An experimental investigation was carried out to find the effect of a strut spanning across the width of a single expansion ramp of a laboratory model scramjet thruster as a thrust vector control d...

An experimental investigation on the use of a rectangular strut in a scramjet thruster for thrust vector control

An experimental investigation was conducted to obtain wall pressure distribution in a convergent divergent nozzle with a strut inserted through the diverging wall and to find out the possible generation of side force. The strut inserted through the nozzle wall represented an active control method for thrust vector control. Laboratory tests were carried out to examine whether this type of strut injection would be effective and serve as an alternative thrust vector control method for the other widely used such as secondary injection thrust vector control. The nozzle model used in the experiments had a design Mach number of 1.84 with a corresponding area ratio of 1.48. The solid strut which was inserted through the diverging wall of the nozzle had a square cross section. Experiments were conducted for identifying three different strut positions from the nozzle throat, i.e. at Ld/3, Ld/2, and 2Ld/3, where Ld was the length of the diverging section of the nozzle. At each strut position, the strut height was varied and the maximum strut height corresponded to the radius of the local cross section where the strut was inserted. The nozzle was operated at overexpansion conditions such as nozzle pressure ratios of 3.4 and 5. The strut side and the opposite side of the nozzle wall had eight wall pressure tappings each and the wall pressure data were obtained using a pressure scanner. The asymmetrical pressure distributions of the strut side and the non-strut side (opposite side) of nozzle wall were used for the calculation of side force and pitching moment in the nominal plane through the wall pressure ports of both sides. The calculated two-dimensional side force, axial force, and pitching moment coefficients were plotted against strut height at each strut position from the nozzle throat. From the experimental data and calculations, it was found that the axial force varied more or less linearly with strut height irrespective of the strut position. However, the side force and pitching moments varied nonlinearly with strut height and the nature of variation of the two was similar. Both the side force and pitching moment exhibited maximum and minimum values at two specific values of the strut height. The change in the strut position did not alter the nature of the above variations and the strut height values for maximum and minimum. The magnitude of the side force was found to be 1–10% of the axial force generated as a fluid dynamic pressure drag. Both positive and negative side force and pitching moments were produced with increase in the strut height.

Experimental study of internal forces and moments generated by strut injection in a supersonic cross-flow in a C-D nozzle

A rectangular strut on the expansion ramp of a scramjet thruster for thrust vector control

Mechanical thrust vector control is a classical and significant branch in the thrust vector control field, offering an extremely reliable control effect. In this article, steady-state and unsteady-state aerodynamic characteristics of the rod thrust vector control technology are numerically investigated in a two-dimensional supersonic nozzle. Complex flow phenomena caused by the penetrating rod in the diverging part of the supersonic nozzle are elucidated with the purpose of a profound understanding of this simple flow control technique for physical applications. Published experimental data are used to validate the dependability of current computational fluid dynamics results. A grid sensitivity study is carried through and analyzed. The result section discusses the impacts of two important factors on steady-state aerodynamic features, involving the rod penetration height and the rod location. Furthermore, unsteady-state flow features are analyzed under various rod penetration heights for the first time. Significant vectoring performance variations and flow topology descriptions are illuminated in full detail. While the rod penetration height increases, the vectoring angle increases, whereas the thrust coefficient decreases. As the rod location moves downstream close to the nozzle exit, the vectoring angle and thrust coefficient increase. In terms of unsteady-state aerodynamic effects, certain pressure oscillations occur upstream of the rod, which resulted from the expanding and shrinking of the upstream anticlockwise separation bubbles.

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Numerical Study on Rod Thrust Vector Control for Physical Applications

Experimental Study of Strut Insertion Technique in a Convergent-Divergent Nozzle for Thrust Vector Control

Wall pressure measurements are made in a convergent-divergent nozzle with strut injection to estimate the internal forces and moments. The strut facing the flow was of rectangular cross section and is placed at two thirds of the diverging length of the nozzle from the throat. The design exit Mach number of the nozzle is 1.84. The strut height varied at constant internal total pressure of 690 kPa. Experiments were conducted to explore the possibility of using a solid strut as an alternative to secondary fluid injection for thrust vector control. The wall pressure distribution of the nozzle is studied to interpret the flow interaction with the strut. The calculations based on the experimental data show that the presence of the strut and a variation in its height produce significant variations in side force and pitching moment which would be useful for thrust vector control.

A. Lakshmi Srinivas

Papers

Experimental Study of the Wall Pressure Distribution in a Convergent-Divergent Nozzle with Strut Injection

Experimental study of internal forces and moments generated by strut injection in a supersonic cross-flow in a C-D nozzle

Experimental Study of Strut Insertion Technique in a Convergent-Divergent Nozzle for Thrust Vector Control