -4 -2

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Start of Injection [CAdeg]

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Case Study – Diesel CFD Combustion Simulation

Combustion Modelling Summary  Combustion modelling experience shows cylinder pressure generally well reproduced – Over-predicted at earlier timings – Under-predicted at later timings – SOC generally captured well  NOx emissions trend well reproduced – NOx decreases with injection retard – Follows cylinder pressure trend • NOx over-predicted at early timings • NOx under-predicted at later timings  CFD analysis provides valuable information and understanding the HSDI combustion processes to support analytical system development

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 Routine application to diesel system development including: – Air motion generation and requirements – Combustion chamber geometric configuration – FIE system configuration
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Agenda

 Background  Combustion System Simulation

 Intake, Exhaust and Aftertreatment System
 Engine Thermal Modelling  Crankcase Breathing  Vehicle Simulation

© Ricardo plc 2005

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Intake, Exhaust and Aftertreatment

Intake System Simulation Applications

 Intake system – 1D performance simulation • Intake system design • Boosting system design and development – 3D CFD • Flow performance prediction • AFR distribution prediction • EGR distribution prediction – Flow testing • Manifold flow assessment
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Intake, Exhaust and Aftertreatment

Exhaust System Simulation Applications

 Exhaust system – 1D performance simulation • Exhaust system design • Boosting systems • Warm-up modelling

– 3D CFD • Flow distribution assessment • Transient performance predictions • Coupled fluid/thermal modelling • Catalyst flow predictions
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Intake, Exhaust and Aftertreatment

Intake and Exhaust System Simulation Methodology
 Coupled 1D/3D simulation used extensively as a routine application on exhaust and intake system modelling – Improved modelling for 1-D simulation – Improved boundary conditions for 3-D simulation – Provide a tool to address a wide range of technical problems • Intake system – Air / EGR distribution • Exhaust system – Flow performance / catalyst flow distribution • EGR system – Flow performance / dynamic behaviour – Assess impact of development on engine performance  Integration is characterised by coupling at a time-step level the 1-D gas dynamic code (WAVE) and a 3-D CFD code (VECTIS/STAR-CD)

© Ricardo plc 2005

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Intake, Exhaust and Aftertreatment

Case Study – Exhaust System Simulation

Background  Base manifold design support project using CFD and FE analysis to drive manifold design

 Vehicle application required use of close coupled catalyst but package constraints were stringent

 Focus of fluid simulation – Assess performance benefit of 4-2-1 compared to 4-1 manifold – Assess catalyst flow distribution and recommend design development – Assess sensor location
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Design 2b

Design 1
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Intake, Exhaust and Aftertreatment

Case Study – Exhaust System Simulation

Analysis Process  Engine package models integrated rapidly into CFD tool and mesh generated automatically  Catalyst model used test data to match test rig pressure drop

1-D flow region

 Coupled 1D/3D analysis undertaken at part load 50 km/hr cruise condition – 1600 rev/min 15 Nm torque  Coupled 1D/3D uses shadow 1-D network for “n” cycles followed by embedded 3-D model with full two-way exchange of boundary conditions at time step level

© Ricardo plc 2005

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Intake, Exhaust and Aftertreatment

Case Study – Exhaust System Simulation

Assessment Criteria  Flow distribution assessed in three ways – Maldistribution - SAE 910200 – Uniformity index (g) - SAE 960564 – Cumulative velocity PDF
Cumulative Probability

Velocity PDF - Full Load
1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 Velocity (m /s)

© Ricardo plc 2005

1   1  2n i 1

n

( wi  wm ean) 2 wm ean
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Intake, Exhaust and Aftertreatment

Case Study – Exhaust System Simulation

Part Load Simulation Results
Velocity PDF
1 0.9 0.8 0.7

Design 1
1.0 0.9 0.8 0.7

Velocity PDF

Design 2b

Cumulative Probability

0.6 0.5 0.4 0.3 0.2 0.1 0 1.00

Cumulative Probability

0.6 0.5 0.4 0.3 0.2 0.1 0.0 1.0 1.5 2.0 Velocity (m /s) 2.5 3.0 Design 1 (Uniformity Index = 0.93) Design 2b (Uniformity Index = 0.99)

1.50

2.00 Velocity (m /s)

2.50

3.00


© Ricardo plc 2005

PDF indicates reasonably well distributed flow Uniformity index = 0.93

 

Velocity PDF indicates better velocity distribution compared to Designs 1 and 2 Uniformity index = 0.99



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Intake, Exhaust and Aftertreatment

Case Study – Exhaust System Simulation

Sensor Location Assessment

 Assessment of sensor location based on individual cylinder contribution to flow at specified sensor location
 Design 1 shows a good balance of individual cylinders present at baseline sensor position

Design 1

Design 2b

© Ricardo plc 2005

 Design 2 shows a poor balance of individual cylinders present at “design” O2 sensor position – Dominated by CYLINDER 2
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Intake, Exhaust and Aftertreatment

Case Study – Exhaust System Simulation

Alternative Lambda/O2 Sensors  Design 2 Part Load – Alternative sensor locations assessed rapidly through extraction of revised simulation results for various locations

Sensor 1

© Ricardo plc 2005

Sensor 2

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Intake, Exhaust and Aftertreatment

Aftertreatment Simulation - Emissions Control Technology (ECT) Model Range
Background  Diesel – Diesel Oxy-Catalyst (DOC) – Diesel Particulate Filter (DPF) • (including CRDPF and CDPF) – Lean NOx Traps (LNT) – Urea Selective Catalyst Reduction (SCR)  Gasoline – Three Way Catalyst (TWC) – Lean NOx Traps (LNT) DPF flow

© Ricardo plc 2005

CRDPF
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Intake, Exhaust and Aftertreatment

Aftertreatment Simulation – Methodology

ECT System Design

DPF SCR
Exhaust system building from component blocks

DOC

Common vectorised approach passes species from unit to unit

DOC
© Ricardo plc 2005

DPF

SCR

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Intake, Exhaust and Aftertreatment

Methodology – ECT General Model Structure

ECT General Model Structure
maf T

Engine
Speed Load

maf P T O2

maf

Thermal sub-model

P

T
O2 NO NO2 Pm

MAPS

emissions

NO NO2 Pm HC

Geometry Material properties
© Ricardo plc 2005

CO
SOx CO2 etc.

Catalysis sub-model

Pressure sub-model

HC CO SOx CO2

etc.
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Case Study – Aftertreatment Assessment of Exhaust System Layout

Background  Project to assess a number of different exhaust configurations in different vehicle packages (Front facing, rear facing, CC CDPF)  Analysis set-up as shown (test data based)  Investigations included assessment of – System specification including insulated pipes – Different catalyst specifications

© Ricardo plc 2005

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Case Study – Aftertreatment Assessment of Exhaust System Layout

Example Cycle Emissions Data
CO cumulative
1.4E-02

Engine out
1.2E-02

1.20 g/km

DOC CC
1.0E-02

DOC UF

8.0E-03

(kg)
6.0E-03 4.0E-03

 Example comparison of cumulative emissions post DOC for under floor against close coupled

0.40 g/km

2.0E-03

0.0E+00 0 200 400 600 800 1000 1200

time (s)

HC cumulative
3.0E-03 Engine out 2.5E-03 DOC CC DOC UF

0.24 g/km

2.0E-03

(kg)

1.5E-03

1.0E-03

0.09 g/km

5.0E-04

© Ricardo plc 2005

0.0E+00 0 200 400 600 time (s) 800 1000 1200

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Case Study – Aftertreatment Assessment of Exhaust System Layout

Conversion Matrix for Assessed System Configurations
Conversion m atrix
85% 83%
B1

81%
CO c onv ersio n (%)

B B2 D E ins D ins

79% 77%
E

75%
A' A ' ins

73% 71%
C2 C3 F C1 F ins

69%
A ins

C

67%
© Ricardo plc 2005

65% 60%

65%

70%

75%

80%

85%
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H C conversion (%)

Aftertreatment Simulation – Methodology

Coupling V-SIM ECT & CFD Methodology  Co-simulation: V-SIM ECT models can be linked to VECTIS or Star CD to increase the resolution of the airflow and concentration distribution over the catalyst front face I.e. SCR system simulation  Link 1-D chemistry and thermal models from the VSIM environment to a CFD airflow prediction model  Investigate parameters including – Light off of close-coupled catalyst – Ammonia slip  Analysis of airflow maldistribution impact on emissions performance and potential cost/benefit ratio investigations from package/aftertreatment configuration changes
© Ricardo plc 2005

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Aftertreatment Simulation – Methodology

Coupling V-SIM ECT & CFD Methodology  CFD simulation at selected engine keypoints – Output transient flow distribution on the catalyst face – Average flow over entire engine cycle

+

+
© Ricardo plc 2005

SUM / Nsteps

+
CYCLE AVERAGE RESULTS
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+

Aftertreatment Simulation – Methodology

Coupling V-SIM ECT & CFD Methodology  CFD simulation output – Discretise front face according to zones of similar mass airflow

© Ricardo plc 2005

 Use outputs from front face discretisation (average airflow in each zone, heat transfer area between zone i and zone j) to connect a set of 1D ECT models together, ultimately providing a 3D model
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Agenda

 Background  Combustion System Simulation

 Intake, Exhaust and Aftertreatment System
 Engine Thermal Modelling  Crankcase Breathing  Vehicle Simulation

© Ricardo plc 2005

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Engine Thermal Modelling

Base Engine Thermal Development

Background  Toolset for application to thermal development of base engine components  Engineering development applied through use of advanced analysis tools providing understanding of principal issues  Fluid simulation analysis capabilities include: – Steady flow coolant circuit simulation coupled to external circuit modelling – Coupled fluid/thermal simulation for steady state and transient engine thermal modelling
© Ricardo plc 2005

COMPLETE ENGINE ASSEMBLY MODELLING
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Engine Thermal Modelling

Base Engine Thermal Development
Background  Principal tools applied – Conjugate heat transfer analysis • Localised coolant warm-up effect modelled with nucleate boiling and buoyancy modelling in low / no flow regimes – Steady state and transient thermal predictions with transient thermal boundary condition application for warm-up/drive cycle simulation – Prediction of: • Peak temperature distribution during early engine definition, capturing cylinder to cylinder variation in metal temperatures • Thermal shock modelling • Engine warm up modelling during cold start • Heat soak thermal prediction • Assessment of thermal sensor location for capture of engine response • Detailed engine thermal mapping for application of controlled cooling flow regimes
0.4 381 1020 1.0
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velocity

temperature

density

Void fraction

Heating surface starts

Heating surface ends

NUCLEATEVelocity (m/s) BOILING VALIDATION 0.20
0.41.0 363 60 0.45 10204 Temperature (K) Density (kg/m3) 3812

© Ricardo plc 2005

0.2 363 60 0.0

Velocity (m/s) Temperature (K) Density (kg/m3) Void fraction

Engine Thermal Modelling

Base Engine Thermal Development

Coolant Flow Simulation  Application of CFD analysis to optimise the coolant flow system for: – Cylinder to cylinder flow distribution – Flow within recommended velocity guidelines – Strategic cooling and heat transfer in critical areas – Minimisation of areas of stagnant flow and excessive flow velocity – Minimum pressure drop – Fast warm-up  Engineering solutions to issues delivered rapidly to address project issues

© Ricardo plc 2005

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Engine Thermal Modelling

Base Engine Thermal Development

Coolant Flow Simulation

 Poor cooling of upstream inlet/exhaust valve bridge

 Features added to guide alternative source of flow

© Ricardo plc 2005

 Head coolant volume reduced by sculptured water jacket (0.7l)
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Engine Thermal Modelling

Base Engine Thermal Development

Nucleate Boiling Study

Head

 Complete engine assembly for half of a V-6 engine
 Fluid flow CFD domain consists of head, gasket and cylinder block – Conventional longitudinal flow regime
Liner1

Coolant in Coolant out

Coolant passage

Liner2 Liner3

 Sub-cooled nucleate boiling model developed for these applications allowed

 Assessment of boiling level and cause within engine structure
© Ricardo plc 2005

Gasket Block
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Engine Thermal Modelling

Base Engine Thermal Development

Nucleate Boiling Study  Comparison of predicted metal temperature field with boiling model

NO NUCLEATE BOILING MODELLED

NUCLEATE BOILING MODELLED
© Ricardo plc 2005

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Engine Thermal Modelling

Base Engine Thermal Development

Nucleate Boiling Study  Nucleate boiling modelling capability allows: – Assessment of risk of boiling onset within engine configuration • prevention of excessive localised boiling leading to erosion issues – Specification of system components to inhibit boiling within engine – Optimisation of cooling system to minimise boiling risk • providing optimised margin allowing for increased local heat transfer should boiling occur

© Ricardo plc 2005

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Engine Thermal Modelling

Engine Transient Thermal Modelling
Analysis Process
 Build complete engine thermal model from CAD data – Typically at least 15 major components 
COMPLETE ENGINE ASSEMBLY MODELLING Steady state or transient thermal boundary conditions calculated

– Information input included • transient engine flow rates • transient fuelling • transient gas temperature data from 1D or test data – Instantaneous heat flux calculated • Based on input data • Distribution data applied and mapped to engine structure  Simulations capabilities include: – Steady state temperature prediction • Fixed heat flux, fixed coolant flow, single time – Fixed engine condition warm-up • Fixed heat flux, fixed coolant flow, single time – Fully transient warm-up or load step engine condition change • Transient heat flux, transient coolant flow, time marching
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Case Study – Engine Transient Thermal Modelling
Engine Thermal Shock Modelling Temperature Distribution After 30 Seconds
CONVENTIONAL WATER PUMP THERMOSAT CLOSED RATED SPEED THERMAL SHOCK FROM 25°C 0 to 30 seconds

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LOW FLOW WARM-UP THERMOSAT CLOSED RATED SPEED THERMAL SHOCK FROM 25°C 0 to 30 seconds
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Case Study – Engine Transient Thermal Modelling

Summary  Transient thermal prediction tools allow system mapping and detailed modelling of powertrain thermal behaviour  Process supports: – Efficient thermal management strategies – Detailed understanding of engine thermal behaviour

© Ricardo plc 2005

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Agenda

 Background  Combustion System Simulation

 Intake, Exhaust and Aftertreatment System
 Engine Thermal Modelling  Crankcase Breathing  Vehicle Simulation

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Crankcase Breathing

Crankcase Breathing Simulation

Background

 Engineering closed crankcase breather systems essential for optimisation of engine performance, emissions and durability
 Engineering issue path – Minimise engine blow-by
• Reduce separator system flow requirements • Minimise oil carryover

– Optimisation of breather system
• Minimise pumping work for transfer of blow-by gas to intake • Optimisation of PCV valve characteristics • Maximise crankcase depression

– Component optimisation
• Separator • PCV valve
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 Engine structural implications – Bulkhead design optimisation – Crankshaft profile
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Crankcase Breathing

Crankcase Breathing Simulation

1D Analysis Methodology  Objectives
– Prediction of crankcase pumping work – Validation of boundary conditions – Investigation into bay-to-bay breather area effects

 Full gas flow path modelled in 1D with WAVE to represent complex 3D geometry
– Blow-by flow applied from test data or simulation – Bulk motion predicted in crankcase system • Interbay breathing • Oil drainback chimneys • Chain/gear case flow • Cam cover flow • PCV valve
Oil drainback chimneys

PCV valve

Blowby

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Chaincase Interbay breathing
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Crankcase Breathing

Crankcase Breathing Simulation

1D Analysis Methodology  Techniques validated for prediction of system dynamic pressures against engine testbed data  Engine performance impact on oil flow levels and rates can be considered – E.g. piston cooling jets draw additional oil from sump around 2000rpm causing level to drop at this point and as speed increases – Simulation varies the oil level with speed
Simulation Test
Range of Fluctuations (Bar) Amplitude (Bar)

Separator In

0.012 0.01 0.008 0.006 0.004 0.002 0 0 1000 2000 3000 4000 5000
Engine Speed (rpm) Test Results Vented to Ambient Simulation Results Vented to Ambient Test Results Closed System Simulation Results Closed System

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Crankcase Bay RD05/406501.1

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Crankcase Breathing

Case Study – Crankcase Breathing Simulation

 V6 Breather Circuit Study – Model generated using WAVEBUILD-3D to represent volumes – 1D model to assess breather system performance based upon areas of concern • Reduce velocity variation at separator inlet to improve separator performance • Reduce regions of high velocity magnitude throughout system – Block transfers from crankcase to V () and can breathe through head passages only (), bypassing V – Use head volumes to damp out pressure fluctuations and provide additional separation
To separator

Vee Head Head

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Crankcase

Fluctuations at separator in are damped by the increased distance and more restrictive passages than baseline which breathes mainly through centre of banks
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Crankcase Breathing

Crankcase Breathing Simulation

Application to Engine Development
 1D Crankcase Simulation – Dynamic system model to match measured high speed crankcase pressures – Provides analysis of system behaviour across engine speed range – Identifies critical speeds for detailed modelling  3D CFD Simulation – Detailed system modelling based on 1D findings – Incorporation of moving geometry • Including complete rotating/reciprocating component motion – Simulation of complete crankcase will not model oil mist directly • Simulation of mist through high density scalar fraction • Liquid modelling for free surface motion possible but adds significant complexity and of low value for dry sump systems – Extraction of detailed pumping work for individual components/system regions • Optimisation of breathing/scavenge flow regimes possible • Optimisation of geometric configuration to minimise aerodynamic/pumping losses
CPMEP with proposed breather removal CPMEP with additional breather channel as suggested by WAVE Original, target CPMEP

© Ricardo plc 2005

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Crankcase Breathing

Crankcase Breathing Simulation

3D Oil Separator Development

 Oil separator development using coupled 1D/3D simulation

 Engineering support to cyclone design  Rapid approach using steady state or transient single phase flow analysis or transient 2 phase flow analysis with wall film modelling
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 Methodology developed to assess separator efficiency based on predicted flow regime
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Crankcase Breathing

Crankcase Breathing Simulation

Case Study – 3D Oil Separator Development – Cyclone Separator Selection
 Choice of cyclone aided by CFD.  VECTIS shows both the single cyclone and multi cyclone display classical behaviour along their entire length  VECTIS predicts the angular velocity down the complete cyclone length  Knowing the velocity profile allows the cyclone to be matched to the oil particle size distribution SWIRL DEGREDATION ALONG HEIGHT
1000

900 rad/s

650 Rad/s

450 rad/s
ANGULAR VELOCITY (rad/s)

900 800 700 600 500 400 300 200 100 0 0 10 20 30 40 50 60 70

Single Cyclone Quad Cyclone

Entry 350 rad/s
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80

90

100

PERCENTAGE OF HEIGHT

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Crankcase Breathing

Crankcase Breathing Simulation

Case Study – 3D Oil Separator Development – Transient Flow Analysis

© Ricardo plc 2005

RD05/406501.1 74

Agenda

 Background  Combustion System Simulation

 Intake, Exhaust and Aftertreatment System
 Engine Thermal Modelling  Crankcase Breathing  Vehicle Simulation

© Ricardo plc 2005

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Vehicle Simulation

Vehicle Simulation

Background  The integrated design of both engine and vehicle hardware are key to meeting performance and emissions targets  Applications include – Matching of engine performance to vehicle weight – Gear ratio selection – Air system control strategy definition and calibration – Boost system selection – Calibration comparison
X1

180 160

Road Speed (km/h)

140 120 100 80 60 40 20 0 0 2 4 6 8 10 12 14 16 Time (s) 18 20 22 24 26 28

1.4 litre turbocharged LBDI Cal 1 1.4 litre turbocharged LBDI Cal 2

X2

Vv VW
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KF ZF FF CF FV ZV

θV

KR

CR ZR

FR

FT

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Vehicle Simulation

Vehicle Simulation

Methodology  Validated steady state WAVE model is converted to transient and coupled to either Vehicle model  ECU developed within Simulink and coupled to vehicle model  The model is run through transient load step / drivecycle manoeuvres

Control systems

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Vehicle Simulation

Case Study – Vehicle Simulation

Validation  Drive cycle simulation shows engine and vehicle response to gear and pedal position for a fixed manoeuvre validate closely to test data

© Ricardo plc 2005

Source:

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Vehicle Simulation

Case Study – Vehicle Simulation

Validation  Drive cycle simulation shows vehicle fuel consumption through a 1200 second NEDC cycle validates closely to test data

© Ricardo plc 2005

Source:

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Vehicle Simulation

Case Study – Vehicle Simulation

Case Study – Boost System Selection Study  A number of alternative boost systems were modelled and their acceleration performance compared – Single stage turbocharger – Supercharger + turbocharger – Supercharger only – Electrically driven compressor (EDC) + turbocharger – Electrically Assisted turbocharger – Two stage turbocharger

© Ricardo plc 2005

Source:

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Vehicle Simulation

Case Study – Vehicle Simulation
Engine Speed 5000 4000 3000 2000 1000 2.5 2 1.5 x 10
5

Boost

Case Study – Boost System Selection Study
1 0.5 0 2 4 6 8 10 12 14 0 0 2
5

 The baseline system (turbocharger only) was validated to measurements  The controllers for each device were tuned to provide optimum performance  Tip in boost response for two systems – Boost system calibration carried out using simulation models

0

4

6

8

10

12

14

Vehicle Speed 0 time= 0sEnginetime= 13.55s 0->100kph= 13.55s 100 Speed

5000 120
100 4000 80 3000 60 2000 40 1000 20

2.5 100 2 80 1.5 60 1 40 0.5 20 0 2 4 6 8 10 12 14

x 10

Boost wheel spd & ang veh spd

Turbocharger Only
2
5

0

0 0 100 x 10 1.5

4 4

6 6

8 8

10 10

12 12

14 14

5000

120 8

4 Vehicle Speed 0 time= 0s 100 time= 13.55s 0->100kph= 13.55s Wastegate Area x 10 Engine Speed

wheel spdand clutch spd & ang gear Boost veh

2.5

100 6 4000 80

80
1 60

2

3000 60 4
40 2000 2 20

1.5
40 0.5 1 20

1000

0

0.5
0 2
4

0
8 300

4

0 10 x

2

4

6 8 Wastegate Area 6 Torque 8

10

12

14

10

12

14

0

0 0

2

4 4

Vehicle Speed 0 time= 0sEnginetime= 13.04s 0->100kph= 13.04s 100 Speed

1.5 5

0x 10-3
x 10
5

2

4

6 8 6 8 gear and clutch 6 Slip 8

10 10

12 12

14 14

10

12

14

wheel spdBoost veh spd & ang

5000 120

6 200

2.5 100 0 2 80 -5 1.5 60 -10
0.5
-15 1 40

100 4000 4 100 80 3000 60 2 0 2000 40 0 -100 1000 0 20
300 0

1

2

4

6 Torque

8

10

12

14

0 -20 0.5 0 20

2
-3

EDC +6 Turbocharger 14 4 6 8 10 12 4 8 10 12 14
Slip

0

2

4

6

8

10

12

14

0 x 10 50 100 1.5
0

2

4

6

8

10

12

14

4 Vehicle Speed 0 time= 0s 100 time= 13.04s 0->100kph= 13.04s Wastegate Area 200 x 10 120 8

wheel spdandang veh spd gear & clutch

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100 100 6 80 60 4
-100 40 0

-5

80
-10 -15 2 4 6 8 10 12 14

1 60

20 20
0 0 x 10
4

40 -20 0.5 0 20 0 0

2

4

6

8

10

12

14

2

4

6

8

10

12

14

2
-3

4

6

8

10

12

14

Source:

Wastegate Area Torque

x 10

gear and clutch Slip

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Vehicle Simulation

Case Study – Vehicle Simulation

Case Study – Boost System Selection Study  Each system was run through the same manoeuvre (3rd gear, 30 km/h, from 0% to 100% Pedal)  For this example the FGT + EDC provided the best response

© Ricardo plc 2005

Source:

RD05/406501.1 82

Thank you for your attention

ありがとうございました

Any Questions? どうぞご質問を

© Ricardo plc 2005

RD05/406501.1 83


				
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