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

Aim- To con duct the full hydro set up for pfi angine and to calculate the engine charactersticts.

Objectives-1.Identify thye compression ratio

2.Identify the combustion efficiency

3.Dretemine powe and Torque.

set up

Geometry-

simulation time parameters-

Boundary condtion

1. Piston temperature - 450K
2. Liner temperature - 450K
3. Head temperature - 450K
4. Spark Plug temperature - 550K
5. Spark Plug electrode temperature - 600K
6. Exhaust ports temperature - 500K
7. Exhaut outflow - 1 bar
8. Exhaust outlflow temperature - 800k
9. Exhaust species concentration - Calculate the stoichiometric condition
10. Exhaust valve top temperature - 525K
11. Exhaust valve angle temperature - 525K
12. Exhaust valve bottom temeprature - 525K
13. Intake port - 1 temperature 425K
14. Intake port - 2 temperature 425K
15. Inflow pressure - 1 bar total pressure
16. Inflow temperature - 363K
17. Inflow species - Air
18. Intake valve top temperature - 480K
19. Intake valve angle temperature - 480K
20. Intake valve bottom temeprature - 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)
  • Air
  • Temperature - 370K
  • Pressure - 1 bar
• Cylinder
  • Pressure - 1.85731 bar
  • Temperature - 1360K
  • Stoichiometric composition

Injection Parameters

1. Fuel flow rate = 7.5e-4 Kg/second
2. Injection start time = -480.0
3. Injection duration = 191.2
4. 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

Spark Ignition Parameters

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

Turblence Model-Defalut Kpsilon RNG model ued as this is recommended for combustion in converge.

Mesh

Grid size of 0.004 was used in all the direction and advap-tive Mesh refinemewnt was used for the cyclinder and the portion of the intake near the cyclinder .The Amr was definedsensitive to velovity and temperature

Fixed embeding was aslo done in the following regions

Results

compression ratio-The compression ratio is defined as the ratio between the volume of the cylinder with the piston in the bottom position, V_bottom (largest volume), and in the top position, V_top (smallest volume).

from above plot the minimimum volume is 5.70326e-5 and the maximum volume is 0.000574187

and the compression ratio is=(5.74187e-5)/(5.70326e-5)=10.06

Hence compression ratio is 10:1

Combustion effiency-the formula to calculate the efficiency is

Efficiency=(Total engery from the combustion process)/(Engery content)

the numertor from above euation is the maximium value of the integrated HR curve as shown below

Engery content of the fuel =Mass of the fuel *Lower heating value of IC8H18

mass of the fuel=44.8MJ/kg

LHV of IC8H18=3e-5

therefore efficiency=((12411/(44.8*3e-5))=92.4%

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

In PFI engine the compressed air and the fuel is ignited by the spark plug which results flame propgation inside the cyclinder as flame propagetes the effiency ,power and the emission are effected hence the the heat from the cyclinder transfered to liner (wall )when it comes to contact with liner hence after some time the spread of the flame stops.Due to the turblance the parameters are effectedhence de to these we use the heat transfer model.

What is the significance of ca10, ca50 and ca90?

The ca10 indiactes the combustion process at crank angle of 10 the significance it indiactesthe start of the combustion and the ca50 indicates the combution process at the crank angle of 50 and its significance is it defines the premixed combustion AND THE START OF THE DIFFUSION combustion of the fuel. and the ca90 indicates the combustion process at the crank angle of 90 and it indicated the end of combustion process.

from the engine performance calculator

WD=486.646N-M

combustion duration=240.199degg

crank nspeed=3000rpm

number of degress per second=18000

time for one degree=5.5555e-05

Time taken for combustion=5.555e-05*240.199=0.01334 sec

power=work done/time taken for combustion

=486.646/0.01334=35.13KW

Torque=power*60/pi*N

=35160*60/2*pi*3000=111.822N-m

https://youtu.be/DwQHLfzGstc

sa