ignition failed for G-equation combustion model

fcl · May 4, 2018, 23:25

Hi，
I'm trying to simulate supercharged condition of methanol engine. In extreme condition, Initial pressure in cylinder is 4 bar. I use G-equation combustion model, with ignition set in the picture. In high speed condition, methanol cannot be ignited.Can anyone give me some advice on how to solve this problem and help me understand things better.

Thanks in advance

xieshengbai · May 14, 2018, 18:22

Hi,

Just according to the picture, it looks fine and the ignition should start immediately when the source term is activated if everything else is correct. However, it is possible that the combustion is not self-sustained, i.e., quenched quickly, due to the high speed. So, please double check how the Q-Eqn function varies in time (you may need a high-frequency output of the post files near the start of the source term and visualize the iso-surface of Q-EQN in EnSight). If you are uncertain, please feel free to send your case to support@convergecfd.com. Thank you.

fcl · May 14, 2018, 21:08

Thank you for your replay, I have sent my case to the support email. I will also check it in your way. I can't understand why ignition process is influenced by piston speed, because ignition should have occured in compression strike. If I set ignition time around TDC, pre-mixed gas well start to burn, but that ignition time is too late for me.

xieshengbai · May 15, 2018, 09:59

Thank you for contacting us. I thought "high speed condition" meant high velocity of the flow. Sorry for the misunderstanding. Anyway, we will check your case setup and, hopefully, we will figure it out.

Quote:

Originally Posted by fcl

Thank you for your replay, I have sent my case to the support email. I will also check it in your way. I can't understand why ignition process is influenced by piston speed, because ignition should have occured in compression strike. If I set ignition time around TDC, pre-mixed gas well start to burn, but that ignition time is too late for me.

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May 14, 2018, 18:22		#2
xieshengbai Member Shengbai Xie Join Date: Aug 2016 Location: Convergent Science, Madison WI Posts: 60 Rep Power: 9	Hi, Just according to the picture, it looks fine and the ignition should start immediately when the source term is activated if everything else is correct. However, it is possible that the combustion is not self-sustained, i.e., quenched quickly, due to the high speed. So, please double check how the Q-Eqn function varies in time (you may need a high-frequency output of the post files near the start of the source term and visualize the iso-surface of Q-EQN in EnSight). If you are uncertain, please feel free to send your case to support@convergecfd.com. Thank you.

May 14, 2018, 21:08		#3
fcl New Member Join Date: Oct 2017 Posts: 14 Rep Power: 8	Thank you for your replay, I have sent my case to the support email. I will also check it in your way. I can't understand why ignition process is influenced by piston speed, because ignition should have occured in compression strike. If I set ignition time around TDC, pre-mixed gas well start to burn, but that ignition time is too late for me.