advanced simulation techniques for ic engines

ADVANCED SIMULATION TECHNIQUES FOR IC ENGINES

ASTICE

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

ENGINE CYCLE SIMULATION

Combustion

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

Gas exchange Mode

• 1D gas dynamic model• Turbocharger Matching

Optimization

• RSM model with DOE• Optimization Using Genetic Algorithm

ENGINE CYCLE SIMULATION-CASE 1

Fit Weibe functio

Generate Model

Single Cylinde

Complete Engine

Run the model

Weibe combustion model

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

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

Model Generation

•Single Cylinder Model•Complete Engine Cycle

Weibe combustion model Model Generation

ENGINE CYCLE SIMULATION-CASE 1Weibe combustion

model Model Generation Single cylinder Model

Single Cylinder results

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

model Model GenerationComplete Engine

Single Cylinder Model

Firing Order/ No. Cylinders

TC and ICmodel

Filling & Emptying Model

Friction Model

Filling & Emptying Model

Filling & Emptying Results

Gas Exchange Diagram

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

Multi-zone spray Model for Diesel combustion

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

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

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

Start of Combustion Premixed combustion

Temperature Distribution in Spray Zones

Peak heat release rate

Temperature Distribution in Spray Zones

Combustion tale

Fuel evaporation & Burn NOx & SOOT

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

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

Thermodynamic Equilibrium

Heat Release

The Burned Zone

Chemical Kinetics

Auto-ignition Knock

The Unburned Zone

CH4HO2

CH3H2O2

Model Validation

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

ENGINE CYCLE SIMULATION- CASE 4

1D gas dynamic model

Significant error

at high speeds

Instability at

low speeds and load

Gas Dynami

c modeli

Filling & Emptying Modeling

1D CFD

Complex program

Better Results

ENGINE CYCLE SIMULATION- CASE 4

1D gas dynamic model

Two-Step lax-Wendroff method

Flow Limit Function

ENGINE CYCLE SIMULATION- CASE 41D gas dynamic model

ENGINE CYCLE SIMULATION- CASE 5 Turbocharger Matching

Marine ManeuveringRail Traction Load acceptance

Steady State Condition

• High efficiency

• Stable Conditions

Criteria for turbo matching

ENGINE CYCLE SIMULATION- CASE 5 Turbocharger Matching/ Transient operation

Load Increase Process

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

OPTIMIZATION PROCESS Design of Experiments

Results Processed at Polynomial Surfaces

Optimization via Genetic Algorithm

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

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

OPTIMIZATION MODEL- DOE METHODS

Box and Dropper

Latin Hypercube

D-Optimum

Full Factorial

evel of

OPTIMIZATION EXAMPLE 1Injection timing VS Speed & fuel amount

Response Surfaces

OPTIMIZATION EXAMPLE 1Injection timing VS Speed & fuel amount

Optimized Map

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

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

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

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

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

Engine

Cooling Circuit Model

Heat Rejection

Heat transfer BCs

Transient Operation of the engine

Transient Thermal Results- Coolant inside head drillings

Transient Thermal Results- Coolant inside Cylinder jackets

Transient Thermal Results- HTC Coolant to liner

Transient Thermal Results- average Liner wall temperatureCoolant Side

Transient Thermal Results- HTC Coolant to head

Transient Thermal Results- average In-Cylinder Gas temperature

To head To Liner- Top

To Liner- Bottom

Transient Thermal Results- average In-Cylinder HTC

To headTo Liner- Top

To Liner- Bottom

Correlated Thermal Results- average In-Cylinder HTC

1D GENERAL FLOW ANALYSIS- UTILITY DESIGN

Combined Heat & Power Generation

CONTROL SYSTEM ANALYSIS-CASE 1

Waste-gate Control

CONTROL SYSTEM ANALYSIS-CASE 2

Throttle Control

DRIVELINE (MAP BASED) SIMULATION

DRIVELINE (MAP BASED) SIMULATION-EXAMPLE

UIC Performance test simulation

CFD- 3D GENERAL FLOW ANALYSIS

3D Flow Through oil jet

2D flow through gas throttle Valve

CFD- 3D COMPRESSIBLE FLOW ANALYSIS

Flow through Modular Pulse Convertor Exhaust

Simulation of paddle wheel test

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

multizone spray model

zone model resultspoints

single weibe modelsoc

premixed weibe exponent

cat engine sim

premixed combustion

multiple weibe modelsoc

controlled combustion

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