Papers by Keyword: Cavity

Abstract: To unravel the flow and heat transfer mechanism of the cavity in supersonic combustion, this paper studied the interaction of cavities and shear-layers by experiments and numerical simulation. The experiments of Nero-particle Plane Laser Scatter (NPLS) and Plane Laser-Induced Fluorescence (PLIF) were conducted to study the cavity shear-layer. In the same supersonic condition the flow was studied by the method of Large Eddy Simulation (LES). And we discussed the cavity shear-layer influence to supersonic flow and combustion, analyzed the evolvement of injection shear-layer, probed into the heat transfer of supersonic combustion, and studied the transpiration cooling of cavities. The results show: in supersonic combustion, the initial flame spreads to the upstream through the cavity shear layer, the highest wall temperature occur at the rear edge of cavity, and transpiration cooling can effectively protect the wall materials.

Abstract: With the rapid development of modern electromagnetics, a lot of electromagnetic field numerical methods are maturing. 3D electromagnetic simulation software HFSS has two solutions including incentive solving and eigenmode solving. When solving the calculation of the structure of eigenmodes or resonant type can use eigenmode solver. Using matlab generate HFSS scripting language-based program to set eigenmode solution is a very convenient and very innovative approach. The program on a circular cavity modeling and eigenmode solution set simulation results meet the design requirements.

Abstract: For the study of effects of perturbation, such as the change in the resonant frequency and in the other parameters of a rectangular cavity, the resonance condition, the resonant wavelength and the resonant frequency are analyzed in this paper, with the help of perturbation method in a resonance cavity of the reflection type. The relation is deduced in detail under two suppose conditions, which is between the resonant frequency and the dielectric constant or the permeability of the medium filled in the cavity. The accurate relation between the changes in the resonant frequency and in the dielectric constant or the permeability is established. This paper provides the scientific basis for research on the intrinsic characteristic of medium.

Abstract: The combination of transverse injection and cavity flame stabilizer is a good way to improve the mixing efficiency and flame stability. In order to study the influence of transverse injection on the flow field of cavity in advanced vortex combustor, the turbulence flow and the fuel distribution under the influence of different assignments of jet holes were simulated numerically. The results show that the different assignments of jet holes have a bigger impact on the geometry and center of vortex, but lesser on the total pressure of combustor. The content of fuel reduces quickly in the jet direction, injection can improve the mixing of fuel and air. The phenomenon of mass diffusion and transport is obvious, it is in favor of flame stability.

Abstract: In this paper, the structure of foam cavity which based on FB100 foamed asphalt testing machine will be analyzed and designed to change its volume. So that, the changes of work pressure about hot asphalt would be caused and the hot asphalt, water, gas would be more uniform contact to improve the effect of foaming properties about asphalt. The models were built with Fluent Software and large number of experiments were be done, the affection and the law of foaming asphalt characteristics which has changed when the volume of asphalt foam device was changed will be verified by analysis, the ideal range of volume about asphalt foam device cavity will be given.

Abstract: For making sure the dry bay ignition and fire, it’s necessary to calculate the number and the sizes of the droplets and determine the mass flow rate of the fuel induced by high-speed impact and penetration of a rigid projectile into fuel tank. An analytical model is founded and the method for calculating the initial leaking velocity of the fuel is determined. It gives the equation for calculating the drop size distributions of fuel and the Sauter mean diameter (SMD) of droplets, through the Maximum Entropy Theory and the conservation for mass. Using the Harmon’s equation for SMD,the fuel droplets SMD can be calculated. Results shows that the initial leaking velocity of the fuel is about linearly increasing with the velocity of the projectile, the SMD of fuel droplets increases with the hole size of the fuel tank which induced by the penetration of the projectile and linearly decreases with the velocity of the projectile. The results can be used for the ignition and fire analysis of the dry bay adjacent to fuel tanks.

Abstract: An advanced structure containing cavities was adopted in distribution layers. A series of large-scale similarity-simulation tests was conducted on the defense effect of the four structures under plane impact loads. Based on the tests results and theoretical analysis conclusions, numerical simulations were developed by LS-DYNA software. The results indicate that the numerical results agree well with the test data; the stress peak was distinctively decayed below the cavities, and the defense effect of circle-section cavity is more effective than square-section cavity while the defense effect was weakened when a thin steel plate was laid above the cavities. Compared with clipping performance of it under the explosion loads of mass ammunition, which of the structure with cavities under plane impact loads is better effective. This work provides an important basis for designing the scientifically safe distribution layers.

Abstract: Longitudinal cavities or pipes are usually developed in a metallic slab or billet produced by continuous casting. In the present study, closure behavior of such cavities by side pressing was investigated by finite-element method. Since the contact surface between the dies and the slab was much longer in the longitudinal direction than in the thickness direction, the slab was compressed under the condition of plane-strain deformation. As a result, the effective strain was found to be an indicator for the void closure. The critical value of the effective strain was dependent upon the aspect ratio of the cross section of the cavity, but not upon its size.

Abstract: The aaviation kerosene is a practical candidate fuel for scramjet engine in the flight regimes of Mach number less than 8, in considerations of safety, economy and portable. In the present paper, the ignition characteristics of a scramjet combustor model fueled by aviation kerosene was experimentally investigated, using the resistance heating direct-connected supersonic combustion facility of Northwestern Polytechnical University. The inflow conditions at the direct-connected combustor entrance were specified as: the nominal Mach of 2.0, the total temperature of 870～930K and the total pressure of about 770kPa. Three combustor performance of difference ER were compared applied CFD simulated. The experimental result suggested that: the cavity design is a key problem for kerosene successful ignition is the combustor; That chooses appropriate gas-oil ratio could increased performance of combustor and kept isolator interfered by gas.

Abstract: Based on the diseases disposal project of Longmen Tunnel in the Fujian provincial road 206, the seismic reinforcement measure of mountain tunnel cavity was studied in this paper. The seismic stability of the mountain tunnel to deal with the cavity behind the lining was calculated and analyzed under the two common disease reinforcement measures, by using a 3-D finite difference method. And the optimal reinforcement scheme also had been determined. The results show that mortar bolt and cover arch can change the maximum principal stress spectral characteristics of surrounding rock, which is beneficial to the seismic resistance. And the results also show that mortar bolt has slightly effect on the bending moment stress of lining.