# Enhancing Ignition Reliability with Tail-Groove Strut Designs in Cavity-Based Combustors
## 3 Results and Discussion
### The Flow Characteristics  
Considering the same operating conditions, the ignition performance is mainly influenced by the following flow characteristics. To better understand the variations in ignition performance, numerical simulations were conducted to analyze the flow patterns and turbulent kinetic energy (k). Figure 12 presents the corresponding results. The figure shows that in the normal strut configuration, two distinct recirculation zones are observed: recirculation A within the cavity and recirculation C at the root of the strut. The airflow in the cavity region is directed towards the area behind the strut due to its influence.  
In contrast, the tail-groove strut configuration features three distinct recirculation zones: recirculation A within the cavity, recirculation B at the junction between the cavity and the strut, and recirculation C at the root of the strut. This is due to the concave wall surface of the tail-groove strut, which constrains the airflow near the wall, causing some of it to flow radially. Additionally, the pressure gradient induces backflow, which subsequently leads to the formation of recirculation B.  
Recirculation B enhances the breakup and atomization of fuel droplets in this region, which improves radial flame propagation performance. Additionally, recirculation B acts as a transitional zone for radial flame propagation, allowing energy accumulation in this area, which in turn boosts the flame's radial propagation. This explains why the tail-groove strut reduced the flame refilling duration.  
As the length \(L\) increases from \(L12D6\) to \(L16D6\), the turbulent kinetic energy in regions 1 and 2, as shown in Figure 12, correspondingly decreases. This reduction in turbulent kinetic energy diminishes the intensity of mixing between the flame and the unburned fuel. Additionally, as \(L\) increases, backflow is noticeably diminished and eventually disappears. This can be attributed to the reduced restriction on the near-wall airflow by the concave wall surface of the tail-groove strut, which weakens the radial flow at \(Z=0\) mm. Furthermore, the alteration in the pressure field also plays a crucial role in the elimination of backflow. The disappearance of backflow results in a concomitant reduction in heat exchange capacity. Consequently, at \(t=10\) ms, the temperature of the flame core in the \(L16D6\) configuration decreases.  
As the depth \(D\) increases from \(L12D6\) to \(L12D10\), the turbulent kinetic energy in region 1 increases, while it decreases in region 2. The increase in turbulence in region 1 enhances the mixing and interaction between the flame and the unburned fuel, leading to a more extensive flame area. However, in region 2, the decrease in turbulence reduces the mixing intensity, leading to a smaller flame area. Additionally, the increase in depth \(D\) causes a  
Figure 12: Flow patterns and turbulent kinetic energy.  
larger recirculation zone B, as the radial flow at the \(Z=0\) plane is enhanced. This change in turbulence distribution leads to a reduction in the overall flame area while simultaneously increasing the temperature of the flame core.