IC Engine System Presented By ANSYS Inc. Outline Background and - - PowerPoint PPT Presentation

IC Engine System

Presented By ANSYS Inc.

• Background and Motivation
• IC Engine System
• Introduction
• Scope
• Properties
• Work flow for cold flow and port flow simulations
• Advanced setup/customization
• Other useful features
• Demo
• Future Plans
• Summary

Outline

In-Cylinder Cooling Jacket Lubrication Intake Exhaust Pumps Turbocharging Among internal combustion engine CFD applications, in‐cylinder flow is of central importance in determining engine efficiency and emissions Fuel Supply

Recent ANSYS Progress in IC Engine Modeling

2010 2009

• Continuous progress with each Fluent release bringing

advancements in physics and meshing

Fluent R12

IC engine report, IC specific vaporization laws, coherent flamelet model, EGR, ignition UDF

Fluent R13

Key‐frame mesh, mesh smoothing, DPM and combustion extensions: multiple spark model, Veynante ECFM for LES, KHRT break‐up model,

Fluent R14.5

Sprays: spray angle vs. crank angle, cone injection sector meshes Mesh related: 2nd order in time MDM, contact detection, cutcell w. BL remesh

2011 2012

Fluent R14

Aftertreatment: selective catalytic reduction, catalytic converter light off Combustion: G‐eqn Multiphase: SSD

* The Workbench IC Engine system uses a well‐tested subset of Fluent features

• Manual Approach for

simulating in‐cylinder flow

– Gather the required user input needed to accurately model the user’s specific engine. – Prepare the Geometry and Mesh:

• Decompose the geometry in a manner suitable for modeling the

motion of valves and piston and then create the mesh

• Manually decomposing the geometry and meshing takes

between 6 hours and a couple of days, depending on experience

• Learning curve for manual geometry decomposition and meshing

is very steep!! – Set‐up and run the simulation:

• Setting up the case requires knowledge of models like dynamic

mesh, reacting flows, discrete‐phase etc. – Analyze and interpret results

Motivation

IC Engine Geometry

Geometry Decomposition Mesh Creation Solver Setup

IC Engine Results

WB‐ICE tool

Perform following operations semi‐ automatically

Geometry Decomposition Solver Setup Mesh Creation

Automatic Report Generation

• IC Engine System
• A new Workbench Analysis System

similar to Fluid‐Flow(Fluent) or Fluid‐Flow (CFX) Analysis Systems

• Reduces the setup time of ICE cold

flow and port flow problems from many hours to few minutes

• First released ANSYS R14
• Supported on Windows and Linux

platforms

• Standard feature included with

ANSYS FLUENT

IC Engine System: Introduction

• Automated geometry preparation and mesh generation

for all 4 stroke engines – any number of valves – all standard shapes of piston at the given crank angle

• Automated case setup for “cold‐flow” and “port‐flow”

type simulations based on the best practices – including mesh motion

• User hooks for complex physics setup, e.g. spray injection,

combustion simulation

• Automated report generation

Scope of IC Engine System

IC Engine System Properties

These IC inputs can be defined as Parameters Can be used to setup a customized case Can be used to perform custom post‐processing For engines with piston pin offset User can hook boundary condition profiles

ANSYS Workbench

Workbench ICE System

DesignModeler FLUENT Solver CFD Post Single Mesh ANSYS Meshing

Multiple Meshes (keyframes) (new R14.5)

Automatically Generated Reports CAD

Cold Flow Simulation Setup Using IC Engine System:

• Automatic preparation of geometry for meshing
• Automatic meshing including inflation layers and

layering zones

• Automatic setup dynamic zones, events, and solver

settings

• HTML report creation
• Reduces the turnaround time (CAD import to CFD

setup) to less than an hour

Cold Flow Simulation using IC Engine System

Geometry Preparation

Geometry Inputs

Basic Geometry Information Valve geometry and profile information Optional Animation Inputs Advanced Options

Mesh Generation

Different Meshing Configurations

4 layers between valve and valve‐seat at fully‐ closed position of valve

• ne layer in the gap at

fully‐closed position of valve

Inflation layer in the port No Inflation layer in the port

Different Meshing Configurations

Different Meshing Configurations

No decomposition in chamber region for engines with very little squish at TDC or pistons with valve recess regions Decomposition in combustion chamber region for layered mesh

• IC Engine System will automatically setup the

problem

– Reads the valve and piston profile – Create various dynamic mesh zones – Create interfaces required for dynamic mesh setup – Set up the dynamic mesh parameters – Create all the required events, to model opening and closing of valves, and corresponding modifications in solver settings and under‐relaxations factors – Set up the required models – Set up the default boundary conditions and material – Set up the default monitors – Initialize and patch the solution

Solver Setup

• Once the solution is complete, tool creates a

detailed report w ith all the settings , events, results and images.

HTML Report

Port Flow Simulation using IC Engine System

• New feature in upcoming ANSYS R14.5 Release
• Prepares the geometry automatically
• Automatic meshing using hybrid and cut‐cell

approaches

• Setup and solution strategy based on the best

practices

• Automatic saving of important images and HTML

report creation

• Reduces the turnaround time (CAD import to CFD

setup) to less than an hour

Port Flow Simulation using IC Engine System

Automatic Geometry Preparation

• Moves the valve to appropriate position
• Deactivates the closed valve and deletes the port

automatically

• Removes the piston‐bowl (if needed) and extend the

cylinder to appropriate length

• Create different shapes of inlet/outlet plenum
• Automatically creates the swirl/tumble planes at the

given position

Original Geometry Input Manager for Port Flow

Final geometry with Inlet and Outlet Plenums, and port deactivated

Automatic Geometry Preparation

Geometry Decomposition

• Cutcell and hybrid meshing support
• Create proper mesh controls and sizing to

get better mesh in the chamber and valve gap

• Boundary layers in both hybrid and cutcell

meshing

Automatic Meshing

Automatic Meshing

• IC Engine System will setup the solver from the best

practices for cutcell and Hybrid meshing

– Set appropriate solver methods and controls – Set the boundary conditions – Defines the default monitors – Does the FMG initialization

• Automatically creates the default swirl plane from

geometry information, and defines custom field functions for swirl

Automatic Solver Setup

HTML Report:

• Demo ( 5‐6 min recorded

demo of cold flow and port flow)

• A strong regression suite

– More than 15 engines with various topologies from different customers are there in our regression suite, which runs on daily basis, to maintain the stability and high quality of software – For each of these engines geometry preparation, meshing, and setup for cold flow case is within 20 min, and for port flow this is within 30 min

Regression and Time Statistics:

Documentation:

• Detailed explanation of all the features with tips on how one can

modify the default behavior of the tool

• Trouble shooting chapters: All the knowledge gained since the

release of 14 has been captured and documented. Separate sections for :

– Geometry check – Geometry preparation – Mesh generation – Solver setting up

• Well documented process explaining how tool can be extended for

some of the features which are not supported by automation

– Decomposing a straight valve engine with pockets for layered meshing – Handling geometries in which solid valves are missing

• Detail steps for setting up and running the tutorials along with Video

tutorials

Extending the Tool (Advanced Users)

• User will be able to setup advanced physics using pre‐

iteration and post‐iteration journal hooks

• Using pre‐iteration journal hooks user should be able to

setup combustion problem in IC Engine system:

• Define profile, udf , and chemkin, file path and also other

variables

• Compile and hook the udf, also define some udf related

variables

• Deactivate port fluid zones
• Set up energy model, turbulence model, species model and

dpm models

• Define injections

Advanced solver setup using journal customization.

Setting up Combustion:

Pre‐iteration Journal Cold‐Flow Setup Combustion Setup with Spray

Pre‐iteration Journal file for combustion:

File Handling Model Control Injection Data Setup Method

• You can create new Zone at

geometry level by defining a Named Selection with prefix “ice‐user‐”

• Extend the boundary

conditions by defining new boundary conditions in “User Boundary Conditions and Monitor Settings”

Creating new zones and defining advanced boundary conditions.

Handling Engines with Crevice Region

Crevice Region Interface Hex Mesh

• Though, right now, the tool will not do any special

treatment for crevice region, one can extend the tool by doing few manual operations to get more control in crevice region

• Separate the crevice volume and define

proper mesh

• Define interfaces to handle this new crevice

volume

Other Useful Features

Key grid support

– Automatic crank angle specific decomposition – Create mesh as per the crank angle position – Parametric support to get meshes at different crank angles

• You can setup up to the mesh once, and then you can

create any number of design points with the exposed parameters like : crank angles, minimum lift, or connecting rod length and update the design points, you will have the appropriate mesh file ready at those given crank angles without any manual intervention

Key grids based on the crank angle

Geometry and Mesh at crank angle near TDC Geometry and Mesh at crank angle near BDC

Usability Features

• Animation of valve and piston motion for the cold flow

simulation at geometry level

• Parameter support for port‐flow solution and mesh

generation in cold flow

• User can start the cold flow simulation from any crank

angle , all the settings will be taken care automatically – This saves a huge amount of time ; earlier people use to reach the required crank angle by mesh motion which takes a lot of time

• Automatic cut planes and views in AMP for better

visualization of the mesh

• Smooth transition from Cold‐flow to Spray and Combustion
• Automated setup for combustion analysis
• Improve meshing options by
• Automatically Switching between different tailored

meshes during simulation (Key‐grid or mesh‐ replacement approach)

Future Plans

Note: The plans are still tentative and time‐lines, priorities etc. needs to be worked out

• New “standard” feature in ANSYS‐FLUENT for In‐

Cylinder simulations

• Automates in‐cylinder model creation
• Extensively tested on different engine

configurations

• Supported on Windows and Linux
• Quick to learn and easy to use!
• Provides hooks for custom in‐cylinder simulations

Summary

Appendix

Work Flow

Mesh configuration of IC Engine system for a typical canted valve engine

No Fluid Zone Name Mesh type 1 fluid‐ch Tet mesh 2 fluid‐valveID‐ ib Sweep mesh with at least one layer at the top 3 fluid‐valveID‐ port Tet mesh with or without prism layer 4 fluid‐valveID‐ vlayer Layered mesh with 1

• r 4 layers

5 fluid‐layer‐ cylinder Layered mesh 6 Fluid‐piston Tet mesh

Various zones and named selection created automatically for a typical

canted valve engine.

Geometry decomposition

Smoothing‐Layering approach

smoothing smoothing layering

To retain at least 4 layers of cells between valve and valve seat, throughout cycle

• Piston should be at TDC

position (in R14.0)

• For Parasolid geometry, set the

Clean Bodies option to ‘No’

• Imported geometry should

have only one flow volume with solid valves

• Ensure that the valves are not

extracted from the port volume in the initial geometry

• Ensure that the valve stem

protrudes out of the port body

• Ensure that the valve is

centrally aligned to the valve

• guide. An off‐centered valve

can result into failures and wrong results

Troubleshooting: Geometry Check

• If cylinder chamber meshing fails

=> Delete its pinch controls and execute the meshing again

• If some faces belonging to a named

selection group are not selected for the Geometry option they belong to, then the warning is displayed

=> Add these faces to the Geometry list of the Named Selection it belongs to

• If there are any small faces causing a

meshing failure, then these faces should be merged with their adjacent faces using Virtual Topology

• If V‐layer meshing fails

=> Try to project and imprint the edge of the valve face on the valve seat, in the direction of the valve

– This will split the valve seat. Then decompose the geometry again. This procedure will create a proper sweep mesh in the vlayer.

Troubleshooting: Mesh Generation

• V‐layer meshing can fail in

some cases where the face has a step.

• Select ‘Show the

Problematic Geometry’ from the context menu of the error message in the Messages window. This will point to the face which has the step

• Reduce the V Layer Slice

Angle parameter in the Input Manager, such that the face is split into two. Then reset the Mesh cell and follow the meshing procedure to re‐mesh the geometry.

Troubleshooting: Mesh Generation

Straight Valve Engines with Valve Pockets

• Fully layered mesh can be

created for straight valve diesel engines with valve pockets ‐ Instructions can be provided upon request (available in R14.5 ICE Manual)

Example: Hex mesh created for layering