Multidimensional Simulation of a Spark Ignited Port Fuel Injected (PFI) Engine using CONVERGE CFD

Geometry Model

Front View Top View

Animation:

INPUTS:

Engine Geometric Parameters:

Bore =0.086 m

Stroke = 0.09 m

Connecting rod length = 0.18 m

RPM = 3000

Run parameters:

Simulation mode: HydroSimulation

time parameters:

Start time - Use your best judgement

end time - Use your best judgement

Boundary conditions:

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 - 525KExhaust

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 - AirIntake valve top temperature - 480K

Intake valve angle temperature - 480K

Intake valve bottom temperature - 480K

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)

AirTemperature - 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

Nozzle positions:

Nozzle diameter = 250 micro-meter

Circular injection radius = Nozzle radiusSpray

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

Spark Ignition Parameters:

Start of spark = -15

degSpark duration = 10 deg

Spark location = -0.003 0 0.0091

Spark radius = 0.0005m

Important Plots obtained for Cylinder region are:

1. Pressure-Crank Plot

This is the typical pressure-crank plot seen in Spark Ignition engine

2. Mean Temperature- Crank(Deg) Plot

We get the highest mean temperature of about 2500k

3. Heat Release Rate (J/time) - Crank(Deg) Plot

• It tells us how much heat energy is released per crank angle
• Here, it is about 52 J/time

4. Integrated Heat Released (J) - Crank(Deg) Plot

In the end, we get the value of 1241.11 J which is the total amount of energy we get from the combustion process alone

5. Species Mass (IC8H18) - Crank angle plot

6. Liquid Spray Drops(ppm) - Crank(Deg) Plot

• With this plot, we can calculate the Lagrangian parcels that are active in the domain
• We peak up to 44058, and as it declines parcels drops due to vaporization and then combustion taking place
• In the end, it comes down to 0 parcels, which means no parcels left in the chamber i.e. complete combustion of fuel & no hydrocarbons are left

Plots regarding Emissions ( Hiroy_Soot, CO2, HC, NOx, CO)

OBJECTIVES to be achieved:

1. What is the Compression Ratio of this Engine?

2. Why do we need a wall heat transfer model? Why can't we predict the wall temperature from the CFD simulation?

3. To calculate the Combustion Efficiency of this Engine.

4. Using the Engine Performance Calculator, determine the Power and Torque of this Engine.

5. What is the Significance of ca10, ca50, ca90?

Compression Ratio of this Engine:

It can be determined with the following plot obtained.

Compression Ratio= Maximum Volume/Minimum Volume

Maximum Volume: 0.000574218 m^3

Minimum Volume: 5.75504e-05 m^3

Therefore, Compression Ratio = 9.94

Wall Heat Transfer Model:

Here in Turbulence Modeling, we have used RANS and Turbulence model as RNG-Epsilon, and wall heat transfer model as 'O'Rourke and Amsden'.

CFD simulations are not capable of predicting the peak values of heat flux and also it does not account for near-wall effects (viscous and non-viscous). And using the wall heat transfer model allow us to capture the near wall transport phenomenon and also allows us to apply the mesh resolutions for first near wall computational cells reaching the buffer or even viscous sublayer region.

Combustion Efficiency of this engine:

Combustion efficiency is a measurement of how well the burnt fuel is being utilized in the combustion process

Combustion efficiency = total heat energy from consumption (from IHR plot) * Total energy content of the fuel (Amount of fuel * Calorific Value)

Total Heat Energy: 1241.11 J

Amount of Fuel: 3e-05 kg

Calorific Value: 44.8 MJ/kg

Combustion Efficiency = 0.9232 = 92.32%

Power and Torque:

Using the engine performance calculator

We know the formula,

Power(P) = (2*π*N*T)/60

Power = Work Done/Duration =468.646/(4*pi/3) =35.130 kW

Torque(T) = 111.8817 N-m at 3000 rpm

The significance of ca10, ca50, ca90:

Crank angle (CA) degree value indicates the per cent amount of combustion that has occurred.

In this case,

The crank angle value at which 10% of combustion has occurred ca10: 6.83717

The crank angle value at which 50% of combustion has occurred ca50: 18.4623

The crank angle value at which 90% of combustion has occurred ca90: 31.701