AVL Fire ESE Diesel Setup

AVL FIRE ESE Diesel simulation set up Objective: to analyze the injection and combustion process in diesel engines. Methodology: simulation is being carried out as close cycle simulation. (IVC to EVO) In which the engine parameters are given as input and further spray and combustion models are used to determine the  process.

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In general data Insert the engine general parameters like, Engine layout, Number of cylinders, Bore and compression ratio.

In movement specification data, insert crank radius and connecting rod length.

Import geometry

Import piston

Select sketcher. Import the cavity profile by selecting the required *.dxf file and click open

Spray axis line

Bumping Clearance

Piston profile Bowl Volume

Select sketcher ….. Injector

Insert the injector parameters from injector drawing, 1)  Number of injector holes 2)  Nozzle position z coordinate ( means nozzle hole vertical distance from cylinder head bottom face, not NTP)

a

a: nozzle position z- coordinate  b: nozzle dia. at hole center position c: nozzle hole inner diameter

c  b

 Nozzle hole outer half cone angle is generally between 6 to 8 deg. Spray angle delta is spray cone angle (SCA), take this value from injector drawing.

Block Structure

If the default parameters do not give the right shape of the Piston Bowl, activate Display / edit characteristic points and set them manually. keep default parameters in selections and const CR tab.

Mesher Based on geometry description, a set of computational mesh covering 360 deg. is created.

Meshing parameters

Such mesh error should not be there*

Use default parameters for boundary layers. Use compensation volume on piston to tune CR to actual CR

Change compensation volume width to 1 to 1.5 mm according to engine. Click on Generate 2D meshes.

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*1: adjust block structure to get correct mesh.

Save the setup in working directory Go to Simulation parameters Run mode

Enter the run mode as crank angle Star angle: IVC End angle: EVO Engine speed: RPM Boundary Conditions

Enter the experimental values of temperature in BC ’s. Fluid properties: keep default Initial Conditions: use conditions at IVC

In initial conditions swirl is swirl x RPM EGR mass fraction: % of EGR in cylinder EGR composition: % of oxygen in EGR (reference FIRE user guide)

All solver settings keep same as FIRE_922 document

In particle introduction methods

In Diagrams: calculate injection rate according to Q = Cd x A x V

Where, A: area of nozzle hole (pi()*0.25*d*d) V: velocity (sqrt. ((2(P line - Pcyl)/rho)) Cd: discharge coefficient Pline : experimental line pressure Pcyl : experimental cylinder pressure rho: density of Diesel

Enter the normalized rate of injection in injection rate, for example

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