Hi

First of all, it is useful to know that the temperature in swirl stabilized system doesn't have a significant role in flashback ,especially that the flame will be lifted into downstream region and the premixed mixture will cool the burner rim. So if you want to detect the temperature close to flashback when the flame propagates either through CIVB or BLF I will recommend to put the thermocouple close to burner rim and attached it to the inner wall.

accept my regards

Also I recommend to read see this article :

https://asmedigitalcollection.asme.org/gasturbinespower/article-abstract/136/2/021502/373493/Influence-of-Burner-Material-Tip-Temperature-and?redirectedFrom=fulltext

Mohammed Alfahham Thanks You for the response. I am following your advice.

Hello Noorul,

Answer to your question shall depend on various factors such as

1. Response time: How quickly do you want to identify the flashback?

2. Mixing tube geometry and flashback modes: Does the flame flashback along the axis or the boundary layer?

Response time is of relevance when you want to quickly identify the flashback. It may be due to experimental objectives (as was the case for me, to employ high-speed cameras) or from the safety perspective since the overheating of the upstream components of the premixed burner increase the possibility of flame propagation into upstream components resulting into DDT (depending on the extent of premixing, and the fuel composition; likely if hydrogen-enriched.)

Mixing tube geometry is important since it determines the dominant mode of propagation. Placing a thermocouple in mixing tube is likely to affect the boundary layer and if boundary layer flashback is the dominant mode, the flashback is likely to occur due to the disturbance offered by the thermocouple. For CIVB-induced flashback, placing a thermocouple in the outer wall could be non-intrusive enough to give clean results.

I am not aware of the combustor geometry you are working with, but I have conducted similar experiments with an optically accessible annular mixing tube. It was never published since it was little relevance to us, but I can share the temperature trend if you are interested.

From a quick-response perspective (< 5ms) we realized that Thermocouple was never a fast-enough flashback detector.

The two easiest ways to detect flashback if you have no optical access to the mixing tube is either with a thin thermocouple (0.3mm) or with a photomultiplier. If you need very fast detection, I would suggest ionization probes.

Your K-type thermocouple has a very large response time as compared to the time scale of the flame flashback. It means that you won’t be able to detect the onset of the flashback. However, after a while sensor will detect the high temperature gases.

I didn’t get your point for such measurements. If you want to mitigate the flame flashback, it is better to use flame arrestor inside the feeding pipe. However, if you want to just detect the onset of the flashback you need high frequency measurement probes e.g. a PMT.

Hi,

As Mohammad Shahsavari mentioned, the response time from the thermocouple is late. Please try with piezo-electric Pressure transducer for the checking the pressure rise due to flashback. You can use the feedback from the pressure transducer for controlling the solenoid valve.

Hope this will help you.