Week 10: Project 1 - FULL HYDRO case set up (PFI)
Aim:
The Main objective of this project was to setup no-hydrodynamics solver transient simulation of a port fuel injection engine using converge CFD.
Introduction
Port injection, the fuel injectors are positioned on the air intake leading to each cylinder of your engine. As your engine sucks in air to later be compressed your fuel injectors will spray a fine mist of fuel that will eventually mix with the ambient air as it gets sucked into your engine.
This allows the air and fuel enough time to mix with each other as they are eventually sucked into the cylinder wall. That air and fuel mixture would then be compressed and then ignited to complete the combustion process of your engine.
Port injection is the other of the two injection technologies and has been around for quite some time.
Benifits of PFI Engine
Since the 1980s, when carburetors were supplanted as the primary fuel injection technology, port injection has been in use. Fuel is injected into your air intake port and drawn into the piston, providing fuel for your engine's combustion stroke.
The advantage of port injection is that it allows air to uniformly mix with the gasoline before it is supplied into the engine cylinder. When the air and fuel mixture is evenly mixed, the combustion process can burn all of the fuel fed into the engine cylinder, which reduces carbon buildup from unburned fuel.
Direct injection allows less time for the fuel to mix with the air entering the cylinder, which can result in hot spots forming inside the engine cylinder. Hot spots are bad because they can cause one place to become significantly hotter than the rest of the engine cylinder walls, rather than uniformly heating them.
STEADY STATE SIMULATION:
These are the simulation we run if are just interested in the end result and not in how those results are getting formed with time. The properties do not change with respect to time or there are no time derivative terms in the equations of motion that govern the fluid flow.
If we want to see how results are changing w.r.t time and how the solution is getting formed over time then we need to run the TRANSIENT STATE SIMULATION.
The time is in Cycles for STEADY STATE SIMULATION whereas time is in Seconds for TRANSIENT STATE SIMULATION.
The project mainly focuses on the following things:-
1. Importing the(.Stl) file on Converge Studio then cleaning up the geometry removing the intersection, patching the new open edge, deleting the unwanted edge, and Fixing the normal orientation of the geometry.
2. Creating Virtual Wind Tunnel using proper Dimension.
3. Case Setup using Converge Studio using proper Solver and Boundary Conditions.
4. Solving the Case Study Files using Cygwin.
5. Post-Processing the result Using ParaView generating plots, contours
1. Importing the Geometry for Geometry Clean Up using Converge Studio and BOundary Flagging
Firstly the Geometry(.stl) was imported in Converge Studio. The diagnostic tool was used to find the open edge, Intersection edges, and other errors like orientation error. Many features were used to repair the geometry like 1. Deleting the edge, node, face. 2. Patching the edge using the patch tool. 3. Stitching the two misalign edges.
The car geometry that was provided had 32 total open edge errors, 1574 intersection. so geometry cleaning plays an important role in setting up a simulation of a engine There were many features that were used to clean the geometry. First, the geometry was checked using the Diagnostic tool to check what kind of error is present then our main target was to repair an open edge without forming an intersection.
First, the surface(Triangle) was deleted shown in green color then the extra edges were removed to make a perfect open loop that can be patch letter. For patching those new open edge the edges were checked and patch repair option was used to patch the open edge method. Then the geometry was checked again to find any error.
Open Edges in the piston wall
Open Edges in the inflow duct
Intersection error
The bpoundary fencing feature was used to mark the fencing in the geomtery and Boundary flagging was done after that selecting the proper number of triangle surfaces. Total 17 Boundary Tags were created in order to define region and physics for engine simulation.
Geomtery of IC Engine was flagged with boundary names represented in above picture along with boundary ID and sum of triangle the particular boundary is created from.
The normal orientation was fixed using automatic option present in Transform>Normal> Automatic fix all the normals.
Normal poitning outward
After transforming the Normals inside geometry
After doing Geometry clean up, The geometry was again finally checked for any error using the Diagnostic tool. At last, all the all errors were repaired as shown in the above picture.
Geometry was finally Cleaned and can be used for further pre processing.
The Geometry with Error can be downloaded from here: Geometry
2.Case-Study Setup
The various parameter was considered while setup this case study. The case study setup dock was used to set up the problem which appears on the right-hand side of the converge studio.
2.1 Application Type:
In order to run a steady-state simulation, firstly, under the Application type in the setup tree, a "Crank angle based IC engine" simulation must be selected.
2.2 Materials:
Under the material tab "Gas simulation" was selected and "Air" as a predefined mixture.
Gas: Air
Global Transport Parameters: Fixed value
by default, the following value is considered.
Prandtl Number : 0.9
Schmidt Number : 0.78
Reaction Mechanism was enabled and the file file was uploaded
3.3 Simulation Parameters
The Transient solver was selected for running this case study along with a "Density-based" solver.
2.4: Boundary Conditions
In this tab, The volumetric region and physics for each boundary were defined.
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 : -480 deg
end time : 240 deg
Boundary conditions
Piston temperature - 450K
Liner temperature - 450K
Head temperature - 450K
Spark Plug temperature - 450K
Spark Plug electrode temperature - 600K
Exhaust ports temperature - 500K
Exhaut outflow - 1 bar
Exhaust outlflow temperature - 800k
Exhaust species concentration - Calculated using 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)
i)ic8h18 - 0.025508
ii)o2 - 0.20157
iii)n2 - 0.77292
iv)Temperature - 390k
v)pressure - 1 bar - Intake port - 2 (away from combustion chamber)
i)Air
ii)Temperature - 370K
iii)Pressure - 1 bar - Cylinder
i)Pressure - 1.85731 bar
ii)Temperature - 1360K
iii)Stoichiometric composition
1)piston
2) Inflow
3)Liner
4)cylinder head
5)Exhaust port
6)outflow
7)Exhaust valve Top
8)Exhaust valve Angle
9)Exhaust valve Bottom
10)Intake port
11)Intake valve Bottom
12)Intake valve Angle
13)Intake valve Top
14)Spark plug
15)Spark plug Terminal
16)Intake port2
2.5: Initial Conditions and Events
4 Volumetric Region was created in order to assign this to all the boundary tag.
Different Volumetric Regions are:-
1. Cyliner Region
Intake Port-1 Region
Intake-Port-2 Region
Exhaust Region
Boundary Flagging according to regions
2.6: Physical Models
A turbulent model was selected out of so many models. RANS standard K-omega SST model was chosen.
2.7: Grid Control
The case study was run using a medium mesh grid size due to less computational resources.
Base mesh sizes are,
S.No. Dx(m) Dy(m) Dz(m)
1 0.004 0.004 0.004
Fixed Embedding
Fixed embedding was done in order to capture more cells near to valve and inside cylinder in order to get more precise data.
Fixed Embedding -1
Fixed Embedding -2
Fixed Embedding - 3
4.7 Output/Post-Processing
after regions and initialization are correctly setup.
Also, while setting up the case, make sure, wall output (BOUNDARIES ONLY) is enabled as this will dump wall averaged output data which is very much important for any IC engine simulation
Post-Variable Selection- Existing value
Output Files- Time interval for writing 3D output files-2 deg
The time interval for writing restart files -0.1 deg
