Surface Preparation & Boundary Flagging: SI8-PFI Engine with No Hydro Setup

OBJECTIVE:

The objective of this study to prepare the surfaces of a SI8-PFI engine model, and flag the necessary boundaries to set up a no hydro simulation case. No hydro simulations are setups in which no fluid interation takes place in the CFD domain. The significance of running such cases is to observe and ensure the proper movement of the certain parts such as valves and piston in the SI8-PFI engine case.

The following parameters shall be considered for setting up the case

Engine Geometric Parameters

  • Bore =0.086 m
  • Stroke = 0.09 m
  • Connecting rod length = 0.18 m
  • RPM = 3000

Run parameters

  • Simulation mode: No Hydro

Simulation time parameters

  • Start time : -520 deg
  • end time : 120 deg

Boundary conditions

  • Piston temperature - 450K
  • Liner temperature - 450K
  • Head temperature - 450K
  • Spark Plug temperature - 550K
  • Spark Plug electrode temperature - 600K
  • Exhaust ports temperature  - 500K
  • Exhaut outflow - 1 bar
  • Exhaust outlflow temperature - 800k
  • Exhaust species concentration - Calculate the stoichiometric condition
  • Exhaust valve top temperature - 525K
  • Exhaust valve angle temperature - 525K
  • Exhaust valve bottom temeprature - 525K
  • Intake port - 1 temperature 425K
  • Intake port - 2 temperature 425K
  • Inflow pressure - 1 bar total pressure
  • Inflow temperature - 363K
  • Inflow species - Air
  • Intake valve top temperature - 480K
  • Intake valve angle temperature - 480K
  • Intake valve bottom temeprature - 480K

Initial conditions

  • Intake port - 1 (closer to combustion chamber)
    • ic8h18 - 0.025508
    • o2 - 0.20157
    • n2 - 0.77292
    • Temperature - 390k
    • pressure - 1 bar
  • Intake port - 2 (away from combustion chamber)
    • Air
    • Temperature - 370K
    • Pressure - 1 bar
  • Cylinder
    • Pressure - 1.85731 bar
    • Temperature - 1360K
    • Stoichiometric composition

The simulation setup process includes three major steps:

1. Preprocessing

    1.1. Geometry Import 

    1.2. Diagnosis

    1.3. Boundary Flagging and Troubleshooting

    1.3. Case Setup

2. Solving

3. Post Processing

   3.1. Animation

 

PROCEDURE:

 1. Preprocessing

1.1. Geometry Import:

The SI8-PFI engine model was directly imported into converge studio for setting up the no hydro case.

Fig: SI8-PFI Engine Geometry 

 1.2. Diagnosis: The diagnosis tool helps in identifying the different problems in the                    geometry. For performing the diagnostics on the model goto Diagnostics Dock>Find>

The Diagnosis tool looks for the following geometric issues

     a. Intersection: Highlights number of triangles with piercing inbetween adjacent two                 triangles

Fig: Intersections- Problem Triangles

     b. Nonmanifold Vertices: Checks for number vertex which are being shared between two           triangles

Fig: Non Manifold Vertices- Problem Triangles   

 c. Open Edge: This highlights the number of edges of a triangle which not shared by any other triangle

Fig: Open Edges- Problem Triangles 

     d. Normal Orientation: This highlights the number of traingles whose normal vector is               not pointing towards the interior of fluid domain

 Fig: Normal Orientation- Problem Triangles 

e. Isolated Triangles: This checks for the number of triangle surrounded by any neighbouring triangles that have different boundary ID number. There were no isolated triangle issues in the model

Boundary Flagging and Troubleshooting:

1. Intersections: For redressing this the fences were created to flag the boundaries accurately

Fig: Cylinder Head Fences 

Apart from this other areas where fences were created were the inlet port, valve top & spark plug

Fig: Inlet Port Fences

 

Fig: Valve Top Fences:

The above fences were created on all the 4 valve tops to solve the issue of disconnect triangles which is a common issue when the boundaries slide during the movement

Ring Triangles: These are created to ensure that during the valve movement the manifold does not gets deformed

2. Nonmanifold Vertices: For solving this issue the triangles highlighted were deleted and the recreated using the create option

3. Open Edges: The open edges were eradicated using the patch tool which creates necessary number of triangles in the open edge blanks to close the surface

4. Normal Orientation: To solve the normal orientation, the normals were flipped to ensure the normal point towards the fluid regime

Fig: Normal Orientation: Section View

After the trouble shooting the diagnostic tool was reused to check any other errors. There were no further issues in the geometry

Fig: Diagnostic Check: No Problem Triangles

Boundary Flagging

1. Goto Boundary>Flag>Create a New Boundary>Create Multiple Boundary>Enter 15 in               "Number of Multiple Boundaries"

2. Select the triangles the assigned it to the respective boundaries

Fig: Boundaries Flagged

Fig: Cylinder Head and Liner

Fig: Cylinder Head

Fig: Inlet and Exhaust Valve: Top, Angle and Bottom

 

 

 Fig: Exhaust Port

Fig: Inlet Port A

 

 Fig: Spark Plug and Terminal

 Fig: Regions Flagged

 

 Fig: Surface with Edges

 Note:

1. The boundaries shown above are coloured by region

2. The purpose of creating two inlet ports was that near to the cylinder region the temperature of the inlet port is higher due to conduction as compared to the port region which is located farther from the cylinder

1.3. Case Setup:

Settings Values to be Entered/Selected
Application IC-Engine (Crank angle-based)
Material Tick on Reaction Mechanism
Gas simulation>No Change
Global Transport Paramters>No  Change
Reaction Mechanism>Import the Mech.dat file provided
Simulation Parameters

Run Paramters>Simulation Mode>select No Hydrodynamic solver
Simulation Time Parameter>
Start Time: -520deg.
End time: 120 deg.
Initial time step:1e-07 s
Minimum time step:1e-08 s
Maximum time step: 0.0001 s
Solver Parameters> No Change

Boundary Conditions 

Piston:
Boundary Type>Wall
Velocity Boundary Conditions: Wall Motion Type>Translating, Surface Movement>moving, select 'Law of Wall' from the list and tick on piston motion button
Temperature Boundary Conditions: select 'Law of Wall' from the list, Temperature value>450k

Inflow:
Boundary Type:Inflow
Pressure Bounary Condition>Specified Value>tick on Total Pressure> Enter a value of 101325.0 Pa
Velocity Boundary Condition>Zero Normal Gradient
Temperature Boundary Conditions>Specified Value>363 k
*Species Boundary Conditions>Add ic8h18:0.025508, o2 - 0.20157, n2 - 0.77292
*These values shall be useful for the full hydrodynamic case, as this a test run the values are irrelevant

Outflow:
Boundary Type: Outflow
Pressure Boundary Condition>Specified Value>Enter 101325.0 Pa
Velocity Boundary Condition>Zero Normal Gradient
Backflow>Specified Value
Temperature Backflow: 800k
*Species Backflow: CO2:H2O:N2::0.192304:0.088559:0.719137
*These values shall be useful for the full hydrodynamic case, as this a test run the values are irrelevant

Liner:
Boundary Wall>Wall
Wall Motion Type>Stationary, select 'law of wall' from the list
Temperature Boundary Condition> Law of Wall, temp value>450k

Cylinder Head:
Boundary Type>Wall, Wall motion>stationary, select 'Law of Wall' in both velocity and temperature boundary condition, temp value>450k

Exhaust Port:
Boundary Type>Wall

Velocity Boundary Conditions>Wall Motion type>stationary. select 'Law of Wall' in both velocity and temperature boundary condition, temp value>800k


Exhaust Valve Top:
Boundary Type>Wall
Velocity Boundary Conditions
Wall Motion type>Translating, Surface Movement>Moving. select 'Law of Wall' and check on the user profile button
Profile:tick on user profile and click on profile configuration
In the Profile Config Window>Type>Cyclic, Period>720, Tick on Valve Paramters, select direction from the option.
Direction(X,Y, Z): Enter the valve normal values, Minimum Lift: 2.0e-04
Import the exhaust_lift.in file and click on accept

Temperature Boundary Conditions:
select 'Law of Wall', enter a value of 525k

Do the same for  Exhaust Valve Angle & Exhaust Valve Bottom boundaries as well

Inlet Port:
Boundary Type>Wall, Wall Motion type>stationary. select 'Law of Wall' in both velocity and temperature boundary condition, temp value>425k

Inlet Port 2:
Boundary Type>Wall, Wall Motion type>stationary. select 'Law of Wall' in both velocity and temperature boundary condition, temp value>425k

Inlet Valve Top:
Boundary type: Wall
Velocity Boundary Conditions:
Wall Motion type>Translating, Surface Movement>Moving. select 'Law of Wall' and check on the user profile button
Profile:tick on user profile and click on profile configuration
In the Profile Config Window>Type>Cyclic, Period>720, Tick on Valve Paramters, select direction from the option.
Direction(X,Y, Z): Enter the valve normal values, Minimum Lift: 2.0e-04
Import the intake_lift.in file and click on accept
Temperature Boundary Conditions:
select 'Law of Wall', enter a value of 480k

Follow the same process for Inlet Valve Angle & Inlet Valve Bottom boundaries as well

Note:

1. The direction values entered for the intake and exhaust valve boundaries (top, angle and bottom) can be obtained from the geometry. For this goto measure>direction>arc normal>select three points on the value shaft top's cross sectional area and click on apply. A message will be displayed on the message log window with the normal values, copy this  value and paste it to the valve normal. The valve normal for inlet and outlet valves shall be different as both the set of valves will be moving along different axes

2. Disconnect Triangles: these traingles are created to control the fluid flwo different two different region. The region around the inlet/exhaust valve angle and the cylinder in one such are where these triangles are created, as the flow between these two regions is established during the intake and exhaust cycle only, for the other cycles: compression and power stroke cycle, there is no flow between these region. So the minimum lift be set in such as way that the following conditions are fulfilled

a. It should not be too big so that very large size disconnect traingles are formed

b. While opening the valves should not collide with the cylinder head/piston

Spark Plug:
Boundary Type>Wall, Wall Motion type>stationary. select 'Law of Wall' in both velocity and temperature boundary condition, temp value>550k

Spark Plug Terminal:
Boundary Type>Wall, Wall Motion type>stationary. select 'Law of Wall' in both velocity and temperature boundary condition, temp value>600k

Assign the regions to the boundaries as per the following:

Boundary Region
Piston Cylinder
Liner Cylinder
CylinderHead Cylinder
Exhaust_Valve_Bottom Cylinder
Inlet_Valve_Bottom Cylinder
Spark_Plug Cylinder
Spark_Plug_Terminal Cylinder
Inlet_Port Inlet_Port1
Inlet_Valve_Top Inlet_Port1
Inlet_Valve_Angle Inlet_Port1
Inflow Inlet_Port2
Inlet_Port2 Inlet_Port2
Outflow Exhaust_Port1
Exhaust_Port Exhaust_Port1
Exhaust_Valve_Top Exhaust_Port1
Exhaust_Valve_Angle Exhaust_Port1

 

Initial Conditions & Events


Regions and Initialization
Add region>Cylinder, Inlet_Port1, Inlet_Port2 and Exhaust_Port1

Cylinder:
Stream ID: 0
Temperature: 1360k
Enter Pressure value:185731.0 Pa
*Species: Add CO2, H2O and N2 put the mole fractions as 0.192304, 0.088559, 0.719137 respectively

Inlet_Port1:
Stream ID: 0
Temperature: 390 k
Enter Pressure value:101325.0 Pa
*Species: Add O2, N2 and IC8H18 put the mole fractions as 0.20157, 0.77292, 0.025508 respectively

Inlet_Port2:
Stream ID: 0
Temperature: 372 k
Enter Pressure value:101325.0 Pa
*Species: Add Air (O2:N2::0.23:0.77)

Exhaust_Port1:
Stream ID: 0
Temperature: 1360k
Enter Pressure value:185731.0 Pa
*Species: Add CO2, H2O and N2 put the mole fractions as 0.192304, 0.088559, 0.719137 respectively

*Note: These values shall be useful for the full hydrodynamic case, as this a test run the values are irrelevant

Events
Tick on Cyclic & Permanent
Cyclic:
Add two events
Event1- Region A: Cylinder, Region B: Inlet_Port1, Event: Valve, Profile: intake_lift.in
Event2- Region A: Cylinder, Region B: Exhaust_Port1, Event: Valve, Profile: exhasut_lift.in
Permanent:
Event1- Region A: Inlet_Port1, Region B: Inlet_Port2, Event:Open

Physical Models Turbulence Modeling-RNG-K Eplison is selected
Grid Controls

Activate Fixed Embeddding from the menu

Base Grid:
Enter the grid values for (dx, dy, dz) as per
dx = 0.004 m; dy = 0.004 m; dz =0.004 m

Fixed Embedding-
Add embedding Intake_Valve_Angle, Exhaust_Valve_Angle, CylinderHead

Intake_Valve_Angle:
Entity Type: Boundary
BoundaryID: Inlet_Valve_Angle
Mode: Permanent
Scale: 3
Embed Layer: 1

Exhaust_Valve_Angle:
Entity Type: Boundary
BoundaryID: Exhaust_Valve_Angle
Mode: Permanent
Scale: 3
Embed Layer: 1

CylinderHead:
Entity Type: Region
Mode: Permanent
Scale: 2
RegionID: Cylinder

Output/Post Processing Post Variable Selection>No Change
Output Files Time Interval for writing 3D output data files: 2 deg
Time Interval for writing text output: 0.1 deg
Time Interval for restarting output: 10.0 s

 

After this all the input files was imported to a seperate folder. Converge creates .txt  files which contains all the values entered while setting up the case for respective settings done above. These input files will be processed by converge using Message Passing Interface (MPI) standard

2. Solving:

For running the simulation, Cygwin tool was used instead of converge studio interface. Cygwin is a POSIX-compatible API which is based on command prompt is used to run the simulation

Steps:

a. Navigated to the folder location containing the input files

b. Entered the command> mpiexec.exe -n 2 converge.exe logfile & : This allows converge to run two processors (selection on number of processor cores present as per the system configuration, can use multiple cores if available) for the parallel processing and load balancing

c. Entered the command> taif -f logfile

d. After the simulation is over. Went back to converge studio>Post-Processing 3D

e. Enter Case Name>"Test", Change the File Type to Paraview VTK in-line binary format

d. Enter the address for the output files>Select all files>Select all Cell Variables>click on Convert

e. After the conversion of the post files to the binary output, open the Test.vtm (group file) file in Paraview

  

3. POST-PROCESSING:

ANIMATION:

No Hydro Simulation: SI8-PFI Engine Isometric View

No Hydro Simulation: SI8-PFI Engine Cutplane View

 

 

 KEY CONCLUSIONS

1. In the animation it is observed that the piston, inlet and outlet valves' movement are in accordance to the desired motion.

2. There were no disconnect triangle errors popping up while running the simulation, which is a common error in cases like this so the same setup shall be carried forward for full hydrodynamic simulation. 


Projects by Gaurav Samanta

Data Analysis
Gaurav Samanta · 2020-01-08 12:32:09

Objective: The objective of this project is to write a code for data analysis from an input file and perform the following operations 1. Compatibility Check: The program will ask for the file name with valid extension which if provided incorrect will terminate the prog Read more

Constraint Minimization
Gaurav Samanta · 2020-01-08 11:52:01

Objective: The objective of this project is to minimize a simple non-linear funtion using Lagrange Multiplier The target equation is: `f(x,y)=5-(x-2)^2-2(y-1)^2` & the constrain equation: `x+4y=3` Theory: In real engineering applications there is a Read more

Curve Fitting
Gaurav Samanta · 2019-12-27 19:42:51

Objective: The objective of this project is to perform a curve fitting between the temperature and Cp values given the data file   Theory:  Curve Fitting: it is a process of constructing a curve that best fits the provided data series. Curve fitting in gene Read more

Ice Breaking Challenge
Gaurav Samanta · 2019-12-27 19:01:57

Objective:  The objective of this project is to determine the minimum pressure required to break a given thickness of ice using an air cushion vehicle through Newton Raphson Method Equation: `p^3(1-beta^2)+(0.4hbeta^2-(sigmah^2)/r^2)p^2+((sigma^2h^4)/(3r^4))p-((s Read more

Objective: The objective of this report is to understand the CAD modeller features in Star CCM+ and use it to generate a 3D model of an Ahmed Body and a Convergent Divergent Nozzle in the same as per the drawing given below   Procedure & Results: Conv Read more

Air Standard Cycle
Gaurav Samanta · 2019-12-10 14:51:18

Objective: The objective of this report is to create a python based Otto Cycle simulator which can create the  PV diagram and give the thermal efficiency of the engine as output  Theory: Otto cycle is the set of processes used by the spark ignition Read more

2R Robotic Arm
Gaurav Samanta · 2019-12-10 14:33:33

 Objective: The objective of this report is to simulate the foward kinematics of a 2R robotic arm using python programming   Theory: Robotic arm manipulators are used in various industry verticals such as automotive, electronics, warehouses and logistic Read more

Solving 2nd order ODE
Gaurav Samanta · 2019-12-10 08:14:29

Objective: The objective of this report is the simulate the transient behaviour of a simple pendulum and the create the animation of its motion for a given time interval Theory: The following equation (Ordinary Differential Equation) for the position of the bob w. Read more

Flow over Bicycle
Gaurav Samanta · 2019-11-22 18:54:05

Objective:   The objective of this  study to understand the change in drag force with respect to velocity different cycling positions and drag coefficeint for constant frontal area and constant velocity.   Theory: Cyclists tend to experien Read more

Objective: The objective of this report is to understand the different steps involved in any CFD simulation and the applications of CFD in Medical, Oil & Gas and Construction Industry 1. Steps involved in a CFD Simulation  Step 1. CAD Modelling/Geometry Impor Read more


Loading...

The End