# Flame Evolution Characteristics for Hydrogen/LPG Co-Combustion in a Counter-Burmer
## 5 Conclusions  
When using a counter-burner, the combustion process is significantly enhanced, as this design contributes to improving the heat exchange between the flame and the surrounding surfaces, which leads to increased heat transfer efficiency and reduced heat loss. The flame generated can be seen as a complex pattern due to the interactions between hydrogen and LPG and the dynamic effects of air flow. The aerodynamics of flame development  
Figure 19: Influence of hydrogen enrichment on peak flame temperature at different equivalence ratios.  
Figure 20: Profile of flame temperature distribution along axial distance of burner.  
during combustion show that the rapid combustion of hydrogen leads to the formation of flame zones with particularly high temperatures at the beginning of ignition, while LPG provides greater stability during the continuous combustion phase. The resulting flame has distinctive characteristics that include variations in intensity and temperatures depending on the mixing ratios. As the proportion of hydrogen in the mixture increases, the flame becomes hotter and less stable, which calls for the use of stability-enhancing techniques such as careful mixing and the use of special burner designs such as a counter-burner that provides an axial flow that enhances flame stability. Combustion also reduces emissions of harmful gasses such as carbon monoxide and nitrogen oxides, especially when the ideal air ratio is achieved. The co-combustion of hydrogen and LPG has different thermal properties that depend largely on the mixing ratios and operating conditions. The combination of hydrogen increases the combustion rates due to its high velocity, which increases the efficiency of the reaction and reduces the combustion time. The following are the major conclusions that can be drawn from this study's findings:
* LPG exhibited the lowest laminar burning velocity; increasing the hydrogen ratio by 10-15% greatly enhanced the combustion rate, with the peak burning velocity attained at a hydrogen ratio of 20%, where the combustion rate exhibited markedly elevated values throughout all equivalency ratio ranges. The results showed that increasing the hydrogen content in the combustion mixture significantly increased the burning velocities. Mixing 20% hydrogen led to an increase in laminar burning velocity of 67.4% at an equivalence ratio equal to one.
* An elevated hydrogen ratio resulted in a higher flame temperature, with 20% H\({}_{2}\) exhibiting the maximum temperature relative to the others. The results showed that mixing 20% hydrogen led to an increase in flame temperature of 20.8% at an equivalence ratio equal to one.
* On the other hand, LPG provided flame stability due to its high density and thermal energy, which contributed to improving the flame quality and preventing unwanted fluctuations.  
[PERSON] contributed to the experimental part, including the fabrication and setup of the combustion system and data collection, and the theoretical part, represented by numerical modeling. Meanwhile [PERSON] and [PERSON] helped with numerical analysis, the results' analysis, and writing this article. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in this study.  
Data are contained within the article.  
The authors are obliged to the University of Technology, Baghdad, Iraq, for providing the Energy and Renewable Energies Technology Center.  
The authors declare no conflicts of interest.