جستجوی مقالات مرتبط با کلیدواژه "برآمدگی" در نشریات گروه "مکانیک"

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 study, the effect of a cylindrical 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 (C-D) nozzle was designed and constructed. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of the nozzle is equipped with pressurized holes to measure pressure variations. Also, there is a duct wall in the nozzle wall to apply a protuberance inside the nozzle. Pressure sensors are used for pressure measurement and also the schlieren system IS used to check the outlet flow field. The total pressure of the compartment is constant at all tests and is 5.7 bar. 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 deviation of the jet stream exited from the C-D nozzle. The maximum jet outlet flow from the nozzle is 5.7 degrees, which occurred at a rate of H/D*=0.4. In addition, these results indicate that with the increase in bulge penetration within the nozzle, the nozzle axial thrust has slightly decreased.

In this study, the effect of a cylindrical protuberance on the thrust vector of a supersonic jet was investigated as a new method in thrust vector control. For this purpose, a C-D nozzle was designed and constructed. The nozzle exit Mach number is 2. The wall of the nozzle is equipped with pressure holes to measure pressure variations. Also, there are several holes in the divergence portion of nozzle wall to apply a protuberance inside the nozzle. Pressure sensors for pressure measurement and also the Schliern system are used to check the outlet flow field. The nozzle pressure ratio in all experiments is constant and in two cases is equal to NPR=6.6 and NPR=9. The protuberance is installed in the nozzle divergence section, at position X⁄L=0.6,0.7,0.8,0.9 and with a constant penetration ratio of H⁄D^* =0.2. The results of this study show that using the protuberance can control the angle of the thrust vector. Also, installing location X⁄L=0.9 is the best position which, in this case the angle of the trusted vector reaches 3.1 degrees. Also, the results reveals that the change in the nozzle pressure ratio in different installing positions has different effects on the thrust vector angle and axial thrust losses.

In this study, the effect of a cylindrical 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 constructed. This nozzle is such that the Mach number is its nominal output in full expansion conditions 2. The wall of the nozzle is equipped with pressurized holes to measure pressure variations. Also, there is a duct wall in 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 of the compartment is constant at all tests and is 5.7bar. 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 deviation of the jet stream exited from the convergent-divergent nozzle. The maximum jet outlet flow from the nozzle is 5.7degrees, which occurred at a rate of H/D*=0/4. In addition, these results indicate that with the increase in bulge penetration within the nozzle, the nozzle axial thrust has slightly decreased.

In this research a final element model for simulating three dimensional deformation in rolling of flat product is modeling in ABAQUS and further developed to study the frictional effects on spread and bulge. To predict the magnitude of bulging , the rolling process is approximated by successive forging steps. The elongation or the average spread at each step from the previous calculations are used in the model. The theoretical results of the model is in a good agreement with the experimental values given by other investigation.