Constrains And Measured Quantities
The study was carried for a low subsonic flow regime which is very typical for a UCAV as Ghatak won’t travel at supersonic speeds. The momentum of the core nozzle was kept constant and the momentum of the secondary nozzle was varied. The surface pressure distribution, exhaust jet velocity, and thrust were measured. It was found that the secondary jet created a virtual exit plane at an angle to the stream-wise direction of the nozzle flow resulting in the turning of the core jet away from the slot of injection and changing the thrust direction.
This model was developed using Catia-V5 which is used to model surfaces and the model was 3D printed using ceramics which points the direction of future manufacturing techniques.
A lot of formulas were used and a lot of data was collected for calculating the results. Pressure readings were conducted at 32 different points indicated by ports in the above picture. For the sake of simplicity, we won’t be diving deep into the actual experiment trials and we will move on to the results and the conclusions of the experiments that were conducted. The below image represents the direction of the thrust vectored and the velocity field of the jet in yaw direction. Here, θ represents the vectored angle of the thrust with respect to the original thrust direction. The velocity profile indicated the direction of the velocity of the fluid in X direction.
The following observations were made from the experiments. The angle of the vectoring was found to be increasing with the increase in the momentum of the secondary jet but to a limit. The vectoring was also found to increase the static pressure at the nozzle inlet which affects the engine performance. The secondary jet was found to reduce the width of the core jet and also created vortexes which helped with the mixing of core and secondary jets and increased the mass entertainment. The core flow behaviour too changed with and without aft-deck. Aft-deck is nothing but the extension that is attached to the lower surface after the nozzle’s exit. The secondary jet was also providing thrust vectoring in pitch direction additional to the yaw direction. Performance of the nozzle was improved with the aft-deck compared to a no aft-deck nozzle.
If we try extending these results for the pitch and the roll directions, we can assume that the secondary jet injection for pitch vectoring will be placed on Z-axis and for vectoring in the roll direction the secondary jet injection will be in the X-axis. It can be observed that a lot of effort has gone into designing the fluid thrust vectoring for Ghatak UCAV. Remember this is only for one direction and for the remaining two directions; the number of experiments and the computational effort will be even greater. (Text Courtesy: AlphaDefense)