Converge CFD

Full hydro simulation of PFI engine using Converge CFD

OBJECTIVE-Simulate a full hydro condition of Port fuel injection engine.

Geometry-A 3d geometry ofPort fuel injection engine was imported to converge for analysis.

Setup-

Application Type-

Crank angle-based IC engine

Physical Parameters:

  1. Bore =0.086 m
  2. Stroke = 0.09 m
  3. Connecting rod length = 0.18 m
  4. RPM = 3000

Materials-

Gas Simulation- The therm.dat file was uploaded to get the thermodynamic properties of the fuel.

Parcel Simulation- IC8H18 was selected from predefined liquids.

Reaction Mechanism

Species-Parcel IC8H18

Mesh-

Simulation Time Parameters:

Run Parameters:

Transient,Full hydrodynamic.

Simulation Time Parameters:

  1. Start time : -520 deg
  2. end time : 120 deg

Boundary Conditions:

Boundary Type-WALL , Wall motion-Translating and Surface-Moving

Law of wall for velocity & temperature boundary conditions

  • Piston-Velocity-piston motion, temperature – 450K
  • Exhaust valve top temperature – 525K, Exhaust lift profile is imported
  • Exhaust valve angle temperature – 525K, Exhaust lift profile is imported
  • Exhaust valve bottom temeprature – 525K, Exhaust lift profile is imported
  • Intake valve top temperature – 480K, intake lift profile is imported
  • Intake valve angle temperature – 480K, intake lift profile is imported
  • Intake valve bottom temeprature – 480K, intake lift profile is imported

Boundary Type-WALL , Wall motion-Stationary and Surface-Fixed

Law of wall for velocity & temperature boundary conditions

  • Liner temperature – 450K
  • Head temperature – 450K
  • Spark Plug temperature – 550K
  • Spark Plug electrode temperature – 600K
  • Exhaust ports temperature  – 500K
  • Intake port – 1 temperature 425K
  • Intake port – 2 temperature 425K

Boundary Type-INFLOW & OUTFLOW

  1. Inflow pressure – 1 bar total pressure
  2. Inflow temperature – 363K
  3. Inflow species – Air
  4. Exhaut outflow – 1 bar
  5. Exhaust outlflow temperature – 800k
  6. Exhaust species concentration – Calculate the stoichiometric condition

Regions and 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
    1. Pressure – 1.85731 bar
    2. Temperature – 1360K
  • Exhaust region same as cylinder region

The below figure shows the different regions in the engine.

Events:

Cyclic event is given with exhaust and intake lift profile

Permanent event is given to intake port 1 & 2 and set to open.

Physical models:

Spray Modelling:

-Frossling model

-collison model-NTC collision,collision outcomes-Post collison outcomes

Injection Parameters:

  1. Fuel flow rate = 7.5e-4 Kg/second
  2. Injection start time = -480.0
  3. Injection duration = 191.2
  4. Fuel temperature = 330K

Rate shape implementation:

Nozzle Positions:

Nozzle diameter = 250 micro-meter

Circular injection radius = Nozzle radius

Spray cone angle = 10

  • Nozzle 0
    • center 0.0823357 0.00100001 0.07019
    • Align Vector -0.732501 0.210489 -0.647408
  • Nozzle 1
    • center 0.0823357 -0.00099999 0.07019
    • Align Vector -0.732501 -0.210489 -0.647408
  • Nozzle 2
    • center 0.0823357 -0.0004 0.07019
    • Align Vector -0.5 -0.2 -0.647408
  • Nozzle 3
    • center 0.0823357 0.0003 0.07019
    • Align Vector -0.5 0.2 -0.647408

Combustion modelling:

Turbulence Modelling:

RANS k-epsilon RNG model

Spray Modelling:

0.04 J of energy

  • Start of spark = -15 deg
  • Spark duration = 10 deg
  • Spark location = -0.003 0 0.0091
  • Spark radius = 0.0005m

Grid Control:

Base Mesh- dx=dy=dz=0.004m

Adaptive Mesh Refinement:

Velocity Adaptive Mesh Refinement

Temperature Adaptive Mesh Refinement:

Fixed Embedding:

Boundary Embedding

Intake valve angle-Permanent, Scale-3, embed layers-1

Exhaust valve angle-Permanent ,Scale-3, embed layers-1

Cylinder Embedding-cylinder

Big Cylinder Embedding-Permanent, Scale-1 ,0.08m

Small Cylinder Embedding-Permanent, Scale-1 ,0.018m

Spherical Embedding-

Spark plug-

Small sphere-Cyclic, Scale-5 ,start time=-16 deg ,end time=7 deg ,radius=0.001m

Large sphere-Cyclic, Scale-3 ,start time=-16 deg ,end time=7 deg ,radius=0.003m

Injector Embedding-

Animation for no hydro condition:

Animation for Full hydro condition:

Results-

Pressure Vs Crank angle:

 

Mass of Liquid parcel present in cylinder at every crank angle:

The below graph shows the amount of liquid drops present at each crank angle.We can see that all the mass has been utilised in combustion and there is no unburnt fuel at the end.

Mass of isoctane present in cylinder at every crank angle:

The below graph shows the amount of IC8H18 present at each crank angle.We can see that all the mass has been utilised in combustion and there is no unburnt fuel at the end.

Compression ratio:

Compression ratio is the ratio of maximum volume of cylinder when the piston is at bottom dead center to the minimum volume of cylinder when the piston ia tdc.

From the below graph we can find the maximum and minimum volume of cylinder and calculate the compression ratio.

Compression ratio=VmaxVmin=Vc+VsVc=0.0005745.723e-5

                              =10.02

Where Vc=clearance volume 

            Vs = swept volume

Why do we need a wall heat transfer model:

Calculate the combustion efficiency of this engine:

Combustion efficiency can be defined as the ratio of total energy released by combustion to the amount of energy contained in the fuel.The energy contained the fuel is called Lower heating value or calorific value.

The below graph indicate the integrated heat released by the combustion process.

Mass of Fuel=3e-5 kg/cycle

Lower heating value of isoctane=43.44 MJ/kg=43.44*3e-5=1303.2 J

Energy released= 1241.15 J

Combustion efficiency=energy released/LCV=1241.15/1303.2=0.952

Combustion efficiency=95.2 %

Power and torque for the engine:

From the engine performance calculator,

Speed =3000 rpm=3000/60 rps

= 50 revolution/sec

=360*50 degree/sec

Combustion time= 240.199 degree

Combustion time in seconds=240.199/(360*50)=0.0133 s

Now,

Work=468.646 N.m

Power=work/time

Power=468.646/0.0133

Power =2πNT60

so,   T=Power⋅602πN

=112.2 W

Significance of ca10, ca50 and ca90:

ca10, ca50 and ca90 refers to the crank angle at which 10,50 and 90 percent of fuel is burnt.

From the results the value are,

ca10=6.837

ca50=18.46

ca90= 31.7

Conclusion:

The full hydro condition of Port fuel injection engine was set and the simulation was run successfully.

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