Week 10: Project 1 - FULL HYDRO case set up (PFI)

Aim - This is full hydro PFI model in which we will be finding these following parameters -

1. 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. Combustion efficiency of this engine
4. Determine the power and torque for this engine.
5. What is the significance of ca10, ca50 and ca90?

Introduction-

In this project we go ahead with boundary flagging geometry created in non hydro case . In this we additional add the nozzle, spray parameters and combustion modelling for hydro PFI model .

These are the following parameters for the engine case setup -

Engine parameters

Bore =0.086 m

Stroke = 0.09 m

Connecting rod length = 0.18 m

RPM = 3000

Run parameters

Simulation mode: No Hydro

Simulation time parameters

Start time : -520 deg

end time : 120 deg

Boundary conditions

Piston

Inflow

Liner

Head

Ext port

Outflow

Ext valve top

Ext valve angle boundary

Ext valve bottom boundary

Inlet port

inlet valve bottom boundary

inlet valve angle boundary

inlet valve top

spark plug terminal

spark plug

inlet port2

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

Pressure - 1.85731 bar

Temperature - 1360K

Stoichiometric composition

Spray modelling -

Select the model for the spray modelling as shown below . and add the injection parametrs and nozzel information as mentioned below.

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 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 -

Select the SAGE model for the combustion modelling. Select the species and put the data .

Spark Ignition Parameters -

Start of spark = -15 deg

Spark duration = 10 deg

Spark location = -0.003 0 0.0091

Spark radius = 0.0005m

Grid size -

Grid size is taken as 0.004.

AMR - AMR is done for the critical area for calculation purpose . In this case AMR is done for the velocity and temprature .

Fixed embedding -

Fixed embedding –

At critical area we used fixed embedding to refine the grid. In given geometry the fixed embedding is done for – Big cylinder embedding , small cylinder embedding, exhaust valve angle and inlet valve angle and injector .

After case set up exports the file to defined folder. Run the simulation in the Cygwin. Generate the output files. As output file is generated run the post processing in Cygwin again. Open the output file in paraview for the mesh view and simulation

Outputs –

PRESSURE Plot for the engine -

It is notice that pressure increases with burning of fuel, reach to maximum and drops after the combustion stroke.

Mean temperature plot cylinder -

Temprature inside the cylinder is steady in starting due to the exhaust gases of last exhuast stroke and increases again rapidly as combustion take place inside the cylinder.

IHR Plot -

IHR basically tells the useful energy released in power stroke. and this energy is used for further cycles of engine and to get desired power output .

Heat release rate -

HRR define the hear release to surrounding . in starting it was near to minimal and increases during the power stroke.

Liquid spray drop plot -

IC8H18 fuel Plot -

Emmision plot

From emission plot indiaction are clear that HC content is high it may due to to rich mixture. On same hand the nox level is compartively low. HC can be control with TWC aftertreatment mehod.

1. compression ratio of this engine

CR of engine is ratio of total volume to the clearance volume.

From volume graph we can calculate the CR.

Total volume – 5.74121 x 10 ^-4 m3

Clearance volume- 5.75786 x 10 ^-5 m3

CR- 5.74121 x 10 ^-4 / 5.75786 x 10 ^-5

CR- 9.971

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

In CFD simulation the thermodynamic data for the parts of engine as input , so wall temperature cant be calculated . That’s why we require heat transfer model to predict the temperature of wall.

3. Combustion efficiency of this engine

Mass of fuel – 0.000003 kg

Calorific value- 43.4 mj/kg

Integraed heat release for PFI is – 1241.04

Combustion efficiency = 1241.04/43.4 x 0.000003 x 1000000

= 95.31 %

4. Determine the power and torque for this engine.

Work done – 468.646 NM

Duration- 240.199 degree

Crank speed – 3000

Degree / sec- 3000/60 X360 = 18000 DEG/SEC

Time for combustion – 240.199/18000 = .0133 sec

Power = W.D / Time = 468.646/ .0133 = 35.23 kw

Power = 2x PIE x N X T / 60

Torque = 35.23 x 1000 x 60 /2 x 3.14 x 3000

Torque – 112.19 N m

5. What is the significance of ca10, ca50 and ca90?

CA10 ,CA50 and CA90 basically tells the fuel combustion rate with respect to crangle .

CA 10 and CA50 shows the heat release 10% na 50 %repectively .

CA10 basically used in the study of start of iginition.CA50 indicates the end of premixed combustion and start of diffusion of fuel .

Conclusion –

For given enigne the HC content is high, we can also see from liquid spray as there some fuel is trapped which is remain unburnt. So to overcome we can increase the pressure of fuel for better atomization. Aftertrement mehtod like TWC can be install to overcome the HC level .