advanced simulation techniques for ic engines

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ADVANCED SIMULATION TECHNIQUES FOR IC ENGINES

ASTICE

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APPLICATION

• Hydraulic System simulation

• Control System Analysis

• Map Based simulation

• 1D general Flow Analysis- utility design

• CFD- 3D Combustion and Emission analysis

Engine Cycle

Simulation

Cooling circuit

simulation

Fuel Injection System Analysis

Driveline Simulation

CFD- 3D Compressible flow analysis

CFD- 3D general flow analysis

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ENGINE CYCLE SIMULATION

Combustion

Model

• Weibe function Model • Multi-zone spray Model • Two-Zone knock model for SI and DF engine

Gas exchange Mode

l

• 1D gas dynamic model• Turbocharger Matching

Optimization

Model

• RSM model with DOE• Optimization Using Genetic Algorithm

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ENGINE CYCLE SIMULATION-CASE 1

Fit Weibe functio

n

Generate Model

Single Cylinde

r

Complete Engine

Cycle

Run the model

Weibe combustion model

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Fit Weibe function to experimental or CFD

heat release

Single DI Weibe Start of combustionCrank angle at 1% burned

Combustion Duration & Weibe exponentCalculated by non-linear least square method

Multiple DI Weibe Start of combustionCrank angle at 0.5% burned

Premixed fraction, Premixed combustion duration , premixed Weibe exponent, mixing controlled combustion duration and mixing

controlled Weibe exponentCalculated by non-linear least square method

Weibe combustion model


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Single Weibe ModelSOC = -5.3Θd = 63.5M = 0.96

Multiple Weibe ModelSOC = -4.1Pf = 0.1Θd_p = 12Mp = 0.5Θd_p = 60Mp = 1.15

Weibe combustion model Fit Weibe function

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Model Generation

•Single Cylinder Model•Complete Engine Cycle

Weibe combustion model Model Generation

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ENGINE CYCLE SIMULATION-CASE 1Weibe combustion

model Model Generation Single cylinder Model

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Zoom

Single Cylinder results

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Scav

engi

ng

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Indicated Power 99.6 kW

•IMEP=25 bar•Indicated Efficiency= 50.6%

Heat transfer to walls19.6 kW

•6.7 kW from Gas to Liner•6.4 kW from Gas to Head•6.5 kW from Gas to Piston

Exhaust Energy77.6 kW

•A fraction is recovered through turbocharger in multi cylinder engine

Fuel Energy

196.8 kW

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model Model GenerationComplete Engine

Cycle

Single Cylinder Model

Firing Order/ No. Cylinders

TC and ICmodel

Filling & Emptying Model

Friction Model

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Cycle

Filling & Emptying Model

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Cycle

Filling & Emptying Results

Gas Exchange Diagram

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Cycle

Filling & Emptying Model Results

Ambient Temp (°C) 25

I/C Water Temp (°C) 33

Power (kWb) 500

Speed (r/min) 1500

BMEP (bar) 21

BSFC (g/kWh) 199

BSAC (kg/kWh) 6.56

Firing Pressure (bar) 170

Boost Pressure Ratio 3.05

Compressor Exit Temp (°C) 171

Air Manifold Temp (°C) 48

Compressor Eff. (%) 76

Turbocharger Eff. (%) 58.5

Surge Margin (%) 26

Exh M’fold Temp Energy Mean (%) 516

Turbine Inlet Temp (Estimated) (°C) 575

Trapped A/F Ratio 25.5:1

Compressor Raw Map

Turbine Raw Map

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Multi-zone spray Model for Diesel combustion

More info: SAE paper No. 2001-01-1246

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Main code

Discharge Coefficient Routine

Spray Penetration Routine

Droplet Evaporation Routine

Sauter Mean Diameter Routine

Air Entrainment Routine

Heat transfer Routine

Multi-zone spray Model for Diesel combustion

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ENGINE CYCLE SIMULATION-CASE 2Multi-zone spray Model for Diesel combustion

Start of Combustion Premixed combustion

Temperature Distribution in Spray Zones

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Peak heat release rate

Temperature Distribution in Spray Zones

Combustion tale

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Fuel evaporation & Burn NOx & SOOT

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Pressure & Temperature Normalized Fuel Injection, Evaporation, Burn and Heat release rate

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Two-Zone knock model for SI and DF engine

The pilot fuel (DF)/Spark (SI) is considered as ignition initiator

The heat released via diesel fuel is entered to model as Weibe

function in DF engines

The ignition delay is calculated from Arrhenius formula

The air and natural gas mixture will be divided into two zones as

soon as combustion starts

The burned zone consists of reacting species and combustion

products.

It is assumed that all of species are in thermodynamic equilibrium

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O O2

N2

OH

H2O

H

CO

CO2

H2

Thermodynamic Equilibrium

Heat Release

The Burned Zone

O2OH

H2O

H

CO

Chemical Kinetics

Auto-ignition Knock

The Unburned Zone

CH4HO2

CH3H2O2

CH2O

CHO

N2

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Model Validation

Continuous lines : Two-Zone model resultsPoints : CAT Engine simulation results (SAE paper)

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ENGINE CYCLE SIMULATION- CASE 4

1D gas dynamic model

Significant error

at high speeds

Instability at

low speeds and load

Gas Dynami

c modeli

ng

Filling & Emptying Modeling

1D CFD

Complex program

Better Results

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ENGINE CYCLE SIMULATION- CASE 4

1D gas dynamic model

Two-Step lax-Wendroff method

Flow Limit Function

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ENGINE CYCLE SIMULATION- CASE 41D gas dynamic model

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ENGINE CYCLE SIMULATION- CASE 5 Turbocharger Matching

Marine ManeuveringRail Traction Load acceptance

Steady State Condition

• High efficiency

• Stable Conditions

Criteria for turbo matching

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ENGINE CYCLE SIMULATION- CASE 5 Turbocharger Matching/ Transient operation

Load Increase Process

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150 Sec Ramp of Throttle from 0-100-Transient Response

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OPTIMIZATION PROCESS Design of Experiments

Results Processed at Polynomial Surfaces

Optimization via Genetic Algorithm

RS

M

Meth

od

olo

gy

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OPTIMIZATION MODEL- RSM Mathematical and statistical technique for empirical model building

The objective is to optimize a response

changes in the input variables identifies the changes in the output response

The RSM is used to design optimization is reducing the cost of expensive methods

The Approximation model function is generally polynomial

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OPTIMIZATION MODEL- DOE

An experiment is a series of tests or simulations, called runs

The objective of DOE is the selection of the points where the response should be evaluated

Optimal design of experiments are associated with the mathematical model of the process

The choice of the design of experiments have an influence on the accuracy of the approximation

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OPTIMIZATION MODEL- DOE METHODS

Box and Dropper

Latin Hypercube

D-Optimum

Full Factorial

Incr

ease

in L

evel of

Acc

ura

cy

Incr

ease

in R

un t

ime

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OPTIMIZATION EXAMPLE 1Injection timing VS Speed & fuel amount

Response Surfaces

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OPTIMIZATION EXAMPLE 1Injection timing VS Speed & fuel amount

Optimized Map

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COOLING CIRCUIT SIMULATION

1D CFD analysis of Flow

Simple and Extended model of Heat

exchanger

Coupled Solution with Engine Cycle Simulation

Transient Simulation

Extended Model of Water pump

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COOLING CIRCUIT SIMULATION-CASE 1

Simple and Extended model of Heat exchanger Simple Model

Inside HX•Volume of Fluid•Pressure drop across HX

Effectiveness of HX

•Outside flow rate•Outside temperatre

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Simple and Extended model of Heat exchanger Extended Model

Inside Flow•Volume of Fluid•Pressure drop across HX•Flow rate•Nu correlation

Outside Flow•Volume of Fluid•Pressure drop across HX•Flow rate•Nu correlation•Effectiveness type

Wall Absorb •Wall material spec•Wall volume

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Simple and Extended model of Heat exchanger

Simple Model

•Acceptable results for cross flow HXs•Reliable for air cooled radiators and condenser

Extended Model

•More accurate model•Rely on experimental data

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Coupled Solution with Engine Cycle Simulation/ Transient/ Extended pump model

Engine

Model

Cooling Circuit Model

Heat Rejection

Heat transfer BCs

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Transient Operation of the engine

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Transient Operation of the engine

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Transient Thermal Results- Coolant inside head drillings

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Transient Thermal Results- Coolant inside Cylinder jackets

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Transient Thermal Results- HTC Coolant to liner

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Transient Thermal Results- average Liner wall temperatureCoolant Side

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Transient Thermal Results- HTC Coolant to head

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Transient Thermal Results- average In-Cylinder Gas temperature


To head To Liner- Top

To Liner- Bottom

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Transient Thermal Results- average In-Cylinder HTC


To headTo Liner- Top

To Liner- Bottom

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Correlated Thermal Results- average In-Cylinder HTC


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1D GENERAL FLOW ANALYSIS- UTILITY DESIGN

Combined Heat & Power Generation

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CONTROL SYSTEM ANALYSIS-CASE 1

Waste-gate Control

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CONTROL SYSTEM ANALYSIS-CASE 2

Throttle Control

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DRIVELINE (MAP BASED) SIMULATION

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DRIVELINE (MAP BASED) SIMULATION

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DRIVELINE (MAP BASED) SIMULATION-EXAMPLE

UIC Performance test simulation

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CFD- 3D GENERAL FLOW ANALYSIS

3D Flow Through oil jet

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2D flow through gas throttle Valve

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CFD- 3D COMPRESSIBLE FLOW ANALYSIS

Flow through Modular Pulse Convertor Exhaust

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Simulation of paddle wheel test

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CFD- 3D COMBUSTION AND EMISSION ANALYSIS DI Diesel combustion Analysis-Temperature

distribution K

350° CA

364° CA

374° CA

advanced simulation techniques for ic engines

Documents

multizone spray model

zone model resultspoints

single weibe modelsoc

premixed weibe exponent

cat engine sim

premixed combustion

multiple weibe modelsoc

controlled combustion