A ramjet combustor is thermal engines that are efficient flight in high speed flow. It ejects and burns fuel in a high speed flow.
It makes sufficiently compressed air by its forward high speed flow of vehicle intake instead of moving parts such as compressor. Eliminating the moving parts makes ramjet lighter. It makes possible efficient flight and power. To stabilize the flame in a high-speed flow, a flame holder is essentially required. But the flame holder also generates a wake.
The mixing zone generated by the flame holder affects the combustor wall directly and leads to serious thermal problems, such as thermal crack and fatigue. Therefore, cooling techniques for ramjet combustors are a core part of engine in the thermal design. Cooling refers to blocking off the combustor wall from the heat, generated during combustion, and maintaining the combustor structure at a low and safe temperature. In general, there are two types of cooling techniques: ablation and film cooling. The film cooling technique, a coolant is injected through holes or slots on the combustor walls. This creates an isolated film between the hot combustion gases and the material, and this film protects the combustor walls from the hot combustion gas.
Film cooling is more complex system than ablation.
However, film cooling is preferred in systems that are operational for extended periods because of its ability to deliver high cooling performance and efficiency over extended periods.
SITVC(Secondary Injection Thrust Vector Control)is using for the rapid altitude control in the flight vehicle by using
secondary injection to supersonic mainstream nozzle flow field.
Compare with mechanical deflector type TVC system, SITVC has a light weight by elimination of complicated mechanical equipment. And it also has a additional thrust by secondary injection.
But secondary injection in supersonic flow accompanied with the complex thermal and flow field by shock/boundary layer interaction. The bow shock is produced at the front of injection jet. And the interaction flows also cause the separation with separation shock to flow field. Moreover strong recirculation flow with reattachment is occurred.
From these three dimensional complex flow, locally high heat and mass transfer is concentrated around the injection hole region. And locally high heat transfer makes the thermal stress. These thermal concentrations cause the thermal fracture. It produced the decrease of system performance and difficulty of maintenance.
In fact, TITAN4 K11 has a thermal damage such as nozzle ablation by strong pressure and high heat transfer. Thus thermal fracture such as ablation by thermal concentration damages the vehicle body and work for dangerous factor in flight. To understanding the thermal characteristic near the secondary injection hole, study about shock/boundary layer interaction by secondary injection should be preceded.