جستجوی مقالات مرتبط با کلیدواژه « دهانه ورودی » در نشریات گروه « مکانیک »

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.

The intake is part of the aircraft, which provides air to the engine uniformly and with a minimum total pressure loss. Today, due to the abundant application of S-shaped inlet, optimization of these inlets has been considered by the researchers. The uniform distribution of the flow at the inlet of the compressor has a direct effect on engine performance. On the other hand, the separation of the flow through the duct reduces the pressure recovery and the engine thrust. In this article, an S-duct intake has been optimized to reduce the total pressure loss and flow distortion. The neural network, coupled with the genetic algorithm, is used to optimize the objectives in the shortest possible time. Two optimizations have been done. In the first case, new geometries have been generated by changing the center line coordinate and the cross-sectional area ratios. The first optimization results in an enhancement of 32.5% for pressure recovery coefficient and a reduction of 35.8% for flow distortion. In the second optimization, the length of the duct has also been decreased. By decreasing the length of the duct, the weight of the aerial vehicle is reduced, and on the other hand, the useful space inside the body is increased. This optimization gave an enhancement of 35.96% for pressure recovery coefficient and a reduction of 39.4% for flow distortion and a 25% reduction in the duct length.

Supersonic inlet has a key role in the performance of air-breathing engine special in ramjet engines. The function of a ramjet engines diffuser is to decelerate the air velocity from its free-stream at the intake to a velocity which is compatible with the available flame velocity. Accurate design of inlet has an important effect on the performance of a ramjet system and its main parameters. In this study, an external compression supersonic inlet designed at Mach 3.  Flow behavior for this type of inlet is more complicated than the two-dimensional inlet. Because of this character, a computer program for solving the equations of supersonic flow through the cone, and the relationship between the parameters and the principles of the inlet has developed which integrates the final geometry, including center body geometrical details, inlet cowling and subsonic channel as . Since viscous forces cannot be ignored because they cause complex shock patterns and flow separation, the simulation and flow behavior pattern is modeled and validated by computational fluid dynamics software. For this purpose, the RNG K-ɛ model was used for flow turbulence modeling and second-order accuracy was used for of convection term. The results show that the designed geometry can meet the desired performance requirements.

Nozzle is an important component of wind tunnel. Its main functions: conversion of static pressure to dynamic pressure and reduction of turbulence intensity and helping in uniformity of the velocity profile in the test section of wind tunnel. In order to reduction of wind tunnel building costs, in some wind tunnel special vertical type, setting chamber may be replaced by a bell mouth at the nozzle inlet. Experimental methods such as hot wire anemometry have been used in this research. Result show that the effect of nozzle in blowing and suction type of wind tunnels is similar. Effect of bell mouth at the nozzle inlet is not significant for turbulence intensity reduction, but bell mouth of the nozzle inlet reduce the losses of nozzle about 7%.