Port Fuel injection Engine Simulation - Full hydrodynamic

Port fuel Injection - Full hydrodynamic Simulation

Objective: To perform full hydro Simulation of the PFI Engine.

Geometry: A premodelled CAD of PFI is imported and boundry flagging is carried out as shown in the figure.

Figure: Model coloured according to the regions and boundaries are flagged.

Boundary Flagging:

• Boundary Flagging of the geometry is carried out and each of the part is assigned to a particular region as shown below.
• For this project, 4 main regions are defined namely:
  • Cylinder region
  • Intake port (consisting of fuel and air mixture as main species)
  • Intake port 2 (consisting of only air as species)
  • Exhaust region
  • Spark plug and terminal are assigned to Cylinder region.

Figure: Assigning each part to a particular region

case Set up:

• It is a IC engine application.
  • Cylinder dimensions like bore,stroke, connecting rod length etc. are entered
    • Bore: 0.086 m
    • Stroke: 0.09 m
    • Connecting Rod length: 0.18 m
• A reaction mechanism file provided is imported that consists of all the species participating in the combustion mechanisms.
• Predefined mixture is air.
• Parcel simulation is selected and IC8H18 is defined as the liquid.
• Simulation mode: Full hydrodynamic Simulation mode is used.
• Simulation time parameters:
  • Start time: -480 CA deg
  • End time: +240 CA deg
  • Initial and minimum time step: 1e-7
  • Maximum time step: 0.0001
• Boundary Conditions:
  • Piston: Wall moving type boundary with imposed temperature of 550 K
  • Cylinder liner: Stationary wall with imposed temperature of 500 K
  • Cylinder head: Stationary wall with imposed temperature of 550 K
  • Exhaust port: Stationary wall with imposed temperature of 550 K
  • Inflow: Atmospheric pressure, temperature of 363K and air is the species.
  • outflow: Atmospheric pressure
  • Exhaust valve top, angle and bottom: It is a wall boundary type. exhaust valve lift profile is imported and imposed temperature is set as 550 K.
  • Intake valve top, angle and bottom boundaries: It is a wall boundary type. Intake valve lift profile is imported and imposed temperature is set as 450 K.
  • Spark plug and terminal: It is a wall boundary with imposed temperature of 650 K
  • Regions and Initializations:
    • cylinder region: CO2, H2O, N2 are the species
    • Intake port region: C8 H18, O2, N2 are the species with imposed temperature of 390 K.
    • Intake port 2 region: air is the species with imposed temperature of 370 K.
    • Exhaust region: CO2, h2O, N2 are the main species/
    • In events: Intake and exhaust valve events are defined as cyclic events and between intake port and intake port 2 regions the event is permanent.
  • Turbulence model: RNG k-ɛ.
  • Base Grid size is 4 mm along x, y, z directions.
  • Fixed embedding is used near the valves and cylinder as shown in the image below.

Figure: Fixed embedding set up

• Time Interval for writing 3D output files is 2 deg, text output: 0.1 deg, restarting output: 10 deg
• Other parameters like Spark timing, injection parameters and other initial conditions are taken from the data provided in the challenge page.
• The input files are exported and simulation was run.

Figure: Exhaust lift profile with max lift of 7.1 mm and intake lift profile with max lift of 8.2 mm.

Results:

• Cylinder Pressure:

Figure: Cylinder pressure vs Crank angle angle diagram

• • The peak firing Pressure is 3.88 MPa. at 24 deg CA after TDC.

• Heat Release Rate (HRR):

Figure: heat release rate

• • The Max heat release rate is 59.35 J/deg @ 18.84 deg CA.
  • The total amount of heat release for the entire cycle is 1241 J.

• Mean in-cylinder temperature:

Figure: The Max Mean Temperature in the Cylinder is around 2483 K.

• Specific heat capacities:

Figure: Specific heat capacity at constant pressure.

Figure: Specific heat capacity at constant Volume.

• • Specific heat capacities vary with crank angle because of variation of pressure and temperature within the cylinder.

• Spray drops:

Figure : liquid spray drops in intake port

Figure : liquid spray drops inside the cylinder

• Fuel Flow:

Figure: Fuel injection profile.

• • Quantity of Iso octane that is present inside the cylinder. Max quantity is 1.45e-6 kg.

Emissions:

Figure: Carbon monoxide Emissions.

• • carbon monoxide emission is a result of incomplete combustion.
  • Max amount of CO is generated at 30 deg ATDC.

Figure: Carbon dioxide Emissions.

• • carbon dioxide emission is a result of complete combustion.

Figure: Soot emission

• • Soot emissions is one of the major problems in Diesel Engine which is also caused due to incomplete combustion and insufficient oxygen.

Figure: NOx emissions

• • NOx emissions are the major problems in diesel engines.
  • They are caused mainly due to very high temperatures and in the above figure we can observe that the Nox emissions are the highest when the Incylinder temperature is maximum ( See mean temperature figure above)

• Animation of Port Fuel Injection: Iso-Octane Flow

Calculations:

• Compression Ratio of the engine is 10.5

• Combustion efficiency = ( heat energy released ) / ( fuel energy supplied)
  • Fuel energy supplied = mass of fuel X Calorific value of the fuel = 3e-5 X 43000 = 1290 J
  • Combustion efficiency = (1241/1290) X 100 = 96.2%

• power = work/Time
  • time per degree calculated from engine speed of 3000rpm is 5.5 X 10 ^-5 sec/deg.
  • Total time for duration of 240.199 deg is 0.0132 sec/cyc.
  • power = 468.64/0.0132 = 35.50 kW.
  • Torque = 113.0 Nm

• CA10, CA50 and CA90 are the parameters that indicate the crank angle at which 10%, 50% and 90% of the mass is burned inside the cylinder. They say how much the Ignition timing is retarded or advanced which has a direct impact on performance parameters like BSFC and Exhaust gas temperature. Thermodynamically the value of CA50 should be around 8 deg CA. But the value may vary depending upon the engine and requirement.

• Other result parameters obtained from Engine Performance calculator is as shown below:

Conclusions:

• PFI simulation is carried out to analyse various performance parameters and engine emissions.