Week-11 : Discretization of 3D intake manifold using GEM-3D
Q:-Tutorial- single cyl DI add case 2 with discretization length 0.1 mm for intake runner and compare with default case 1
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- Parameters-Torque, BSFC, max cylinder pressure
- simulation time
Ans:- As shown below, the case setup of CI Single cylinder Engine in which air enter at ambient temperature and Pressure passes through runner, throttle valve to Combustion Chamber. GT Power is a 1D simulation Process but actual Engine components like inlet manifold and Exhaust Manifold has 3D complex Shapes. The simulation through these 3D components can be accurately Captured through 3D CFD analysis Softwares.
In GT Power to capture accurate result of these components in 1D simulation,Discritization is significant method in which components are divided into small volumes.This method helps to capture accurate result in 1D simulation. The discretization length should be 0.4 time of cylinder Bore for inletmanifold and 0.55 time Cylinder Bore for Exhuast Manifold.The Discritization length can be less than for After Treatment System to get accurate result. With decrease of Discritization length,the process time to get result is increased. Discritization length is directly Proportional to simulation time.So avoid unnecesserly decrease of Discritization length to get result in less Simulation time.
The below case is run with two case Setup in which first case run with Discritization length of 40mm and Second case with Discritization length of 0.1 mm.
The Fuel injection Data is given below with injection Timming of -5 deg and Injection Duration is 18deg
AS shown below Run case with two case Setup.
Engine speed= 3600 RPM
Case-1 Descritization Length = 40mm
Case-2 Descritization Length = 0.1 mm
As shown below the computation Time for First case in which Descritization Length is 40mm is 3.62 Second. As simulation time depends on Descritization Length,first case take very less time to show results.
As shown below the computation Time for Second case in which Descritization Length is 0.1mm is 40min and 50Second. As simulation time depends on Descritization Length,Second case take more time to capture result.
The results of both cases open in GT Power are given below.
Engine Geometry as follow below
As Shown below
Brake Power= 36.3 kw (Case-1)
Brake Power = 36.2 kw (Case-2)
Brake Torque = 96.2 Nm (Case-1)
Brake Torque = 95.9 Nm (Case-2)
BSFC = 238.2 g/kwhr (Case-1)
BSFC = 238.9 g/kwhr (Case-2)
As Shown below
Maximum Pressure = 117.11 bar (Case-1)
Maximum Pressure = 115.18 bar (Case-2)
Explore tutorial no 2 (GEM3D) - “Building intake manifold from STL model”
Ans:- GTspace claim is software in which we can open other 3D file formats like parasolid, Igs,Proe,catia, solidworks,stl ect formats. GTspace claim used to repair 3d Files. Open Inletmanifold in GT space claim as shown below. GEM3D tool is used to divide this 3d Model into small volume and convert into layout for GT Power.
Open Inletmanifold stl file in Gem3D in surface file.The component comes as single part in GEM3D and seperate componet into small volume at places where there is abrupt changes.
Divide component with seperate by curve Option as shown below
As shown below component is divided where section is changing. Delete inlet and outlet surfaces.
Use option cut with 3 point cutting Plane as shown below and adjust cutting plane with control Plane and accurately cut inletmanifold.
Right click on inletmanifold piece and select option convert shape to component,the below dialogue box will Open.Select option pipe in flow volume.The marking of Port 1 amd 2 should be along inlet to outlet flow respectively.check making accurately and convert making position if not ok.
Define Pipe conversion Geometry as shown below and define wall thickness,wall Temperature,Material surface finish, flowing fluid initial Condition like temperature, pressure and air as composition. Do this process of all other Pipes.
As shown below all pipes are converted GEM3D.
Define Inlet port and outlet Port with defferent port ID as shown below and define connection between pipe and rectangular section and set flow coefficient to 0.95 so that flow should be smooth flowing.
Divide other abruots parts into simple volumes and convert into shapes in GEM3D option as shown below. Now Model is ready to convert into GT Model.
Set geometry as shown below and use option export to GT Model and as given below discritization length is 40mm which is 0.4 times of cylinder bore 100 mm.
Arrange GT Model Layout as shown below , the 3D inlet manifold is converted into 1D model with discretization length of 40mm and inlet Parameters. Now GT power can used this model and get accurate result in simulation.
