جستجوی مقالات مرتبط با کلیدواژه « Experimental aerodynamics » در نشریات گروه « فنی و مهندسی »

In this study, the effect of protuberance on the thrust vector of a supersonic jet was investigated as a new method in thrust vector control. For this purpose, a convergent-divergent nozzle was designed and fabricated. This nozzle is such that the nominal Mach number in the nozzle exit in full expansion condition is 2. The wall of the nozzle is equipped with pressure holes to measure pressure variations. Also, there is a hole on the nozzle wall to apply a protuberance inside the nozzle. Pressure sensors for pressure measurement and also the Schlieren system are used to check the outlet flow field. The total pressure in all experiments is constant and equal to NPR=6.6. Three-dimensional and multi-block numerical code is used for flow modeling. Also, the turbulence model k-ε, RNG is used to model the nozzle flow. An unstructured mesh has been used for modeling the flow field within the nozzle and the outside domain. The results of this study show that the depth of penetration of the protuberance in the flow field has a significant effect on the amount of deviation and even the direction of the jet stream exited from the convergent-divergent nozzle. The maximum deviation of the jet outlet from the nozzle is 9.8 degrees, which is equal to a penetration ratio of 0.4. In addition, these results indicate that with the increase in protuberance penetration within the nozzle, the nozzle axial thrust has slightly decreased.

In this study, effects of the use of dual transverse protuberances (DTP) as a new, low cost and simple method in controlling the thrust vector in a C-D  nozzle, whose nominal Mach number is 2, was investigated. The protuberances used are two cylindrical shapes that are placed in front of the flow in the divergence part of  nozzle. Protuberances are installed in 80% of the length of the nozzle divergence section from nozzle throat, transversely and at a 45° angle to each other. The flow field was investigated by schlieren imaging, along with measuring the pressure distributions on the nozzle walls. The results show that using the DTP in the nozzle can increase the angle of the thrust vector to 3.5 degrees in the examined conditions. Also,it can be achived in compare to using a single protobrance with lower thrust loss up to 5.5%.

In this research, the effect of several unconventional obstructions with cubic, spherical, cylindrical, and cone geometries on the propulsion vector of a convergent-divergent micro nozzle as a new method in propulsion vector control is experimentally investigated. For this purpose, a convergent-divergent nozzle was designed and constructed in small dimensions. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of this nozzle is designed to measure pressure variations with pressure holes. Also, in the nozzle wall, a duct has been created to apply a bulge inside the nozzle. Pressure sensors and the shadograph system have been used to pressure measurement and check the outlet flow field respectively. The total pressure of the calming chamber is constant in all experiments and is equal to 5.5 times. The results of this study show that the maximum deviation is related to an obstruction with a cubic geometry which is 2.1 degrees. Also, the geometries that have sharp corners are more shock-shaped and hit the opposite wall. In this research, the shock formed by a cubic barrier has hit the opposite wall, but with a spherical shaped and cone-shaped barrier, the shock comes out from the nozzle. Also, these results indicate that the axial force of the nozzle has been reduced to a very small extent.