Flame Temperature Estimation: Challenges and Techniques to Tackle Them

Flame Temperature Estimation: Challenges and Techniques to Tackle Them

En'Urga Inc.

The flame temperature estimation helps engineers, researchers, and analysts have a better understanding of combustion processes in metallurgical furnaces, internal combustion engines, and reaction engines. Besides, it also plays an important in temperature control systems. Around 30% of all measurements taken during research and industrial operations are temperature measurements as they assist in getting to know more about physical, chemical and biological processes. 


However, estimating the flame temperature is not an easy task. There are certain challenges and obstacles that prevent from estimating the correct temperature of flames. 


In this blog, we are going to discuss why flame temperature estimation is a tricky process and what solutions are there to achieve this. 


Challenges and Issues of Flame Temperature Estimation


In the temperatures with higher magnitude, the rate of accuracy and reliability of temperature results is greatly reduced due to several reasons:

flame temperature estimation



#First Reason

The flame (with high temperature) doesn’t achieve the complete thermodynamic equilibrium state as an immense amount of energy is released during the burning process and it is unevenly distributed on degrees of molecules’ freedom.  


This is why three values of energy and temperatures are mostly considered - effective rotation, vibration, and translation energies. 


#Second Reason:

Active substances such as free radicals OH and CH are present in the flame which can readily react with any surface that comes into contact with the flame. This may lead to the release of heat energy. This released heat energy can further heat the surface to a temperature higher than the flame temperature. This may result in the wrong estimation of flame temperature. 


#Third Reason:

Factors like a wide temperature range, temperature gradient, and dynamics of combustion processes need to be considered during the process. 


#Fourth Reason:

Chemiluminescence - the phenomenon of light produced from a chemical reaction affects the flame temperature estimation. 


Due to so many undesirable effects on measurement, there exist several methods and measurement tools, each of which is used based on certain conditions. 


Solution for Flame Temperature Estimation

When it comes to measuring temperature, there are three methods available:

  • Contact Method
  • Non-Contact Method
  • Scattering Spectroscopy


In the first method, contact devices such as thermocouples and resistance thermometers are used to measure the temperature of solids. They are not effective in flame temperature measurement because most of them cannot withstand temperatures higher than 1500 degrees Celsius. 


Non-contact methods can be used for flame temperature measurement as it includes high accuracy and the possibility of use for a wide range of temperatures. These methods are divided into two categories: active and passive.


While the active methods are based on analytic’s irradiation by laser, the popular passive method in use is the absorption and emission techniques.  


Emission/Absorption Spectroscopy 

Nowadays, spectrophotometric techniques based on emission, absorption, or scattering are frequently used for qualitative as well as quantitative analyses. These techniques are mainly used to study and analyze unstable flames and short processes. 


One thing to note here is that the use of this flame temperature estimation method must be preceded by spectral research of the object for a detailed analysis of the emitting properties of the medium.