[00:00:06]
>> Next up John Long suppression of combustion instability. So today I'm going to talk about combustion instability 1st of all what is the combustor. When you look at the airplane there is a circular thing attached to the wing that is the combustor and the combustion instability is a situation when the combustor is vibrating then why the vibrating Well you may have an experience of blowing air into a bottle and here sound right and that is because when you blow the air the air molecules are vibrate at the natural frequency of the bottle the same phenomenon happening happen in the combustor as well the bottle corresponds to the combustor and blowing air corresponds to flame and the combustion instability of course when the flame via very set the natural frequency of the combustor and when the amplitude of the vibration is too large the combustor maybe destroyed this is why it's a serious problem in the combustion industry so to suppress instability we use a damping device which is literally a device that dampens a vibration but here's a really important engineering question Where should we install this damping device Well to answer this question let's think about the swing example imagine that your child is playing on a swing a let's say you want to stop the swinging then where are you going to hold it well you're not going to hold the top of the swing because there is no swinging at all rather you're going to hold the bottom of the swing because death still the Kishen that we're the swing is the largest.

[00:01:59]
Similarly when you want to suppress the vibration the optimal location for the damping device would be a position where the amplitude of the vibration is the largest and this is why it is very important to identify the amplitude distribution instead of the combustor then the follow up question would be how can you find out the amplitude distribution Well the 1st thing we can do is to install the hundreds of thousands of sensors all around the combustor which is not practical and very expensive the better way is to install only a few sensors and from those sensor measurements we can reconstruct the amplitude distribution inside of the combustor So my research is about how many senses do we need at least and where is the optimal sense of location to reconstruct the amplitude distribution in that way we can estimate the amplitude distribution instead of the combustor and determine the optimal location for the damping device and finally suppress the instability Thank you.