CFD Online Discussion Forums

CFD Online Discussion Forums (
-   AVL FIRE (
-   -   CI simulation (

yousefzadeh August 31, 2013 08:51

CI simulation
I'm a novice user in AVL FIRE. i want to simulate the closed Cycle of CI Combustion. of course my compression ratio is 11 & for this reason i used high temprature in beginning of cycle (550 K in BDC). injection is done in 697 deg ,but i have a very weak ignition. for example my burnt fuel mass fraction is 0.000005 in 720 deg & maximum rate of heat release is 2 j/deg!!! as a another result i have a motoring pressure for my pressure diagram!! I checked any data, but i didnt have any success in my problem..
tnx for any help & proposal.

kimmhw September 1, 2013 21:17


Even though your information is not enough, please check..
- initial cylinder pressure
- injected/evaporated/remaining fuel mass
- cylinder pressure/temperature trace during simulation

If Breakup/Evaporation are OK, you should check the combustion parameters.

After check, please show more information.

yousefzadeh September 2, 2013 02:12

i checked all of this parameter that you said before, & they are not logical for self ignition.
but i got a great point that fractions of air components are not logical at all. in fla file & species mass fraction:
for example O2 mass fraction is about 1e-10 & N2 is about 0.7!! i think this is my problem, that i dont have any choises in fluid propertis for air..
combustion model is eddy beak up
my initial pressure is 256000 Pa.
tnx for any suggestion.

kimmhw September 2, 2013 21:30

looks strange.
I guess you defined EGR mass fraction in initial condition.
Please describe your inputs in "Standard species transport" of INITIAL CONDITIONS.
Did you also check spray evaporation?

yousefzadeh September 3, 2013 02:51

yeah,your guess is true. i had a mistake that defined the EGR mass fraction in initial condition. after solving this problem i run my case & there are some results that obtained:

max Rate of Heat release: 29 j/deg
max burnt fuel mass fraction:0.008
max mass fuel evaporated: about 8e-5 kg
fuel mass: 0.00037 kg

i dont have a good fuel evaporation & i can't find this reason..
fuel is diesel & maximum temprature is 1100 K.


mehi December 15, 2013 12:56

hi guys!
im recently working by fame engin plus.any body knows in fame engin plus at input surface section what is the range of cranck angle(valid from... to... cranck angle)?

All times are GMT -4. The time now is 03:05.