FULL HYDRO case set up (PFI)

Objective:-

Simulate PFI - engine in Converge CFD

Geometry

The prepared geometry from the previous section has been used in the present simulation.

Simulation

Type of Simulation 

Crank angle-based IC engine simulation

The given parameters were, 

RPM of 3000

Connecting rod of length 0.18m

Stroke of length 0.09m

Bore of depth 0.086m

Materials

The therm.dat file was used to uplod the chemical elements comprising the gas from combustion.

IC8H18 was used as parcel fluid

Simulation Time Parameters

Start degree : -520deg

End Degree 120 deg

The simulation is choosen as transient with full hydrodynamic mode.

Boundary Conditions:

Piston, Intake valve manifold and Exhaust valve manifold comprising of top, angle and bottom have been given wall boundary with translating, surface boundary condition.

The intake manifold is given temperature of 480K and exhaust at 525K.

The lift file has been provided along with the simulation.

 

Liner and header temperature has been given as 450K

Spark Plug is given 550K and its terminal is given 600K.

Exhaust port is given 500K

Intake port is given a temperature boundary of 425K 

Inflow has been given a pressure boundary of 1bar.

Temperature is set to 363K

Inflow species is Air

Exhaust outflow at 1bar

Exhaust outflow temperature is 800K

Exhaust species concentration were calculated and given input

 

Regions and Initial Conditions:

Four regions has been declared 

Intake Port 1

ic8h18 = 0.025508

o2 = 0.20157

n2 = 0.77292

Temperature = 390K

Pressure = 1bar

Intake Port 2

Air

Temperature 370K

Pressure - 1bar

Cylinder/Exhaust

Pressure - 1.85731 bar

Temperature - 1360K

The regions designated to the boundaries are :-

Events

Cyclic Event is given with exhaust and intake profile. Once the combustion is over the cylinder regions connects with the exhaust regions.

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

Spray Modelling

Frossling model has been choosen as the spray model. Collusion model has been choosen as NTC collision

 

Fluel flow rate is 7.5e-5Kg/s

Injection starts at -480deg

Injection duration = 191.2 deg

Fuel Temperature is given as 330K

 

Trapezoidal curve has been choosen as the injection rate shape.

in 4 steps

where, 2nd and 3rd spep has maximum rate and first and last step has zero rate.

 

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

Turbulence Modelling

RANS K - epsilon RNg model has been choosen with default parameters

 

Spray Modelling

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

 

Grid Size

Base Mesh element size is of 0.004 m in all the axis

Adaptive Mesh

 

Fixed Embedding

Boundary Embedding

Intake Valve angle -permanent, Scale - 3, embed layers - 1

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

Region 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 - 16deg, end time = 7 deg, radius = 0.003m

Injector Embedding

Mode - Cyclic

period = 720deg

scale = 4

start time = -480, end time - 286

injector id = injector_0

radius1 = 0.002m

radius2 = 0.004m

length = 0.02m

Result And Discussions:

 

Pressure vs Crank Angle: -

Liquid Parcel in Cylinder vs Crank Angle: -

Fuel Present is cylinder vs Crank Angle: -

 

Mass of isooctane present in the cylinder

1. Calculation of Compression Ratio

The ratio of maximum or the total volume to the minimum volume of the cylinder in which piston traverses is called compression ratio.

 

Compression Ratio = 0.000574/0.00005723 ~ 10.2

2. Need for a wall heat transfer model

Wall Heat transfer model is required as the thermal simulation should be accurate for enabling accurate calculation of engine efficiency.

3. Calculation of Combustion Efficiency

The ratio of the energy recovered by burning fuel to that of its calorific value is called combustion efficiency.

Since the half-rate of fuel is given as 3e-5kg/cycle, also the calorific value of isooctane is 43.44MJ/kg , 

the calorific value of the injected fuel is 1303.2J

From the above plot, the energy released is calulated to be 1241.15J

This the combustion efficiency is 95.2%

4. Engine Power and Torque Calculation

Speed of the engine is 3000 rpm or 18000 deg/sec

Combustion time from above:- 240.199deg

 

Combustion time in seconds = 240.199/18000 = 0.0133s

 

From the above data Gross work = 468.646Nm

Power = 468.646/0.0133 = 2pi*NT/60

Now, T = 112.2W

5. Significance of ca10, ca50 and ca90

caXX refers to the crank angle at which XX percent of fuel is burnt.

 

Geometry Animation

Temperature Animation