# Enhancing Ignition Reliability with Tail-Groove Strut Designs in Cavity-Based Combustors
## 3 Results and Discussion
### Dynamic Ignition Process
#### 3.1.2 Flame-Propagation Performance  
The ignition processes in the tail-groove strut across five configurations, along with a normal strut, were investigated to gain a deeper understanding of how these configurations influence ignition characteristics. As discussed in Section 3.1.1, a temperature threshold of 1800 K was selected as the criterion for successful flame propagation. Figures 10 and 11 compare the effects of the \(L\) and \(D\) parameters on flame propagation performance in cavity-based integrated combustors, with operating conditions set at \(V=100\,\mathrm{m/s}\) and \(T=700\,\mathrm{K}\).  
Figure 8: Ignition process using CFD and high-speed camera.  
Figure 9: The radial flame distance using CFD.  
The figure reveals that the tail-groove strut designs achieve greater flame propagation distances compared to the normal strut. Specifically, in the case of the \(L16D6\) configuration, the flame reaches the root of the radial stabilizer within 25 ms. In contrast, the flame in the normal strut configuration has not yet reached the radial stabilizer root, even after 30 ms. Furthermore, an increase in the length \(L\) and \(D\) of the tail-groove strut correlates with a higher radial flame propagation performance. This improvement is attributed to the reduced flame refilling duration, which enhances the overall efficiency of flame propagation.  
Notably, Figure 11 shows that increasing \(D\) from 8 mm to 10 mm does not affect the radial flame propagation performance, indicating the existence of a critical depth, \(D_{Cri}\). Beyond this critical depth, further increases in \(D\) do not affect the radial flame propagation performance. Additionally, a comparison of the \(L12D8\) and \(L16D6\) configurations reveals that, despite having the same tail-slot volume, their radial flame propagation performances differ. When compared to the \(L12D6\) configuration, increasing \(D\) is found to accelerate the flame propagation rate more effectively than increasing \(L\). Specifically, the \(L16D6\) configuration completes flame propagation in 25 ms, whereas the \(L12D8\) configuration achieves this in 23 ms.  
At \(t=10\) ms, it is observed that, as \(L\) increases, the temperature of the flame core decreases, although the flame area remains unchanged. This is due to the larger tail-slot volume requiring more heat to fill, leading to a lower core temperature. In contrast, increasing \(D\) results in a decrease in flame area but an increase in core temperature. The  
Figure 11: The radial flame distance and the instantaneous temperature contour plot at \(Z=0\) mm, as shown in Figure 1. From top to bottom, the configurations are as follows: Normal, \(L12D6\), \(L12D8\), and \(L12D10\).  
Figure 10: The radial flame distance and the instantaneous temperature contour plot at \(Z=0\) mm, as shown in Figure 1. From top to bottom, the configurations are as follows: Normal, \(L8D6\), \(L12D6\), and \(L16D6\).  
implications of these changes will be further discussed in the following section, focusing on the flow field characteristics.