FULL HYDRO case set up (PFI) & Simulation of 4V- Spark Ignition Engine

Procedures:

1. Preparing an IC Engine to stimulate with no hydro solver using Converge CFD.
2. Solve the surface error issues faced in the ICE CAD model.
3. Setting up the boundary conditions & simulation setup.
4. Base Grid meshing is to be
   • dx = dy = dz = 0.0004m.
5. Using CYGWIN to execute the CFD solver.
6. Check the case for the correct mechanical simulations (like the motion of valves with respect to time) before running the case with FULL Hydro Setup.
7. After verifying the mechanical simulations solve the case with Full Hydro Setup.
8. Use Converge CFD to post convert the output files to ParaView format.
9. Paraview to Post Processing the results.

Inputs (Engine Parameters):

• Bore =0.086 m
• Stroke = 0.09 m
• Connecting rod length = 0.18 m
• RPM = 3000
• Simulation mode: No Hydro
• Start time: -520 deg
• end time: 120 deg
• Piston temperature - 450K
• Liner temperature - 450K
• Head temperature - 450K
• Spark Plug temperature - 550K
• Spark Plug electrode temperature - 600K
• Exhaust ports temperature - 500K
• Exhaust outflow - 1 bar
• Exhaust outflow temperature - 800k
• Exhaust species concentration - Calculate the stoichiometric condition
• Exhaust valve top temperature - 525K
• Exhaust valve angle temperature - 525K
• Exhaust valve bottom temperature - 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 temperature - 480K
• 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
  • Pressure - 1.85731 bar
  • Temperature - 1360K
  • Stoichiometric composition
• Injection Parameters
  • Fuel flow rate = 7.5e-4 Kg/second
  • Injection start time = -480.0
  • Injection duration = 191.2
  • Fuel temperature = 330K
• Spark Ignition Parameters
  • Start of spark = -15 deg CA
  • Spark duration = 10 deg CA
  • Spark location = -0.003 0 0.0091
  • Spark radius = 0.0005m

1:- Pre-Processing & Setting up Boundry Conditions:

2:- Processing:

2.1:- Meshing:

2.2:- Active Mesh Refinement Setup: (section along spark plug)

Adaptive mesh refinement is enabled in this case setup with respect to regional velocity & temperature for accurately capturing the sudden pressure, velocity & temperature changes in that region during the combustion process.

2.3:- Active Mesh Refinement Setup: (section along Valves)

Adaptive mesh refinement is enabled in this case setup with respect to regional velocity & temperature for accurately capturing the flow over the valve areas.

3.1- No HYDRO Simulation:

No Hydro Simulation is done before running Full Hydro solver as it consumes more computational time. This helps us to verify the proper mechanical simulation of valves with respect to crank angle.

4.1- Full Hydro Case Setup:

In this case, we use IC8H18 species as a combustion medium which is set to be injected through the intake valve at the respective crank angle. These parcels will be mixed with Intake air mostly containing Oxygen & Nitrogen with the mass fraction of 0.20157 & 0.77292. The mass fraction of IC8H18 is set to be 0.025508.

5:- Processing Data:

5.1- Pressure Date:

In this system, high pressure was found to be 3.89Mpa which is generated during the compression stroke.

5.2- Volume Data:

5.3- Density Data:

The higher density was found to be 8.68 kg/m^3 which is generated during the compression stroke. This is because of the piston which compresses the fuel-air mixture to the required compression ratio before the ignition period.

5.4- Species Data:

The above plot shows us the species particles (IC8H18) at the Combustion chamber region. From the plot, we can see that the number of species tends to zero after power stroke which indicates the fuel is burnt completely.

The above plot shows us the species particles (IC8H18) at the Intake Valve region. From the plot, we can see that some of the fuel is found stuck in the valve region even after power stroke. This can be neglected as the amount of fuel found to be stuck is low.

5.5- Temperature Data:

5.6- Emission Data:

6:- Calculation:

6.1- Compression Ratio:

We know that Compression Ratio = (Total Volume / Swept Volume). From plot 5.2, the total volume is found to be 0.000574219 & Swept Volume is 5.70340e-5

Compression Ratio = 10.068

6.2- Heat Transfer Model:

The mechanism of heat transfer at the walls is mainly comprised of two parts. Convective and radiative. In CFD simulation only the fluid parameters were flagged and solved using the Reynold Averaged Navier Stokes Equation under which the temperature boundary condition is defined by the law of wall. Heat transfer through the combustion chamber affects largely engine efficiency, emissions & engine component Thermo-mechanical reliability. As a consequence, a correct estimation of the wall heat fluxes is mandatory which is difficult to capture in CFD simulation as governing equations solves only the fluid parameters, not solids. Also, it take more time to calculate the Heat Transfer at walls with the system in turbulent condition. This makes the wall temperature to fluctuate from actual in CFD simulations. Thus wall heat transfer model is required to define the precise wall temperature.

6.3- Combustion Efficiency:

The Integrated Heat Release (iHR) found during the simulation is 1241 J

Calorific Value (Cv) of fuel is 1112.4 J/kg

Total Injected Fuel Mass (T)= 3*e^-5 kg

Combustion Efficiency=( Heat Provided to the System/Heat Released by the system ) * 100

here

Heat Released by the system = iHR * T = 0.03723 J

Heat Provided to the system = Cv * T = 0.033372 J

Combustion Efficiency = 89.6 %

6.4- Performance Calculator:

Torque Calculation can be done by Power(P) = (2*π*N*T)/60

here P is the power obtained during the combustion cycle

N is the engine RPM

T is the Torque

We know P=468.646 Nm

N=3000 rpm

Substituting known values 468.646 = (2*3.14*3000*T)/60

We get Torque (T) = 1.49 N-m

6.5- Crank Angle with respect to fuel combustion:

Crank Angle is the angle of rotation of crankshaft measured from the position at which the piston reached the top position called Top dead center (TDC). With the use of thermodynamic models, the rate of heat release and mass fraction burned curves are calculated and from the latter the CA50 parameter (crank angle fifty), which is the angle in which 50% of the total fuel has been burned. This process of obtaining the optimum combustion value typically leads to a value of CA50. CA10 refers to the crank angle during the 10% of the fuel burnt at the start of the combustion cycle & CA90 refers to the crank angle during the 90% of the fuel burnt at the end of the combustion cycle.

From the performance test conducted on Converge Studio, we get the Crank Angle at 10% of fuel burnt is 6.8°, 50% is 18.5°, 90% is 31.7°.

7.1- Post Processing:

The above animation clip shows how the air(white points) from the Intake Manifold is mixed up with the fuel(red points) from the injector during the Intake stroke.

The above animation clip shows the temperature changes during the engine combustion process.