جستجوی مقالات مرتبط با کلیدواژه « Total Pressure Recovery » در نشریات گروه « مکانیک »

This study deals with the numerical investigation of the effects of the of multi row disks on the performance parameters of an axisymmetric supersonic air inlet of the mixed compression type at free stream Mach number of 2. Inlet performance parameters include drag coefficient, distortion coefficient, total pressure recovery and mass flow ratio. The multi row disk concept is one of the new methods to control the flow and the boundary layer. In this study, after validating the results of numerical simulation with the help of experimental results, the desired inlet has been investigated in terms of performance parameters in different back pressure ratios. Then, the effects of number of disks, length and depth of the cavities were also investigated. The results showed that using the multi row disks has a favorable effect on the drag coefficient and mass flow ratio. It was also observed that the use of multi row disks postpones the subcritical operating condition, which is operationally very beneficial for the aerial vehicle, because it makes the flight envelope of the vehicle wider.

Air intakes play an important role in the operation of aircrafts, so their optimal performance can have a significant effect on the performance of the propulsion system. The purpose of this study was to design and optimize an axisymmetric air intake for a mass flow rate of 10 kg / sec in a free-stream Mach number of 2.5 at sea-level conditions. In the present study, pressure recovery and flow distortion coefficients are selected as functional parameters for optimization. Initially, the parametric design of the intake and the selection of geometric parameters were dealt with, and then the interval of the parameter changes was determined. In this research, the NSGA-II multi-objective genetic algorithm was used as an optimization algorithm; artificial neural network was used to predict intake performance in the optimization loop; for training neural networks 243 Initial geometry has been designed and numerically solved. The genetic algorithm that used has 20 population per generation and 1000 generations. After 1000 generations, the resulting population is selected as optimal geometries. At the end of the optimization, the pressure recovery and flow distortion were improved by 4.4% and 49%, which indicates the efficiency of the optimization process.

A supersonic axisymmetric mixed compression air intake has been experimentally studied in a wind tunnel at three free stream Mach numbers of 1.8, 2.0 and 2.2 at zero degrees angle of attack. Shadowgraph flow visualization has been used as well as the pressure transducers. By applying a suction slot over the external compression surface upstream of the throat, the effects of changing the area of the bleed entrance and exit on the intake performance parameters such as mass flow ratio, total pressure recovery, flow distortion and bleed mass flow ratio have been investigated. The results showed that by increasing the area of the bleed entrance, total pressure recovery increases in critical and subcritical conditions and if simultaneously the area of the bleed exit increases, the pressure recovery will be further improved, especially in subcritical condition. The results also indicated that if the area of the bleed entrance becomes very large, it can have an adverse effect on the intake performance, especially in critical condition even worse than the no bleed case. However, using a large bleed entrance can postpone the buzz onset at off-design conditions.

Investigation of the intake performance is one of the most important topics in the aerodynamic design of the aerial vehicles. In this study, the performance of a supersonic axisymmetric mixed compression intake that was designed for free stream Mach number of 2, has been investigated at zero degrees angle of attack. Then by applying a heat source and changing its position, effects of this source on the intake performance has been studied. The flow has been simulated by a computational fluid dynamic code which in RANS equations have been discretized using the explicit method. The practical results were achieved by testing in the wind tunnel at Imam Hossein University have been used to validate the numerical simulation. Results show that a heat source located at the proper location could have desirable effects on the total pressure recovery, mass flow ratio and drag coefficient of the intake. The critical back pressure ratio also increases which widens the intake operating region. However, the flow distortion will increase a bit. At design Mach number and critical condition, 9.68% increase in total pressure recovery, 26.6% decrease in drag coefficient, 16.16% increase in mass flow ratio, 8.7% increase in critical back pressure ratio and 17.13% increase in flow distortion have been observed.