Thank you for your comment. A loudspeaker is placed below the burner to induce the flow pulsation (fuel and air are premixed upstream the burner). The flow is laminar. If we add turbulence in the flow, phenomena remain broadly the same, but the sound emitted by the flame in motion will contain many broadband noise. This noise will be due to the turbulence of the flame. The flame will be a little compacted and the flame front will be wrinkled by the large structures of the turbulent flow.
ru-vid.com3Kkf2fD3-d4?feature=share Is tgis the same concept or would it be classed more so as a pupse jet engine im still unsure combustion is happening in the t section ive measure 132hz fro. This particular set up except i do not have a speaker conected to it
This is interesting! Could you please explain what is going on there further? How were you able to subject the upstream flow to harmonic oscillation? Is that flame an unstable laminar flame or a turbulent flame? Does the acoustic properties change when you change the turbulence intensity? Nice video!
Thank you for your interest. There is always an average outflow of around 1.5 or 2 m/s. When the pulsation of the flow is very strong, there may be, during a small fraction of the oscillation cycle of the flow, a reverse flow but which displaces the premixed gases, in the opposite direction, by only a few millimeters, which is not enough to create a flashback. With laser techniques (Particle Imaging Velocity and Laser Doppler Velocity), it is possible to visualize the oscillations of the flow and measure instantaneous velocities.
thank you for the response. I asked cause around 0:56 the edge of this "crater" seems to have an "8"-shaped "bend" to it.. Was wondering if the circle seen from above oscillates in somewhat similar fashion watch?v=VfHZ_dzyePk. Though at much higher frequencies and with very small amplitudes that we cant really see. all the best.
What led to the transition to the V-flame? It appears the inputs didn't change, so is the M-flame simply unstable to sufficiently large random perturbation?
Thank you for your interest in this research. The aim of this experiment is to analyze the dynamics of a flame subjected to an acoustic excitation according to its initial geometry. I was able to define gas flow rate and mixing conditions with which it is possible to have several flame geometries: conical, "M" and "V". The geometry depends on the conditions of ignition or stabilization. I ignite at the outside of the burner to have the conical flame. Then, without changing the flow or the mixture, I come with a metal tool to make a point of attachment on the central rod. But this "M" flame is robust. To lift the outer edge of the flame I slightly increases the air flow (36 s on the film). The flame goes into "V", then I reduce the flow to recover the initial conditions (to 40 s on the film). We see a red vertical band on the film during these 3s, it is the operator who goes behind to adjust the flow. I hope I have clarified this mystery.
Hello, Thanks for your interest. This video is obviously too short to present all the details. There is a loudspeaker at the base of the burner. I can send you a publication that gives the details of the experimental setup and shows the behavior of the flame according to the injected frequencies, but for that I would need an email address. Without acoustic excitation the V-flame is relatively stable, although there is a slight flapping at the top. With the flow there are always vortices that are created on the lips of the burner and that come to interact with the top of the V-flame. V-Flames and M-flames are very robust without acoustic excitation. They can remain indefinitely in their position if they are not disturbed. Best regards
i am a jet engine mechanic looking to go to engineering school, I am researching, for fun, combustor instabilities and any progress with lean mix burners and alt fuels. Flame temps and alt fuels vs progress in the instabilities research.
